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procio.c
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procio.c
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/*
* procio.c -- Replace stdio for read and write on files below
* proc to be able to read and write large buffers as well.
*
* Copyright (C) 2017 Werner Fink
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef _GNU_SOURCE
# define _GNU_SOURCE
#endif
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
typedef struct pcookie {
char *buf;
size_t count;
size_t length;
off_t offset;
int fd;
int delim;
int final:1;
} pcookie_t;
static ssize_t proc_read(void *, char *, size_t);
static ssize_t proc_write(void *, const char *, size_t);
static int proc_close(void *);
__extension__
static cookie_io_functions_t procio = {
.read = proc_read,
.write = proc_write,
.seek = NULL,
.close = proc_close,
};
FILE *fprocopen(const char *path, const char *mode)
{
pcookie_t *cookie = NULL;
FILE *handle = NULL;
mode_t flags = 0;
size_t len = 0;
int c, delim;
if (!mode || !(len = strlen(mode))) {
errno = EINVAL;
goto out;
}
/* No append mode possible */
switch (mode[0]) {
case 'r':
flags |= O_RDONLY;
break;
case 'w':
flags |= O_WRONLY|O_TRUNC;
break;
default:
errno = EINVAL;
goto out;
}
delim = ','; /* default delimeter is the colon */
for (c = 1; c < len; c++) {
switch (mode[c]) {
case '\0':
break;
case '+':
errno = EINVAL;
goto out;
case 'e':
flags |= O_CLOEXEC;
continue;
case 'b':
case 'm':
case 'x':
/* ignore this */
continue;
default:
if (mode[c] == ' ' || (mode[c] >= ',' && mode[c] <= '.') || mode[c] == ':')
delim = mode[c];
else {
errno = EINVAL;
goto out;
}
break;
}
break;
}
cookie = (pcookie_t *)malloc(sizeof(pcookie_t));
if (!cookie)
goto out;
cookie->count = BUFSIZ;
cookie->buf = (char *)malloc(cookie->count);
if (!cookie->buf) {
int errsv = errno;
free(cookie);
errno = errsv;
goto out;
}
cookie->final = 0;
cookie->offset = 0;
cookie->length = 0;
cookie->delim = delim;
cookie->fd = openat(AT_FDCWD, path, flags);
if (cookie->fd < 0) {
int errsv = errno;
free(cookie->buf);
free(cookie);
errno = errsv;
goto out;
}
handle = fopencookie(cookie, mode, procio);
if (!handle) {
int errsv = errno;
close(cookie->fd);
free(cookie->buf);
free(cookie);
errno = errsv;
goto out;
}
out:
return handle;
}
static
ssize_t proc_read(void *c, char *buf, size_t count)
{
pcookie_t *cookie = c;
ssize_t len = -1;
void *ptr;
if (cookie->count < count) {
ptr = realloc(cookie->buf, count);
if (!ptr)
goto out;
cookie->buf = ptr;
cookie->count = count;
}
while (!cookie->final) {
len = read(cookie->fd, cookie->buf, cookie->count);
if (len <= 0) {
if (len == 0) {
/* EOF */
cookie->final = 1;
cookie->buf[cookie->length] = '\0';
break;
}
goto out; /* error or done */
}
cookie->length = len;
if (cookie->length < cookie->count)
continue;
/* Likly to small buffer here */
lseek(cookie->fd, 0, SEEK_SET); /* reset for a retry */
ptr = realloc(cookie->buf, cookie->count += BUFSIZ);
if (!ptr)
goto out;
cookie->buf = ptr;
}
len = count;
if (cookie->length - cookie->offset < len)
len = cookie->length - cookie->offset;
if (len < 0)
len = 0;
if (len) {
(void)memcpy(buf, cookie->buf+cookie->offset, len);
cookie->offset += len;
} else
len = EOF;
out:
return len;
}
#define LINELEN 4096
static
ssize_t proc_write(void *c, const char *buf, size_t count)
{
pcookie_t *cookie = c;
ssize_t len = -1;
void *ptr;
if (!count) {
len = 0;
goto out;
}
/* NL is the final input */
cookie->final = memrchr(buf, '\n', count) ? 1 : 0;
while (cookie->count < cookie->offset + count) {
ptr = realloc(cookie->buf, cookie->count += count);
if (!ptr)
goto out;
cookie->buf = ptr;
}
len = count;
(void)memcpy(cookie->buf+cookie->offset, buf, count);
cookie->offset += count;
if (cookie->final) {
len = write(cookie->fd, cookie->buf, cookie->offset);
if (len < 0 && errno == EINVAL) {
size_t offset;
off_t amount;
char *token;
/*
* Oops buffer might be to large, split buffer into
* pieces at delimeter if provided
*/
if (!cookie->delim)
goto out; /* Hey dude?! */
offset = 0;
do {
token = NULL;
if (cookie->offset > LINELEN)
token = (char*)memrchr(cookie->buf+offset, cookie->delim, LINELEN);
else
token = (char*)memrchr(cookie->buf+offset, '\n', cookie->offset);
if (token)
*token = '\n';
else {
errno = EINVAL;
len = -1;
goto out; /* Wrong/Missing delimeter? */
}
if (offset > 0)
lseek(cookie->fd, 1, SEEK_CUR);
amount = token-(cookie->buf+offset)+1;
ptr = cookie->buf+offset;
len = write(cookie->fd, ptr, amount);
if (len < 1 || len >= cookie->offset)
break;
offset += len;
cookie->offset -= len;
} while (cookie->offset > 0);
}
if (len > 0)
len = count;
}
out:
return len;
}
static
int proc_close(void *c)
{
pcookie_t *cookie = c;
close(cookie->fd);
free(cookie->buf);
free(cookie);
return 0;
}