blob: 13918a73f593a1dd9fb37664ecaa4e3c7d0f5569 [file] [log] [blame]
/*
* fast fgets() replacement for log parsing
*
* Copyright 2000-2009 Willy Tarreau <w@1wt.eu>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* This function manages its own buffer and returns a pointer to that buffer
* in order to avoid expensive memory copies. It also checks for line breaks
* 32 bits at a time. It could be improved a lot using mmap() but we would
* not be allowed to replace trailing \n with zeroes and we would be limited
* to small log files on 32-bit machines.
*
*/
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
// return 1 if the integer contains at least one zero byte
static inline unsigned int has_zero(unsigned int x)
{
if (!(x & 0xFF000000U) ||
!(x & 0xFF0000U) ||
!(x & 0xFF00U) ||
!(x & 0xFFU))
return 1;
return 0;
}
#define FGETS2_BUFSIZE (256*1024)
const char *fgets2(FILE *stream)
{
static char buffer[FGETS2_BUFSIZE + 5];
static char *end = buffer;
static char *line = buffer;
char *next;
int ret;
next = line;
while (1) {
/* this is a speed-up, we read 32 bits at once and check for an
* LF character there. We stop if found then continue one at a
* time.
*/
while (next < end && (((unsigned long)next) & 3) && *next != '\n')
next++;
/* now next is multiple of 4 or equal to end */
while (next <= (end-32)) {
if (has_zero(*(unsigned int *)next ^ 0x0A0A0A0A))
break;
next += 4;
if (has_zero(*(unsigned int *)next ^ 0x0A0A0A0A))
break;
next += 4;
if (has_zero(*(unsigned int *)next ^ 0x0A0A0A0A))
break;
next += 4;
if (has_zero(*(unsigned int *)next ^ 0x0A0A0A0A))
break;
next += 4;
if (has_zero(*(unsigned int *)next ^ 0x0A0A0A0A))
break;
next += 4;
if (has_zero(*(unsigned int *)next ^ 0x0A0A0A0A))
break;
next += 4;
if (has_zero(*(unsigned int *)next ^ 0x0A0A0A0A))
break;
next += 4;
if (has_zero(*(unsigned int *)next ^ 0x0A0A0A0A))
break;
next += 4;
}
/* we finish if needed. Note that next might be slightly higher
* than end here because we might have gone past it above.
*/
while (next < end) {
if (*next == '\n') {
const char *start = line;
*next = '\0';
line = next + 1;
return start;
}
next++;
}
/* we found an incomplete line. First, let's move the
* remaining part of the buffer to the beginning, then
* try to complete the buffer with a new read.
*/
if (line > buffer) {
if (end != line)
memmove(buffer, line, end - line);
end = buffer + (end - line);
next = end;
line = buffer;
} else {
if (end == buffer + FGETS2_BUFSIZE)
return NULL;
}
ret = read(fileno(stream), end, buffer + FGETS2_BUFSIZE - end);
if (ret <= 0) {
if (end == line)
return NULL;
*end = '\0';
return line;
}
end += ret;
/* search for '\n' again */
}
}
#ifdef BENCHMARK
int main() {
const char *p;
unsigned int lines = 0;
while ((p=fgets2(stdin)))
lines++;
printf("lines=%d\n", lines);
return 0;
}
#endif