#include "cache.h"
#include "config.h"
#include "grep.h"
#include "userdiff.h"
#include "xdiff-interface.h"
#include "diff.h"
#include "diffcore.h"
#include "commit.h"
#include "quote.h"

static int grep_source_load(struct grep_source *gs);
static int grep_source_is_binary(struct grep_source *gs);

static struct grep_opt grep_defaults;

static void std_output(struct grep_opt *opt, const void *buf, size_t size)
{
        fwrite(buf, size, 1, stdout);
}

static void color_set(char *dst, const char *color_bytes)
{
        xsnprintf(dst, COLOR_MAXLEN, "%s", color_bytes);
}

/*
 * Initialize the grep_defaults template with hardcoded defaults.
 * We could let the compiler do this, but without C99 initializers
 * the code gets unwieldy and unreadable, so...
 */
void init_grep_defaults(void)
{
        struct grep_opt *opt = &grep_defaults;
        static int run_once;

        if (run_once)
                return;
        run_once++;

        memset(opt, 0, sizeof(*opt));
        opt->relative = 1;
        opt->pathname = 1;
        opt->max_depth = -1;
        opt->pattern_type_option = GREP_PATTERN_TYPE_UNSPECIFIED;
        color_set(opt->color_context, "");
        color_set(opt->color_filename, "");
        color_set(opt->color_function, "");
        color_set(opt->color_lineno, "");
        color_set(opt->color_columnno, "");
        color_set(opt->color_match_context, GIT_COLOR_BOLD_RED);
        color_set(opt->color_match_selected, GIT_COLOR_BOLD_RED);
        color_set(opt->color_selected, "");
        color_set(opt->color_sep, GIT_COLOR_CYAN);
        opt->color = -1;
        opt->output = std_output;
}

static int parse_pattern_type_arg(const char *opt, const char *arg)
{
        if (!strcmp(arg, "default"))
                return GREP_PATTERN_TYPE_UNSPECIFIED;
        else if (!strcmp(arg, "basic"))
                return GREP_PATTERN_TYPE_BRE;
        else if (!strcmp(arg, "extended"))
                return GREP_PATTERN_TYPE_ERE;
        else if (!strcmp(arg, "fixed"))
                return GREP_PATTERN_TYPE_FIXED;
        else if (!strcmp(arg, "perl"))
                return GREP_PATTERN_TYPE_PCRE;
        die("bad %s argument: %s", opt, arg);
}

/*
 * Read the configuration file once and store it in
 * the grep_defaults template.
 */
int grep_config(const char *var, const char *value, void *cb)
{
        struct grep_opt *opt = &grep_defaults;
        char *color = NULL;

        if (userdiff_config(var, value) < 0)
                return -1;

        if (!strcmp(var, "grep.extendedregexp")) {
                opt->extended_regexp_option = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp(var, "grep.patterntype")) {
                opt->pattern_type_option = parse_pattern_type_arg(var, value);
                return 0;
        }

        if (!strcmp(var, "grep.linenumber")) {
                opt->linenum = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp(var, "grep.column")) {
                opt->columnnum = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp(var, "grep.fullname")) {
                opt->relative = !git_config_bool(var, value);
                return 0;
        }

        if (!strcmp(var, "color.grep"))
                opt->color = git_config_colorbool(var, value);
        else if (!strcmp(var, "color.grep.context"))
                color = opt->color_context;
        else if (!strcmp(var, "color.grep.filename"))
                color = opt->color_filename;
        else if (!strcmp(var, "color.grep.function"))
                color = opt->color_function;
        else if (!strcmp(var, "color.grep.linenumber"))
                color = opt->color_lineno;
        else if (!strcmp(var, "color.grep.column"))
                color = opt->color_columnno;
        else if (!strcmp(var, "color.grep.matchcontext"))
                color = opt->color_match_context;
        else if (!strcmp(var, "color.grep.matchselected"))
                color = opt->color_match_selected;
        else if (!strcmp(var, "color.grep.selected"))
                color = opt->color_selected;
        else if (!strcmp(var, "color.grep.separator"))
                color = opt->color_sep;
        else if (!strcmp(var, "color.grep.match")) {
                int rc = 0;
                if (!value)
                        return config_error_nonbool(var);
                rc |= color_parse(value, opt->color_match_context);
                rc |= color_parse(value, opt->color_match_selected);
                return rc;
        }

        if (color) {
                if (!value)
                        return config_error_nonbool(var);
                return color_parse(value, color);
        }
        return 0;
}

/*
 * Initialize one instance of grep_opt and copy the
 * default values from the template we read the configuration
 * information in an earlier call to git_config(grep_config).
 */
void grep_init(struct grep_opt *opt, const char *prefix)
{
        struct grep_opt *def = &grep_defaults;

        memset(opt, 0, sizeof(*opt));
        opt->prefix = prefix;
        opt->prefix_length = (prefix && *prefix) ? strlen(prefix) : 0;
        opt->pattern_tail = &opt->pattern_list;
        opt->header_tail = &opt->header_list;

        opt->color = def->color;
        opt->extended_regexp_option = def->extended_regexp_option;
        opt->pattern_type_option = def->pattern_type_option;
        opt->linenum = def->linenum;
        opt->columnnum = def->columnnum;
        opt->max_depth = def->max_depth;
        opt->pathname = def->pathname;
        opt->relative = def->relative;
        opt->output = def->output;

        color_set(opt->color_context, def->color_context);
        color_set(opt->color_filename, def->color_filename);
        color_set(opt->color_function, def->color_function);
        color_set(opt->color_lineno, def->color_lineno);
        color_set(opt->color_columnno, def->color_columnno);
        color_set(opt->color_match_context, def->color_match_context);
        color_set(opt->color_match_selected, def->color_match_selected);
        color_set(opt->color_selected, def->color_selected);
        color_set(opt->color_sep, def->color_sep);
}

static void grep_set_pattern_type_option(enum grep_pattern_type pattern_type, struct grep_opt *opt)
{
        /*
         * When committing to the pattern type by setting the relevant
         * fields in grep_opt it's generally not necessary to zero out
         * the fields we're not choosing, since they won't have been
         * set by anything. The extended_regexp_option field is the
         * only exception to this.
         *
         * This is because in the process of parsing grep.patternType
         * & grep.extendedRegexp we set opt->pattern_type_option and
         * opt->extended_regexp_option, respectively. We then
         * internally use opt->extended_regexp_option to see if we're
         * compiling an ERE. It must be unset if that's not actually
         * the case.
         */
        if (pattern_type != GREP_PATTERN_TYPE_ERE &&
            opt->extended_regexp_option)
                opt->extended_regexp_option = 0;

        switch (pattern_type) {
        case GREP_PATTERN_TYPE_UNSPECIFIED:
                /* fall through */

        case GREP_PATTERN_TYPE_BRE:
                break;

        case GREP_PATTERN_TYPE_ERE:
                opt->extended_regexp_option = 1;
                break;

        case GREP_PATTERN_TYPE_FIXED:
                opt->fixed = 1;
                break;

        case GREP_PATTERN_TYPE_PCRE:
#ifdef USE_LIBPCRE2
                opt->pcre2 = 1;
#else
                /*
                 * It's important that pcre1 always be assigned to
                 * even when there's no USE_LIBPCRE* defined. We still
                 * call the PCRE stub function, it just dies with
                 * "cannot use Perl-compatible regexes[...]".
                 */
                opt->pcre1 = 1;
#endif
                break;
        }
}

void grep_commit_pattern_type(enum grep_pattern_type pattern_type, struct grep_opt *opt)
{
        if (pattern_type != GREP_PATTERN_TYPE_UNSPECIFIED)
                grep_set_pattern_type_option(pattern_type, opt);
        else if (opt->pattern_type_option != GREP_PATTERN_TYPE_UNSPECIFIED)
                grep_set_pattern_type_option(opt->pattern_type_option, opt);
        else if (opt->extended_regexp_option)
                /*
                 * This branch *must* happen after setting from the
                 * opt->pattern_type_option above, we don't want
                 * grep.extendedRegexp to override grep.patternType!
                 */
                grep_set_pattern_type_option(GREP_PATTERN_TYPE_ERE, opt);
}

