src/png/pngwio.c

   1
   2 /* pngwio.c - functions for data output
   3  *
   4  * Last changed in libpng 1.2.13 November 13, 2006
   5  * For conditions of distribution and use, see copyright notice in png.h
   6  * Copyright (c) 1998-2006 Glenn Randers-Pehrson
   7  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
   8  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
   9  *
  10  * This file provides a location for all output.  Users who need
  11  * special handling are expected to write functions that have the same
  12  * arguments as these and perform similar functions, but that possibly
  13  * use different output methods.  Note that you shouldn't change these
  14  * functions, but rather write replacement functions and then change
  15  * them at run time with png_set_write_fn(...).
  16  */
  17
  18 #define PNG_INTERNAL
  19 #include "png.h"
  20 #ifdef PNG_WRITE_SUPPORTED
  21
  22 /* Write the data to whatever output you are using.  The default routine
  23    writes to a file pointer.  Note that this routine sometimes gets called
  24    with very small lengths, so you should implement some kind of simple
  25    buffering if you are using unbuffered writes.  This should never be asked
  26    to write more than 64K on a 16 bit machine.  */
  27
  28 void /* PRIVATE */
  29 png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  30 {
  31    if (png_ptr->write_data_fn != NULL )
  32       (*(png_ptr->write_data_fn))(png_ptr, data, length);
  33    else
  34       png_error(png_ptr, "Call to NULL write function");
  35 }
  36
  37 #if !defined(PNG_NO_STDIO)
  38 /* This is the function that does the actual writing of data.  If you are
  39    not writing to a standard C stream, you should create a replacement
  40    write_data function and use it at run time with png_set_write_fn(), rather
  41    than changing the library. */
  42 #ifndef USE_FAR_KEYWORD
  43 void PNGAPI
  44 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  45 {
  46    png_uint_32 check;
  47
  48    if(png_ptr == NULL) return;
  49 #if defined(_WIN32_WCE)
  50    if ( !WriteFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
  51       check = 0;
  52 #else
  53    check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
  54 #endif
  55    if (check != length)
  56       png_error(png_ptr, "Write Error");
  57 }
  58 #else
  59 /* this is the model-independent version. Since the standard I/O library
  60    can't handle far buffers in the medium and small models, we have to copy
  61    the data.
  62 */
  63
  64 #define NEAR_BUF_SIZE 1024
  65 #define MIN(a,b) (a <= b ? a : b)
  66
  67 void PNGAPI
  68 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  69 {
  70    png_uint_32 check;
  71    png_byte *near_data;  /* Needs to be "png_byte *" instead of "png_bytep" */
  72    png_FILE_p io_ptr;
  73
  74    if(png_ptr == NULL) return;
  75    /* Check if data really is near. If so, use usual code. */
  76    near_data = (png_byte *)CVT_PTR_NOCHECK(data);
  77    io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
  78    if ((png_bytep)near_data == data)
  79    {
  80 #if defined(_WIN32_WCE)
  81       if ( !WriteFile(io_ptr, near_data, length, &check, NULL) )
  82          check = 0;
  83 #else
  84       check = fwrite(near_data, 1, length, io_ptr);
  85 #endif
  86    }
  87    else
  88    {
  89       png_byte buf[NEAR_BUF_SIZE];
  90       png_size_t written, remaining, err;
  91       check = 0;
  92       remaining = length;
  93       do
  94       {
  95          written = MIN(NEAR_BUF_SIZE, remaining);
  96          png_memcpy(buf, data, written); /* copy far buffer to near buffer */
  97 #if defined(_WIN32_WCE)
  98          if ( !WriteFile(io_ptr, buf, written, &err, NULL) )
  99             err = 0;
 100 #else
 101          err = fwrite(buf, 1, written, io_ptr);
 102 #endif
 103          if (err != written)
 104             break;
 105          else
 106             check += err;
 107          data += written;
 108          remaining -= written;
 109       }
 110       while (remaining != 0);
 111    }
 112    if (check != length)
 113       png_error(png_ptr, "Write Error");
 114 }
 115
 116 #endif
 117 #endif
 118
 119 /* This function is called to output any data pending writing (normally
 120    to disk).  After png_flush is called, there should be no data pending
 121    writing in any buffers. */
 122 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 123 void /* PRIVATE */
 124 png_flush(png_structp png_ptr)
 125 {
 126    if (png_ptr->output_flush_fn != NULL)
 127       (*(png_ptr->output_flush_fn))(png_ptr);
 128 }
 129
 130 #if !defined(PNG_NO_STDIO)
 131 void PNGAPI
 132 png_default_flush(png_structp png_ptr)
 133 {
 134 #if !defined(_WIN32_WCE)
 135    png_FILE_p io_ptr;
 136 #endif
 137    if(png_ptr == NULL) return;
 138 #if !defined(_WIN32_WCE)
 139    io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
 140    if (io_ptr != NULL)
 141       fflush(io_ptr);
 142 #endif
 143 }
 144 #endif
 145 #endif
 146
 147 /* This function allows the application to supply new output functions for
 148    libpng if standard C streams aren't being used.
