/* * 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;  /* Entropy decoding: either Huffman or arithmetic coding. */  if (cinfo->arith_code)    jinit_arith_decoder(cinfo);  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;  }}