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++ /*
++ * jdtrans.c
++ *
++ * This file was part of the Independent JPEG Group's software:
++ * Copyright (C) 1995-1997, Thomas G. Lane.
++ * libjpeg-turbo Modifications:
++ * Copyright (C) 2020, 2022, D. R. Commander.
++ * For conditions of distribution and use, see the accompanying README.ijg
++ * 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"
++ #include "jpegapicomp.h"
++
++
++ /* Forward declarations */
++ LOCAL(void) transdecode_master_selection(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->master->lossless)
++ ERREXIT(cinfo, JERR_NOTIMPL);
++
++ 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. */
++ if (cinfo->data_precision == 12)
++ j12init_d_coef_controller(cinfo, TRUE);
++ else
++ 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;
++ }
++ }