static struct grep_pat *create_grep_pat(const char *pat, size_t patlen,
                                        const char *origin, int no,
                                        enum grep_pat_token t,
                                        enum grep_header_field field)
{
        struct grep_pat *p = xcalloc(1, sizeof(*p));
        p->pattern = xmemdupz(pat, patlen);
        p->patternlen = patlen;
        p->origin = origin;
        p->no = no;
        p->token = t;
        p->field = field;
        return p;
}

static void do_append_grep_pat(struct grep_pat ***tail, struct grep_pat *p)
{
        **tail = p;
        *tail = &p->next;
        p->next = NULL;

        switch (p->token) {
        case GREP_PATTERN: /* atom */
        case GREP_PATTERN_HEAD:
        case GREP_PATTERN_BODY:
                for (;;) {
                        struct grep_pat *new_pat;
                        size_t len = 0;
                        char *cp = p->pattern + p->patternlen, *nl = NULL;
                        while (++len <= p->patternlen) {
                                if (*(--cp) == '\n') {
                                        nl = cp;
                                        break;
                                }
                        }
                        if (!nl)
                                break;
                        new_pat = create_grep_pat(nl + 1, len - 1, p->origin,
                                                  p->no, p->token, p->field);
                        new_pat->next = p->next;
                        if (!p->next)
                                *tail = &new_pat->next;
                        p->next = new_pat;
                        *nl = '\0';
                        p->patternlen -= len;
                }
                break;
        default:
                break;
        }
}

void append_header_grep_pattern(struct grep_opt *opt,
                                enum grep_header_field field, const char *pat)
{
        struct grep_pat *p = create_grep_pat(pat, strlen(pat), "header", 0,
                                             GREP_PATTERN_HEAD, field);
        if (field == GREP_HEADER_REFLOG)
                opt->use_reflog_filter = 1;
        do_append_grep_pat(&opt->header_tail, p);
}

void append_grep_pattern(struct grep_opt *opt, const char *pat,
                         const char *origin, int no, enum grep_pat_token t)
{
        append_grep_pat(opt, pat, strlen(pat), origin, no, t);
}

void append_grep_pat(struct grep_opt *opt, const char *pat, size_t patlen,
                     const char *origin, int no, enum grep_pat_token t)
{
        struct grep_pat *p = create_grep_pat(pat, patlen, origin, no, t, 0);
        do_append_grep_pat(&opt->pattern_tail, p);
}

struct grep_opt *grep_opt_dup(const struct grep_opt *opt)
{
        struct grep_pat *pat;
        struct grep_opt *ret = xmalloc(sizeof(struct grep_opt));
        *ret = *opt;

        ret->pattern_list = NULL;
        ret->pattern_tail = &ret->pattern_list;

        for(pat = opt->pattern_list; pat != NULL; pat = pat->next)
        {
                if(pat->token == GREP_PATTERN_HEAD)
                        append_header_grep_pattern(ret, pat->field,
                                                   pat->pattern);
                else
                        append_grep_pat(ret, pat->pattern, pat->patternlen,
                                        pat->origin, pat->no, pat->token);
        }

        return ret;
}

static NORETURN void compile_regexp_failed(const struct grep_pat *p,
                const char *error)
{
        char where[1024];

        if (p->no)
                xsnprintf(where, sizeof(where), "In '%s' at %d, ", p->origin, p->no);
        else if (p->origin)
                xsnprintf(where, sizeof(where), "%s, ", p->origin);
        else
                where[0] = 0;

        die("%s'%s': %s", where, p->pattern, error);
}

static int is_fixed(const char *s, size_t len)
{
        size_t i;

        for (i = 0; i < len; i++) {
                if (is_regex_special(s[i]))
                        return 0;
        }

        return 1;
}

static int has_null(const char *s, size_t len)
{
        /*
         * regcomp cannot accept patterns with NULs so when using it
         * we consider any pattern containing a NUL fixed.
         */
        if (memchr(s, 0, len))
                return 1;

        return 0;
}

#ifdef USE_LIBPCRE1
static void compile_pcre1_regexp(struct grep_pat *p, const struct grep_opt *opt)
{
        const char *error;
        int erroffset;
        int options = PCRE_MULTILINE;

        if (opt->ignore_case) {
                if (has_non_ascii(p->pattern))
                        p->pcre1_tables = pcre_maketables();
                options |= PCRE_CASELESS;
        }
        if (is_utf8_locale() && has_non_ascii(p->pattern))
                options |= PCRE_UTF8;

        p->pcre1_regexp = pcre_compile(p->pattern, options, &error, &erroffset,
                                      p->pcre1_tables);
        if (!p->pcre1_regexp)
                compile_regexp_failed(p, error);

        p->pcre1_extra_info = pcre_study(p->pcre1_regexp, GIT_PCRE_STUDY_JIT_COMPILE, &error);
        if (!p->pcre1_extra_info && error)
                die("%s", error);

#ifdef GIT_PCRE1_USE_JIT
        pcre_config(PCRE_CONFIG_JIT, &p->pcre1_jit_on);
        if (p->pcre1_jit_on == 1) {
                p->pcre1_jit_stack = pcre_jit_stack_alloc(1, 1024 * 1024);
                if (!p->pcre1_jit_stack)
                        die("Couldn't allocate PCRE JIT stack");
                pcre_assign_jit_stack(p->pcre1_extra_info, NULL, p->pcre1_jit_stack);
        } else if (p->pcre1_jit_on != 0) {
                BUG("The pcre1_jit_on variable should be 0 or 1, not %d",
                    p->pcre1_jit_on);
        }
#endif
}

static int pcre1match(struct grep_pat *p, const char *line, const char *eol,
                regmatch_t *match, int eflags)
{
        int ovector[30], ret, flags = 0;

        if (eflags & REG_NOTBOL)
                flags |= PCRE_NOTBOL;

#ifdef GIT_PCRE1_USE_JIT
        if (p->pcre1_jit_on) {
                ret = pcre_jit_exec(p->pcre1_regexp, p->pcre1_extra_info, line,
                                    eol - line, 0, flags, ovector,
                                    ARRAY_SIZE(ovector), p->pcre1_jit_stack);
        } else
#endif
        {
                ret = pcre_exec(p->pcre1_regexp, p->pcre1_extra_info, line,
                                eol - line, 0, flags, ovector,
                                ARRAY_SIZE(ovector));
        }

        if (ret < 0 && ret != PCRE_ERROR_NOMATCH)
                die("pcre_exec failed with error code %d", ret);
        if (ret > 0) {
                ret = 0;
                match->rm_so = ovector[0];
                match->rm_eo = ovector[1];
        }

        return ret;
}

static void free_pcre1_regexp(struct grep_pat *p)
{
        pcre_free(p->pcre1_regexp);
#ifdef GIT_PCRE1_USE_JIT
        if (p->pcre1_jit_on) {
                pcre_free_study(p->pcre1_extra_info);
                pcre_jit_stack_free(p->pcre1_jit_stack);
        } else
#endif
        {
                pcre_free(p->pcre1_extra_info);
        }
        pcre_free((void *)p->pcre1_tables);
}
#else /* !USE_LIBPCRE1 */
static void compile_pcre1_regexp(struct grep_pat *p, const struct grep_opt *opt)
{
        die("cannot use Perl-compatible regexes when not compiled with USE_LIBPCRE");
}

static int pcre1match(struct grep_pat *p, const char *line, const char *eol,
                regmatch_t *match, int eflags)
{
        return 1;
}

static void free_pcre1_regexp(struct grep_pat *p)
{
}
#endif /* !USE_LIBPCRE1 */

#ifdef USE_LIBPCRE2
static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt)
{
        int error;
        PCRE2_UCHAR errbuf[256];
        PCRE2_SIZE erroffset;
        int options = PCRE2_MULTILINE;
        const uint8_t *character_tables = NULL;
        int jitret;
        int patinforet;
        size_t jitsizearg;

        assert(opt->pcre2);

        p->pcre2_compile_context = NULL;

        if (opt->ignore_case) {
                if (has_non_ascii(p->pattern)) {
                        character_tables = pcre2_maketables(NULL);
                        p->pcre2_compile_context = pcre2_compile_context_create(NULL);
                        pcre2_set_character_tables(p->pcre2_compile_context, character_tables);
                }
                options |= PCRE2_CASELESS;
        }
        if (is_utf8_locale() && has_non_ascii(p->pattern))
                options |= PCRE2_UTF;

        p->pcre2_pattern = pcre2_compile((PCRE2_SPTR)p->pattern,
                                         p->patternlen, options, &error, &erroffset,
                                         p->pcre2_compile_context);

        if (p->pcre2_pattern) {
                p->pcre2_match_data = pcre2_match_data_create_from_pattern(p->pcre2_pattern, NULL);
                if (!p->pcre2_match_data)
                        die("Couldn't allocate PCRE2 match data");
        } else {
                pcre2_get_error_message(error, errbuf, sizeof(errbuf));
                compile_regexp_failed(p, (const char *)&errbuf);
        }

        pcre2_config(PCRE2_CONFIG_JIT, &p->pcre2_jit_on);
        if (p->pcre2_jit_on == 1) {
                jitret = pcre2_jit_compile(p->pcre2_pattern, PCRE2_JIT_COMPLETE);
                if (jitret)
                        die("Couldn't JIT the PCRE2 pattern '%s', got '%d'\n", p->pattern, jitret);

