1 

     2 /* pngwio.c - functions for data output

     3  *

     4  * Last changed in libpng 1.2.30 [August 15, 2008]

     5  * For conditions of distribution and use, see copyright notice in png.h

     6  * Copyright (c) 1998-2008 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 */