/*=========================================================================
 
 Program:   ORFEO Toolbox
 Language:  C++
 Date:      $Date$
 Version:   $Revision$
 
 
 Copyright (c) Centre National d'Etudes Spatiales. All rights reserved.
 See OTBCopyright.txt for details.
 
 This software is distributed WITHOUT ANY WARRANTY; without even
 the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 PURPOSE.  See the above copyright notices for more information.
 
 =========================================================================*/

/*
 * jdatasrc.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains decompression data source routines for the case of
 * reading JPEG data from a file (or any stdio stream).  While these routines
 * are sufficient for most applications, some will want to use a different
 * source manager.
 * IMPORTANT: we assume that fread() will correctly transcribe an array of
 * JOCTETs from 8-bit-wide elements on external storage.  If char is wider
 * than 8 bits on your machine, you may need to do some tweaking.
 */

/* this is not a core library module, so it doesn't define JPEG_INTERNALS */

#include <ossim/imaging/ossimJpegStdIOSrc.h>

#include <csetjmp>                     /** for jmp_buf */
#include <jpeglib.h>                   /** for jpeg stuff */
#include <jerror.h>


#define INPUT_BUF_SIZE  4096  /* choose an efficiently fread'able size */

#define JFREAD(file,buf,sizeofbuf)  \
((size_t) fread((void *) (buf), (size_t) 1, (size_t) (sizeofbuf), (file)))

/*
 * In ANSI C, and indeed any rational implementation, size_t is also the
 * type returned by sizeof().  However, it seems there are some irrational
 * implementations out there, in which sizeof() returns an int even though
 * size_t is defined as long or unsigned long.  To ensure consistent results
 * we always use this SIZEOF() macro in place of using sizeof() directly.
 */

#define SIZEOF(object)  ((size_t) sizeof(object))

extern "C"
{
   
   /* Expanded data source object for stdio input */
   
   typedef struct {
      struct jpeg_source_mgr pub;  /* public fields */
      
      FILE * infile;    /* source stream */
      JOCTET * buffer;    /* start of buffer */
      boolean start_of_file;  /* have we gotten any data yet? */
   } ossimJpegStdIOSourceMgr;
   
   typedef ossimJpegStdIOSourceMgr * ossimJpegStdIOSourceMgrPtr;
   
   
   
   /*
    * Initialize source --- called by jpeg_read_header
    * before any data is actually read.
    */
   
   void ossimJpegStdIOSrc_init_source (j_decompress_ptr cinfo)
   {
      ossimJpegStdIOSourceMgrPtr src = (ossimJpegStdIOSourceMgrPtr) cinfo->src;
      
      /* We reset the empty-input-file flag for each image,
       * but we don't clear the input buffer.
       * This is correct behavior for reading a series of images from one source.
       */
      src->start_of_file = TRUE;
   }
   
   
   /*
    * Fill the input buffer --- called whenever buffer is emptied.
    *
    * In typical applications, this should read fresh data into the buffer
    * (ignoring the current state of next_input_byte & bytes_in_buffer),
    * reset the pointer & count to the start of the buffer, and return TRUE
    * indicating that the buffer has been reloaded.  It is not necessary to
    * fill the buffer entirely, only to obtain at least one more byte.
    *
    * There is no such thing as an EOF return.  If the end of the file has been
    * reached, the routine has a choice of ERREXIT() or inserting fake data into
    * the buffer.  In most cases, generating a warning message and inserting a
    * fake EOI marker is the best course of action --- this will allow the
    * decompressor to output however much of the image is there.  However,
    * the resulting error message is misleading if the real problem is an empty
    * input file, so we handle that case specially.
    *
    * In applications that need to be able to suspend compression due to input
    * not being available yet, a FALSE return indicates that no more data can be
    * obtained right now, but more may be forthcoming later.  In this situation,
    * the decompressor will return to its caller (with an indication of the
    * number of scanlines it has read, if any).  The application should resume
    * decompression after it has loaded more data into the input buffer.  Note
    * that there are substantial restrictions on the use of suspension --- see
    * the documentation.
    *
    * When suspending, the decompressor will back up to a convenient restart point
    * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
    * indicate where the restart point will be if the current call returns FALSE.
    * Data beyond this point must be rescanned after resumption, so move it to
    * the front of the buffer rather than discarding it.
    */
   
   boolean
   ossimJpegStdIOSrc_fill_input_buffer (j_decompress_ptr cinfo)
   {
      ossimJpegStdIOSourceMgrPtr src = (ossimJpegStdIOSourceMgrPtr) cinfo->src;
      size_t nbytes;
      
