src/png/pngwio.c

   1
   2 /* pngwio.c - functions for data output
   3  *
   4  * libpng 1.0.3 - January 14, 1999
   5  * For conditions of distribution and use, see copyright notice in png.h
   6  * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
   7  * Copyright (c) 1996, 1997 Andreas Dilger
   8  * Copyright (c) 1998, 1999 Glenn Randers-Pehrson
   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
  21 /* Write the data to whatever output you are using.  The default routine
  22    writes to a file pointer.  Note that this routine sometimes gets called
  23    with very small lengths, so you should implement some kind of simple
  24    buffering if you are using unbuffered writes.  This should never be asked
  25    to write more than 64K on a 16 bit machine.  */
  26
  27 void
  28 png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  29 {
  30    if (png_ptr->write_data_fn != NULL )
  31       (*(png_ptr->write_data_fn))(png_ptr, data, length);
  32    else
  33       png_error(png_ptr, "Call to NULL write function");
  34 }
  35
  36 #if !defined(PNG_NO_STDIO)
  37 /* This is the function that does the actual writing of data.  If you are
  38    not writing to a standard C stream, you should create a replacement
  39    write_data function and use it at run time with png_set_write_fn(), rather
  40    than changing the library. */
  41 #ifndef USE_FAR_KEYWORD
  42 static void
  43 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  44 {
  45    png_uint_32 check;
  46
  47    check = fwrite(data, 1, length, (FILE *)(png_ptr->io_ptr));
  48    if (check != length)
  49    {
  50       png_error(png_ptr, "Write Error");
  51    }
  52 }
  53 #else
  54 /* this is the model-independent version. Since the standard I/O library
  55    can't handle far buffers in the medium and small models, we have to copy
  56    the data.
  57 */
  58
  59 #define NEAR_BUF_SIZE 1024
  60 #define MIN(a,b) (a <= b ? a : b)
  61
  62 static void
  63 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  64 {
  65    png_uint_32 check;
  66    png_byte *near_data;  /* Needs to be "png_byte *" instead of "png_bytep" */
  67    FILE *io_ptr;
  68
  69    /* Check if data really is near. If so, use usual code. */
  70    near_data = (png_byte *)CVT_PTR_NOCHECK(data);
  71    io_ptr = (FILE *)CVT_PTR(png_ptr->io_ptr);
  72    if ((png_bytep)near_data == data)
  73    {
  74       check = fwrite(near_data, 1, length, io_ptr);
  75    }
  76    else
  77    {
  78       png_byte buf[NEAR_BUF_SIZE];
  79       png_size_t written, remaining, err;
  80       check = 0;
  81       remaining = length;
  82       do
  83       {
  84          written = MIN(NEAR_BUF_SIZE, remaining);
  85          png_memcpy(buf, data, written); /* copy far buffer to near buffer */
  86          err = fwrite(buf, 1, written, io_ptr);
  87          if (err != written)
  88             break;
  89          else
  90             check += err;
  91          data += written;
  92          remaining -= written;
  93       }
  94       while (remaining != 0);
  95    }
  96    if (check != length)
  97    {
  98       png_error(png_ptr, "Write Error");
  99    }
 100 }
 101
 102 #endif
 103 #endif
 104
 105 /* This function is called to output any data pending writing (normally
 106    to disk).  After png_flush is called, there should be no data pending
 107    writing in any buffers. */
 108 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 109 void
 110 png_flush(png_structp png_ptr)
 111 {
 112    if (png_ptr->output_flush_fn != NULL)
 113       (*(png_ptr->output_flush_fn))(png_ptr);
 114 }
 115
 116 #if !defined(PNG_NO_STDIO)
 117 static void
 118 png_default_flush(png_structp png_ptr)
 119 {
 120    FILE *io_ptr;
 121    io_ptr = (FILE *)CVT_PTR((png_ptr->io_ptr));
 122    if (io_ptr != NULL)
 123       fflush(io_ptr);
 124 }
 125 #endif
 126 #endif
 127
 128 /* This function allows the application to supply new output functions for
 129    libpng if standard C streams aren't being used.
 130
 131    This function takes as its arguments:
 132    png_ptr       - pointer to a png output data structure
 133    io_ptr        - pointer to user supplied structure containing info about
 134                    the output functions.  May be NULL.
 135    write_data_fn - pointer to a new output function that takes as its
 136                    arguments a pointer to a png_struct, a pointer to
 137                    data to be written, and a 32-bit unsigned int that is
 138                    the number of bytes to be written.  The new write
 139                    function should call png_error(png_ptr, "Error msg")
 140                    to exit and output any fatal error messages.
 141    flush_data_fn - pointer to a new flush function that takes as its
 142                    arguments a pointer to a png_struct.  After a call to
 143                    the flush function, there should be no data in any buffers
 144                    or pending transmission.  If the output method doesn't do
 145                    any buffering of ouput, a function prototype must still be
 146                    supplied although it doesn't have to do anything.  If
 147                    PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
 148                    time, output_flush_fn will be ignored, although it must be
 149                    supplied for compatibility. */
 150 void
 151 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
 152    png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
 153 {
 154    png_ptr->io_ptr = io_ptr;
 155
 156 #if !defined(PNG_NO_STDIO)
 157    if (write_data_fn != NULL)
 158       png_ptr->write_data_fn = write_data_fn;
 159    else
 160       png_ptr->write_data_fn = png_default_write_data;
 161 #else
 162    png_ptr->write_data_fn = write_data_fn;
 163 #endif
 164
 165 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 166 #if !defined(PNG_NO_STDIO)
 167    if (output_flush_fn != NULL)
 168       png_ptr->output_flush_fn = output_flush_fn;
 169    else
 170       png_ptr->output_flush_fn = png_default_flush;
 171 #else
 172    png_ptr->output_flush_fn = output_flush_fn;
 173 #endif
 174 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
 175
 176    /* It is an error to read while writing a png file */
 177    if (png_ptr->read_data_fn != NULL)
 178    {
 179       png_ptr->read_data_fn = NULL;
 180       png_warning(png_ptr,
 181          "Attempted to set both read_data_fn and write_data_fn in");
 182       png_warning(png_ptr,
 183          "the same structure.  Resetting read_data_fn to NULL.");
 184    }
 185 }
 186
 187 #if defined(USE_FAR_KEYWORD)
 188 #if defined(_MSC_VER)
 189 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
 190 {
 191    void *near_ptr;
 192    void FAR *far_ptr;
 193    FP_OFF(near_ptr) = FP_OFF(ptr);
 194    far_ptr = (void FAR *)near_ptr;
 195    if(check != 0)
 196       if(FP_SEG(ptr) != FP_SEG(far_ptr))
 197          png_error(png_ptr,"segment lost in conversion");
 198    return(near_ptr);
 199 }
 200 #  else
 201 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
 202 {
 203    void *near_ptr;
 204    void FAR *far_ptr;
 205    near_ptr = (void FAR *)ptr;
 206    far_ptr = (void FAR *)near_ptr;
 207    if(check != 0)
 208       if(far_ptr != ptr)
 209          png_error(png_ptr,"segment lost in conversion");
 210    return(near_ptr);
 211 }
 212 #   endif
 213 #   endif