                /*
                 * The pcre2_config(PCRE2_CONFIG_JIT, ...) call just
                 * tells us whether the library itself supports JIT,
                 * but to see whether we're going to be actually using
                 * JIT we need to extract PCRE2_INFO_JITSIZE from the
                 * pattern *after* we do pcre2_jit_compile() above.
                 *
                 * This is because if the pattern contains the
                 * (*NO_JIT) verb (see pcre2syntax(3))
                 * pcre2_jit_compile() will exit early with 0. If we
                 * then proceed to call pcre2_jit_match() further down
                 * the line instead of pcre2_match() we'll either
                 * segfault (pre PCRE 10.31) or run into a fatal error
                 * (post PCRE2 10.31)
                 */
                patinforet = pcre2_pattern_info(p->pcre2_pattern, PCRE2_INFO_JITSIZE, &jitsizearg);
                if (patinforet)
                        BUG("pcre2_pattern_info() failed: %d", patinforet);
                if (jitsizearg == 0) {
                        p->pcre2_jit_on = 0;
                        return;
                }

                p->pcre2_jit_stack = pcre2_jit_stack_create(1, 1024 * 1024, NULL);
                if (!p->pcre2_jit_stack)
                        die("Couldn't allocate PCRE2 JIT stack");
                p->pcre2_match_context = pcre2_match_context_create(NULL);
                if (!p->pcre2_match_context)
                        die("Couldn't allocate PCRE2 match context");
                pcre2_jit_stack_assign(p->pcre2_match_context, NULL, p->pcre2_jit_stack);
        } else if (p->pcre2_jit_on != 0) {
                BUG("The pcre2_jit_on variable should be 0 or 1, not %d",
                    p->pcre1_jit_on);
        }
}

static int pcre2match(struct grep_pat *p, const char *line, const char *eol,
                regmatch_t *match, int eflags)
{
        int ret, flags = 0;
        PCRE2_SIZE *ovector;
        PCRE2_UCHAR errbuf[256];

        if (eflags & REG_NOTBOL)
                flags |= PCRE2_NOTBOL;

        if (p->pcre2_jit_on)
                ret = pcre2_jit_match(p->pcre2_pattern, (unsigned char *)line,
                                      eol - line, 0, flags, p->pcre2_match_data,
                                      NULL);
        else
                ret = pcre2_match(p->pcre2_pattern, (unsigned char *)line,
                                  eol - line, 0, flags, p->pcre2_match_data,
                                  NULL);

        if (ret < 0 && ret != PCRE2_ERROR_NOMATCH) {
                pcre2_get_error_message(ret, errbuf, sizeof(errbuf));
                die("%s failed with error code %d: %s",
                    (p->pcre2_jit_on ? "pcre2_jit_match" : "pcre2_match"), ret,
                    errbuf);
        }
        if (ret > 0) {
                ovector = pcre2_get_ovector_pointer(p->pcre2_match_data);
                ret = 0;
                match->rm_so = (int)ovector[0];
                match->rm_eo = (int)ovector[1];
        }

        return ret;
}

static void free_pcre2_pattern(struct grep_pat *p)
{
        pcre2_compile_context_free(p->pcre2_compile_context);
        pcre2_code_free(p->pcre2_pattern);
        pcre2_match_data_free(p->pcre2_match_data);
        pcre2_jit_stack_free(p->pcre2_jit_stack);
        pcre2_match_context_free(p->pcre2_match_context);
}
#else /* !USE_LIBPCRE2 */
static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt)
{
        /*
         * Unreachable until USE_LIBPCRE2 becomes synonymous with
         * USE_LIBPCRE. See the sibling comment in
         * grep_set_pattern_type_option().
         */
        die("cannot use Perl-compatible regexes when not compiled with USE_LIBPCRE");
}

static int pcre2match(struct grep_pat *p, const char *line, const char *eol,
                regmatch_t *match, int eflags)
{
        return 1;
}

static void free_pcre2_pattern(struct grep_pat *p)
{
}
#endif /* !USE_LIBPCRE2 */

static void compile_fixed_regexp(struct grep_pat *p, struct grep_opt *opt)
{
        struct strbuf sb = STRBUF_INIT;
        int err;
        int regflags = 0;

        basic_regex_quote_buf(&sb, p->pattern);
        if (opt->ignore_case)
                regflags |= REG_ICASE;
        err = regcomp(&p->regexp, sb.buf, regflags);
        if (opt->debug)
                fprintf(stderr, "fixed %s\n", sb.buf);
        strbuf_release(&sb);
        if (err) {
                char errbuf[1024];
                regerror(err, &p->regexp, errbuf, sizeof(errbuf));
                compile_regexp_failed(p, errbuf);
        }
}

static void compile_regexp(struct grep_pat *p, struct grep_opt *opt)
{
        int ascii_only;
        int err;
        int regflags = REG_NEWLINE;

        p->word_regexp = opt->word_regexp;
        p->ignore_case = opt->ignore_case;
        ascii_only     = !has_non_ascii(p->pattern);

        /*
         * Even when -F (fixed) asks us to do a non-regexp search, we
         * may not be able to correctly case-fold when -i
         * (ignore-case) is asked (in which case, we'll synthesize a
         * regexp to match the pattern that matches regexp special
         * characters literally, while ignoring case differences).  On
         * the other hand, even without -F, if the pattern does not
         * have any regexp special characters and there is no need for
         * case-folding search, we can internally turn it into a
         * simple string match using kws.  p->fixed tells us if we
         * want to use kws.
         */
        if (opt->fixed ||
            has_null(p->pattern, p->patternlen) ||
            is_fixed(p->pattern, p->patternlen))
                p->fixed = !p->ignore_case || ascii_only;

        if (p->fixed) {
                p->kws = kwsalloc(p->ignore_case ? tolower_trans_tbl : NULL);
                kwsincr(p->kws, p->pattern, p->patternlen);
                kwsprep(p->kws);
                return;
        } else if (opt->fixed) {
                /*
                 * We come here when the pattern has the non-ascii
                 * characters we cannot case-fold, and asked to
                 * ignore-case.
                 */
                compile_fixed_regexp(p, opt);
                return;
        }

        if (opt->pcre2) {
                compile_pcre2_pattern(p, opt);
                return;
        }

        if (opt->pcre1) {
                compile_pcre1_regexp(p, opt);
                return;
        }

        if (p->ignore_case)
                regflags |= REG_ICASE;
        if (opt->extended_regexp_option)
                regflags |= REG_EXTENDED;
        err = regcomp(&p->regexp, p->pattern, regflags);
        if (err) {
                char errbuf[1024];
                regerror(err, &p->regexp, errbuf, 1024);
                compile_regexp_failed(p, errbuf);
        }
}

static struct grep_expr *compile_pattern_or(struct grep_pat **);
static struct grep_expr *compile_pattern_atom(struct grep_pat **list)
{
        struct grep_pat *p;
        struct grep_expr *x;

        p = *list;
        if (!p)
                return NULL;
        switch (p->token) {
        case GREP_PATTERN: /* atom */
        case GREP_PATTERN_HEAD:
        case GREP_PATTERN_BODY:
                x = xcalloc(1, sizeof (struct grep_expr));
                x->node = GREP_NODE_ATOM;
                x->u.atom = p;
                *list = p->next;
                return x;
        case GREP_OPEN_PAREN:
                *list = p->next;
                x = compile_pattern_or(list);
                if (!*list || (*list)->token != GREP_CLOSE_PAREN)
                        die("unmatched parenthesis");
                *list = (*list)->next;
                return x;
        default:
                return NULL;
        }
}