      nbytes = JFREAD(src->infile, src->buffer, INPUT_BUF_SIZE);
      
      if (nbytes <= 0) {
         if (src->start_of_file)  /* Treat empty input file as fatal error */
            ERREXIT(cinfo, JERR_INPUT_EMPTY);
         WARNMS(cinfo, JWRN_JPEG_EOF);
         /* Insert a fake EOI marker */
         src->buffer[0] = (JOCTET) 0xFF;
         src->buffer[1] = (JOCTET) JPEG_EOI;
         nbytes = 2;
      }
      
      src->pub.next_input_byte = src->buffer;
      src->pub.bytes_in_buffer = nbytes;
      src->start_of_file = FALSE;
      
      return TRUE;
   }
   
   
   /*
    * Skip data --- used to skip over a potentially large amount of
    * uninteresting data (such as an APPn marker).
    *
    * Writers of suspendable-input applications must note that skip_input_data
    * is not granted the right to give a suspension return.  If the skip extends
    * beyond the data currently in the buffer, the buffer can be marked empty so
    * that the next read will cause a fill_input_buffer call that can suspend.
    * Arranging for additional bytes to be discarded before reloading the input
    * buffer is the application writer's problem.
    */
   
   void
   ossimJpegStdIOSrc_skip_input_data (j_decompress_ptr cinfo, long num_bytes)
   {
      ossimJpegStdIOSourceMgrPtr src = (ossimJpegStdIOSourceMgrPtr) cinfo->src;
      
      /* Just a dumb implementation for now.  Could use fseek() except
       * it doesn't work on pipes.  Not clear that being smart is worth
       * any trouble anyway --- large skips are infrequent.
       */
      if (num_bytes > 0) {
         while (num_bytes > (long) src->pub.bytes_in_buffer) {
            num_bytes -= (long) src->pub.bytes_in_buffer;
            (void) ossimJpegStdIOSrc_fill_input_buffer(cinfo);
            /* note we assume that fill_input_buffer will never return FALSE,
             * so suspension need not be handled.
             */
         }
         src->pub.next_input_byte += (size_t) num_bytes;
         src->pub.bytes_in_buffer -= (size_t) num_bytes;
      }
   }
   
   
   /*
    * An additional method that can be provided by data source modules is the
    * resync_to_restart method for error recovery in the presence of RST markers.
    * For the moment, this source module just uses the default resync method
    * provided by the JPEG library.  That method assumes that no backtracking
    * is possible.
    */
   
   
   /*
    * Terminate source --- called by jpeg_finish_decompress
    * after all data has been read.  Often a no-op.
    *
    * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
    * application must deal with any cleanup that should happen even
    * for error exit.
    */
   
   void
   ossimJpegStdIOSrc_term_source (j_decompress_ptr cinfo)
   {
      (void)cinfo;
      /* no work necessary here */
   }
   
   
   /*
    * Prepare for input from a stdio stream.
    * The caller must have already opened the stream, and is responsible
    * for closing it after finishing decompression.
    */
   
   /* void ossimJpegStdIOSrc (j_decompress_ptr cinfo, FILE * infile) */
   void ossimJpegStdIOSrc (jpeg_decompress_struct* cinfo, FILE * infile)      
   {
      ossimJpegStdIOSourceMgrPtr src;
      
      /* The source object and input buffer are made permanent so that a series
       * of JPEG images can be read from the same file by calling jpeg_stdio_src
       * only before the first one.  (If we discarded the buffer at the end of
       * one image, we'd likely lose the start of the next one.)
       * This makes it unsafe to use this manager and a different source
       * manager serially with the same JPEG object.  Caveat programmer.
       */
      if (cinfo->src == NULL) {  /* first time for this JPEG object? */
         cinfo->src = (struct jpeg_source_mgr *)
         (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
                                     SIZEOF(ossimJpegStdIOSourceMgr));
         src = (ossimJpegStdIOSourceMgrPtr) cinfo->src;
         src->buffer = (JOCTET *)
         (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
                                     INPUT_BUF_SIZE * SIZEOF(JOCTET));
      }
      
      src = (ossimJpegStdIOSourceMgrPtr) cinfo->src;
      src->pub.init_source = ossimJpegStdIOSrc_init_source;
      src->pub.fill_input_buffer = ossimJpegStdIOSrc_fill_input_buffer;
      src->pub.skip_input_data = ossimJpegStdIOSrc_skip_input_data;
      src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
      src->pub.term_source = ossimJpegStdIOSrc_term_source;
      src->infile = infile;
      src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
      src->pub.next_input_byte = NULL; /* until buffer loaded */
   }
}
