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/*
* Copyright 2019 Intel Corporation
* SPDX-License-Identifier: MIT
*/
#include "os_file.h"
#include <errno.h>
#include <stdlib.h>
#if defined(__linux__)
#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
static ssize_t
readN(int fd, char *buf, size_t len)
{
int err = -ENODATA;
size_t total = 0;
do {
ssize_t ret = read(fd, buf + total, len - total);
if (ret < 0)
ret = -errno;
if (ret == -EINTR || ret == -EAGAIN)
continue;
if (ret <= 0) {
err = ret;
break;
}
total += ret;
} while (total != len);
return total ? total : err;
}
char *
os_read_file(const char *filename)
{
/* Note that this also serves as a slight margin to avoid a 2x grow when
* the file is just a few bytes larger when we read it than when we
* fstat'ed it.
* The string's NULL terminator is also included in here.
*/
size_t len = 64;
int fd = open(filename, O_RDONLY);
if (fd == -1) {
/* errno set by open() */
return NULL;
}
/* Pre-allocate a buffer at least the size of the file if we can read
* that information.
*/
struct stat stat;
if (fstat(fd, &stat) == 0)
len += stat.st_size;
char *buf = malloc(len);
if (!buf) {
close(fd);
errno = -ENOMEM;
return NULL;
}
ssize_t read;
size_t offset = 0, remaining = len - 1;
while ((read = readN(fd, buf + offset, remaining)) == remaining) {
char *newbuf = realloc(buf, 2 * len);
if (!newbuf) {
free(buf);
close(fd);
errno = -ENOMEM;
return NULL;
}
buf = newbuf;
len *= 2;
offset += read;
remaining = len - offset - 1;
}
close(fd);
if (read > 0)
offset += read;
buf[offset] = '\0';
return buf;
}
#else
char *
os_read_file(const char *filename)
{
errno = -ENOSYS;
return NULL;
}
#endif
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