static struct grep_expr *compile_pattern_not(struct grep_pat **list)
{
        struct grep_pat *p;
        struct grep_expr *x;

        p = *list;
        if (!p)
                return NULL;
        switch (p->token) {
        case GREP_NOT:
                if (!p->next)
                        die("--not not followed by pattern expression");
                *list = p->next;
                x = xcalloc(1, sizeof (struct grep_expr));
                x->node = GREP_NODE_NOT;
                x->u.unary = compile_pattern_not(list);
                if (!x->u.unary)
                        die("--not followed by non pattern expression");
                return x;
        default:
                return compile_pattern_atom(list);
        }
}

static struct grep_expr *compile_pattern_and(struct grep_pat **list)
{
        struct grep_pat *p;
        struct grep_expr *x, *y, *z;

        x = compile_pattern_not(list);
        p = *list;
        if (p && p->token == GREP_AND) {
                if (!p->next)
                        die("--and not followed by pattern expression");
                *list = p->next;
                y = compile_pattern_and(list);
                if (!y)
                        die("--and not followed by pattern expression");
                z = xcalloc(1, sizeof (struct grep_expr));
                z->node = GREP_NODE_AND;
                z->u.binary.left = x;
                z->u.binary.right = y;
                return z;
        }
        return x;
}

static struct grep_expr *compile_pattern_or(struct grep_pat **list)
{
        struct grep_pat *p;
        struct grep_expr *x, *y, *z;

        x = compile_pattern_and(list);
        p = *list;
        if (x && p && p->token != GREP_CLOSE_PAREN) {
                y = compile_pattern_or(list);
                if (!y)
                        die("not a pattern expression %s", p->pattern);
                z = xcalloc(1, sizeof (struct grep_expr));
                z->node = GREP_NODE_OR;
                z->u.binary.left = x;
                z->u.binary.right = y;
                return z;
        }
        return x;
}

static struct grep_expr *compile_pattern_expr(struct grep_pat **list)
{
        return compile_pattern_or(list);
}

static void indent(int in)
{
        while (in-- > 0)
                fputc(' ', stderr);
}

static void dump_grep_pat(struct grep_pat *p)
{
        switch (p->token) {
        case GREP_AND: fprintf(stderr, "*and*"); break;
        case GREP_OPEN_PAREN: fprintf(stderr, "*(*"); break;
        case GREP_CLOSE_PAREN: fprintf(stderr, "*)*"); break;
        case GREP_NOT: fprintf(stderr, "*not*"); break;
        case GREP_OR: fprintf(stderr, "*or*"); break;

        case GREP_PATTERN: fprintf(stderr, "pattern"); break;
        case GREP_PATTERN_HEAD: fprintf(stderr, "pattern_head"); break;
        case GREP_PATTERN_BODY: fprintf(stderr, "pattern_body"); break;
        }

        switch (p->token) {
        default: break;
        case GREP_PATTERN_HEAD:
                fprintf(stderr, "<head %d>", p->field); break;
        case GREP_PATTERN_BODY:
                fprintf(stderr, "<body>"); break;
        }
        switch (p->token) {
        default: break;
        case GREP_PATTERN_HEAD:
        case GREP_PATTERN_BODY:
        case GREP_PATTERN:
                fprintf(stderr, "%.*s", (int)p->patternlen, p->pattern);
                break;
        }
        fputc('\n', stderr);
}

static void dump_grep_expression_1(struct grep_expr *x, int in)
{
        indent(in);
        switch (x->node) {
        case GREP_NODE_TRUE:
                fprintf(stderr, "true\n");
                break;
        case GREP_NODE_ATOM:
                dump_grep_pat(x->u.atom);
                break;
        case GREP_NODE_NOT:
                fprintf(stderr, "(not\n");
                dump_grep_expression_1(x->u.unary, in+1);
                indent(in);
                fprintf(stderr, ")\n");
                break;
        case GREP_NODE_AND:
                fprintf(stderr, "(and\n");
                dump_grep_expression_1(x->u.binary.left, in+1);
                dump_grep_expression_1(x->u.binary.right, in+1);
                indent(in);
                fprintf(stderr, ")\n");
                break;
        case GREP_NODE_OR:
                fprintf(stderr, "(or\n");
                dump_grep_expression_1(x->u.binary.left, in+1);
                dump_grep_expression_1(x->u.binary.right, in+1);
                indent(in);
                fprintf(stderr, ")\n");
                break;
        }
}

static void dump_grep_expression(struct grep_opt *opt)
{
        struct grep_expr *x = opt->pattern_expression;

        if (opt->all_match)
                fprintf(stderr, "[all-match]\n");
        dump_grep_expression_1(x, 0);
        fflush(NULL);
}

static struct grep_expr *grep_true_expr(void)
{
        struct grep_expr *z = xcalloc(1, sizeof(*z));
        z->node = GREP_NODE_TRUE;
        return z;
}

static struct grep_expr *grep_or_expr(struct grep_expr *left, struct grep_expr *right)
{
        struct grep_expr *z = xcalloc(1, sizeof(*z));
        z->node = GREP_NODE_OR;
        z->u.binary.left = left;
        z->u.binary.right = right;
        return z;
}

static struct grep_expr *prep_header_patterns(struct grep_opt *opt)
{
        struct grep_pat *p;
        struct grep_expr *header_expr;
        struct grep_expr *(header_group[GREP_HEADER_FIELD_MAX]);
        enum grep_header_field fld;

        if (!opt->header_list)
                return NULL;

        for (p = opt->header_list; p; p = p->next) {
                if (p->token != GREP_PATTERN_HEAD)
                        BUG("a non-header pattern in grep header list.");
                if (p->field < GREP_HEADER_FIELD_MIN ||
                    GREP_HEADER_FIELD_MAX <= p->field)
                        BUG("unknown header field %d", p->field);
                compile_regexp(p, opt);
        }

        for (fld = 0; fld < GREP_HEADER_FIELD_MAX; fld++)
                header_group[fld] = NULL;

        for (p = opt->header_list; p; p = p->next) {
                struct grep_expr *h;
                struct grep_pat *pp = p;

                h = compile_pattern_atom(&pp);
                if (!h || pp != p->next)
                        BUG("malformed header expr");
                if (!header_group[p->field]) {
                        header_group[p->field] = h;
                        continue;
                }
                header_group[p->field] = grep_or_expr(h, header_group[p->field]);
        }

        header_expr = NULL;

        for (fld = 0; fld < GREP_HEADER_FIELD_MAX; fld++) {
                if (!header_group[fld])
                        continue;
                if (!header_expr)
                        header_expr = grep_true_expr();
                header_expr = grep_or_expr(header_group[fld], header_expr);
        }
        return header_expr;
}

static struct grep_expr *grep_splice_or(struct grep_expr *x, struct grep_expr *y)
{
        struct grep_expr *z = x;

        while (x) {
                assert(x->node == GREP_NODE_OR);
                if (x->u.binary.right &&
                    x->u.binary.right->node == GREP_NODE_TRUE) {
                        x->u.binary.right = y;
                        break;
                }
                x = x->u.binary.right;
        }
        return z;
}

static void compile_grep_patterns_real(struct grep_opt *opt)
{
        struct grep_pat *p;
        struct grep_expr *header_expr = prep_header_patterns(opt);

        for (p = opt->pattern_list; p; p = p->next) {
                switch (p->token) {
                case GREP_PATTERN: /* atom */
                case GREP_PATTERN_HEAD:
                case GREP_PATTERN_BODY:
                        compile_regexp(p, opt);
                        break;
                default:
                        opt->extended = 1;
                        break;
                }
        }

        if (opt->all_match || header_expr)
                opt->extended = 1;
        else if (!opt->extended && !opt->debug)
                return;

        p = opt->pattern_list;
        if (p)
                opt->pattern_expression = compile_pattern_expr(&p);
        if (p)
                die("incomplete pattern expression: %s", p->pattern);

        if (!header_expr)
                return;

        if (!opt->pattern_expression)
                opt->pattern_expression = header_expr;
        else if (opt->all_match)
                opt->pattern_expression = grep_splice_or(header_expr,
                                                         opt->pattern_expression);
        else
                opt->pattern_expression = grep_or_expr(opt->pattern_expression,
                                                       header_expr);
        opt->all_match = 1;
}

