src/png/pngwio.c

   1
   2 /* pngwio.c - functions for data output
   3  *
   4  * libpng 1.0.1
   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, Glenn Randers-Pehrson
   9  * March 15, 1998
  10  *
  11  * This file provides a location for all output.  Users which need
  12  * special handling are expected to write functions which have the same
  13  * arguments as these, and perform similar functions, but possibly use
  14  * different output methods.  Note that you shouldn't change these
  15  * functions, but rather write replacement functions and then change
  16  * them at run time with png_set_write_fn(...).
  17  */
  18
  19 #define PNG_INTERNAL
  20 #include "png.h"
  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 then 64K on a 16 bit machine.  */
  27
  28 void
  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 which 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 static void
  44 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  45 {
  46    png_uint_32 check;
  47
  48    check = fwrite(data, 1, length, (FILE *)(png_ptr->io_ptr));
  49    if (check != length)
  50    {
  51       png_error(png_ptr, "Write Error");
  52    }
  53 }
  54 #else
  55 /* this is the model-independent version. Since the standard I/O library
  56    can't handle far buffers in the medium and small models, we have to copy
  57    the data.
  58 */
  59
  60 #define NEAR_BUF_SIZE 1024
  61 #define MIN(a,b) (a <= b ? a : b)
  62
  63 static void
  64 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
  65 {
  66    png_uint_32 check;
  67    png_byte *near_data;  /* Needs to be "png_byte *" instead of "png_bytep" */
  68    FILE *io_ptr;
  69
  70    /* Check if data really is near. If so, use usual code. */
  71    near_data = (png_byte *)CVT_PTR_NOCHECK(data);
  72    io_ptr = (FILE *)CVT_PTR(png_ptr->io_ptr);
  73    if ((png_bytep)near_data == data)
  74    {
  75       check = fwrite(near_data, 1, length, io_ptr);
  76    }
  77    else
  78    {
  79       png_byte buf[NEAR_BUF_SIZE];
  80       png_size_t written, remaining, err;
  81       check = 0;
  82       remaining = length;
  83       do
  84       {
  85          written = MIN(NEAR_BUF_SIZE, remaining);
  86          png_memcpy(buf, data, written); /* copy far buffer to near buffer */
  87          err = fwrite(buf, 1, written, io_ptr);
  88          if (err != written)
  89             break;
  90          else
  91             check += err;
  92          data += written;
  93          remaining -= written;
  94       }
  95       while (remaining != 0);
  96    }
  97    if (check != length)
  98    {
  99       png_error(png_ptr, "Write Error");
 100    }
 101 }
 102
 103 #endif
 104 #endif
 105
 106 /* This function is called to output any data pending writing (normally
 107    to disk).  After png_flush is called, there should be no data pending
 108    writing in any buffers. */
 109 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 110 void
 111 png_flush(png_structp png_ptr)
 112 {
 113    if (png_ptr->output_flush_fn != NULL)
 114       (*(png_ptr->output_flush_fn))(png_ptr);
 115 }
 116
 117 #if !defined(PNG_NO_STDIO)
 118 static void
 119 png_default_flush(png_structp png_ptr)
 120 {
 121    FILE *io_ptr;
 122    io_ptr = (FILE *)CVT_PTR((png_ptr->io_ptr));
 123    if (io_ptr != NULL)
 124       fflush(io_ptr);
 125 }
 126 #endif
 127 #endif
 128
 129 /* This function allows the application to supply new output functions for
 130    libpng if standard C streams aren't being used.
 131
 132    This function takes as its arguments:
 133    png_ptr       - pointer to a png output data structure
 134    io_ptr        - pointer to user supplied structure containing info about
 135                    the output functions.  May be NULL.
 136    write_data_fn - pointer to a new output function which takes as its
 137                    arguments a pointer to a png_struct, a pointer to
 138                    data to be written, and a 32-bit unsigned int which is
 139                    the number of bytes to be written.  The new write
 140                    function should call png_error(png_ptr, "Error msg")
 141                    to exit and output any fatal error messages.
 142    flush_data_fn - pointer to a new flush function which takes as its
 143                    arguments a pointer to a png_struct.  After a call to
 144                    the flush function, there should be no data in any buffers
 145                    or pending transmission.  If the output method doesn't do
 146                    any buffering of ouput, a function prototype must still be
 147                    supplied although it doesn't have to do anything.  If
 148                    PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
 149                    time, output_flush_fn will be ignored, although it must be
 150                    supplied for compatibility. */
 151 void
 152 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
 153    png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
 154 {
 155    png_ptr->io_ptr = io_ptr;
 156
 157 #if !defined(PNG_NO_STDIO)
 158    if (write_data_fn != NULL)
 159       png_ptr->write_data_fn = write_data_fn;
 160    else
 161       png_ptr->write_data_fn = png_default_write_data;
 162 #else
 163    png_ptr->write_data_fn = write_data_fn;
 164 #endif
 165
 166 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 167 #if !defined(PNG_NO_STDIO)
 168    if (output_flush_fn != NULL)
 169       png_ptr->output_flush_fn = output_flush_fn;
 170    else
 171       png_ptr->output_flush_fn = png_default_flush;
 172 #else
 173    png_ptr->output_flush_fn = output_flush_fn;
 174 #endif
 175 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
 176
 177    /* It is an error to read while writing a png file */
 178    png_ptr->read_data_fn = NULL;
 179 }
 180
 181 #if defined(USE_FAR_KEYWORD)
 182 #if defined(_MSC_VER)
 183 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
 184 {
 185    void *near_ptr;
 186    void FAR *far_ptr;
 187    FP_OFF(near_ptr) = FP_OFF(ptr);
 188    far_ptr = (void FAR *)near_ptr;
 189    if(check != 0)
 190       if(FP_SEG(ptr) != FP_SEG(far_ptr))
 191          png_error(png_ptr,"segment lost in conversion");
 192    return(near_ptr);
 193 }
 194 #  else
 195 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
 196 {
 197    void *near_ptr;
 198    void FAR *far_ptr;
 199    near_ptr = (void FAR *)ptr;
 200    far_ptr = (void FAR *)near_ptr;
 201    if(check != 0)
 202       if(far_ptr != ptr)
 203          png_error(png_ptr,"segment lost in conversion");
 204    return(near_ptr);
 205 }
 206 #   endif
 207 #   endif