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 source tree.
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8 | */
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9 | #include "libbb.h"
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10 |
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11 | #define ZIPPED (ENABLE_FEATURE_SEAMLESS_LZMA \
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12 | || ENABLE_FEATURE_SEAMLESS_BZ2 \
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13 | || ENABLE_FEATURE_SEAMLESS_GZ \
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14 | /* || ENABLE_FEATURE_SEAMLESS_Z */ \
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15 | )
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16 |
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17 | #if ZIPPED
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18 | # include "archive.h"
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19 | #endif
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20 |
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21 |
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22 | /* Suppose that you are a shell. You start child processes.
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23 | * They work and eventually exit. You want to get user input.
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24 | * You read stdin. But what happens if last child switched
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25 | * its stdin into O_NONBLOCK mode?
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26 | *
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27 | * *** SURPRISE! It will affect the parent too! ***
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28 | * *** BIG SURPRISE! It stays even after child exits! ***
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29 | *
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30 | * This is a design bug in UNIX API.
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31 | * fcntl(0, F_SETFL, fcntl(0, F_GETFL) | O_NONBLOCK);
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32 | * will set nonblocking mode not only on _your_ stdin, but
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33 | * also on stdin of your parent, etc.
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34 | *
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35 | * In general,
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36 | * fd2 = dup(fd1);
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37 | * fcntl(fd2, F_SETFL, fcntl(fd2, F_GETFL) | O_NONBLOCK);
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38 | * sets both fd1 and fd2 to O_NONBLOCK. This includes cases
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39 | * where duping is done implicitly by fork() etc.
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40 | *
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41 | * We need
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42 | * fcntl(fd2, F_SETFD, fcntl(fd2, F_GETFD) | O_NONBLOCK);
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43 | * (note SETFD, not SETFL!) but such thing doesn't exist.
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44 | *
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45 | * Alternatively, we need nonblocking_read(fd, ...) which doesn't
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46 | * require O_NONBLOCK dance at all. Actually, it exists:
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47 | * n = recv(fd, buf, len, MSG_DONTWAIT);
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48 | * "MSG_DONTWAIT:
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49 | * Enables non-blocking operation; if the operation
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50 | * would block, EAGAIN is returned."
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51 | * but recv() works only for sockets!
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52 | *
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53 | * So far I don't see any good solution, I can only propose
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54 | * that affected readers should be careful and use this routine,
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55 | * which detects EAGAIN and uses poll() to wait on the fd.
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56 | * Thankfully, poll() doesn't care about O_NONBLOCK flag.
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57 | */
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58 | ssize_t FAST_FUNC nonblock_safe_read(int fd, void *buf, size_t count)
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59 | {
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60 | struct pollfd pfd[1];
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61 | ssize_t n;
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62 |
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63 | while (1) {
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64 | n = safe_read(fd, buf, count);
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65 | if (n >= 0 || errno != EAGAIN)
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66 | return n;
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67 | /* fd is in O_NONBLOCK mode. Wait using poll and repeat */
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68 | pfd[0].fd = fd;
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69 | pfd[0].events = POLLIN;
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70 | safe_poll(pfd, 1, -1); /* note: this pulls in printf */
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71 | }
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72 | }
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73 |
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74 | // Reads one line a-la fgets (but doesn't save terminating '\n').
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75 | // Reads byte-by-byte. Useful when it is important to not read ahead.
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76 | // Bytes are appended to pfx (which must be malloced, or NULL).
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77 | char* FAST_FUNC xmalloc_reads(int fd, char *buf, size_t *maxsz_p)
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78 | {
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79 | char *p;
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80 | size_t sz = buf ? strlen(buf) : 0;
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81 | size_t maxsz = maxsz_p ? *maxsz_p : (INT_MAX - 4095);
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82 |
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83 | goto jump_in;
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84 | while (sz < maxsz) {
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85 | if ((size_t)(p - buf) == sz) {
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86 | jump_in:
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87 | buf = xrealloc(buf, sz + 128);
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88 | p = buf + sz;
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89 | sz += 128;
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90 | }
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91 | /* nonblock_safe_read() because we are used by e.g. shells */
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92 | if (nonblock_safe_read(fd, p, 1) != 1) { /* EOF/error */
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93 | if (p == buf) { /* we read nothing */
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94 | free(buf);
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95 | return NULL;
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96 | }
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97 | break;
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98 | }
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99 | if (*p == '\n')
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100 | break;
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101 | p++;
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102 | }
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103 | *p = '\0';
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104 | if (maxsz_p)
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105 | *maxsz_p = p - buf;
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106 | p++;
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107 | return xrealloc(buf, p - buf);
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108 | }
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109 |
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110 | // Read (potentially big) files in one go. File size is estimated
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111 | // by stat. Extra '\0' byte is appended.
