src/png/pngwio.c

   1
   2 /* pngwio.c - functions for data output
   3  *
   4  * Last changed in libpng 1.5.0 [January 6, 2011]
   5  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
   6  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
   7  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
   8  *
   9  * This code is released under the libpng license.
  10  * For conditions of distribution and use, see the disclaimer
  11  * and license in png.h
  12  *
  13  * This file provides a location for all output.  Users who need
  14  * special handling are expected to write functions that have the same
  15  * arguments as these and perform similar functions, but that possibly
  16  * use different output methods.  Note that you shouldn't change these
  17  * functions, but rather write replacement functions and then change
  18  * them at run time with png_set_write_fn(...).
  19  */
  20
  21 #include "pngpriv.h"
  22
  23 #ifdef PNG_WRITE_SUPPORTED
  24
  25 /* Write the data to whatever output you are using.  The default routine
  26  * writes to a file pointer.  Note that this routine sometimes gets called
  27  * with very small lengths, so you should implement some kind of simple
  28  * buffering if you are using unbuffered writes.  This should never be asked
  29  * to write more than 64K on a 16 bit machine.
  30  */
  31
  32 void /* PRIVATE */
  33 png_write_data(png_structp png_ptr, png_const_bytep data, png_size_t length)
  34 {
  35    /* NOTE: write_data_fn must not change the buffer! */
  36    if (png_ptr->write_data_fn != NULL )
  37       (*(png_ptr->write_data_fn))(png_ptr, (png_bytep)data, length);
  38
  39    else
  40       png_error(png_ptr, "Call to NULL write function");
  41 }
  42
  43 #ifdef PNG_STDIO_SUPPORTED
  44 /* This is the function that does the actual writing of data.  If you are
  45  * not writing to a standard C stream, you should create a replacement
  46  * write_data function and use it at run time with png_set_write_fn(), rather
  47  * than changing the library.
  48  */
  49 #ifndef USE_FAR_KEYWORD
  50 void PNGCBAPI
  51 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  52 {
  53    png_size_t check;
  54
  55    if (png_ptr == NULL)
  56       return;
  57
  58    check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
  59
  60    if (check != length)
  61       png_error(png_ptr, "Write Error");
  62 }
  63 #else
  64 /* This is the model-independent version. Since the standard I/O library
  65  * can't handle far buffers in the medium and small models, we have to copy
  66  * the data.
  67  */
  68
  69 #define NEAR_BUF_SIZE 1024
  70 #define MIN(a,b) (a <= b ? a : b)
  71
  72 void PNGCBAPI
  73 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  74 {
  75    png_uint_32 check;
  76    png_byte *near_data;  /* Needs to be "png_byte *" instead of "png_bytep" */
  77    png_FILE_p io_ptr;
  78
  79    if (png_ptr == NULL)
  80       return;
  81
  82    /* Check if data really is near. If so, use usual code. */
  83    near_data = (png_byte *)CVT_PTR_NOCHECK(data);
  84    io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
  85
  86    if ((png_bytep)near_data == data)
  87    {
  88       check = fwrite(near_data, 1, length, io_ptr);
  89    }
  90
  91    else
  92    {
  93       png_byte buf[NEAR_BUF_SIZE];
  94       png_size_t written, remaining, err;
  95       check = 0;
  96       remaining = length;
  97
  98       do
  99       {
 100          written = MIN(NEAR_BUF_SIZE, remaining);
 101          png_memcpy(buf, data, written); /* Copy far buffer to near buffer */
 102          err = fwrite(buf, 1, written, io_ptr);
 103
 104          if (err != written)
 105             break;
 106
 107          else
 108             check += err;
 109
 110          data += written;
 111          remaining -= written;
 112       }
 113       while (remaining != 0);
 114    }
 115
 116    if (check != length)
 117       png_error(png_ptr, "Write Error");
 118 }
 119
 120 #endif
 121 #endif
 122
 123 /* This function is called to output any data pending writing (normally
 124  * to disk).  After png_flush is called, there should be no data pending
 125  * writing in any buffers.
