src/png/pngwio.c

   1
   2 /* pngwio.c - functions for data output
   3  *
   4  * Last changed in libpng 1.4.0 [January 3, 2010]
   5  * Copyright (c) 1998-2010 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 #define PNG_NO_PEDANTIC_WARNINGS
  22 #include "png.h"
  23 #ifdef PNG_WRITE_SUPPORTED
  24 #include "pngpriv.h"
  25
  26 /* Write the data to whatever output you are using.  The default routine
  27  * writes to a file pointer.  Note that this routine sometimes gets called
  28  * with very small lengths, so you should implement some kind of simple
  29  * buffering if you are using unbuffered writes.  This should never be asked
  30  * to write more than 64K on a 16 bit machine.
  31  */
  32
  33 void /* PRIVATE */
  34 png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  35 {
  36    if (png_ptr->write_data_fn != NULL )
  37       (*(png_ptr->write_data_fn))(png_ptr, data, length);
  38    else
  39       png_error(png_ptr, "Call to NULL write function");
  40 }
  41
  42 #ifdef PNG_STDIO_SUPPORTED
  43 /* This is the function that does the actual writing of data.  If you are
  44  * not writing to a standard C stream, you should create a replacement
  45  * write_data function and use it at run time with png_set_write_fn(), rather
  46  * than changing the library.
  47  */
  48 #ifndef USE_FAR_KEYWORD
  49 void PNGAPI
  50 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  51 {
  52    png_uint_32 check;
  53
  54    if (png_ptr == NULL)
  55       return;
  56    check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
  57    if (check != length)
  58       png_error(png_ptr, "Write Error");
  59 }
  60 #else
  61 /* This is the model-independent version. Since the standard I/O library
  62  * can't handle far buffers in the medium and small models, we have to copy
  63  * the data.
  64  */
  65
  66 #define NEAR_BUF_SIZE 1024
  67 #define MIN(a,b) (a <= b ? a : b)
  68
  69 void PNGAPI
  70 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  71 {
  72    png_uint_32 check;
  73    png_byte *near_data;  /* Needs to be "png_byte *" instead of "png_bytep" */
  74    png_FILE_p io_ptr;
  75
  76    if (png_ptr == NULL)
  77       return;
  78    /* Check if data really is near. If so, use usual code. */
  79    near_data = (png_byte *)CVT_PTR_NOCHECK(data);
  80    io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
  81    if ((png_bytep)near_data == data)
  82    {
  83       check = fwrite(near_data, 1, length, io_ptr);
  84    }
  85    else
  86    {
  87       png_byte buf[NEAR_BUF_SIZE];
  88       png_size_t written, remaining, err;
  89       check = 0;
  90       remaining = length;
  91       do
  92       {
  93          written = MIN(NEAR_BUF_SIZE, remaining);
  94          png_memcpy(buf, data, written); /* Copy far buffer to near buffer */
  95          err = fwrite(buf, 1, written, io_ptr);
  96          if (err != written)
  97             break;
  98
  99          else
 100             check += err;
 101
 102          data += written;
 103          remaining -= written;
 104       }
 105       while (remaining != 0);
 106    }
 107    if (check != length)
 108       png_error(png_ptr, "Write Error");
 109 }
 110
 111 #endif
 112 #endif
 113
 114 /* This function is called to output any data pending writing (normally
 115  * to disk).  After png_flush is called, there should be no data pending
 116  * writing in any buffers.
 117  */
 118 #ifdef PNG_WRITE_FLUSH_SUPPORTED
 119 void /* PRIVATE */
 120 png_flush(png_structp png_ptr)
 121 {
 122    if (png_ptr->output_flush_fn != NULL)
 123       (*(png_ptr->output_flush_fn))(png_ptr);
 124 }
 125
 126 #ifdef PNG_STDIO_SUPPORTED
 127 void PNGAPI
 128 png_default_flush(png_structp png_ptr)
 129 {
 130    png_FILE_p io_ptr;
 131    if (png_ptr == NULL)
 132       return;
 133    io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
 134    fflush(io_ptr);
 135 }
 136 #endif
 137 #endif
 138
 139 /* This function allows the application to supply new output functions for
 140  * libpng if standard C streams aren't being used.
