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 /*

  * jdtrans.c

  *

  * Copyright (C) 1995-1997, 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 library routines for transcoding decompression,

  * that is, reading raw DCT coefficient arrays from an input JPEG file.

  * The routines in jdapimin.c will also be needed by a transcoder.

  */

 #define JPEG_INTERNALS

 #include "jinclude.h"

 #include "jpeglib.h"

 /* Forward declarations */

 LOCAL(void) transdecode_master_selection JPP((j_decompress_ptr cinfo));

 /*

  * Read the coefficient arrays from a JPEG file.

  * jpeg_read_header must be completed before calling this.

  *

  * The entire image is read into a set of virtual coefficient-block arrays,

  * one per component.  The return value is a pointer to the array of

  * virtual-array descriptors.  These can be manipulated directly via the

  * JPEG memory manager, or handed off to jpeg_write_coefficients().

  * To release the memory occupied by the virtual arrays, call

  * jpeg_finish_decompress() when done with the data.

  *

  * An alternative usage is to simply obtain access to the coefficient arrays

  * during a buffered-image-mode decompression operation.  This is allowed

  * after any jpeg_finish_output() call.  The arrays can be accessed until

  * jpeg_finish_decompress() is called.  (Note that any call to the library

  * may reposition the arrays, so don't rely on access_virt_barray() results

  * to stay valid across library calls.)

  *

  * Returns NULL if suspended.  This case need be checked only if

  * a suspending data source is used.

  */

 GLOBAL(jvirt_barray_ptr *)

 jpeg_read_coefficients (j_decompress_ptr cinfo)

 {

   if (cinfo->global_state == DSTATE_READY) {

     /* First call: initialize active modules */

     transdecode_master_selection(cinfo);

     cinfo->global_state = DSTATE_RDCOEFS;

   }

   if (cinfo->global_state == DSTATE_RDCOEFS) {

     /* Absorb whole file into the coef buffer */

     for (;;) {

       int retcode;

       /* Call progress monitor hook if present */

       if (cinfo->progress != NULL)

 	(*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);

       /* Absorb some more input */

       retcode = (*cinfo->inputctl->consume_input) (cinfo);

       if (retcode == JPEG_SUSPENDED)

 	return NULL;

       if (retcode == JPEG_REACHED_EOI)

 	break;

       /* Advance progress counter if appropriate */

       if (cinfo->progress != NULL &&

 	  (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {

 	if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {

 	  /* startup underestimated number of scans; ratchet up one scan */

 	  cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;

 	}

       }

     }

     /* Set state so that jpeg_finish_decompress does the right thing */

     cinfo->global_state = DSTATE_STOPPING;

   }

   /* At this point we should be in state DSTATE_STOPPING if being used

    * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access

    * to the coefficients during a full buffered-image-mode decompression.

    */

   if ((cinfo->global_state == DSTATE_STOPPING ||

        cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {

     return cinfo->coef->coef_arrays;

   }

   /* Oops, improper usage */

   ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);

   return NULL;			/* keep compiler happy */

 }

 /*

  * Master selection of decompression modules for transcoding.

  * This substitutes for jdmaster.c's initialization of the full decompressor.

  */

 LOCAL(void)

 transdecode_master_selection (j_decompress_ptr cinfo)

 {

   /* This is effectively a buffered-image operation. */

   cinfo->buffered_image = TRUE;

 #if JPEG_LIB_VERSION >= 80

   /* Compute output image dimensions and related values. */

   jpeg_core_output_dimensions(cinfo);

 #endif

   /* Entropy decoding: either Huffman or arithmetic coding. */

   if (cinfo->arith_code) {

 #ifdef D_ARITH_CODING_SUPPORTED

     jinit_arith_decoder(cinfo);

 #else

     ERREXIT(cinfo, JERR_ARITH_NOTIMPL);

 #endif

   } else {

     if (cinfo->progressive_mode) {

 #ifdef D_PROGRESSIVE_SUPPORTED

       jinit_phuff_decoder(cinfo);

 #else

       ERREXIT(cinfo, JERR_NOT_COMPILED);

 #endif

     } else

       jinit_huff_decoder(cinfo);

   }

   /* Always get a full-image coefficient buffer. */

   jinit_d_coef_controller(cinfo, TRUE);

   /* We can now tell the memory manager to allocate virtual arrays. */

   (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);

   /* Initialize input side of decompressor to consume first scan. */

   (*cinfo->inputctl->start_input_pass) (cinfo);

   /* Initialize progress monitoring. */

   if (cinfo->progress != NULL) {

     int nscans;

     /* Estimate number of scans to set pass_limit. */

     if (cinfo->progressive_mode) {

       /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */

       nscans = 2 + 3 * cinfo->num_components;

     } else if (cinfo->inputctl->has_multiple_scans) {

       /* For a nonprogressive multiscan file, estimate 1 scan per component. */

       nscans = cinfo->num_components;

     } else {

       nscans = 1;

     }

     cinfo->progress->pass_counter = 0L;

     cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;

     cinfo->progress->completed_passes = 0;

     cinfo->progress->total_passes = 1;

   }

 }