Genesis commit

1 files changed, 274 insertions, 0 deletions

diff --git a/grab.c b/grab.c
new file mode 100644
index 0000000..9fdfbd0
--- /dev/null
+++ b/grab.c
@@ -0,0 +1,274 @@
+#include <assert.h>
+#include <err.h>
+#include <limits.h>
+#include <locale.h>
+#include <regex.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "da.h"
+
+#ifndef REG_STARTEND
+#	error "REG_STARTEND not defined"
+#endif
+
+#define die(...)  err(EXIT_FAILURE, __VA_ARGS__);
+#define diex(...) errx(EXIT_FAILURE, __VA_ARGS__);
+
+#define EEARLY "Input string terminated prematurely"
+
+struct op {
+	char c;
+	regex_t pat;
+};
+
+struct ops {
+	struct op *buf;
+	size_t len, cap;
+};
+
+struct chars {
+	char *buf;
+	size_t len, cap;
+};
+
+struct sv {
+	char *p;
+	size_t len;
+};
+
+typedef unsigned char uchar;
+typedef void (*cmd_func)(struct sv, struct ops, size_t);
+
+static void cmdg(struct sv, struct ops, size_t);
+static void cmdx(struct sv, struct ops, size_t);
+
+static void grab(struct ops, FILE *, const char *);
+static void putsv(struct sv);
+static regex_t mkregex(char *, size_t);
+static struct ops comppat(char *);
+
+static bool xisspace(char);
+static char *xstrchrnul(const char *, char);
+
+static int rv = EXIT_SUCCESS;
+static const char *delim = "\n";
+static const cmd_func op_table[UCHAR_MAX] = {
+	['g'] = cmdg,
+	['v'] = cmdg,
+	['x'] = cmdx,
+	// ['y'] = cmdy,
+};
+
+static void
+usage(const char *s)
+{
+	fprintf(stderr, "Usage: %s [-d string] pattern [file ...]\n", s);
+	exit(EXIT_FAILURE);
+}
+
+int
+main(int argc, char **argv)
+{
+	int rv, opt;
+	struct ops ops;
+
+	if (argc < 2)
+		usage(argv[0]);
+
+	setlocale(LC_ALL, "");
+
+	while ((opt = getopt(argc, argv, "d:")) != -1) {
+		switch (opt) {
+		case 'd':
+			delim = optarg;
+			break;
+		default:
+			usage(argv[0]);
+		}
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	ops = comppat(argv[0]);
+	if (argc == 1)
+		grab(ops, stdin, "-");
+	else {
+		for (int i = 1; i < argc; i++) {
+			FILE *fp;
+
+			if (strcmp(argv[i], "-") == 0) {
+				grab(ops, stdin, "-");
+			} else if ((fp = fopen(argv[i], "r")) == NULL) {
+				warn("fopen: %s", argv[i]);
+				rv = EXIT_FAILURE;
+			} else {
+				grab(ops, fp, argv[i]);
+				fclose(fp);
+			}
+		}
+	}
+
+#ifdef GRAB_DEBUG
+	for (size_t i = 0; i < ops.len; i++)
+		regfree(&ops.buf[i].pat);
+	free(ops.buf);
+#endif
+
+	return rv;
+}
+
+struct ops
+comppat(char *s)
+{
+#define skip_ws(p) for (; *(p) && xisspace(*(p)); (p)++)
+	struct ops ops;
+
+	da_init(&ops, 8);
+	skip_ws(s);
+	if (!*s)
+		diex(EEARLY);
+
+	do {
+		char delim;
+		char *p;
+		struct op op;
+
+		op.c = *s;
+		if (!op_table[(uchar)op.c])
+			diex("Invalid operator ‘%c’", *s);
+		if (!(delim = *++s))
+			diex(EEARLY);
+
+		p = ++s;
+		s = xstrchrnul(s, delim);
+		op.pat = mkregex(p, s - p);
+		da_append(&ops, op);
+
+		if (*s)
+			s++;
+		skip_ws(s);
+	} while (*s && *(s + 1));
+
+	return ops;
+#undef skip_ws
+}
+
+void
+grab(struct ops ops, FILE *stream, const char *filename)
+{
+	size_t n;
+	struct chars chars = {0};
+
+	do {
+		static_assert(sizeof(char) == 1, "sizeof(char) != 1; wtf?");
+		chars.cap += BUFSIZ;
+		if ((chars.buf = realloc(chars.buf, chars.cap)) == NULL)
+			die("realloc");
+		chars.len += n = fread(chars.buf + chars.len, 1, BUFSIZ, stream);
+	} while (n == BUFSIZ);
+
+	if (ferror(stream)) {
+		warn("fread: %s", filename);
+		rv = EXIT_FAILURE;
+	} else
+		cmdx((struct sv){.p = chars.buf, .len = chars.len}, ops, 0);
+
+	free(chars.buf);
+}
+
+void
+cmdx(struct sv sv, struct ops ops, size_t i)
+{
+	regmatch_t pm = {
+		.rm_so = 0,
+		.rm_eo = sv.len,
+	};
+	struct op op = ops.buf[i];
+
+	do {
+		struct sv nsv;
+
+		if (regexec(&op.pat, sv.p, 1, &pm, REG_STARTEND) == REG_NOMATCH)
+			break;
+		nsv = (struct sv){.p = sv.p + pm.rm_so, .len = pm.rm_eo - pm.rm_so};
+		if (i + 1 == ops.len)
+			putsv(nsv);
+		else
+			op_table[(uchar)ops.buf[i + 1].c](nsv, ops, i + 1);
+
+		if (pm.rm_so == pm.rm_eo)
+			pm.rm_eo++;
+		pm = (regmatch_t){
+			.rm_so = pm.rm_eo,
+			.rm_eo = sv.len,
+		};
+	} while (pm.rm_so < pm.rm_eo);
+}
+
+void
+cmdg(struct sv sv, struct ops ops, size_t i)
+{
+	int r;
+	regmatch_t pm = {
+		.rm_so = 0,
+		.rm_eo = sv.len,
+	};
+	struct op op = ops.buf[i];
+
+	r = regexec(&op.pat, sv.p, 1, &pm, REG_STARTEND);
+	if ((r == REG_NOMATCH && op.c == 'g') || (r != REG_NOMATCH && op.c == 'v'))
+		return;
+
+	if (i + 1 == ops.len)
+		putsv(sv);
+	else
+		op_table[(uchar)ops.buf[i + 1].c](sv, ops, i + 1);
+}
+
+void
+putsv(struct sv sv)
+{
+	fwrite(sv.p, 1, sv.len, stdout);
+	fputs(delim, stdout);
+}
+
+regex_t
+mkregex(char *s, size_t n)
+{
+	char c = s[n];
+	int ret;
+	regex_t r;
+
+	s[n] = 0;
+	if ((ret = regcomp(&r, s, REG_EXTENDED | REG_NEWLINE)) != 0) {
+		char emsg[128];
+		regerror(ret, &r, emsg, sizeof(emsg));
+		diex("Failed to compile regex: %s", emsg);
+	}
+	s[n] = c;
+
+	return r;
+}
+
+bool
+xisspace(char c)
+{
+	return c == ' ' || c == '\t' || c == '\n';
+}
+
+char *
+xstrchrnul(const char *s, char c)
+{
+	for (; *s; s++) {
+		if (*s == '\\')
+			s++;
+		else if (*s == c)
+			break;
+	}
+	return (char *)s;
+}