void compile_grep_patterns(struct grep_opt *opt)
{
        compile_grep_patterns_real(opt);
        if (opt->debug)
                dump_grep_expression(opt);
}

static void free_pattern_expr(struct grep_expr *x)
{
        switch (x->node) {
        case GREP_NODE_TRUE:
        case GREP_NODE_ATOM:
                break;
        case GREP_NODE_NOT:
                free_pattern_expr(x->u.unary);
                break;
        case GREP_NODE_AND:
        case GREP_NODE_OR:
                free_pattern_expr(x->u.binary.left);
                free_pattern_expr(x->u.binary.right);
                break;
        }
        free(x);
}

void free_grep_patterns(struct grep_opt *opt)
{
        struct grep_pat *p, *n;

        for (p = opt->pattern_list; p; p = n) {
                n = p->next;
                switch (p->token) {
                case GREP_PATTERN: /* atom */
                case GREP_PATTERN_HEAD:
                case GREP_PATTERN_BODY:
                        if (p->kws)
                                kwsfree(p->kws);
                        else if (p->pcre1_regexp)
                                free_pcre1_regexp(p);
                        else if (p->pcre2_pattern)
                                free_pcre2_pattern(p);
                        else
                                regfree(&p->regexp);
                        free(p->pattern);
                        break;
                default:
                        break;
                }
                free(p);
        }

        if (!opt->extended)
                return;
        free_pattern_expr(opt->pattern_expression);
}

static char *end_of_line(char *cp, unsigned long *left)
{
        unsigned long l = *left;
        while (l && *cp != '\n') {
                l--;
                cp++;
        }
        *left = l;
        return cp;
}

static int word_char(char ch)
{
        return isalnum(ch) || ch == '_';
}

static void output_color(struct grep_opt *opt, const void *data, size_t size,
                         const char *color)
{
        if (want_color(opt->color) && color && color[0]) {
                opt->output(opt, color, strlen(color));
                opt->output(opt, data, size);
                opt->output(opt, GIT_COLOR_RESET, strlen(GIT_COLOR_RESET));
        } else
                opt->output(opt, data, size);
}

static void output_sep(struct grep_opt *opt, char sign)
{
        if (opt->null_following_name)
                opt->output(opt, "\0", 1);
        else
                output_color(opt, &sign, 1, opt->color_sep);
}

static void show_name(struct grep_opt *opt, const char *name)
{
        output_color(opt, name, strlen(name), opt->color_filename);
        opt->output(opt, opt->null_following_name ? "\0" : "\n", 1);
}

static int fixmatch(struct grep_pat *p, char *line, char *eol,
                    regmatch_t *match)
{
        struct kwsmatch kwsm;
        size_t offset = kwsexec(p->kws, line, eol - line, &kwsm);
        if (offset == -1) {
                match->rm_so = match->rm_eo = -1;
                return REG_NOMATCH;
        } else {
                match->rm_so = offset;
                match->rm_eo = match->rm_so + kwsm.size[0];
                return 0;
        }
}

static int patmatch(struct grep_pat *p, char *line, char *eol,
                    regmatch_t *match, int eflags)
{
        int hit;

        if (p->fixed)
                hit = !fixmatch(p, line, eol, match);
        else if (p->pcre1_regexp)
                hit = !pcre1match(p, line, eol, match, eflags);
        else if (p->pcre2_pattern)
                hit = !pcre2match(p, line, eol, match, eflags);
        else
                hit = !regexec_buf(&p->regexp, line, eol - line, 1, match,
                                   eflags);

        return hit;
}

static int strip_timestamp(char *bol, char **eol_p)
{
        char *eol = *eol_p;
        int ch;

        while (bol < --eol) {
                if (*eol != '>')
                        continue;
                *eol_p = ++eol;
                ch = *eol;
                *eol = '\0';
                return ch;
        }
        return 0;
}

static struct {
        const char *field;
        size_t len;
} header_field[] = {
        { "author ", 7 },
        { "committer ", 10 },
        { "reflog ", 7 },
};

static int match_one_pattern(struct grep_pat *p, char *bol, char *eol,
                             enum grep_context ctx,
                             regmatch_t *pmatch, int eflags)
{
        int hit = 0;
        int saved_ch = 0;
        const char *start = bol;

        if ((p->token != GREP_PATTERN) &&
            ((p->token == GREP_PATTERN_HEAD) != (ctx == GREP_CONTEXT_HEAD)))
                return 0;

        if (p->token == GREP_PATTERN_HEAD) {
                const char *field;
                size_t len;
                assert(p->field < ARRAY_SIZE(header_field));
                field = header_field[p->field].field;
                len = header_field[p->field].len;
                if (strncmp(bol, field, len))
                        return 0;
                bol += len;
                switch (p->field) {
                case GREP_HEADER_AUTHOR:
                case GREP_HEADER_COMMITTER:
                        saved_ch = strip_timestamp(bol, &eol);
                        break;
                default:
                        break;
                }
        }

 again:
        hit = patmatch(p, bol, eol, pmatch, eflags);

        if (hit && p->word_regexp) {
                if ((pmatch[0].rm_so < 0) ||
                    (eol - bol) < pmatch[0].rm_so ||
                    (pmatch[0].rm_eo < 0) ||
                    (eol - bol) < pmatch[0].rm_eo)
                        die("regexp returned nonsense");

                /* Match beginning must be either beginning of the
                 * line, or at word boundary (i.e. the last char must
                 * not be a word char).  Similarly, match end must be
                 * either end of the line, or at word boundary
                 * (i.e. the next char must not be a word char).
                 */
                if ( ((pmatch[0].rm_so == 0) ||
                      !word_char(bol[pmatch[0].rm_so-1])) &&
                     ((pmatch[0].rm_eo == (eol-bol)) ||
                      !word_char(bol[pmatch[0].rm_eo])) )
                        ;
                else
                        hit = 0;

                /* Words consist of at least one character. */
                if (pmatch->rm_so == pmatch->rm_eo)
                        hit = 0;

                if (!hit && pmatch[0].rm_so + bol + 1 < eol) {
                        /* There could be more than one match on the
                         * line, and the first match might not be
                         * strict word match.  But later ones could be!
                         * Forward to the next possible start, i.e. the
                         * next position following a non-word char.
                         */
                        bol = pmatch[0].rm_so + bol + 1;
                        while (word_char(bol[-1]) && bol < eol)
                                bol++;
                        eflags |= REG_NOTBOL;
                        if (bol < eol)
                                goto again;
                }
        }
        if (p->token == GREP_PATTERN_HEAD && saved_ch)
                *eol = saved_ch;
        if (hit) {
                pmatch[0].rm_so += bol - start;
                pmatch[0].rm_eo += bol - start;
        }
        return hit;
}

static int match_expr_eval(struct grep_opt *opt, struct grep_expr *x, char *bol,
                           char *eol, enum grep_context ctx, ssize_t *col,
                           ssize_t *icol, int collect_hits)
{
        int h = 0;

        if (!x)
                die("Not a valid grep expression");
        switch (x->node) {
        case GREP_NODE_TRUE:
                h = 1;
                break;
        case GREP_NODE_ATOM:
                {
                        regmatch_t tmp;
                        h = match_one_pattern(x->u.atom, bol, eol, ctx,
                                              &tmp, 0);
                        if (h && (*col < 0 || tmp.rm_so < *col))
                                *col = tmp.rm_so;
                }
                break;
        case GREP_NODE_NOT:
                /*
                 * Upon visiting a GREP_NODE_NOT, col and icol become swapped.
                 */
                h = !match_expr_eval(opt, x->u.unary, bol, eol, ctx, icol, col,
                                     0);
                break;
        case GREP_NODE_AND:
                h = match_expr_eval(opt, x->u.binary.left, bol, eol, ctx, col,
                                    icol, 0);
                if (h || opt->columnnum) {
                        /*
                         * Don't short-circuit AND when given --column, since a
                         * NOT earlier in the tree may turn this into an OR. In
                         * this case, see the below comment.
                         */
                        h &= match_expr_eval(opt, x->u.binary.right, bol, eol,
                                             ctx, col, icol, 0);
                }
                break;
        case GREP_NODE_OR:
                if (!(collect_hits || opt->columnnum)) {
                        /*
                         * Don't short-circuit OR when given --column (or
                         * collecting hits) to ensure we don't skip a later
                         * child that would produce an earlier match.
                         */
                        return (match_expr_eval(opt, x->u.binary.left, bol, eol,
                                                ctx, col, icol, 0) ||
                                match_expr_eval(opt, x->u.binary.right, bol,
                                                eol, ctx, col, icol, 0));
                }
                h = match_expr_eval(opt, x->u.binary.left, bol, eol, ctx, col,
                                    icol, 0);
                if (collect_hits)
                        x->u.binary.left->hit |= h;
                h |= match_expr_eval(opt, x->u.binary.right, bol, eol, ctx, col,
                                     icol, collect_hits);
                break;
        default:
                die("Unexpected node type (internal error) %d", x->node);
        }
        if (collect_hits)
                x->hit |= h;
        return h;
}

