--- /dev/null
+/*
+ * jdmainct.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 the main buffer controller for decompression.
+ * The main buffer lies between the JPEG decompressor proper and the
+ * post-processor; it holds downsampled data in the JPEG colorspace.
+ *
+ * Note that this code is bypassed in raw-data mode, since the application
+ * supplies the equivalent of the main buffer in that case.
+ */
+
+#define JPEG_INTERNALS
+#include "jinclude.h"
+#include "jpeglib.h"
+
+
+/*
+ * In the current system design, the main buffer need never be a full-image
+ * buffer; any full-height buffers will be found inside the coefficient or
+ * postprocessing controllers. Nonetheless, the main controller is not
+ * trivial. Its responsibility is to provide context rows for upsampling/
+ * rescaling, and doing this in an efficient fashion is a bit tricky.
+ *
+ * Postprocessor input data is counted in "row groups". A row group
+ * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
+ * sample rows of each component. (We require DCT_scaled_size values to be
+ * chosen such that these numbers are integers. In practice DCT_scaled_size
+ * values will likely be powers of two, so we actually have the stronger
+ * condition that DCT_scaled_size / min_DCT_scaled_size is an integer.)
+ * Upsampling will typically produce max_v_samp_factor pixel rows from each
+ * row group (times any additional scale factor that the upsampler is
+ * applying).
+ *
+ * The coefficient controller will deliver data to us one iMCU row at a time;
+ * each iMCU row contains v_samp_factor * DCT_scaled_size sample rows, or
+ * exactly min_DCT_scaled_size row groups. (This amount of data corresponds
+ * to one row of MCUs when the image is fully interleaved.) Note that the
+ * number of sample rows varies across components, but the number of row
+ * groups does not. Some garbage sample rows may be included in the last iMCU
+ * row at the bottom of the image.
+ *
+ * Depending on the vertical scaling algorithm used, the upsampler may need
+ * access to the sample row(s) above and below its current input row group.
+ * The upsampler is required to set need_context_rows TRUE at global selection
+ * time if so. When need_context_rows is FALSE, this controller can simply
+ * obtain one iMCU row at a time from the coefficient controller and dole it
+ * out as row groups to the postprocessor.
+ *
+ * When need_context_rows is TRUE, this controller guarantees that the buffer
+ * passed to postprocessing contains at least one row group's worth of samples
+ * above and below the row group(s) being processed. Note that the context
+ * rows "above" the first passed row group appear at negative row offsets in
+ * the passed buffer. At the top and bottom of the image, the required
+ * context rows are manufactured by duplicating the first or last real sample
+ * row; this avoids having special cases in the upsampling inner loops.
+ *
+ * The amount of context is fixed at one row group just because that's a
+ * convenient number for this controller to work with. The existing
+ * upsamplers really only need one sample row of context. An upsampler
+ * supporting arbitrary output rescaling might wish for more than one row
+ * group of context when shrinking the image; tough, we don't handle that.
+ * (This is justified by the assumption that downsizing will be handled mostly
+ * by adjusting the DCT_scaled_size values, so that the actual scale factor at
+ * the upsample step needn't be much less than one.)
+ *
+ * To provide the desired context, we have to retain the last two row groups
+ * of one iMCU row while reading in the next iMCU row. (The last row group
+ * can't be processed until we have another row group for its below-context,
+ * and so we have to save the next-to-last group too for its above-context.)
+ * We could do this most simply by copying data around in our buffer, but
+ * that'd be very slow. We can avoid copying any data by creating a rather
+ * strange pointer structure. Here's how it works. We allocate a workspace
+ * consisting of M+2 row groups (where M = min_DCT_scaled_size is the number
+ * of row groups per iMCU row). We create two sets of redundant pointers to
+ * the workspace. Labeling the physical row groups 0 to M+1, the synthesized
+ * pointer lists look like this:
+ * M+1 M-1
+ * master pointer --> 0 master pointer --> 0
+ * 1 1
+ * ... ...
+ * M-3 M-3
+ * M-2 M
+ * M-1 M+1
+ * M M-2
+ * M+1 M-1
+ * 0 0
+ * We read alternate iMCU rows using each master pointer; thus the last two
+ * row groups of the previous iMCU row remain un-overwritten in the workspace.
