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1 |
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2 /* pngrio.c - functions for data input |
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3 * |
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4 * Last changed in libpng 1.2.37 [June 4, 2009] |
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5 * Copyright (c) 1998-2009 Glenn Randers-Pehrson |
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6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) |
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7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) |
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8 * |
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9 * This code is released under the libpng license. |
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10 * For conditions of distribution and use, see the disclaimer |
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11 * and license in png.h |
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12 * |
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13 * This file provides a location for all input. Users who need |
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14 * special handling are expected to write a function that has the same |
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15 * arguments as this and performs a similar function, but that possibly |
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16 * has a different input method. Note that you shouldn't change this |
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17 * function, but rather write a replacement function and then make |
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18 * libpng use it at run time with png_set_read_fn(...). |
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19 */ |
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20 |
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21 #define PNG_INTERNAL |
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22 #include "png.h" |
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23 #if defined(PNG_READ_SUPPORTED) |
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24 |
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25 /* Read the data from whatever input you are using. The default routine |
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26 * reads from a file pointer. Note that this routine sometimes gets called |
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27 * with very small lengths, so you should implement some kind of simple |
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28 * buffering if you are using unbuffered reads. This should never be asked |
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29 * to read more then 64K on a 16 bit machine. |
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30 */ |
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31 void /* PRIVATE */ |
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32 png_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
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33 { |
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34 png_debug1(4, "reading %d bytes", (int)length); |
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35 if (png_ptr->read_data_fn != NULL) |
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36 (*(png_ptr->read_data_fn))(png_ptr, data, length); |
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37 else |
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38 png_error(png_ptr, "Call to NULL read function"); |
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39 } |
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40 |
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41 #if !defined(PNG_NO_STDIO) |
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42 /* This is the function that does the actual reading of data. If you are |
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43 * not reading from a standard C stream, you should create a replacement |
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44 * read_data function and use it at run time with png_set_read_fn(), rather |
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45 * than changing the library. |
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46 */ |
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47 #ifndef USE_FAR_KEYWORD |
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48 void PNGAPI |
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49 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
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50 { |
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51 png_size_t check; |
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52 |
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53 if (png_ptr == NULL) |
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54 return; |
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55 /* fread() returns 0 on error, so it is OK to store this in a png_size_t |
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56 * instead of an int, which is what fread() actually returns. |
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57 */ |
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58 #if defined(_WIN32_WCE) |
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59 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) ) |
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60 check = 0; |
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61 #else |
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62 check = (png_size_t)fread(data, (png_size_t)1, length, |
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63 (png_FILE_p)png_ptr->io_ptr); |
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64 #endif |
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65 |
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66 if (check != length) |
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67 png_error(png_ptr, "Read Error"); |
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68 } |
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69 #else |
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70 /* This is the model-independent version. Since the standard I/O library |
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71 can't handle far buffers in the medium and small models, we have to copy |
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72 the data. |
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73 */ |
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74 |
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75 #define NEAR_BUF_SIZE 1024 |
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76 #define MIN(a,b) (a <= b ? a : b) |
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77 |
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78 static void PNGAPI |
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79 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
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80 { |
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81 int check; |
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82 png_byte *n_data; |
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83 png_FILE_p io_ptr; |
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84 |
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85 if (png_ptr == NULL) |
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86 return; |
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87 /* Check if data really is near. If so, use usual code. */ |
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88 n_data = (png_byte *)CVT_PTR_NOCHECK(data); |
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89 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr); |
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90 if ((png_bytep)n_data == data) |
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91 { |
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92 #if defined(_WIN32_WCE) |
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93 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) ) |
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94 check = 0; |
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95 #else |
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96 check = fread(n_data, 1, length, io_ptr); |
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97 #endif |
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98 } |
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99 else |
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100 { |
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101 png_byte buf[NEAR_BUF_SIZE]; |
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102 png_size_t read, remaining, err; |
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103 check = 0; |
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104 remaining = length; |
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105 do |
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106 { |
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107 read = MIN(NEAR_BUF_SIZE, remaining); |
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108 #if defined(_WIN32_WCE) |
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109 if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) ) |
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110 err = 0; |
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111 #else |
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112 err = fread(buf, (png_size_t)1, read, io_ptr); |
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113 #endif |
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114 png_memcpy(data, buf, read); /* copy far buffer to near buffer */ |
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115 if (err != read) |
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116 break; |
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117 else |
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118 check += err; |
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119 data += read; |
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120 remaining -= read; |
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121 } |
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122 while (remaining != 0); |
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123 } |
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124 if ((png_uint_32)check != (png_uint_32)length) |
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125 png_error(png_ptr, "read Error"); |
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126 } |
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127 #endif |
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128 #endif |
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129 |
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130 /* This function allows the application to supply a new input function |
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131 * for libpng if standard C streams aren't being used. |
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132 * |
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133 * This function takes as its arguments: |
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134 * png_ptr - pointer to a png input data structure |
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135 * io_ptr - pointer to user supplied structure containing info about |
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136 * the input functions. May be NULL. |
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137 * read_data_fn - pointer to a new input function that takes as its |
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138 * arguments a pointer to a png_struct, a pointer to |
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139 * a location where input data can be stored, and a 32-bit |
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140 * unsigned int that is the number of bytes to be read. |
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141 * To exit and output any fatal error messages the new write |
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142 * function should call png_error(png_ptr, "Error msg"). |
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143 * May be NULL, in which case libpng's default function will |
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144 * be used. |
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145 */ |
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146 void PNGAPI |
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147 png_set_read_fn(png_structp png_ptr, png_voidp io_ptr, |
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148 png_rw_ptr read_data_fn) |
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149 { |
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150 if (png_ptr == NULL) |
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151 return; |
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152 png_ptr->io_ptr = io_ptr; |
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153 |
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154 #if !defined(PNG_NO_STDIO) |
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155 if (read_data_fn != NULL) |
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156 png_ptr->read_data_fn = read_data_fn; |
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157 else |
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158 png_ptr->read_data_fn = png_default_read_data; |
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159 #else |
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160 png_ptr->read_data_fn = read_data_fn; |
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161 #endif |
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162 |
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163 /* It is an error to write to a read device */ |
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164 if (png_ptr->write_data_fn != NULL) |
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165 { |
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166 png_ptr->write_data_fn = NULL; |
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167 png_warning(png_ptr, |
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168 "It's an error to set both read_data_fn and write_data_fn in the "); |
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169 png_warning(png_ptr, |
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170 "same structure. Resetting write_data_fn to NULL."); |
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171 } |
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172 |
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173 #if defined(PNG_WRITE_FLUSH_SUPPORTED) |
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174 png_ptr->output_flush_fn = NULL; |
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175 #endif |
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176 } |
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177 #endif /* PNG_READ_SUPPORTED */ |