 141  *
 142  * This function takes as its arguments:
 143  * png_ptr       - pointer to a png output data structure
 144  * io_ptr        - pointer to user supplied structure containing info about
 145  *                 the output functions.  May be NULL.
 146  * write_data_fn - pointer to a new output function that takes as its
 147  *                 arguments a pointer to a png_struct, a pointer to
 148  *                 data to be written, and a 32-bit unsigned int that is
 149  *                 the number of bytes to be written.  The new write
 150  *                 function should call png_error(png_ptr, "Error msg")
 151  *                 to exit and output any fatal error messages.  May be
 152  *                 NULL, in which case libpng's default function will
 153  *                 be used.
 154  * flush_data_fn - pointer to a new flush function that takes as its
 155  *                 arguments a pointer to a png_struct.  After a call to
 156  *                 the flush function, there should be no data in any buffers
 157  *                 or pending transmission.  If the output method doesn't do
 158  *                 any buffering of output, a function prototype must still be
 159  *                 supplied although it doesn't have to do anything.  If
 160  *                 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
 161  *                 time, output_flush_fn will be ignored, although it must be
 162  *                 supplied for compatibility.  May be NULL, in which case
 163  *                 libpng's default function will be used, if
 164  *                 PNG_WRITE_FLUSH_SUPPORTED is defined.  This is not
 165  *                 a good idea if io_ptr does not point to a standard
 166  *                 *FILE structure.
 167  */
 168 void PNGAPI
 169 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
 170    png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
 171 {
 172    if (png_ptr == NULL)
 173       return;
 174
 175    png_ptr->io_ptr = io_ptr;
 176
 177 #ifdef PNG_STDIO_SUPPORTED
 178    if (write_data_fn != NULL)
 179       png_ptr->write_data_fn = write_data_fn;
 180
 181    else
 182       png_ptr->write_data_fn = png_default_write_data;
 183 #else
 184    png_ptr->write_data_fn = write_data_fn;
 185 #endif
 186
 187 #ifdef PNG_WRITE_FLUSH_SUPPORTED
 188 #ifdef PNG_STDIO_SUPPORTED
 189    if (output_flush_fn != NULL)
 190       png_ptr->output_flush_fn = output_flush_fn;
 191
 192    else
 193       png_ptr->output_flush_fn = png_default_flush;
 194 #else
 195    png_ptr->output_flush_fn = output_flush_fn;
 196 #endif
 197 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
 198
 199    /* It is an error to read while writing a png file */
 200    if (png_ptr->read_data_fn != NULL)
 201    {
 202       png_ptr->read_data_fn = NULL;
 203       png_warning(png_ptr,
 204          "Attempted to set both read_data_fn and write_data_fn in");
 205       png_warning(png_ptr,
 206          "the same structure.  Resetting read_data_fn to NULL");
 207    }
 208 }
 209
 210 #ifdef USE_FAR_KEYWORD
 211 #ifdef _MSC_VER
 212 void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
 213 {
 214    void *near_ptr;
 215    void FAR *far_ptr;
 216    FP_OFF(near_ptr) = FP_OFF(ptr);
 217    far_ptr = (void FAR *)near_ptr;
 218
 219    if (check != 0)
 220       if (FP_SEG(ptr) != FP_SEG(far_ptr))
 221          png_error(png_ptr, "segment lost in conversion");
 222
 223    return(near_ptr);
 224 }
 225 #  else
 226 void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
 227 {
 228    void *near_ptr;
 229    void FAR *far_ptr;
 230    near_ptr = (void FAR *)ptr;
 231    far_ptr = (void FAR *)near_ptr;
 232
 233    if (check != 0)
 234       if (far_ptr != ptr)
 235          png_error(png_ptr, "segment lost in conversion");
 236
 237    return(near_ptr);
 238 }
 239 #   endif
 240 #   endif
 241 #endif /* PNG_WRITE_SUPPORTED */