static int match_expr(struct grep_opt *opt, char *bol, char *eol,
                      enum grep_context ctx, ssize_t *col,
                      ssize_t *icol, int collect_hits)
{
        struct grep_expr *x = opt->pattern_expression;
        return match_expr_eval(opt, x, bol, eol, ctx, col, icol, collect_hits);
}

static int match_line(struct grep_opt *opt, char *bol, char *eol,
                      ssize_t *col, ssize_t *icol,
                      enum grep_context ctx, int collect_hits)
{
        struct grep_pat *p;
        int hit = 0;

        if (opt->extended)
                return match_expr(opt, bol, eol, ctx, col, icol,
                                  collect_hits);

        /* we do not call with collect_hits without being extended */
        for (p = opt->pattern_list; p; p = p->next) {
                regmatch_t tmp;
                if (match_one_pattern(p, bol, eol, ctx, &tmp, 0)) {
                        hit |= 1;
                        if (!opt->columnnum) {
                                /*
                                 * Without --column, any single match on a line
                                 * is enough to know that it needs to be
                                 * printed. With --column, scan _all_ patterns
                                 * to find the earliest.
                                 */
                                break;
                        }
                        if (*col < 0 || tmp.rm_so < *col)
                                *col = tmp.rm_so;
                }
        }
        return hit;
}

static int match_next_pattern(struct grep_pat *p, char *bol, char *eol,
                              enum grep_context ctx,
                              regmatch_t *pmatch, int eflags)
{
        regmatch_t match;

        if (!match_one_pattern(p, bol, eol, ctx, &match, eflags))
                return 0;
        if (match.rm_so < 0 || match.rm_eo < 0)
                return 0;
        if (pmatch->rm_so >= 0 && pmatch->rm_eo >= 0) {
                if (match.rm_so > pmatch->rm_so)
                        return 1;
                if (match.rm_so == pmatch->rm_so && match.rm_eo < pmatch->rm_eo)
                        return 1;
        }
        pmatch->rm_so = match.rm_so;
        pmatch->rm_eo = match.rm_eo;
        return 1;
}

static int next_match(struct grep_opt *opt, char *bol, char *eol,
                      enum grep_context ctx, regmatch_t *pmatch, int eflags)
{
        struct grep_pat *p;
        int hit = 0;

        pmatch->rm_so = pmatch->rm_eo = -1;
        if (bol < eol) {
                for (p = opt->pattern_list; p; p = p->next) {
                        switch (p->token) {
                        case GREP_PATTERN: /* atom */
                        case GREP_PATTERN_HEAD:
                        case GREP_PATTERN_BODY:
                                hit |= match_next_pattern(p, bol, eol, ctx,
                                                          pmatch, eflags);
                                break;
                        default:
                                break;
                        }
                }
        }
        return hit;
}

static void show_line(struct grep_opt *opt, char *bol, char *eol,
                      const char *name, unsigned lno, ssize_t cno, char sign)
{
        int rest = eol - bol;
        const char *match_color, *line_color = NULL;

        if (opt->file_break && opt->last_shown == 0) {
                if (opt->show_hunk_mark)
                        opt->output(opt, "\n", 1);
        } else if (opt->pre_context || opt->post_context || opt->funcbody) {
                if (opt->last_shown == 0) {
                        if (opt->show_hunk_mark) {
                                output_color(opt, "--", 2, opt->color_sep);
                                opt->output(opt, "\n", 1);
                        }
                } else if (lno > opt->last_shown + 1) {
                        output_color(opt, "--", 2, opt->color_sep);
                        opt->output(opt, "\n", 1);
                }
        }
        if (opt->heading && opt->last_shown == 0) {
                output_color(opt, name, strlen(name), opt->color_filename);
                opt->output(opt, "\n", 1);
        }
        opt->last_shown = lno;

        if (!opt->heading && opt->pathname) {
                output_color(opt, name, strlen(name), opt->color_filename);
                output_sep(opt, sign);
        }
        if (opt->linenum) {
                char buf[32];
                xsnprintf(buf, sizeof(buf), "%d", lno);
                output_color(opt, buf, strlen(buf), opt->color_lineno);
                output_sep(opt, sign);
        }
        /*
         * Treat 'cno' as the 1-indexed offset from the start of a non-context
         * line to its first match. Otherwise, 'cno' is 0 indicating that we are
         * being called with a context line.
         */
        if (opt->columnnum && cno) {
                char buf[32];
                xsnprintf(buf, sizeof(buf), "%"PRIuMAX, (uintmax_t)cno);
                output_color(opt, buf, strlen(buf), opt->color_columnno);
                output_sep(opt, sign);
        }
        if (opt->color) {
                regmatch_t match;
                enum grep_context ctx = GREP_CONTEXT_BODY;
                int ch = *eol;
                int eflags = 0;

                if (sign == ':')
                        match_color = opt->color_match_selected;
                else
                        match_color = opt->color_match_context;
                if (sign == ':')
                        line_color = opt->color_selected;
                else if (sign == '-')
                        line_color = opt->color_context;
                else if (sign == '=')
                        line_color = opt->color_function;
                *eol = '\0';
                while (next_match(opt, bol, eol, ctx, &match, eflags)) {
                        if (match.rm_so == match.rm_eo)
                                break;

                        output_color(opt, bol, match.rm_so, line_color);
                        output_color(opt, bol + match.rm_so,
                                     match.rm_eo - match.rm_so, match_color);
                        bol += match.rm_eo;
                        rest -= match.rm_eo;
                        eflags = REG_NOTBOL;
                }
                *eol = ch;
        }
        output_color(opt, bol, rest, line_color);
        opt->output(opt, "\n", 1);
}

#ifndef NO_PTHREADS
int grep_use_locks;

/*
 * This lock protects access to the gitattributes machinery, which is
 * not thread-safe.
 */
pthread_mutex_t grep_attr_mutex;

static inline void grep_attr_lock(void)
{
        if (grep_use_locks)
                pthread_mutex_lock(&grep_attr_mutex);
}

static inline void grep_attr_unlock(void)
{
        if (grep_use_locks)
                pthread_mutex_unlock(&grep_attr_mutex);
}

/*
 * Same as git_attr_mutex, but protecting the thread-unsafe object db access.
 */
pthread_mutex_t grep_read_mutex;

#else
#define grep_attr_lock()
#define grep_attr_unlock()
#endif

static int match_funcname(struct grep_opt *opt, struct grep_source *gs, char *bol, char *eol)
{
        xdemitconf_t *xecfg = opt->priv;
        if (xecfg && !xecfg->find_func) {
                grep_source_load_driver(gs);
                if (gs->driver->funcname.pattern) {
                        const struct userdiff_funcname *pe = &gs->driver->funcname;
                        xdiff_set_find_func(xecfg, pe->pattern, pe->cflags);
                } else {
                        xecfg = opt->priv = NULL;
                }
        }

        if (xecfg) {
                char buf[1];
                return xecfg->find_func(bol, eol - bol, buf, 1,
                                        xecfg->find_func_priv) >= 0;
        }

        if (bol == eol)
                return 0;
        if (isalpha(*bol) || *bol == '_' || *bol == '$')
                return 1;
        return 0;
}

static void show_funcname_line(struct grep_opt *opt, struct grep_source *gs,
                               char *bol, unsigned lno)
{
        while (bol > gs->buf) {
                char *eol = --bol;

                while (bol > gs->buf && bol[-1] != '\n')
                        bol--;
                lno--;

                if (lno <= opt->last_shown)
                        break;

                if (match_funcname(opt, gs, bol, eol)) {
                        show_line(opt, bol, eol, gs->name, lno, 0, '=');
                        break;
                }
        }
}

static int is_empty_line(const char *bol, const char *eol);

static void show_pre_context(struct grep_opt *opt, struct grep_source *gs,
                             char *bol, char *end, unsigned lno)
{
        unsigned cur = lno, from = 1, funcname_lno = 0, orig_from;
        int funcname_needed = !!opt->funcname, comment_needed = 0;

        if (opt->pre_context < lno)
                from = lno - opt->pre_context;
        if (from <= opt->last_shown)
                from = opt->last_shown + 1;
        orig_from = from;
        if (opt->funcbody) {
                if (match_funcname(opt, gs, bol, end))
                        comment_needed = 1;
                else
                        funcname_needed = 1;
                from = opt->last_shown + 1;
        }