 149
 150    This function takes as its arguments:
 151    png_ptr       - pointer to a png output data structure
 152    io_ptr        - pointer to user supplied structure containing info about
 153                    the output functions.  May be NULL.
 154    write_data_fn - pointer to a new output function that takes as its
 155                    arguments a pointer to a png_struct, a pointer to
 156                    data to be written, and a 32-bit unsigned int that is
 157                    the number of bytes to be written.  The new write
 158                    function should call png_error(png_ptr, "Error msg")
 159                    to exit and output any fatal error messages.
 160    flush_data_fn - pointer to a new flush function that takes as its
 161                    arguments a pointer to a png_struct.  After a call to
 162                    the flush function, there should be no data in any buffers
 163                    or pending transmission.  If the output method doesn't do
 164                    any buffering of ouput, a function prototype must still be
 165                    supplied although it doesn't have to do anything.  If
 166                    PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
 167                    time, output_flush_fn will be ignored, although it must be
 168                    supplied for compatibility. */
 169 void PNGAPI
 170 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
 171    png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
 172 {
 173    if(png_ptr == NULL) return;
 174    png_ptr->io_ptr = io_ptr;
 175
 176 #if !defined(PNG_NO_STDIO)
 177    if (write_data_fn != NULL)
 178       png_ptr->write_data_fn = write_data_fn;
 179    else
 180       png_ptr->write_data_fn = png_default_write_data;
 181 #else
 182    png_ptr->write_data_fn = write_data_fn;
 183 #endif
 184
 185 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 186 #if !defined(PNG_NO_STDIO)
 187    if (output_flush_fn != NULL)
 188       png_ptr->output_flush_fn = output_flush_fn;
 189    else
 190       png_ptr->output_flush_fn = png_default_flush;
 191 #else
 192    png_ptr->output_flush_fn = output_flush_fn;
 193 #endif
 194 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
 195
 196    /* It is an error to read while writing a png file */
 197    if (png_ptr->read_data_fn != NULL)
 198    {
 199       png_ptr->read_data_fn = NULL;
 200       png_warning(png_ptr,
 201          "Attempted to set both read_data_fn and write_data_fn in");
 202       png_warning(png_ptr,
 203          "the same structure.  Resetting read_data_fn to NULL.");
 204    }
 205 }
 206
 207 #if defined(USE_FAR_KEYWORD)
 208 #if defined(_MSC_VER)
 209 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
 210 {
 211    void *near_ptr;
 212    void FAR *far_ptr;
 213    FP_OFF(near_ptr) = FP_OFF(ptr);
 214    far_ptr = (void FAR *)near_ptr;
 215    if(check != 0)
 216       if(FP_SEG(ptr) != FP_SEG(far_ptr))
 217          png_error(png_ptr,"segment lost in conversion");
 218    return(near_ptr);
 219 }
 220 #  else
 221 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
 222 {
 223    void *near_ptr;
 224    void FAR *far_ptr;
 225    near_ptr = (void FAR *)ptr;
 226    far_ptr = (void FAR *)near_ptr;
 227    if(check != 0)
 228       if(far_ptr != ptr)
 229          png_error(png_ptr,"segment lost in conversion");
 230    return(near_ptr);
 231 }
 232 #   endif
 233 #   endif
 234 #endif /* PNG_WRITE_SUPPORTED */