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fdlinecombine.c
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fdlinecombine.c
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/*
* Read multiple streams and combine them to single output (linewise)
*
* Created by Vitaly Shukela ("_Vi") in 2011. License=MIT.
*/
#include <stdio.h>
#include <sys/select.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
//#define dbgprintf fprintf
#define dbgprintf(...)
#define MAXFD 1024
#define DEFAULT_READ_SIZE 4096
char* separator="\n";
int separator_length = 1;
struct fdinfo {
char* buffer;
int bufsize;
int offset;
int fd;
/* Increases when too little data received. Decreases when full buffer of data received. */
int little_data_hyster;
};
struct fdinfo* fds;
int num_active_fds;
int numfds;
fd_set rfds;
int no_chopped_data;
void closefd(struct fdinfo* f) {
close(f->fd);
FD_CLR(f->fd, &rfds);
if(f->offset && !no_chopped_data) {
/* Data without trailing end-of-line remaining. Flush them and add end-of-line ourselves. */
fwrite(f->buffer, 1, f->offset, stdout);
fwrite(separator, 1, separator_length, stdout);
}
free(f->buffer);
--num_active_fds;
f->fd = -1;
}
char* realloc_buffer(struct fdinfo* f, int newsize, int obligatory) {
char* buffer;
if(newsize<DEFAULT_READ_SIZE) {
/* Integer overflow? */
buffer=NULL;
} else {
buffer = (char*) realloc(f->buffer, newsize);
}
if(!buffer) {
if(obligatory) {
fprintf(stderr, "Out of memory on fd %d\n", f->fd);
fflush(stderr);
/* refusing to reallocate, returning the old buffer */
f->bufsize=-1;
} else {
/* Can't reallocate, but don't really need to. Just leave the buffer as it was. */
}
} else {
f->buffer = buffer;
f->bufsize=newsize;
}
f->little_data_hyster=0;
return f->buffer;
}
void write_and_move_tail(struct fdinfo* f, int length, int tail_length) {
fwrite(f->buffer, 1, length, stdout);
memmove(f->buffer, f->buffer+length, tail_length);
f->offset = tail_length;
}
/* if SEPARATOR environment variable is set than read that file handle (or name) for line separator value */
void read_separator(const char* sepenv) {
int fd;
int ret;
if(!sscanf(sepenv, "%i", &fd)) {
open_again:
fd = open(sepenv, O_RDONLY, 0022);
if(fd == -1) {
if ( errno==EINTR || errno==EAGAIN ) goto open_again;
fprintf(stderr, "%s ", sepenv);
perror("open");
fprintf(stderr, "SEPARATOR environment variable should be \n"
" name of file or file descriptor to read separator value from\n");
exit(2);
}
}
FILE* f = fdopen(fd, "r");
if(!f) {
perror("fdopen");
exit(1);
}
separator = (char*) malloc(1024);
if(!separator) {
perror("malloc");
exit(1);
}
ret = fread(separator, 1, 1024, f);
separator_length = ret;
if(ret==1024) {
separator = (char*) realloc(separator, 65500);
if(!separator) {
perror("realloc");
exit(1);
}
ret = fread(separator+1024, 1, 65500-1024, f);
if(ret == 65500-1024) {
fprintf(stderr, "Separator is too long. Maximum separator size is 65499 bytes.");
exit(3);
}
separator_length+=ret;
}
fclose(f);
}
int main(int argc, char* argv[]) {
int i;
int sret;
int ret;
int maxfd;
const char* sepenv = getenv("SEPARATOR");
if(sepenv) {
read_separator(sepenv);
}
no_chopped_data = getenv("NO_CHOPPED_DATA") ? 1 : 0;
if (argc <= 1) {
fprintf(stderr,
"Usage: fdlinecombine fd1 fd2 ... fdN\n"
" Read multiple input streams and multiplex them into stdout\n"
" Parameters should be file descriptor numbers or file names\n"
"\n"
" Environment variables:\n"
" SEPARATOR - fd number of file name to read separator from (default separator is single newline)\n"
" NO_CHOPPED_DATA - if set, don't output trailing line without separator at the end\n"
" \n"
" Advanced example (bash):\n"
" SEPARATOR=10 ./fdlinecombine 0 5 6 <(echo HEADER; echo ---) \\\n"
" 5< <(nc -lp 9979 < /dev/null) \\\n"
" 6< <(perl -e '$|=1; sleep 2 and print \"TIMER\\n---\\n\" while true' < /dev/null) \\\n"
" 10< <(printf -- '\\n---\\n') > out \n"
" This will transfer data from stdin, opened TCP port and periodic timer\n"
" to file \"out\" using \"---\" line as separator.\n"
);
return 0; /* No fds (therefore no output) is correct degenerate case */
}
numfds = argc-1;
num_active_fds = numfds;
fds = (struct fdinfo*) malloc(numfds*sizeof(*fds));
if (fds==NULL) {
perror("malloc");
return 1;