        /* Rewind. */
        while (bol > gs->buf && cur > from) {
                char *next_bol = bol;
                char *eol = --bol;

                while (bol > gs->buf && bol[-1] != '\n')
                        bol--;
                cur--;
                if (comment_needed && (is_empty_line(bol, eol) ||
                                       match_funcname(opt, gs, bol, eol))) {
                        comment_needed = 0;
                        from = orig_from;
                        if (cur < from) {
                                cur++;
                                bol = next_bol;
                                break;
                        }
                }
                if (funcname_needed && match_funcname(opt, gs, bol, eol)) {
                        funcname_lno = cur;
                        funcname_needed = 0;
                        if (opt->funcbody)
                                comment_needed = 1;
                        else
                                from = orig_from;
                }
        }

        /* We need to look even further back to find a function signature. */
        if (opt->funcname && funcname_needed)
                show_funcname_line(opt, gs, bol, cur);

        /* Back forward. */
        while (cur < lno) {
                char *eol = bol, sign = (cur == funcname_lno) ? '=' : '-';

                while (*eol != '\n')
                        eol++;
                show_line(opt, bol, eol, gs->name, cur, 0, sign);
                bol = eol + 1;
                cur++;
        }
}

static int should_lookahead(struct grep_opt *opt)
{
        struct grep_pat *p;

        if (opt->extended)
                return 0; /* punt for too complex stuff */
        if (opt->invert)
                return 0;
        for (p = opt->pattern_list; p; p = p->next) {
                if (p->token != GREP_PATTERN)
                        return 0; /* punt for "header only" and stuff */
        }
        return 1;
}

static int look_ahead(struct grep_opt *opt,
                      unsigned long *left_p,
                      unsigned *lno_p,
                      char **bol_p)
{
        unsigned lno = *lno_p;
        char *bol = *bol_p;
        struct grep_pat *p;
        char *sp, *last_bol;
        regoff_t earliest = -1;

        for (p = opt->pattern_list; p; p = p->next) {
                int hit;
                regmatch_t m;

                hit = patmatch(p, bol, bol + *left_p, &m, 0);
                if (!hit || m.rm_so < 0 || m.rm_eo < 0)
                        continue;
                if (earliest < 0 || m.rm_so < earliest)
                        earliest = m.rm_so;
        }

        if (earliest < 0) {
                *bol_p = bol + *left_p;
                *left_p = 0;
                return 1;
        }
        for (sp = bol + earliest; bol < sp && sp[-1] != '\n'; sp--)
                ; /* find the beginning of the line */
        last_bol = sp;

        for (sp = bol; sp < last_bol; sp++) {
                if (*sp == '\n')
                        lno++;
        }
        *left_p -= last_bol - bol;
        *bol_p = last_bol;
        *lno_p = lno;
        return 0;
}

static int fill_textconv_grep(struct userdiff_driver *driver,
                              struct grep_source *gs)
{
        struct diff_filespec *df;
        char *buf;
        size_t size;

        if (!driver || !driver->textconv)
                return grep_source_load(gs);

        /*
         * The textconv interface is intimately tied to diff_filespecs, so we
         * have to pretend to be one. If we could unify the grep_source
         * and diff_filespec structs, this mess could just go away.
         */
        df = alloc_filespec(gs->path);
        switch (gs->type) {
        case GREP_SOURCE_OID:
                fill_filespec(df, gs->identifier, 1, 0100644);
                break;
        case GREP_SOURCE_FILE:
                fill_filespec(df, &null_oid, 0, 0100644);
                break;
        default:
                BUG("attempt to textconv something without a path?");
        }

        /*
         * fill_textconv is not remotely thread-safe; it may load objects
         * behind the scenes, and it modifies the global diff tempfile
         * structure.
         */
        grep_read_lock();
        size = fill_textconv(driver, df, &buf);
        grep_read_unlock();
        free_filespec(df);

        /*
         * The normal fill_textconv usage by the diff machinery would just keep
         * the textconv'd buf separate from the diff_filespec. But much of the
         * grep code passes around a grep_source and assumes that its "buf"
         * pointer is the beginning of the thing we are searching. So let's
         * install our textconv'd version into the grep_source, taking care not
         * to leak any existing buffer.
         */
        grep_source_clear_data(gs);
        gs->buf = buf;
        gs->size = size;

        return 0;
}

static int is_empty_line(const char *bol, const char *eol)
{
        while (bol < eol && isspace(*bol))
                bol++;
        return bol == eol;
}

static int grep_source_1(struct grep_opt *opt, struct grep_source *gs, int collect_hits)
{
        char *bol;
        char *peek_bol = NULL;
        unsigned long left;
        unsigned lno = 1;
        unsigned last_hit = 0;
        int binary_match_only = 0;
        unsigned count = 0;
        int try_lookahead = 0;
        int show_function = 0;
        struct userdiff_driver *textconv = NULL;
        enum grep_context ctx = GREP_CONTEXT_HEAD;
        xdemitconf_t xecfg;

        if (!opt->output)
                opt->output = std_output;

        if (opt->pre_context || opt->post_context || opt->file_break ||
            opt->funcbody) {
                /* Show hunk marks, except for the first file. */
                if (opt->last_shown)
                        opt->show_hunk_mark = 1;
                /*
                 * If we're using threads then we can't easily identify
                 * the first file.  Always put hunk marks in that case
                 * and skip the very first one later in work_done().
                 */
                if (opt->output != std_output)
                        opt->show_hunk_mark = 1;
        }
        opt->last_shown = 0;

        if (opt->allow_textconv) {
                grep_source_load_driver(gs);
                /*
                 * We might set up the shared textconv cache data here, which
                 * is not thread-safe.
                 */
                grep_attr_lock();
                textconv = userdiff_get_textconv(gs->driver);
                grep_attr_unlock();
        }

        /*
         * We know the result of a textconv is text, so we only have to care
         * about binary handling if we are not using it.
         */
        if (!textconv) {
                switch (opt->binary) {
                case GREP_BINARY_DEFAULT:
                        if (grep_source_is_binary(gs))
                                binary_match_only = 1;
                        break;
                case GREP_BINARY_NOMATCH:
                        if (grep_source_is_binary(gs))
                                return 0; /* Assume unmatch */
                        break;
                case GREP_BINARY_TEXT:
                        break;
                default:
                        BUG("unknown binary handling mode");
                }
        }

        memset(&xecfg, 0, sizeof(xecfg));
        opt->priv = &xecfg;

        try_lookahead = should_lookahead(opt);

        if (fill_textconv_grep(textconv, gs) < 0)
                return 0;

        bol = gs->buf;
        left = gs->size;
        while (left) {
                char *eol, ch;
                int hit;
                ssize_t cno;
                ssize_t col = -1, icol = -1;

                /*
                 * look_ahead() skips quickly to the line that possibly
                 * has the next hit; don't call it if we need to do
                 * something more than just skipping the current line
                 * in response to an unmatch for the current line.  E.g.
                 * inside a post-context window, we will show the current
                 * line as a context around the previous hit when it
                 * doesn't hit.
                 */
                if (try_lookahead
                    && !(last_hit
                         && (show_function ||
                             lno <= last_hit + opt->post_context))
                    && look_ahead(opt, &left, &lno, &bol))
                        break;
                eol = end_of_line(bol, &left);
                ch = *eol;
                *eol = 0;

                if ((ctx == GREP_CONTEXT_HEAD) && (eol == bol))
                        ctx = GREP_CONTEXT_BODY;

                hit = match_line(opt, bol, eol, &col, &icol, ctx, collect_hits);
                *eol = ch;

                if (collect_hits)
                        goto next_line;

