1 /*-
2 * Copyright (C) 2013 Pietro Cerutti <gahr@FreeBSD.org>
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23 * SUCH DAMAGE.
24 */
25
26 #include <sys/cdefs.h>
27
28 #include <errno.h>
29 #include <fcntl.h>
30 #include <stdio.h>
31 #include <stdlib.h>
32 #include <string.h>
33
34 #include "local.h"
35
36 // See http://pubs.opengroup.org/onlinepubs/9699919799/functions/fmemopen.html
37 // and http://man7.org/linux/man-pages/man3/fmemopen.3.html for documentation.
38
39 struct fmemopen_cookie {
40 char* buf;
41 char* allocation;
42 size_t capacity;
43 size_t size;
44 size_t offset;
45 bool append;
46 };
47
fmemopen_read(void * cookie,char * buf,int n)48 static int fmemopen_read(void* cookie, char* buf, int n) {
49 fmemopen_cookie* ck = static_cast<fmemopen_cookie*>(cookie);
50
51 if (static_cast<size_t>(n) > ck->size - ck->offset) n = ck->size - ck->offset;
52
53 if (n > 0) {
54 memmove(buf, ck->buf + ck->offset, n);
55 ck->offset += n;
56 }
57 return n;
58 }
59
fmemopen_write(void * cookie,const char * buf,int n)60 static int fmemopen_write(void* cookie, const char* buf, int n) {
61 fmemopen_cookie* ck = static_cast<fmemopen_cookie*>(cookie);
62
63 // We don't need to add the trailing NUL if there's already a trailing NUL
64 // in the data we're writing.
65 size_t space_for_null = (n > 0 && buf[n - 1] != '\0') ? 1 : 0;
66
67 // Undo any seeking/reading on an append-only stream.
68 if (ck->append) ck->offset = ck->size;
69
70 // How much can we actually fit?
71 if (static_cast<size_t>(n) + space_for_null > ck->capacity - ck->offset) {
72 n = ck->capacity - ck->offset - space_for_null;
73 // Give up if we don't even have room for one byte of userdata.
74 if (n <= 0) {
75 errno = ENOSPC;
76 return -1;
77 }
78 }
79
80 if (n > 0) {
81 memmove(ck->buf + ck->offset, buf, n);
82 ck->offset += n;
83 // Is this the furthest we've ever been?
84 if (ck->offset >= ck->size) {
85 if (buf[n - 1] != '\0') ck->buf[ck->offset] = '\0';
86 ck->size = ck->offset;
87 }
88 }
89 return n;
90 }
91
fmemopen_seek(void * cookie,fpos_t offset,int whence)92 static fpos_t fmemopen_seek(void* cookie, fpos_t offset, int whence) {
93 fmemopen_cookie* ck = static_cast<fmemopen_cookie*>(cookie);
94
95 if (whence == SEEK_SET && (offset >= 0 && static_cast<size_t>(offset) <= ck->capacity)) {
96 return (ck->offset = offset);
97 } else if (whence == SEEK_CUR && (ck->offset + offset <= ck->capacity)) {
98 return (ck->offset += offset);
99 } else if (whence == SEEK_END && (offset <= 0 && static_cast<size_t>(-offset) <= ck->size)) {
100 return (ck->offset = ck->size + offset);
101 }
102 errno = EINVAL;
103 return -1;
104 }
105
fmemopen_close(void * cookie)106 static int fmemopen_close(void* cookie) {
107 fmemopen_cookie* ck = static_cast<fmemopen_cookie*>(cookie);
108 free(ck->allocation);
109 free(ck);
110 return 0;
111 }
112
fmemopen(void * buf,size_t capacity,const char * mode)113 FILE* fmemopen(void* buf, size_t capacity, const char* mode) {
114 int flags;
115 if (__sflags(mode, &flags) == 0) {
116 errno = EINVAL;
117 return nullptr;
118 }
119
120 fmemopen_cookie* ck = static_cast<fmemopen_cookie*>(calloc(sizeof(fmemopen_cookie), 1));
121 if (ck == nullptr) return nullptr;
122
123 ck->buf = static_cast<char*>(buf);
124 ck->capacity = capacity;
125
126 if (ck->buf == nullptr) ck->buf = ck->allocation = static_cast<char*>(calloc(capacity, 1));
127 if (ck->buf == nullptr) {
128 free(ck);
129 return nullptr;
130 }
131
132 FILE* fp = funopen(ck,
133 (flags & O_WRONLY) ? nullptr : fmemopen_read,
134 (flags & O_RDONLY) ? nullptr : fmemopen_write,
135 fmemopen_seek,
136 fmemopen_close);
137 if (fp == nullptr) {
138 fmemopen_close(ck);
139 return nullptr;
140 }
141
142 if (mode[0] == 'a') {
143 ck->size = strnlen(ck->buf, ck->capacity);
144 ck->offset = ck->size;
145 ck->append = true;
146 } else if (mode[0] == 'r') {
147 ck->size = capacity;
148 ck->offset = 0;
149 } else if (mode[0] == 'w') {
150 ck->size = 0;
151 ck->offset = 0;
152 if (capacity > 0) {
153 ck->buf[0] = '\0';
154 }
155 }
156
157 return fp;
158 }
159