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2296
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1
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2 /* pngwio.c - functions for data output
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3 *
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4 * Last changed in libpng 1.6.9 [February 6, 2014]
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5 * Copyright (c) 1998-2014 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 output. Users who need
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14 * special handling are expected to write functions that have the same
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15 * arguments as these and perform similar functions, but that possibly
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16 * use different output methods. Note that you shouldn't change these
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17 * functions, but rather write replacement functions and then change
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18 * them at run time with png_set_write_fn(...).
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19 */
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20
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21 #include "pngpriv.h"
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22
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23 #ifdef PNG_WRITE_SUPPORTED
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24
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25 /* Write the data to whatever output you are using. The default routine
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26 * writes to 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 writes. This should never be asked
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29 * to write more than 64K on a 16 bit machine.
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30 */
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31
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32 void /* PRIVATE */
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33 png_write_data(png_structrp png_ptr, png_const_bytep data, png_size_t length)
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34 {
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35 /* NOTE: write_data_fn must not change the buffer! */
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36 if (png_ptr->write_data_fn != NULL )
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37 (*(png_ptr->write_data_fn))(png_ptr, png_constcast(png_bytep,data),
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38 length);
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39
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40 else
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41 png_error(png_ptr, "Call to NULL write function");
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42 }
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43
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44 #ifdef PNG_STDIO_SUPPORTED
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45 /* This is the function that does the actual writing of data. If you are
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46 * not writing to a standard C stream, you should create a replacement
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47 * write_data function and use it at run time with png_set_write_fn(), rather
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48 * than changing the library.
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49 */
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50 void PNGCBAPI
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51 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
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52 {
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53 png_size_t check;
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54
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55 if (png_ptr == NULL)
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56 return;
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57
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58 check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
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59
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60 if (check != length)
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61 png_error(png_ptr, "Write Error");
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62 }
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63 #endif
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64
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65 /* This function is called to output any data pending writing (normally
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66 * to disk). After png_flush is called, there should be no data pending
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67 * writing in any buffers.
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68 */
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69 #ifdef PNG_WRITE_FLUSH_SUPPORTED
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70 void /* PRIVATE */
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71 png_flush(png_structrp png_ptr)
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72 {
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73 if (png_ptr->output_flush_fn != NULL)
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74 (*(png_ptr->output_flush_fn))(png_ptr);
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75 }
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76
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77 # ifdef PNG_STDIO_SUPPORTED
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78 void PNGCBAPI
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79 png_default_flush(png_structp png_ptr)
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80 {
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81 png_FILE_p io_ptr;
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82
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83 if (png_ptr == NULL)
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84 return;
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85
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86 io_ptr = png_voidcast(png_FILE_p, (png_ptr->io_ptr));
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87 fflush(io_ptr);
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88 }
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89 # endif
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90 #endif
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91
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92 /* This function allows the application to supply new output functions for
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93 * libpng if standard C streams aren't being used.
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94 *
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95 * This function takes as its arguments:
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96 * png_ptr - pointer to a png output data structure
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97 * io_ptr - pointer to user supplied structure containing info about
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98 * the output functions. May be NULL.
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99 * write_data_fn - pointer to a new output function that takes as its
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100 * arguments a pointer to a png_struct, a pointer to
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101 * data to be written, and a 32-bit unsigned int that is
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102 * the number of bytes to be written. The new write
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103 * function should call png_error(png_ptr, "Error msg")
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104 * to exit and output any fatal error messages. May be
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105 * NULL, in which case libpng's default function will
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106 * be used.
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107 * flush_data_fn - pointer to a new flush function that takes as its
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108 * arguments a pointer to a png_struct. After a call to
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109 * the flush function, there should be no data in any buffers
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110 * or pending transmission. If the output method doesn't do
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111 * any buffering of output, a function prototype must still be
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112 * supplied although it doesn't have to do anything. If
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113 * PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
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114 * time, output_flush_fn will be ignored, although it must be
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115 * supplied for compatibility. May be NULL, in which case
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116 * libpng's default function will be used, if
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117 * PNG_WRITE_FLUSH_SUPPORTED is defined. This is not
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118 * a good idea if io_ptr does not point to a standard
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119 * *FILE structure.
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120 */
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121 void PNGAPI
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122 png_set_write_fn(png_structrp png_ptr, png_voidp io_ptr,
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123 png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
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124 {
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125 if (png_ptr == NULL)
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126 return;
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127
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128 png_ptr->io_ptr = io_ptr;
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129
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130 #ifdef PNG_STDIO_SUPPORTED
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131 if (write_data_fn != NULL)
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132 png_ptr->write_data_fn = write_data_fn;
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133
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134 else
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135 png_ptr->write_data_fn = png_default_write_data;
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136 #else
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137 png_ptr->write_data_fn = write_data_fn;
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138 #endif
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139
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140 #ifdef PNG_WRITE_FLUSH_SUPPORTED
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141 # ifdef PNG_STDIO_SUPPORTED
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142
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143 if (output_flush_fn != NULL)
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144 png_ptr->output_flush_fn = output_flush_fn;
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145
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146 else
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147 png_ptr->output_flush_fn = png_default_flush;
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148
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149 # else
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150 png_ptr->output_flush_fn = output_flush_fn;
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151 # endif
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152 #else
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153 PNG_UNUSED(output_flush_fn)
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154 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
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155
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156 #ifdef PNG_READ_SUPPORTED
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157 /* It is an error to read while writing a png file */
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158 if (png_ptr->read_data_fn != NULL)
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159 {
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160 png_ptr->read_data_fn = NULL;
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161
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162 png_warning(png_ptr,
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163 "Can't set both read_data_fn and write_data_fn in the"
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164 " same structure");
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165 }
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166 #endif
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167 }
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168 #endif /* PNG_WRITE_SUPPORTED */
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