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112 | void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p)
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113 | {
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114 | char *buf;
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115 | size_t size, rd_size, total;
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116 | size_t to_read;
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117 | struct stat st;
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118 |
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119 | to_read = maxsz_p ? *maxsz_p : (INT_MAX - 4095); /* max to read */
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120 |
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121 | /* Estimate file size */
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122 | st.st_size = 0; /* in case fstat fails, assume 0 */
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123 | fstat(fd, &st);
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124 | /* /proc/N/stat files report st_size 0 */
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125 | /* In order to make such files readable, we add small const */
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126 | size = (st.st_size | 0x3ff) + 1;
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127 |
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128 | total = 0;
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129 | buf = NULL;
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130 | while (1) {
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131 | if (to_read < size)
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132 | size = to_read;
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133 | buf = xrealloc(buf, total + size + 1);
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134 | rd_size = full_read(fd, buf + total, size);
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135 | if ((ssize_t)rd_size == (ssize_t)(-1)) { /* error */
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136 | free(buf);
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137 | return NULL;
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138 | }
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139 | total += rd_size;
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140 | if (rd_size < size) /* EOF */
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141 | break;
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142 | if (to_read <= rd_size)
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143 | break;
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144 | to_read -= rd_size;
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145 | /* grow by 1/8, but in [1k..64k] bounds */
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146 | size = ((total / 8) | 0x3ff) + 1;
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147 | if (size > 64*1024)
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148 | size = 64*1024;
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149 | }
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150 | buf = xrealloc(buf, total + 1);
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151 | buf[total] = '\0';
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152 |
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153 | if (maxsz_p)
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154 | *maxsz_p = total;
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155 | return buf;
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156 | }
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157 |
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158 | #ifdef USING_LSEEK_TO_GET_SIZE
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159 | /* Alternatively, file size can be obtained by lseek to the end.
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160 | * The code is slightly bigger. Retained in case fstat approach
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161 | * will not work for some weird cases (/proc, block devices, etc).
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162 | * (NB: lseek also can fail to work for some weird files) */
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163 |
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164 | // Read (potentially big) files in one go. File size is estimated by
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165 | // lseek to end.
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166 | void* FAST_FUNC xmalloc_open_read_close(const char *filename, size_t *maxsz_p)
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167 | {
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168 | char *buf;
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169 | size_t size;
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170 | int fd;
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171 | off_t len;
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172 |
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173 | fd = open(filename, O_RDONLY);
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174 | if (fd < 0)
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175 | return NULL;
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176 |
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177 | /* /proc/N/stat files report len 0 here */
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178 | /* In order to make such files readable, we add small const */
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179 | size = 0x3ff; /* read only 1k on unseekable files */
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180 | len = lseek(fd, 0, SEEK_END) | 0x3ff; /* + up to 1k */
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181 | if (len != (off_t)-1) {
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182 | xlseek(fd, 0, SEEK_SET);
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183 | size = maxsz_p ? *maxsz_p : (INT_MAX - 4095);
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184 | if (len < size)
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185 | size = len;
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186 | }
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187 |
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188 | buf = xmalloc(size + 1);
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189 | size = read_close(fd, buf, size);
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190 | if ((ssize_t)size < 0) {
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191 | free(buf);
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192 | return NULL;
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193 | }
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194 | buf = xrealloc(buf, size + 1);
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195 | buf[size] = '\0';
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196 |
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197 | if (maxsz_p)
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198 | *maxsz_p = size;
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199 | return buf;
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200 | }
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201 | #endif
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202 |
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203 | // Read (potentially big) files in one go. File size is estimated
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204 | // by stat.
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205 | void* FAST_FUNC xmalloc_open_read_close(const char *filename, size_t *maxsz_p)
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206 | {
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207 | char *buf;
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208 | int fd;
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209 |
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210 | fd = open(filename, O_RDONLY);
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211 | if (fd < 0)
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212 | return NULL;
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213 |
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214 | buf = xmalloc_read(fd, maxsz_p);
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215 | close(fd);
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216 | return buf;
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217 | }
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218 |
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219 | /* Die with an error message if we can't read the entire buffer. */
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220 | void FAST_FUNC xread(int fd, void *buf, size_t count)
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221 | {
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222 | if (count) {
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223 | ssize_t size = full_read(fd, buf, count);
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224 | if ((size_t)size != count)
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225 | bb_error_msg_and_die("short read");
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226 | }
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227 | }
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228 |
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229 | /* Die with an error message if we can't read one character. */
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230 | unsigned char FAST_FUNC xread_char(int fd)
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231 | {
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232 | char tmp;
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233 | xread(fd, &tmp, 1);
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234 | return tmp;
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235 | }
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236 |
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237 | void* FAST_FUNC xmalloc_xopen_read_close(const char *filename, size_t *maxsz_p)
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238 | {
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239 | void *buf = xmalloc_open_read_close(filename, maxsz_p);
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240 | if (!buf)
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241 | bb_perror_msg_and_die("can't read '%s'", filename);
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242 | return buf;
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243 | }
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244 |
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245 | /* Used by e.g. rpm which gives us a fd without filename,
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246 | * thus we can't guess the format from filename's extension.
