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#include <stdio.h>
#include <fcntl.h>
#include <poll.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#define BUFLEN 1024
#define DEBUG 0
#define pr_debug(fmt, args...) if (DEBUG) printf(fmt, ##args)
struct getline_states {
char *base;
char *cur;
size_t size;
size_t read;
char *next;
};
ssize_t fdgetline(int fd, struct getline_states *line) {
char *str;
ssize_t nread;
if (line->base == NULL) {
/* First pass: init state */
line->size = 120;
line->base = malloc(line->size);
if (line->base == NULL)
return -ENOMEM;
line->base[0] = '\0';
line->read = 0;
line->next = line->base;
line->cur = NULL;
}
/* Do we already have a full line in buffer? */
if (line->read > 0 && (str = strchr(line->next, '\n'))) {
line->cur = line->next;
line->next = str+1;
str[0] = '\0';
pr_debug("next already buffered, %p %p: %s\n", str, line->cur, line->cur);
return 1;
}
/* No such luck, move current to base and read what we can */
if (line->cur && line->cur != line->base) {
pr_debug("moving cur: %p, base: %p, read: %zd, moving %zd\n",
line->cur, line->base, line->read, line->cur - line->base);
line->read -= line->cur - line->base;
line->next -= line->cur - line->base;
memmove(line->base, line->cur, line->read + 1); /* also move trailing \0 */
line->cur = line->base;
}
/* search from here */
while (1) {
errno = 0;
nread = read(fd, line->base + line->read, line->size - line->read - 1);
if (nread < 0) {
if (errno == EAGAIN)
return 0;
break;
}
if (nread == 0) {
/* EOF */
return -1;
}
pr_debug("read %zd\n", nread);
line->read += nread;
line->base[line->read] = '\0';
/* Check if we have a full line now */
if ((str = strchr(line->next, '\n'))) {
line->cur = line->next;
line->next = str + 1;
str[0] = '\0';
pr_debug("found stuff, %p %p %p: %s\n", str, line->base, line->cur, line->cur);
return 1;
}
/* realloc bigger buffer and try again if sensible */
if (line->size - line->read > 100)
continue;
if (line->size > 1024) {
/* pretend this was a full line.. */
line->cur = line->next;
line->next = line->base + line->read;
return 1;
}
line->size *= 2;
pr_debug("growing buffer to %zd\n", line->size);
char *newbase = realloc(line->base, line->size);
if (newbase == NULL)
return -ENOMEM;
if (line->cur) {
pr_debug("base-cur was %p-%p, new %p-%p\n", line->base, line->cur, newbase, newbase + (line->cur - line->base));
line->cur = newbase + (line->cur - line->base);
}
line->next = newbase + (line->next - line->base);
line->base = newbase;
}
pr_debug("read failed? %zd %d\n", nread, errno);
if (errno)
return -errno;
return -1; /* unknown error? */
}
int main(int argc, char **argv)
{
int flags, fd = 0;
ssize_t nread;
struct pollfd pollfd;
struct getline_states line = { 0 };
/* non-buffered output */
setlinebuf(stdout);
/* make stream non-block */
flags = fcntl(fd, F_GETFL);
flags |= O_NONBLOCK;
fcntl(fd, F_SETFL, flags);
pollfd.fd = fd;
pollfd.events = POLLIN;
while (poll(&pollfd, 1, -1) > 0) {
line.cur = NULL;
while ((nread = fdgetline(fd, &line)) > 0);
if (line.cur)
printf("%s\n", line.cur);
/* eof or error */
if (nread < 0)
break;
/* throttle in case something tries to wake us up every few ms... */
sleep(1);
}
return 0;
}
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