src/png/pngwio.c

   1
   2 /* pngwio.c - functions for data output
   3  *
   4  * libpng 1.2.5rc3 - September 18, 2002
   5  * For conditions of distribution and use, see copyright notice in png.h
   6  * Copyright (c) 1998-2002 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 defined(_WIN32_WCE)
  49    if ( !WriteFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
  50       check = 0;
  51 #else
  52    check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
  53 #endif
  54    if (check != length)
  55       png_error(png_ptr, "Write Error");
  56 }
  57 #else
  58 /* this is the model-independent version. Since the standard I/O library
  59    can't handle far buffers in the medium and small models, we have to copy
  60    the data.
  61 */
  62
  63 #define NEAR_BUF_SIZE 1024
  64 #define MIN(a,b) (a <= b ? a : b)
  65
  66 void PNGAPI
  67 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  68 {
  69    png_uint_32 check;
  70    png_byte *near_data;  /* Needs to be "png_byte *" instead of "png_bytep" */
  71    png_FILE_p io_ptr;
  72
  73    /* Check if data really is near. If so, use usual code. */
  74    near_data = (png_byte *)CVT_PTR_NOCHECK(data);
  75    io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
  76    if ((png_bytep)near_data == data)
  77    {
  78 #if defined(_WIN32_WCE)
  79       if ( !WriteFile(io_ptr, near_data, length, &check, NULL) )
  80          check = 0;
  81 #else
  82       check = fwrite(near_data, 1, length, io_ptr);
  83 #endif
  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 #if defined(_WIN32_WCE)
  96          if ( !WriteFile(io_ptr, buf, written, &err, NULL) )
  97             err = 0;
  98 #else
  99          err = fwrite(buf, 1, written, io_ptr);
 100 #endif
 101          if (err != written)
 102             break;
 103          else
 104             check += err;
 105          data += written;
 106          remaining -= written;
 107       }
 108       while (remaining != 0);
 109    }
 110    if (check != length)
 111       png_error(png_ptr, "Write Error");
 112 }
 113
 114 #endif
 115 #endif
 116
 117 /* This function is called to output any data pending writing (normally
 118    to disk).  After png_flush is called, there should be no data pending
 119    writing in any buffers. */
 120 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 121 void /* PRIVATE */
 122 png_flush(png_structp png_ptr)
 123 {
 124    if (png_ptr->output_flush_fn != NULL)
 125       (*(png_ptr->output_flush_fn))(png_ptr);
 126 }
 127
 128 #if !defined(PNG_NO_STDIO)
 129 void PNGAPI
 130 png_default_flush(png_structp png_ptr)
 131 {
 132 #if !defined(_WIN32_WCE)
 133    png_FILE_p io_ptr;
 134    io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
 135    if (io_ptr != NULL)
 136       fflush(io_ptr);
 137 #endif
 138 }
 139 #endif
 140 #endif
 141
 142 /* This function allows the application to supply new output functions for
 143    libpng if standard C streams aren't being used.
 144
 145    This function takes as its arguments:
 146    png_ptr       - pointer to a png output data structure
 147    io_ptr        - pointer to user supplied structure containing info about
 148                    the output functions.  May be NULL.
 149    write_data_fn - pointer to a new output function that takes as its
 150                    arguments a pointer to a png_struct, a pointer to
 151                    data to be written, and a 32-bit unsigned int that is
 152                    the number of bytes to be written.  The new write
 153                    function should call png_error(png_ptr, "Error msg")
 154                    to exit and output any fatal error messages.
 155    flush_data_fn - pointer to a new flush function that takes as its
 156                    arguments a pointer to a png_struct.  After a call to
 157                    the flush function, there should be no data in any buffers
 158                    or pending transmission.  If the output method doesn't do
 159                    any buffering of ouput, a function prototype must still be
 160                    supplied although it doesn't have to do anything.  If
 161                    PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
 162                    time, output_flush_fn will be ignored, although it must be
 163                    supplied for compatibility. */
 164 void PNGAPI
 165 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
 166    png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
 167 {
 168    png_ptr->io_ptr = io_ptr;
 169
 170 #if !defined(PNG_NO_STDIO)
 171    if (write_data_fn != NULL)
 172       png_ptr->write_data_fn = write_data_fn;
 173    else
 174       png_ptr->write_data_fn = png_default_write_data;
 175 #else
 176    png_ptr->write_data_fn = write_data_fn;
 177 #endif
 178
 179 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 180 #if !defined(PNG_NO_STDIO)
 181    if (output_flush_fn != NULL)
 182       png_ptr->output_flush_fn = output_flush_fn;
 183    else
 184       png_ptr->output_flush_fn = png_default_flush;
 185 #else
 186    png_ptr->output_flush_fn = output_flush_fn;
 187 #endif
 188 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
 189
 190    /* It is an error to read while writing a png file */
 191    if (png_ptr->read_data_fn != NULL)
 192    {
 193       png_ptr->read_data_fn = NULL;
 194       png_warning(png_ptr,
 195          "Attempted to set both read_data_fn and write_data_fn in");
 196       png_warning(png_ptr,
 197          "the same structure.  Resetting read_data_fn to NULL.");
 198    }
 199 }
 200
 201 #if defined(USE_FAR_KEYWORD)
 202 #if defined(_MSC_VER)
 203 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
 204 {
 205    void *near_ptr;
 206    void FAR *far_ptr;
 207    FP_OFF(near_ptr) = FP_OFF(ptr);
 208    far_ptr = (void FAR *)near_ptr;
 209    if(check != 0)
 210       if(FP_SEG(ptr) != FP_SEG(far_ptr))
 211          png_error(png_ptr,"segment lost in conversion");
 212    return(near_ptr);
 213 }
 214 #  else
 215 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
 216 {
 217    void *near_ptr;
 218    void FAR *far_ptr;
 219    near_ptr = (void FAR *)ptr;
 220    far_ptr = (void FAR *)near_ptr;
 221    if(check != 0)
 222       if(far_ptr != ptr)
 223          png_error(png_ptr,"segment lost in conversion");
 224    return(near_ptr);
 225 }
 226 #   endif
 227 #   endif
 228 #endif /* PNG_WRITE_SUPPORTED */