1 /*- 2 * Copyright (C) 2013 Pietro Cerutti <gahr (at) 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 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 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 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 } 105 106 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 } 112 113 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 ck->buf[0] = '\0'; 153 } 154 155 return fp; 156 } 157
