Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 1 | /* vi: set sw=4 ts=4: */ |
| 2 | /* |
| 3 | * Utility routines. |
| 4 | * |
| 5 | * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org> |
| 6 | * |
| 7 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. |
| 8 | */ |
| 9 | |
| 10 | #include "libbb.h" |
| 11 | |
| 12 | ssize_t safe_read(int fd, void *buf, size_t count) |
| 13 | { |
| 14 | ssize_t n; |
| 15 | |
| 16 | do { |
| 17 | n = read(fd, buf, count); |
| 18 | } while (n < 0 && errno == EINTR); |
| 19 | |
| 20 | return n; |
| 21 | } |
| 22 | |
Denis Vlasenko | e376d45 | 2008-02-20 22:23:24 +0000 | [diff] [blame] | 23 | /* Suppose that you are a shell. You start child processes. |
| 24 | * They work and eventually exit. You want to get user input. |
| 25 | * You read stdin. But what happens if last child switched |
| 26 | * its stdin into O_NONBLOCK mode? |
| 27 | * |
| 28 | * *** SURPRISE! It will affect the parent too! *** |
| 29 | * *** BIG SURPRISE! It stays even after child exits! *** |
| 30 | * |
| 31 | * This is a design bug in UNIX API. |
| 32 | * fcntl(0, F_SETFL, fcntl(0, F_GETFL, 0) | O_NONBLOCK); |
| 33 | * will set nonblocking mode not only on _your_ stdin, but |
| 34 | * also on stdin of your parent, etc. |
| 35 | * |
| 36 | * In general, |
| 37 | * fd2 = dup(fd1); |
| 38 | * fcntl(fd2, F_SETFL, fcntl(fd2, F_GETFL, 0) | O_NONBLOCK); |
| 39 | * sets both fd1 and fd2 to O_NONBLOCK. This includes cases |
| 40 | * where duping is done implicitly by fork() etc. |
| 41 | * |
| 42 | * We need |
| 43 | * fcntl(fd2, F_SETFD, fcntl(fd2, F_GETFD, 0) | O_NONBLOCK); |
| 44 | * (note SETFD, not SETFL!) but such thing doesn't exist. |
| 45 | * |
| 46 | * Alternatively, we need nonblocking_read(fd, ...) which doesn't |
| 47 | * require O_NONBLOCK dance at all. Actually, it exists: |
| 48 | * n = recv(fd, buf, len, MSG_DONTWAIT); |
| 49 | * "MSG_DONTWAIT: |
| 50 | * Enables non-blocking operation; if the operation |
| 51 | * would block, EAGAIN is returned." |
| 52 | * but recv() works only for sockets! |
| 53 | * |
| 54 | * So far I don't see any good solution, I can only propose |
| 55 | * that affected readers should be careful and use this routine, |
| 56 | * which detects EAGAIN and uses poll() to wait on the fd. |
Denis Vlasenko | 081efd1 | 2008-02-20 22:57:24 +0000 | [diff] [blame] | 57 | * Thankfully, poll() doesn't care about O_NONBLOCK flag. |
Denis Vlasenko | e376d45 | 2008-02-20 22:23:24 +0000 | [diff] [blame] | 58 | */ |
| 59 | ssize_t nonblock_safe_read(int fd, void *buf, size_t count) |
| 60 | { |
| 61 | struct pollfd pfd[1]; |
| 62 | ssize_t n; |
| 63 | |
| 64 | while (1) { |
| 65 | n = safe_read(fd, buf, count); |
| 66 | if (n >= 0 || errno != EAGAIN) |
| 67 | return n; |
| 68 | /* fd is in O_NONBLOCK mode. Wait using poll and repeat */ |
| 69 | pfd[0].fd = fd; |
| 70 | pfd[0].events = POLLIN; |
| 71 | safe_poll(pfd, 1, -1); |
| 72 | } |
| 73 | } |
| 74 | |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 75 | /* |
| 76 | * Read all of the supplied buffer from a file. |
| 77 | * This does multiple reads as necessary. |
| 78 | * Returns the amount read, or -1 on an error. |
| 79 | * A short read is returned on an end of file. |
| 80 | */ |
