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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 1.2.30 [August 15, 2008] |
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5 * For conditions of distribution and use, see copyright notice in png.h |
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6 * Copyright (c) 1998-2008 Glenn Randers-Pehrson |
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7 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) |
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8 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) |
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9 * |
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10 * This file provides a location for all input. Users who need |
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11 * special handling are expected to write a function that has the same |
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12 * arguments as this and performs a similar function, but that possibly |
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13 * has a different input method. Note that you shouldn't change this |
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14 * function, but rather write a replacement function and then make |
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15 * libpng use it at run time with png_set_read_fn(...). |
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16 */ |
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17 |
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18 #define PNG_INTERNAL |
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19 #include "png.h" |
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20 #if defined(PNG_READ_SUPPORTED) |
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21 |
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22 /* Read the data from whatever input you are using. The default routine |
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23 reads from a file pointer. Note that this routine sometimes gets called |
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24 with very small lengths, so you should implement some kind of simple |
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25 buffering if you are using unbuffered reads. This should never be asked |
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26 to read more then 64K on a 16 bit machine. */ |
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27 void /* PRIVATE */ |
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28 png_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
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29 { |
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30 png_debug1(4, "reading %d bytes\n", (int)length); |
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31 if (png_ptr->read_data_fn != NULL) |
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32 (*(png_ptr->read_data_fn))(png_ptr, data, length); |
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33 else |
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34 png_error(png_ptr, "Call to NULL read function"); |
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35 } |
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36 |
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37 #if !defined(PNG_NO_STDIO) |
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38 /* This is the function that does the actual reading of data. If you are |
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39 not reading from a standard C stream, you should create a replacement |
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40 read_data function and use it at run time with png_set_read_fn(), rather |
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41 than changing the library. */ |
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42 #ifndef USE_FAR_KEYWORD |
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43 void PNGAPI |
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44 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
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45 { |
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46 png_size_t check; |
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47 |
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48 if (png_ptr == NULL) return; |
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49 /* fread() returns 0 on error, so it is OK to store this in a png_size_t |
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50 * instead of an int, which is what fread() actually returns. |
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51 */ |
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52 #if defined(_WIN32_WCE) |
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53 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) ) |
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54 check = 0; |
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55 #else |
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56 check = (png_size_t)fread(data, (png_size_t)1, length, |
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57 (png_FILE_p)png_ptr->io_ptr); |
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58 #endif |
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59 |
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60 if (check != length) |
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61 png_error(png_ptr, "Read Error"); |
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62 } |
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63 #else |
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64 /* this is the model-independent version. Since the standard I/O library |
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65 can't handle far buffers in the medium and small models, we have to copy |
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66 the data. |
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67 */ |
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68 |
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69 #define NEAR_BUF_SIZE 1024 |
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70 #define MIN(a,b) (a <= b ? a : b) |
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71 |
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72 static void PNGAPI |
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73 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
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74 { |
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75 int check; |
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76 png_byte *n_data; |
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77 png_FILE_p io_ptr; |
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78 |
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79 if (png_ptr == NULL) return; |
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80 /* Check if data really is near. If so, use usual code. */ |
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81 n_data = (png_byte *)CVT_PTR_NOCHECK(data); |
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82 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr); |
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83 if ((png_bytep)n_data == data) |
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84 { |
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85 #if defined(_WIN32_WCE) |
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86 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) ) |
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87 check = 0; |
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88 #else |
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89 check = fread(n_data, 1, length, io_ptr); |
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90 #endif |
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91 } |
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92 else |
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93 { |
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94 png_byte buf[NEAR_BUF_SIZE]; |
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95 png_size_t read, remaining, err; |
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96 check = 0; |
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97 remaining = length; |
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98 do |
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99 { |
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100 read = MIN(NEAR_BUF_SIZE, remaining); |
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101 #if defined(_WIN32_WCE) |
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102 if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) ) |
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103 err = 0; |
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104 #else |
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105 err = fread(buf, (png_size_t)1, read, io_ptr); |
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106 #endif |
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107 png_memcpy(data, buf, read); /* copy far buffer to near buffer */ |
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108 if (err != read) |
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109 break; |
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110 else |
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111 check += err; |
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112 data += read; |
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113 remaining -= read; |
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114 } |
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115 while (remaining != 0); |
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116 } |
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117 if ((png_uint_32)check != (png_uint_32)length) |
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118 png_error(png_ptr, "read Error"); |
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119 } |
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120 #endif |
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121 #endif |
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122 |
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123 /* This function allows the application to supply a new input function |
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124 for libpng if standard C streams aren't being used. |
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125 |
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126 This function takes as its arguments: |
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127 png_ptr - pointer to a png input data structure |
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128 io_ptr - pointer to user supplied structure containing info about |
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129 the input functions. May be NULL. |
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130 read_data_fn - pointer to a new input function that takes as its |
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131 arguments a pointer to a png_struct, a pointer to |
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132 a location where input data can be stored, and a 32-bit |
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133 unsigned int that is the number of bytes to be read. |
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134 To exit and output any fatal error messages the new write |
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135 function should call png_error(png_ptr, "Error msg"). */ |
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136 void PNGAPI |
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137 png_set_read_fn(png_structp png_ptr, png_voidp io_ptr, |
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138 png_rw_ptr read_data_fn) |
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139 { |
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140 if (png_ptr == NULL) return; |
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141 png_ptr->io_ptr = io_ptr; |
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142 |
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143 #if !defined(PNG_NO_STDIO) |
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144 if (read_data_fn != NULL) |
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145 png_ptr->read_data_fn = read_data_fn; |
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146 else |
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147 png_ptr->read_data_fn = png_default_read_data; |
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148 #else |
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149 png_ptr->read_data_fn = read_data_fn; |
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150 #endif |
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151 |
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152 /* It is an error to write to a read device */ |
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153 if (png_ptr->write_data_fn != NULL) |
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154 { |
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155 png_ptr->write_data_fn = NULL; |
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156 png_warning(png_ptr, |
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157 "It's an error to set both read_data_fn and write_data_fn in the "); |
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158 png_warning(png_ptr, |
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159 "same structure. Resetting write_data_fn to NULL."); |
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160 } |
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161 |
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162 #if defined(PNG_WRITE_FLUSH_SUPPORTED) |
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163 png_ptr->output_flush_fn = NULL; |
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164 #endif |
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165 } |
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166 #endif /* PNG_READ_SUPPORTED */ |