1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * Utility routines.
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4 | *
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5 | * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
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6 | *
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7 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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8 | */
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9 |
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10 | #include "libbb.h"
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11 |
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12 | ssize_t safe_read(int fd, void *buf, size_t count)
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13 | {
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14 | ssize_t n;
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15 |
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16 | do {
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17 | n = read(fd, buf, count);
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18 | } while (n < 0 && errno == EINTR);
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19 |
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20 | return n;
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21 | }
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22 |
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23 | /*
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24 | * Read all of the supplied buffer from a file.
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25 | * This does multiple reads as necessary.
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26 | * Returns the amount read, or -1 on an error.
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27 | * A short read is returned on an end of file.
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28 | */
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29 | ssize_t full_read(int fd, void *buf, size_t len)
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30 | {
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31 | ssize_t cc;
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32 | ssize_t total;
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33 |
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34 | total = 0;
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35 |
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36 | while (len) {
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37 | cc = safe_read(fd, buf, len);
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38 |
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39 | if (cc < 0)
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40 | return cc; /* read() returns -1 on failure. */
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41 | if (cc == 0)
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42 | break;
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43 | buf = ((char *)buf) + cc;
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44 | total += cc;
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45 | len -= cc;
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46 | }
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47 |
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48 | return total;
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49 | }
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50 |
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51 | // Die with an error message if we can't read the entire buffer.
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52 | void xread(int fd, void *buf, size_t count)
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53 | {
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54 | if (count) {
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55 | ssize_t size = full_read(fd, buf, count);
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56 | if (size != count)
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57 | bb_error_msg_and_die("short read");
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58 | }
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59 | }
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60 |
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61 | // Die with an error message if we can't read one character.
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62 | unsigned char xread_char(int fd)
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63 | {
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64 | char tmp;
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65 | xread(fd, &tmp, 1);
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66 | return tmp;
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67 | }
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68 |
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69 | // Read one line a-la fgets. Works only on seekable streams
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70 | char *reads(int fd, char *buffer, size_t size)
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71 | {
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72 | char *p;
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73 |
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74 | if (size < 2)
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75 | return NULL;
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76 | size = full_read(fd, buffer, size-1);
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77 | if ((ssize_t)size <= 0)
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78 | return NULL;
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79 |
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80 | buffer[size] = '\0';
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81 | p = strchr(buffer, '\n');
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82 | if (p) {
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83 | off_t offset;
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84 | *p++ = '\0';
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85 | // avoid incorrect (unsigned) widening
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86 | offset = (off_t)(p-buffer) - (off_t)size;
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87 | // set fd position right after '\n'
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88 | if (offset && lseek(fd, offset, SEEK_CUR) == (off_t)-1)
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89 | return NULL;
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90 | }
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91 | return buffer;
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92 | }
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93 |
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94 | // Read one line a-la fgets. Reads byte-by-byte.
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95 | // Useful when it is important to not read ahead.
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96 | char *xmalloc_reads(int fd, char *buf)
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97 | {
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98 | char *p;
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99 | int sz = buf ? strlen(buf) : 0;
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100 |
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101 | goto jump_in;
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102 | while (1) {
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103 | if (p - buf == sz) {
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104 | jump_in:
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105 | buf = xrealloc(buf, sz + 128);
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106 | p = buf + sz;
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107 | sz += 128;
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108 | }
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109 | if (safe_read(fd, p, 1) != 1) { /* EOF/error */
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110 | if (p == buf) {
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111 | /* we read nothing [and buf was NULL initially] */
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112 | free(buf);
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113 | return NULL;
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114 | }
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115 | break;
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116 | }
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117 | if (*p == '\n')
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118 | break;
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119 | p++;
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120 | }
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121 | *p++ = '\0';
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122 | return xrealloc(buf, p - buf);
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123 | }
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124 |
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125 | ssize_t read_close(int fd, void *buf, size_t size)
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126 | {
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127 | /*int e;*/
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128 | size = full_read(fd, buf, size);
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129 | /*e = errno;*/
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130 | close(fd);
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131 | /*errno = e;*/
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132 | return size;
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133 | }
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134 |
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135 | ssize_t open_read_close(const char *filename, void *buf, size_t size)
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136 | {
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137 | int fd = open(filename, O_RDONLY);
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138 | if (fd < 0)
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139 | return fd;
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140 | return read_close(fd, buf, size);
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141 | }
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142 |
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143 | // Read (potentially big) files in one go. File size is estimated by
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144 | // lseek to end.
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145 | void *xmalloc_open_read_close(const char *filename, size_t *sizep)
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146 | {
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147 | char *buf;
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148 | size_t size = sizep ? *sizep : INT_MAX;
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149 | int fd;
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150 | off_t len;
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151 |
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152 | fd = xopen(filename, O_RDONLY);
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153 | /* /proc/N/stat files report len 0 here */
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154 | /* In order to make such files readable, we add small const */
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155 | len = xlseek(fd, 0, SEEK_END) | 0x3ff; /* + up to 1k */
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156 | xlseek(fd, 0, SEEK_SET);
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157 | if (len < size)
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158 | size = len;
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159 | buf = xmalloc(size + 1);
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160 | size = read_close(fd, buf, size);
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161 | if ((ssize_t)size < 0)
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162 | bb_perror_msg_and_die("'%s'", filename);
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163 | xrealloc(buf, size + 1);
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164 | buf[size] = '\0';
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165 | if (sizep)
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166 | *sizep = size;
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167 | return buf;
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168 | }
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