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247 | */
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248 | #if ZIPPED
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249 | void FAST_FUNC setup_unzip_on_fd(int fd /*, int fail_if_not_detected*/)
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250 | {
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251 | const int fail_if_not_detected = 1;
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252 | union {
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253 | uint8_t b[4];
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254 | uint16_t b16[2];
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255 | uint32_t b32[1];
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256 | } magic;
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257 | int offset = -2;
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258 | # if BB_MMU
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259 | IF_DESKTOP(long long) int FAST_FUNC (*xformer)(int src_fd, int dst_fd);
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260 | enum { xformer_prog = 0 };
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261 | # else
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262 | enum { xformer = 0 };
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263 | const char *xformer_prog;
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264 | # endif
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265 |
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266 | /* .gz and .bz2 both have 2-byte signature, and their
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267 | * unpack_XXX_stream wants this header skipped. */
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268 | xread(fd, magic.b16, sizeof(magic.b16[0]));
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269 | if (ENABLE_FEATURE_SEAMLESS_GZ
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270 | && magic.b16[0] == GZIP_MAGIC
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271 | ) {
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272 | # if BB_MMU
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273 | xformer = unpack_gz_stream;
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274 | # else
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275 | xformer_prog = "gunzip";
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276 | # endif
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277 | goto found_magic;
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278 | }
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279 | if (ENABLE_FEATURE_SEAMLESS_BZ2
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280 | && magic.b16[0] == BZIP2_MAGIC
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281 | ) {
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282 | # if BB_MMU
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283 | xformer = unpack_bz2_stream;
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284 | # else
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285 | xformer_prog = "bunzip2";
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286 | # endif
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287 | goto found_magic;
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288 | }
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289 | if (ENABLE_FEATURE_SEAMLESS_XZ
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290 | && magic.b16[0] == XZ_MAGIC1
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291 | ) {
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292 | offset = -6;
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293 | xread(fd, magic.b32, sizeof(magic.b32[0]));
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294 | if (magic.b32[0] == XZ_MAGIC2) {
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295 | # if BB_MMU
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296 | xformer = unpack_xz_stream;
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297 | /* unpack_xz_stream wants fd at position 6, no need to seek */
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298 | //xlseek(fd, offset, SEEK_CUR);
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299 | # else
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300 | xformer_prog = "unxz";
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301 | # endif
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302 | goto found_magic;
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303 | }
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304 | }
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305 |
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306 | /* No known magic seen */
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307 | if (fail_if_not_detected)
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308 | bb_error_msg_and_die("no gzip"
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309 | IF_FEATURE_SEAMLESS_BZ2("/bzip2")
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310 | IF_FEATURE_SEAMLESS_XZ("/xz")
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311 | " magic");
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312 | xlseek(fd, offset, SEEK_CUR);
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313 | return;
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314 |
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315 | found_magic:
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316 | # if !BB_MMU
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317 | /* NOMMU version of open_transformer execs
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318 | * an external unzipper that wants
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319 | * file position at the start of the file */
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320 | xlseek(fd, offset, SEEK_CUR);
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321 | # endif
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322 | open_transformer(fd, xformer, xformer_prog);
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323 | }
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324 | #endif /* ZIPPED */
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325 |
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326 | int FAST_FUNC open_zipped(const char *fname)
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327 | {
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328 | #if !ZIPPED
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329 | return open(fname, O_RDONLY);
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330 | #else
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331 | char *sfx;
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332 | int fd;
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333 |
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334 | fd = open(fname, O_RDONLY);
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335 | if (fd < 0)
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336 | return fd;
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337 |
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338 | sfx = strrchr(fname, '.');
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339 | if (sfx) {
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340 | sfx++;
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341 | if (ENABLE_FEATURE_SEAMLESS_LZMA && strcmp(sfx, "lzma") == 0)
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342 | /* .lzma has no header/signature, just trust it */
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343 | open_transformer(fd, unpack_lzma_stream, "unlzma");
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344 | else
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345 | if ((ENABLE_FEATURE_SEAMLESS_GZ && strcmp(sfx, "gz") == 0)
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346 | || (ENABLE_FEATURE_SEAMLESS_BZ2 && strcmp(sfx, "bz2") == 0)
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347 | || (ENABLE_FEATURE_SEAMLESS_XZ && strcmp(sfx, "xz") == 0)
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348 | ) {
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349 | setup_unzip_on_fd(fd /*, fail_if_not_detected: 1*/);
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350 | }
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351 | }
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352 |
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353 | return fd;
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354 | #endif
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355 | }
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356 |
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357 | void* FAST_FUNC xmalloc_open_zipped_read_close(const char *fname, size_t *maxsz_p)
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358 | {
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359 | int fd;
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360 | char *image;
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361 |
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362 | fd = open_zipped(fname);
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363 | if (fd < 0)
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364 | return NULL;
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365 |
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366 | image = xmalloc_read(fd, maxsz_p);
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367 | if (!image)
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368 | bb_perror_msg("read error from '%s'", fname);
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369 | close(fd);
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370 |
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371 | return image;
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372 | }
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