src/util/os_file.c

   1 /*
   2  * Copyright 2019 Intel Corporation
   3  * SPDX-License-Identifier: MIT
   4  */
   5
   6 #include "os_file.h"
   7
   8 #include <errno.h>
   9 #include <stdlib.h>
  10
  11 #if defined(__linux__)
  12
  13 #include <fcntl.h>
  14 #include <sys/stat.h>
  15 #include <unistd.h>
  16
  17
  18 static ssize_t
  19 readN(int fd, char *buf, size_t len)
  20 {
  21    int err = -ENODATA;
  22    size_t total = 0;
  23    do {
  24       ssize_t ret = read(fd, buf + total, len - total);
  25
  26       if (ret < 0)
  27          ret = -errno;
  28
  29       if (ret == -EINTR || ret == -EAGAIN)
  30          continue;
  31
  32       if (ret <= 0)
  33          break;
  34
  35       total += ret;
  36    } while (total != len);
  37
  38    return total ? total : err;
  39 }
  40
  41 static char *
  42 read_grow(int fd)
  43 {
  44    size_t len = 64;
  45
  46    char *buf = malloc(len);
  47    if (!buf) {
  48       close(fd);
  49       errno = -ENOMEM;
  50       return NULL;
  51    }
  52
  53    ssize_t read;
  54    size_t offset = 0, remaining = len - 1;
  55    while ((read = readN(fd, buf + offset, remaining)) == remaining) {
  56       char *newbuf = realloc(buf, 2 * len);
  57       if (!newbuf) {
  58          free(buf);
  59          close(fd);
  60          errno = -ENOMEM;
  61          return NULL;
  62       }
  63
  64       buf = newbuf;
  65       len *= 2;
  66       offset += read;
  67       remaining = len - offset - 1;
  68    }
  69
  70    close(fd);
  71
  72    if (read > 0)
  73       offset += read;
  74
  75    buf[offset] = '\0';
  76
  77    return buf;
  78 }
  79
  80 char *
  81 os_read_file(const char *filename)
  82 {
  83    size_t len = 0;
  84
  85    int fd = open(filename, O_RDONLY);
  86    if (fd == -1) {
  87       /* errno set by open() */
  88       return NULL;
  89    }
  90
  91    struct stat stat;
  92    if (fstat(fd, &stat) == 0)
  93       len = stat.st_size;
  94
  95    if (!len)
  96       return read_grow(fd);
  97
  98    /* add NULL terminator */
  99    len++;
 100
 101    char *buf = malloc(len);
 102    if (!buf) {
 103       close(fd);
 104       errno = -ENOMEM;
 105       return NULL;
 106    }
 107
 108    ssize_t read = readN(fd, buf, len - 1);
 109
 110    close(fd);
 111
 112    if (read == -1)
 113       return NULL;
 114
 115    buf[read] = '\0';
 116
 117    return buf;
 118 }
 119
 120 #else
 121
 122 char *
 123 os_read_file(const char *filename)
 124 {
 125    errno = -ENOSYS;
 126    return NULL;
 127 }
 128
 129 #endif