regexx/examples/rxgrep.c

/* rxgrep - a small grep-like example program built on regexx, demonstrating
 * the library across its three data modes (Section 9.3) and both its
 * matching and substitution API (Section 9.1). See README.md for usage.
 *
 * This is example code, not part of the library; it is not held to the
 * same naming-convention rule as regexx.c/regexx.h (concept.md 9.0),
 * since it is an ordinary application, not part of the `re`-mirroring
 * surface.
 */
#include "regexx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static void usage(const char *prog) {
    fprintf(stderr,
        "usage: %s [-i] [-n] [-c] [-o] [-v] [-m MODE] PATTERN FILE\n"
        "       %s [-m MODE] --sub REPL PATTERN FILE\n"
        "\n"
        "  -i          ignore case (IGNORECASE)\n"
        "  -n          prefix each match with its 1-based line number\n"
        "  -c          print only a count of matching lines\n"
        "  -o          print only the matched text, not the whole line\n"
        "  -v          print lines that do NOT match\n"
        "  -m MODE     ascii (default), utf8, or binary\n"
        "  --sub REPL  replace every match with REPL and print the result\n",
        prog, prog);
}

static int mode_flag(const char *m) {
    if (strcmp(m, "ascii") == 0) return ASCII;
    if (strcmp(m, "utf8") == 0) return UTF8;
    if (strcmp(m, "binary") == 0) return BINARY;
    fprintf(stderr, "unknown mode '%s' (expected ascii, utf8, or binary)\n", m);
    exit(2);
}

typedef struct { long lineno; int with_lineno; } MatchLinePrint;
static void print_one_match(void *ctx, const Match *m_const) {
    MatchLinePrint *p = ctx;
    Match *m = (Match *)m_const;
    const char *g; size_t glen;
    Match_group(m, NULL, 0, &g, &glen);
    if (p->with_lineno) printf("%ld:", p->lineno);
    fwrite(g, 1, glen, stdout);
    printf("\n");
}

int main(int argc, char **argv) {
    int flags = 0;
    int opt_n = 0, opt_c = 0, opt_o = 0, opt_v = 0;
    const char *sub_repl = NULL;
    int mode = ASCII;
    int i = 1;
    for (; i < argc; i++) {
        const char *a = argv[i];
        if (strcmp(a, "-m") == 0 && i + 1 < argc) { mode = mode_flag(argv[++i]); continue; }
        if (strcmp(a, "--sub") == 0 && i + 1 < argc) { sub_repl = argv[++i]; continue; }
        if (strcmp(a, "-h") == 0 || strcmp(a, "--help") == 0) { usage(argv[0]); return 0; }
        if (a[0] == '-' && a[1] != '-' && a[1] != '\0') {
            int bad = 0;
            for (const char *c = a + 1; *c; c++) {
                switch (*c) {
                    case 'i': flags |= IGNORECASE; break;
                    case 'n': opt_n = 1; break;
                    case 'c': opt_c = 1; break;
                    case 'o': opt_o = 1; break;
                    case 'v': opt_v = 1; break;
                    default: bad = 1; break;
                }
            }
            if (!bad) continue;
        }
        break;
    }
    if (argc - i != 2) { usage(argv[0]); return 2; }
    const char *pattern = argv[i], *path = argv[i + 1];

    PatternError err; memset(&err, 0, sizeof err);
    Pattern *pat = re_compile(pattern, strlen(pattern), flags | mode, &err);
    if (!pat) {
        fprintf(stderr, "%s: pattern error at position %lld: %s\n", argv[0], (long long)err.pos, err.msg);
        return 2;
    }

    if (sub_repl) {
        Input *file = Input_from_file(path, &err);
        if (!file) {
            fprintf(stderr, "%s: cannot read '%s': %s\n", argv[0], path, err.msg ? err.msg : "unknown error");
            Pattern_free(pat);
            return 2;
        }
        char *out; size_t outlen;
        int n;
        if (Pattern_subn(pat, file, sub_repl, NULL, NULL, 0, &out, &outlen, &n) < 0) {
            fprintf(stderr, "%s: matching failed (input too large/complex for this pattern, see README.md)\n", argv[0]);
            Input_free(file); Pattern_free(pat);
            return 1;
        }
        fwrite(out, 1, outlen, stdout);
        fprintf(stderr, "%d replacement(s)\n", n);
        free(out);
        Input_free(file); Pattern_free(pat);
        return n > 0 ? 0 : 1;
    }

    /* Line oriented search: split on raw 0x0A, which is what every one
     * of the three modes (BINARY, ASCII, UTF8) agrees is a line break
     * (concept.md 7.2 notes 0x0A never appears inside a multi-byte
     * UTF-8 sequence), then search within each line's [pos, endpos).
     * Input's internals are intentionally opaque outside regexx.c
     * (concept.md 9.0), so each line is handed to the library as its
     * own small Input built with Input_from_buffer. */
    FILE *fp = fopen(path, "rb");
    if (!fp) { fprintf(stderr, "%s: cannot reopen '%s'\n", argv[0], path); return 2; }
    fseek(fp, 0, SEEK_END);
    long fsize = ftell(fp);
    rewind(fp);
    char *filebuf = malloc((size_t)fsize > 0 ? (size_t)fsize : 1);
    size_t got = fread(filebuf, 1, (size_t)fsize, fp);
    fclose(fp);

    long lineno = 0;
    size_t line_start = 0;
    int matched_lines = 0;
    for (size_t pos = 0; pos <= got; pos++) {
        if (pos == got || filebuf[pos] == '\n') {
            lineno++;
            size_t line_len = pos - line_start;
            Input *lin = Input_from_buffer((const uint8_t *)(filebuf + line_start), line_len);
            Match m; memset(&m, 0, sizeof m);
            int r = Pattern_search(pat, lin, 0, -1, &m);
            int is_match = (r == 1);
            if (is_match) Match_free(&m);
            if (is_match != opt_v) {
                matched_lines++;
                if (!opt_c) {
                    if (opt_o && is_match) {
                        /* -o: every match on the line gets its own
                         * output line, demonstrating Pattern_finditer. */
                        MatchLinePrint ctx = { lineno, opt_n };
                        Pattern_finditer(pat, lin, 0, -1, print_one_match, &ctx);
                    } else {
                        if (opt_n) printf("%ld:", lineno);
                        fwrite(filebuf + line_start, 1, line_len, stdout);
                        printf("\n");
                    }
                }
            }
            Input_free(lin);
            line_start = pos + 1;
        }
    }
    if (opt_c) printf("%d\n", matched_lines);

    free(filebuf);
    Pattern_free(pat);
    return matched_lines > 0 ? 0 : 1;
}