| 81 | ssize_t full_read(int fd, void *buf, size_t len) |
| 82 | { |
| 83 | ssize_t cc; |
| 84 | ssize_t total; |
| 85 | |
| 86 | total = 0; |
| 87 | |
| 88 | while (len) { |
| 89 | cc = safe_read(fd, buf, len); |
| 90 | |
Denis Vlasenko | 394eebe | 2008-02-25 20:30:24 +0000 | [diff] [blame] | 91 | if (cc < 0) { |
| 92 | if (total) { |
| 93 | /* we already have some! */ |
| 94 | /* user can do another read to know the error code */ |
| 95 | return total; |
| 96 | } |
| 97 | return cc; /* read() returns -1 on failure. */ |
| 98 | } |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 99 | if (cc == 0) |
| 100 | break; |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 101 | buf = ((char *)buf) + cc; |
| 102 | total += cc; |
| 103 | len -= cc; |
| 104 | } |
| 105 | |
| 106 | return total; |
| 107 | } |
| 108 | |
| 109 | // Die with an error message if we can't read the entire buffer. |
| 110 | void xread(int fd, void *buf, size_t count) |
| 111 | { |
| 112 | if (count) { |
| 113 | ssize_t size = full_read(fd, buf, count); |
| 114 | if (size != count) |
| 115 | bb_error_msg_and_die("short read"); |
| 116 | } |
| 117 | } |
| 118 | |
| 119 | // Die with an error message if we can't read one character. |
| 120 | unsigned char xread_char(int fd) |
| 121 | { |
| 122 | char tmp; |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 123 | xread(fd, &tmp, 1); |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 124 | return tmp; |
| 125 | } |
| 126 | |
| 127 | // Read one line a-la fgets. Works only on seekable streams |
| 128 | char *reads(int fd, char *buffer, size_t size) |
| 129 | { |
| 130 | char *p; |
| 131 | |
| 132 | if (size < 2) |
| 133 | return NULL; |
| 134 | size = full_read(fd, buffer, size-1); |
| 135 | if ((ssize_t)size <= 0) |
| 136 | return NULL; |
| 137 | |
| 138 | buffer[size] = '\0'; |
| 139 | p = strchr(buffer, '\n'); |
| 140 | if (p) { |
| 141 | off_t offset; |
| 142 | *p++ = '\0'; |
Denis Vlasenko | b141b9b | 2006-10-31 22:46:08 +0000 | [diff] [blame] | 143 | // avoid incorrect (unsigned) widening |
| 144 | offset = (off_t)(p-buffer) - (off_t)size; |
Denis Vlasenko | 3a34d0c | 2007-01-12 22:10:34 +0000 | [diff] [blame] | 145 | // set fd position right after '\n' |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 146 | if (offset && lseek(fd, offset, SEEK_CUR) == (off_t)-1) |
| 147 | return NULL; |
| 148 | } |
| 149 | return buffer; |
| 150 | } |
| 151 | |
Denis Vlasenko | d67cef2 | 2007-06-13 06:47:47 +0000 | [diff] [blame] | 152 | // Read one line a-la fgets. Reads byte-by-byte. |
| 153 | // Useful when it is important to not read ahead. |
Denis Vlasenko | e376d45 | 2008-02-20 22:23:24 +0000 | [diff] [blame] | 154 | // Bytes are appended to pfx (which must be malloced, or NULL). |
Denis Vlasenko | d67cef2 | 2007-06-13 06:47:47 +0000 | [diff] [blame] | 155 | char *xmalloc_reads(int fd, char *buf) |
| 156 | { |
| 157 | char *p; |
| 158 | int sz = buf ? strlen(buf) : 0; |
| 159 | |
| 160 | goto jump_in; |
| 161 | while (1) { |
| 162 | if (p - buf == sz) { |
| 163 | jump_in: |
| 164 | buf = xrealloc(buf, sz + 128); |
| 165 | p = buf + sz; |
| 166 | sz += 128; |
| 167 | } |
Denis Vlasenko | e376d45 | 2008-02-20 22:23:24 +0000 | [diff] [blame] | 168 | /* nonblock_safe_read() because we are used by e.g. shells */ |
