/* holes - find holes (= runs of zero bytes) in input files */

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

ssize_t minlen = 64;
char byte = 0;
int ret = 0;
char *argv0;
ssize_t total, totalz;

void
holes(FILE *input, char *filename)
{
	off_t offset = 0;
	off_t run = 0;
	static char buf[16384];

	int len;
	int i;
	char *d;

	while ((len = fread(buf, 1, sizeof buf, input)) >= 1) {
		if (run == 0) {
			d = memchr(buf, byte, len);
			if (!d) {
				offset += len;
				continue;
			}
			i = d - buf;
			offset += i;
		} else {
			i = 0;
		}
		for (; i < len; i++) {
			if (buf[i] == byte) {
				run++;
			} else {
				if (run >= minlen) {
					if (filename)
						printf("%s: ", filename);
					printf("%08lx %ld\n", offset - run, run);
					totalz += run;
				}
				run = 0;
			}
			offset++;
		}
	}
	if (ferror(input)) {
		fprintf(stderr, "%s: can't read '%s': %s\n",
		    argv0, filename ? filename : "-", strerror(errno));
		ret = 1;
		return;
	}

	if (offset == 0 ||      // empty file
	    run >= minlen) {
		if (filename)
			printf("%s: ", filename);
		printf("%08lx %ld\n", offset - run, run);
		totalz += run;
	}

	total += offset;
}

int
main(int argc, char *argv[])
{
	int c, i;
	long b;
	char *e;
	int sflag = 0;

	argv0 = argv[0];

	while ((c = getopt(argc, argv, "b:n:s")) != -1)
		switch (c) {
		case 'b':
			errno = 0;
			b = strtol(optarg, &e, 0);
			if (errno != 0 || *e || b < 0 || b > 256) {
				fprintf(stderr,
				    "%s: can't parse byte '%s'.\n",
				    argv0, optarg);
				exit(2);
			}
			byte = b;
			break;
		case 'n':
			errno = 0;
			minlen = strtoll(optarg, &e, 0);
			if (errno != 0 || *e) {
				fprintf(stderr,
				    "%s: can't parse length '%s'.\n",
				    argv0, optarg);
				exit(2);
			}
			if (minlen < 1) {
				fprintf(stderr,
				    "%s: MINLEN must not be smaller than 1.\n",
				    argv0);
				exit(2);
			}
			break;
		case 's': sflag++; break;
		default:
			fprintf(stderr,
			    "Usage: %s [-b BYTE] [-n MINLEN] [-s] [FILES...]\n",
			    argv0);
			exit(2);
		}

	if (optind == argc)
		holes(stdin, 0);
	else
		for (i = optind; i < argc; i++) {
			FILE *input = (strcmp(argv[i], "-") == 0) ?
			    stdin : fopen(argv[i], "rb");

			if (!input) {
				fprintf(stderr, "%s: can't open file '%s': %s\n",
				    argv0, argv[i], strerror(errno));
				ret = 1;
			} else {
				holes(input, argc - optind > 1 ? argv[i] : 0);
			}
		}

	if (sflag)
		printf("total %jd/%jd (%.2f%%)\n",
		    totalz, total,
		    total == 0 ? 0.0 : 100.0*totalz / total);

	return ret;
}