1/* read-file.c -- read file contents into a string
2 Copyright (C) 2006, 2009-2013 Free Software Foundation, Inc.
3 Written by Simon Josefsson and Bruno Haible.
4
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3, or (at your option)
8 any later version.
9
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, see <http://www.gnu.org/licenses/>. */
17
18#include <config.h>
19
20#include "read-file.h"
21
22/* Get fstat. */
23#include <sys/stat.h>
24
25/* Get ftello. */
26#include <stdio.h>
27
28/* Get SIZE_MAX. */
29#include <stdint.h>
30
31/* Get malloc, realloc, free. */
32#include <stdlib.h>
33
34/* Get errno. */
35#include <errno.h>
36
37/* Read a STREAM and return a newly allocated string with the content,
38 and set *LENGTH to the length of the string. The string is
39 zero-terminated, but the terminating zero byte is not counted in
40 *LENGTH. On errors, *LENGTH is undefined, errno preserves the
41 values set by system functions (if any), and NULL is returned. */
42char *
43fread_file (FILE *stream, size_t *length)
44{
45 char *buf = NULL;
46 size_t alloc = BUFSIZ;
47
48 /* For a regular file, allocate a buffer that has exactly the right
49 size. This avoids the need to do dynamic reallocations later. */
50 {
51 struct stat st;
52
53 if (fstat (fileno (stream), &st) >= 0 && S_ISREG (st.st_mode))
54 {
55 off_t pos = ftello (stream);
56
57 if (pos >= 0 && pos < st.st_size)
58 {
59 off_t alloc_off = st.st_size - pos;
60
61 /* '1' below, accounts for the trailing NUL. */
62 if (SIZE_MAX - 1 < alloc_off)
63 {
64 errno = ENOMEM;
65 return NULL;
66 }
67
68 alloc = alloc_off + 1;
69 }
70 }
71 }
72
73 if (!(buf = malloc (alloc)))
74 return NULL; /* errno is ENOMEM. */
75
76 {
77 size_t size = 0; /* number of bytes read so far */
78 int save_errno;
79
80 for (;;)
81 {
82 /* This reads 1 more than the size of a regular file
83 so that we get eof immediately. */
84 size_t requested = alloc - size;
85 size_t count = fread (buf + size, 1, requested, stream);
86 size += count;
87
88 if (count != requested)
89 {
90 save_errno = errno;
91 if (ferror (stream))
92 break;
93
94 /* Shrink the allocated memory if possible. */
95 if (size < alloc - 1)
96 {
97 char *smaller_buf = realloc (buf, size + 1);
98 if (smaller_buf != NULL)
99 buf = smaller_buf;
100 }
101
102 buf[size] = '\0';
103 *length = size;
104 return buf;
105 }
106
107 {
108 char *new_buf;
109
110 if (alloc == SIZE_MAX)
111 {
112 save_errno = ENOMEM;
113 break;
114 }
115
116 if (alloc < SIZE_MAX - alloc / 2)
117 alloc = alloc + alloc / 2;
118 else
119 alloc = SIZE_MAX;
120
121 if (!(new_buf = realloc (buf, alloc)))
122 {
123 save_errno = errno;
124 break;
125 }
126
127 buf = new_buf;
128 }
129 }
130
131 free (buf);
132 errno = save_errno;
133 return NULL;
134 }
135}
136
137static char *
138internal_read_file (const char *filename, size_t *length, const char *mode)
139{
140 FILE *stream = fopen (filename, mode);
141 char *out;
142 int save_errno;
143
144 if (!stream)
145 return NULL;
146
147 out = fread_file (stream, length);
148
149 save_errno = errno;
150
151 if (fclose (stream) != 0)
152 {
153 if (out)
154 {
155 save_errno = errno;
156 free (out);
157 }
158 errno = save_errno;
159 return NULL;
160 }
161
162 return out;
163}
164
165/* Open and read the contents of FILENAME, and return a newly
166 allocated string with the content, and set *LENGTH to the length of
167 the string. The string is zero-terminated, but the terminating
168 zero byte is not counted in *LENGTH. On errors, *LENGTH is
169 undefined, errno preserves the values set by system functions (if
170 any), and NULL is returned. */
171char *
172read_file (const char *filename, size_t *length)
173{
174 return internal_read_file (filename, length, "r");
175}
176
177/* Open (on non-POSIX systems, in binary mode) and read the contents
178 of FILENAME, and return a newly allocated string with the content,
179 and set LENGTH to the length of the string. The string is
180 zero-terminated, but the terminating zero byte is not counted in
181 the LENGTH variable. On errors, *LENGTH is undefined, errno
182 preserves the values set by system functions (if any), and NULL is
183 returned. */
184char *
185read_binary_file (const char *filename, size_t *length)
186{
187 return internal_read_file (filename, length, "rb");
188}
189