                /* "grep -v -e foo -e bla" should list lines
                 * that do not have either, so inversion should
                 * be done outside.
                 */
                if (opt->invert)
                        hit = !hit;
                if (opt->unmatch_name_only) {
                        if (hit)
                                return 0;
                        goto next_line;
                }
                if (hit) {
                        count++;
                        if (opt->status_only)
                                return 1;
                        if (opt->name_only) {
                                show_name(opt, gs->name);
                                return 1;
                        }
                        if (opt->count)
                                goto next_line;
                        if (binary_match_only) {
                                opt->output(opt, "Binary file ", 12);
                                output_color(opt, gs->name, strlen(gs->name),
                                             opt->color_filename);
                                opt->output(opt, " matches\n", 9);
                                return 1;
                        }
                        /* Hit at this line.  If we haven't shown the
                         * pre-context lines, we would need to show them.
                         */
                        if (opt->pre_context || opt->funcbody)
                                show_pre_context(opt, gs, bol, eol, lno);
                        else if (opt->funcname)
                                show_funcname_line(opt, gs, bol, lno);
                        cno = opt->invert ? icol : col;
                        if (cno < 0) {
                                /*
                                 * A negative cno indicates that there was no
                                 * match on the line. We are thus inverted and
                                 * being asked to show all lines that _don't_
                                 * match a given expression. Therefore, set cno
                                 * to 0 to suggest the whole line matches.
                                 */
                                cno = 0;
                        }
                        show_line(opt, bol, eol, gs->name, lno, cno + 1, ':');
                        last_hit = lno;
                        if (opt->funcbody)
                                show_function = 1;
                        goto next_line;
                }
                if (show_function && (!peek_bol || peek_bol < bol)) {
                        unsigned long peek_left = left;
                        char *peek_eol = eol;

                        /*
                         * Trailing empty lines are not interesting.
                         * Peek past them to see if they belong to the
                         * body of the current function.
                         */
                        peek_bol = bol;
                        while (is_empty_line(peek_bol, peek_eol)) {
                                peek_bol = peek_eol + 1;
                                peek_eol = end_of_line(peek_bol, &peek_left);
                        }

                        if (match_funcname(opt, gs, peek_bol, peek_eol))
                                show_function = 0;
                }
                if (show_function ||
                    (last_hit && lno <= last_hit + opt->post_context)) {
                        /* If the last hit is within the post context,
                         * we need to show this line.
                         */
                        show_line(opt, bol, eol, gs->name, lno, col + 1, '-');
                }

        next_line:
                bol = eol + 1;
                if (!left)
                        break;
                left--;
                lno++;
        }

        if (collect_hits)
                return 0;

        if (opt->status_only)
                return opt->unmatch_name_only;
        if (opt->unmatch_name_only) {
                /* We did not see any hit, so we want to show this */
                show_name(opt, gs->name);
                return 1;
        }

        xdiff_clear_find_func(&xecfg);
        opt->priv = NULL;

        /* NEEDSWORK:
         * The real "grep -c foo *.c" gives many "bar.c:0" lines,
         * which feels mostly useless but sometimes useful.  Maybe
         * make it another option?  For now suppress them.
         */
        if (opt->count && count) {
                char buf[32];
                if (opt->pathname) {
                        output_color(opt, gs->name, strlen(gs->name),
                                     opt->color_filename);
                        output_sep(opt, ':');
                }
                xsnprintf(buf, sizeof(buf), "%u\n", count);
                opt->output(opt, buf, strlen(buf));
                return 1;
        }
        return !!last_hit;
}

static void clr_hit_marker(struct grep_expr *x)
{
        /* All-hit markers are meaningful only at the very top level
         * OR node.
         */
        while (1) {
                x->hit = 0;
                if (x->node != GREP_NODE_OR)
                        return;
                x->u.binary.left->hit = 0;
                x = x->u.binary.right;
        }
}

static int chk_hit_marker(struct grep_expr *x)
{
        /* Top level nodes have hit markers.  See if they all are hits */
        while (1) {
                if (x->node != GREP_NODE_OR)
                        return x->hit;
                if (!x->u.binary.left->hit)
                        return 0;
                x = x->u.binary.right;
        }
}

int grep_source(struct grep_opt *opt, struct grep_source *gs)
{
        /*
         * we do not have to do the two-pass grep when we do not check
         * buffer-wide "all-match".
         */
        if (!opt->all_match)
                return grep_source_1(opt, gs, 0);

        /* Otherwise the toplevel "or" terms hit a bit differently.
         * We first clear hit markers from them.
         */
        clr_hit_marker(opt->pattern_expression);
        grep_source_1(opt, gs, 1);

        if (!chk_hit_marker(opt->pattern_expression))
                return 0;

        return grep_source_1(opt, gs, 0);
}

int grep_buffer(struct grep_opt *opt, char *buf, unsigned long size)
{
        struct grep_source gs;
        int r;

        grep_source_init(&gs, GREP_SOURCE_BUF, NULL, NULL, NULL);
        gs.buf = buf;
        gs.size = size;

        r = grep_source(opt, &gs);

        grep_source_clear(&gs);
        return r;
}

void grep_source_init(struct grep_source *gs, enum grep_source_type type,
                      const char *name, const char *path,
                      const void *identifier)
{
        gs->type = type;
        gs->name = xstrdup_or_null(name);
        gs->path = xstrdup_or_null(path);
        gs->buf = NULL;
        gs->size = 0;
        gs->driver = NULL;

        switch (type) {
        case GREP_SOURCE_FILE:
                gs->identifier = xstrdup(identifier);
                break;
        case GREP_SOURCE_OID:
                gs->identifier = oiddup(identifier);
                break;
        case GREP_SOURCE_BUF:
                gs->identifier = NULL;
                break;
        }
}

void grep_source_clear(struct grep_source *gs)
{
        FREE_AND_NULL(gs->name);
        FREE_AND_NULL(gs->path);
        FREE_AND_NULL(gs->identifier);
        grep_source_clear_data(gs);
}

void grep_source_clear_data(struct grep_source *gs)
{
        switch (gs->type) {
        case GREP_SOURCE_FILE:
        case GREP_SOURCE_OID:
                FREE_AND_NULL(gs->buf);
                gs->size = 0;
                break;
        case GREP_SOURCE_BUF:
                /* leave user-provided buf intact */
                break;
        }
}

static int grep_source_load_oid(struct grep_source *gs)
{
        enum object_type type;

        grep_read_lock();
        gs->buf = read_object_file(gs->identifier, &type, &gs->size);
        grep_read_unlock();

        if (!gs->buf)
                return error(_("'%s': unable to read %s"),
                             gs->name,
                             oid_to_hex(gs->identifier));
        return 0;
}

static int grep_source_load_file(struct grep_source *gs)
{
        const char *filename = gs->identifier;
        struct stat st;
        char *data;
        size_t size;
        int i;

        if (lstat(filename, &st) < 0) {
        err_ret:
                if (errno != ENOENT)
                        error_errno(_("failed to stat '%s'"), filename);
                return -1;
        }
        if (!S_ISREG(st.st_mode))
                return -1;
        size = xsize_t(st.st_size);
        i = open(filename, O_RDONLY);
        if (i < 0)
                goto err_ret;
        data = xmallocz(size);
        if (st.st_size != read_in_full(i, data, size)) {
                error_errno(_("'%s': short read"), filename);
                close(i);
                free(data);
                return -1;
        }
        close(i);

        gs->buf = data;
        gs->size = size;
        return 0;
}

static int grep_source_load(struct grep_source *gs)
{
        if (gs->buf)
                return 0;

        switch (gs->type) {
        case GREP_SOURCE_FILE:
                return grep_source_load_file(gs);
        case GREP_SOURCE_OID:
                return grep_source_load_oid(gs);
        case GREP_SOURCE_BUF:
                return gs->buf ? 0 : -1;
        }
        BUG("invalid grep_source type to load");
}

void grep_source_load_driver(struct grep_source *gs)
{
        if (gs->driver)
                return;

        grep_attr_lock();
        if (gs->path)
                gs->driver = userdiff_find_by_path(gs->path);
        if (!gs->driver)
                gs->driver = userdiff_find_by_name("default");
        grep_attr_unlock();
}

static int grep_source_is_binary(struct grep_source *gs)
{
        grep_source_load_driver(gs);
        if (gs->driver->binary != -1)
                return gs->driver->binary;

        if (!grep_source_load(gs))
                return buffer_is_binary(gs->buf, gs->size);

        return 0;
}