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#define _GNU_SOURCE
#include <sys/stat.h>
#include <err.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <x86intrin.h>
#include <bsd/stdlib.h>
#define MIN(x, y) ((x) < (y) ? (x) : (y))
static char *readfile(const char *, size_t *);
static bool
skpcmnt(const char **ptr, const char *end)
{
int nst = 0;
const char *p = *ptr, needles[] = {'/', '*', 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0};
const __m128i set = _mm_loadu_si128((const __m128i *)needles);
while (p < end) {
ptrdiff_t len = end - p;
size_t blksz = MIN(len, 16);
__m128i blk = _mm_loadu_si128((const __m128i *)p);
int off = _mm_cmpestri(set, 2, blk, blksz, _SIDD_CMP_EQUAL_ANY);
if (off == 16) {
p += 16;
continue;
}
if (p[off] == '*' && p[off + 1] == '/') {
p += off + 2;
if (--nst == 0) {
*ptr = p;
return true;
}
} else if (p[off] == '/' && p[off + 1] == '*') {
p += off + 2;
nst++;
} else
p += off + 1;
}
return false;
}
int
main(int argc, char **argv)
{
if (argc != 2) {
fprintf(stderr, "Usage: %s file\n", getprogname());
exit(EXIT_FAILURE);
}
size_t len;
int rv = EXIT_SUCCESS;
const char *beg = readfile(argv[1], &len);
const char *end = beg + len;
clock_t tmbeg = clock();
while ((beg = memmem(beg, end - beg, "/*", 2)) != NULL) {
if (!skpcmnt((const char **)&beg, end)) {
warnx("Unterminated comment!");
rv = EXIT_FAILURE;
break;
}
}
clock_t tmend = clock();
printf("Elapsed time: %.3fs\n", (double)(tmend - tmbeg) / CLOCKS_PER_SEC);
return rv;
}
char *
readfile(const char *filename, size_t *n)
{
int fd = open(filename, O_RDONLY);
if (fd == -1)
err(1, "open: %s", filename);
struct stat sb;
if (fstat(fd, &sb) == -1)
err(1, "fstat: %s", filename);
char *p = malloc(sb.st_size + 4);
if (p == NULL)
err(1, "malloc");
ssize_t nr;
for (size_t off = 0; (nr = read(fd, p + off, sb.st_blksize)) > 0; off += nr)
;
if (nr == -1)
err(1, "read: %s", filename);
p[sb.st_size + 0] =
p[sb.st_size + 1] =
p[sb.st_size + 2] =
p[sb.st_size + 3] = 0;
*n = sb.st_size;
close(fd);
return p;
}
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