 126  */
 127 #ifdef PNG_WRITE_FLUSH_SUPPORTED
 128 void /* PRIVATE */
 129 png_flush(png_structp png_ptr)
 130 {
 131    if (png_ptr->output_flush_fn != NULL)
 132       (*(png_ptr->output_flush_fn))(png_ptr);
 133 }
 134
 135 #  ifdef PNG_STDIO_SUPPORTED
 136 void PNGCBAPI
 137 png_default_flush(png_structp png_ptr)
 138 {
 139    png_FILE_p io_ptr;
 140
 141    if (png_ptr == NULL)
 142       return;
 143
 144    io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
 145    fflush(io_ptr);
 146 }
 147 #  endif
 148 #endif
 149
 150 /* This function allows the application to supply new output functions for
 151  * libpng if standard C streams aren't being used.
 152  *
 153  * This function takes as its arguments:
 154  * png_ptr       - pointer to a png output data structure
 155  * io_ptr        - pointer to user supplied structure containing info about
 156  *                 the output functions.  May be NULL.
 157  * write_data_fn - pointer to a new output function that takes as its
 158  *                 arguments a pointer to a png_struct, a pointer to
 159  *                 data to be written, and a 32-bit unsigned int that is
 160  *                 the number of bytes to be written.  The new write
 161  *                 function should call png_error(png_ptr, "Error msg")
 162  *                 to exit and output any fatal error messages.  May be
 163  *                 NULL, in which case libpng's default function will
 164  *                 be used.
 165  * flush_data_fn - pointer to a new flush function that takes as its
 166  *                 arguments a pointer to a png_struct.  After a call to
 167  *                 the flush function, there should be no data in any buffers
 168  *                 or pending transmission.  If the output method doesn't do
 169  *                 any buffering of output, a function prototype must still be
 170  *                 supplied although it doesn't have to do anything.  If
 171  *                 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
 172  *                 time, output_flush_fn will be ignored, although it must be
 173  *                 supplied for compatibility.  May be NULL, in which case
 174  *                 libpng's default function will be used, if
 175  *                 PNG_WRITE_FLUSH_SUPPORTED is defined.  This is not
 176  *                 a good idea if io_ptr does not point to a standard
 177  *                 *FILE structure.
 178  */
 179 void PNGAPI
 180 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
 181     png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
 182 {
 183    if (png_ptr == NULL)
 184       return;
 185
 186    png_ptr->io_ptr = io_ptr;
 187
 188 #ifdef PNG_STDIO_SUPPORTED
 189    if (write_data_fn != NULL)
 190       png_ptr->write_data_fn = write_data_fn;
 191
 192    else
 193       png_ptr->write_data_fn = png_default_write_data;
 194 #else
 195    png_ptr->write_data_fn = write_data_fn;
 196 #endif
 197
 198 #ifdef PNG_WRITE_FLUSH_SUPPORTED
 199 #  ifdef PNG_STDIO_SUPPORTED
 200
 201    if (output_flush_fn != NULL)
 202       png_ptr->output_flush_fn = output_flush_fn;
 203
 204    else
 205       png_ptr->output_flush_fn = png_default_flush;
 206
 207 #  else
 208    png_ptr->output_flush_fn = output_flush_fn;
 209 #  endif
 210 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
 211
 212    /* It is an error to read while writing a png file */
 213    if (png_ptr->read_data_fn != NULL)
 214    {
 215       png_ptr->read_data_fn = NULL;
 216
 217       png_warning(png_ptr,
 218           "Can't set both read_data_fn and write_data_fn in the"
 219           " same structure");
 220    }
 221 }
 222
 223 #ifdef USE_FAR_KEYWORD
 224 #  ifdef _MSC_VER
 225 void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
 226 {
 227    void *near_ptr;
 228    void FAR *far_ptr;
 229    FP_OFF(near_ptr) = FP_OFF(ptr);
 230    far_ptr = (void FAR *)near_ptr;
 231
 232    if (check != 0)
 233       if (FP_SEG(ptr) != FP_SEG(far_ptr))
 234          png_error(png_ptr, "segment lost in conversion");
 235
 236    return(near_ptr);
 237 }
 238 #  else
 239 void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
 240 {
 241    void *near_ptr;
 242    void FAR *far_ptr;
 243    near_ptr = (void FAR *)ptr;
 244    far_ptr = (void FAR *)near_ptr;
 245
 246    if (check != 0)
 247       if (far_ptr != ptr)
 248          png_error(png_ptr, "segment lost in conversion");
 249
 250    return(near_ptr);
 251 }
 252 #  endif
 253 #endif
 254 #endif /* PNG_WRITE_SUPPORTED */