}
for(i=1; i<argc; ++i) {
struct fdinfo* f = fds+(i-1);
if(!sscanf(argv[i], "%i", &f->fd)) {
open_again:
f->fd = open(argv[i], O_RDONLY, 0022);
if(f->fd == -1) {
if ( errno==EINTR || errno==EAGAIN ) goto open_again;
fprintf(stderr, "%s ", argv[i]);
perror("open");
fprintf(stderr, "All arguments must be file descriptor numbers or file names\n");
return 2;
}
}
f->buffer = (char*) malloc(DEFAULT_READ_SIZE);
if (!f->buffer) {
perror("malloc");
return 1;
}
f->bufsize = DEFAULT_READ_SIZE;
f->offset = 0;
}
for(;;) { /* select loop */
FD_ZERO(&rfds);
maxfd=0;
for(i=0; i<numfds; ++i) {
struct fdinfo* f = fds+i;
if (f->fd >= 0) {
FD_SET(f->fd, &rfds);
if(maxfd < f->fd+1) maxfd = f->fd+1;
fcntl(f->fd, F_SETFL, O_NONBLOCK);
}
}
sret = select(maxfd, &rfds, NULL, NULL, NULL);
if (sret==-1) {
perror("select");
return 1;
}
for(i=0; i<numfds; ++i) {
struct fdinfo* f = fds+i;
if(f->fd==-1) continue;
if(!FD_ISSET(f->fd, &rfds)) continue;
int j;
int offset = f->offset;
char* buffer = f->buffer;
ret = read(f->fd, buffer+offset, f->bufsize-offset);
if (ret==-1) {
if (errno == EAGAIN || errno == EINTR) {
continue;
}
dbgprintf(stderr, "fd %d failed\n", f->fd);
closefd(f);
continue;
} else
if (ret == 0) {
closefd(f);
continue;
}
/* Manage buffer size to keep output fast (can dynamically shrink and enlarge buffers) */
if (ret == f->bufsize - f->offset) {
/* Maximum possible bytes received. Better to enlarge buffer. */
--f->little_data_hyster;
/* Don't enlarge buffer just to read more than megabyte chunks */
/* Also don't enlarge buffer here upon the first request - enlarge if it is trend */
if(ret < 1024*1024 && f->little_data_hyster<-3) {
dbgprintf(stderr, "Much data: enlarging buffer from %d to %d\n", f->bufsize, f->bufsize*2);
buffer = realloc_buffer(f, f->bufsize*2, 0);
}
} else {
if (f->little_data_hyster<0) f->little_data_hyster=0;
}
/* Buffer is too large - can shrink */
if ( (ret < (f->bufsize - offset)/4) && (f->bufsize>DEFAULT_READ_SIZE*2) ) {
if (offset < DEFAULT_READ_SIZE) { // Don't shrink if it is just a looong line
++f->little_data_hyster;
if(f->little_data_hyster>5) { // Don't shink-grow-shink-grow the buffer rapidly
dbgprintf(stderr, "Little data: shrinking buffer from %d to %d\n",
f->bufsize, offset+ret+DEFAULT_READ_SIZE);
buffer = realloc_buffer(f, offset+ret+DEFAULT_READ_SIZE, 0);
}
}
} else {
if(f->little_data_hyster>0) f->little_data_hyster=0;
}
/*
* "debt" newly_received_data free_buffer
* SSSSSSSSSSSSSSSSSSSSSSSSSSNNNNNNNNNNNNNseparatorNNNNNNN--------------
* ^ ^ ^ ^ ^ ^
* 0 offset offset+j | offset+ret bufsize
* |
* offset+j+separator_length
*/
/* Scan new data for newlines. Two implementations: fast (for single-character separator) and safe */
if (separator_length==1) {
/* use latest possible separator */
for(j=ret-1; j!=-1; --j) {
if (buffer[offset+j]==*separator) {
write_and_move_tail(f, offset+j+separator_length, ret-j-separator_length);
offset = f->offset;
buffer = f->buffer;
fflush(stdout);
break;
}
}
if(j==-1) {
/* No newline in newly received data */
offset+=ret;
f->offset = offset;
}
} else {
/* use earliest possible separator, repeat until not found */
int found_flag=0;
for(j=-separator_length+1; j<=(ret-separator_length); ++j) {
if(offset+j<0) continue;
if (!memcmp(buffer+offset+j, separator, separator_length)) {
write_and_move_tail(f, offset+j+separator_length, ret-j-separator_length);
buffer = f->buffer;
offset = f->offset;
found_flag=1;
break;
}
}
if(found_flag) {
for(j=0; j<=offset-separator_length; ++j) {
if (!memcmp(buffer+j, separator, separator_length)) {
write_and_move_tail(f, j+separator_length, offset-separator_length-j);
buffer = f->buffer;
offset = f->offset;
j=0;
}
}
}
if(found_flag) {
fflush(stdout);
} else {
f->offset = offset+=ret;
}
}
/* enlarge buffer if we don't have space to read more data
* (used if too long lines)
*/
if(f->bufsize - offset < DEFAULT_READ_SIZE && f->bufsize>0) {
dbgprintf(stderr, "Long line: enlarging buffer from %d to %d\n", f->bufsize, f->bufsize * 2);
buffer = realloc_buffer(f, f->bufsize * 2, 1);
}
if (f->bufsize==-1) {
closefd(f);
}
} /* fds loops */
if (num_active_fds==0) return 0; /* All inputs finished */
} /* main loop */
free(fds);
if(sepenv) {
free(separator);
}
}