| 169 | if (nonblock_safe_read(fd, p, 1) != 1) { /* EOF/error */ |
Denis Vlasenko | f99afb5 | 2008-02-24 23:32:36 +0000 | [diff] [blame] | 170 | if (p == buf) { /* we read nothing */ |
Denis Vlasenko | d67cef2 | 2007-06-13 06:47:47 +0000 | [diff] [blame] | 171 | free(buf); |
| 172 | return NULL; |
| 173 | } |
| 174 | break; |
| 175 | } |
| 176 | if (*p == '\n') |
| 177 | break; |
| 178 | p++; |
| 179 | } |
| 180 | *p++ = '\0'; |
| 181 | return xrealloc(buf, p - buf); |
| 182 | } |
| 183 | |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 184 | ssize_t read_close(int fd, void *buf, size_t size) |
| 185 | { |
Denis Vlasenko | 98ebab8 | 2007-06-30 14:47:41 +0000 | [diff] [blame] | 186 | /*int e;*/ |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 187 | size = full_read(fd, buf, size); |
Denis Vlasenko | 98ebab8 | 2007-06-30 14:47:41 +0000 | [diff] [blame] | 188 | /*e = errno;*/ |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 189 | close(fd); |
Denis Vlasenko | 98ebab8 | 2007-06-30 14:47:41 +0000 | [diff] [blame] | 190 | /*errno = e;*/ |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 191 | return size; |
| 192 | } |
| 193 | |
| 194 | ssize_t open_read_close(const char *filename, void *buf, size_t size) |
| 195 | { |
| 196 | int fd = open(filename, O_RDONLY); |
| 197 | if (fd < 0) |
| 198 | return fd; |
| 199 | return read_close(fd, buf, size); |
| 200 | } |
| 201 | |
Denis Vlasenko | d67cef2 | 2007-06-13 06:47:47 +0000 | [diff] [blame] | 202 | // Read (potentially big) files in one go. File size is estimated by |
| 203 | // lseek to end. |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 204 | void *xmalloc_open_read_close(const char *filename, size_t *sizep) |
| 205 | { |
| 206 | char *buf; |
| 207 | size_t size = sizep ? *sizep : INT_MAX; |
Denis Vlasenko | d67cef2 | 2007-06-13 06:47:47 +0000 | [diff] [blame] | 208 | int fd; |
| 209 | off_t len; |
| 210 | |
| 211 | fd = xopen(filename, O_RDONLY); |
Denis Vlasenko | b131b27 | 2006-12-17 17:30:01 +0000 | [diff] [blame] | 212 | /* /proc/N/stat files report len 0 here */ |
| 213 | /* In order to make such files readable, we add small const */ |
Denis Vlasenko | d67cef2 | 2007-06-13 06:47:47 +0000 | [diff] [blame] | 214 | len = xlseek(fd, 0, SEEK_END) | 0x3ff; /* + up to 1k */ |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 215 | xlseek(fd, 0, SEEK_SET); |
Denis Vlasenko | d67cef2 | 2007-06-13 06:47:47 +0000 | [diff] [blame] | 216 | if (len < size) |
| 217 | size = len; |
Denis Vlasenko | b131b27 | 2006-12-17 17:30:01 +0000 | [diff] [blame] | 218 | buf = xmalloc(size + 1); |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 219 | size = read_close(fd, buf, size); |
| 220 | if ((ssize_t)size < 0) |
Denis Vlasenko | 8e858e2 | 2007-03-07 09:35:43 +0000 | [diff] [blame] | 221 | bb_perror_msg_and_die("'%s'", filename); |
Denis Vlasenko | b131b27 | 2006-12-17 17:30:01 +0000 | [diff] [blame] | 222 | xrealloc(buf, size + 1); |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 223 | buf[size] = '\0'; |
Denis Vlasenko | d67cef2 | 2007-06-13 06:47:47 +0000 | [diff] [blame] | 224 | if (sizep) |
| 225 | *sizep = size; |
Denis Vlasenko | ea62077 | 2006-10-14 02:23:43 +0000 | [diff] [blame] | 226 | return buf; |
| 227 | } |