+ * The pointer lists are set up so that the required context rows appear to
+ * be adjacent to the proper places when we pass the pointer lists to the
+ * upsampler.
+ *
+ * The above pictures describe the normal state of the pointer lists.
+ * At top and bottom of the image, we diddle the pointer lists to duplicate
+ * the first or last sample row as necessary (this is cheaper than copying
+ * sample rows around).
+ *
+ * This scheme breaks down if M < 2, ie, min_DCT_scaled_size is 1. In that
+ * situation each iMCU row provides only one row group so the buffering logic
+ * must be different (eg, we must read two iMCU rows before we can emit the
+ * first row group). For now, we simply do not support providing context
+ * rows when min_DCT_scaled_size is 1. That combination seems unlikely to
+ * be worth providing --- if someone wants a 1/8th-size preview, they probably
+ * want it quick and dirty, so a context-free upsampler is sufficient.
+ */
+
+
+/* Private buffer controller object */
+
+typedef struct {
+ struct jpeg_d_main_controller pub; /* public fields */
+
+ /* Pointer to allocated workspace (M or M+2 row groups). */
+ JSAMPARRAY buffer[MAX_COMPONENTS];
+
+ boolean buffer_full; /* Have we gotten an iMCU row from decoder? */
+ JDIMENSION rowgroup_ctr; /* counts row groups output to postprocessor */
+
+ /* Remaining fields are only used in the context case. */
+
+ /* These are the master pointers to the funny-order pointer lists. */
+ JSAMPIMAGE xbuffer[2]; /* pointers to weird pointer lists */
+
+ int whichptr; /* indicates which pointer set is now in use */
+ int context_state; /* process_data state machine status */
+ JDIMENSION rowgroups_avail; /* row groups available to postprocessor */
+ JDIMENSION iMCU_row_ctr; /* counts iMCU rows to detect image top/bot */
+} my_main_controller;
+
+typedef my_main_controller * my_main_ptr;
+
+/* context_state values: */
+#define CTX_PREPARE_FOR_IMCU 0 /* need to prepare for MCU row */
+#define CTX_PROCESS_IMCU 1 /* feeding iMCU to postprocessor */
+#define CTX_POSTPONED_ROW 2 /* feeding postponed row group */
+
+
+/* Forward declarations */
+METHODDEF(void) process_data_simple_main
+ JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
+ JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
+METHODDEF(void) process_data_context_main
+ JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
+ JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
+#ifdef QUANT_2PASS_SUPPORTED
+METHODDEF(void) process_data_crank_post
+ JPP((j_decompress_ptr cinfo, JSAMPARRAY output_buf,
+ JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail));
+#endif
+
+
+LOCAL(void)
+alloc_funny_pointers (j_decompress_ptr cinfo)
+/* Allocate space for the funny pointer lists.
+ * This is done only once, not once per pass.
+ */
+{
+ my_main_ptr main = (my_main_ptr) cinfo->main;
+ int ci, rgroup;
+ int M = cinfo->min_DCT_scaled_size;
+ jpeg_component_info *compptr;
+ JSAMPARRAY xbuf;
+
+ /* Get top-level space for component array pointers.
+ * We alloc both arrays with one call to save a few cycles.
+ */
+ main->xbuffer[0] = (JSAMPIMAGE)
+ (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+ cinfo->num_components * 2 * SIZEOF(JSAMPARRAY));
+ main->xbuffer[1] = main->xbuffer[0] + cinfo->num_components;
+
+ for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+ ci++, compptr++) {
+ rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
+ cinfo->min_DCT_scaled_size; /* height of a row group of component */
+ /* Get space for pointer lists --- M+4 row groups in each list.
+ * We alloc both pointer lists with one call to save a few cycles.
+ */
+ xbuf = (JSAMPARRAY)
+ (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+ 2 * (rgroup * (M + 4)) * SIZEOF(JSAMPROW));
+ xbuf += rgroup; /* want one row group at negative offsets */
+ main->xbuffer[0][ci] = xbuf;
+ xbuf += rgroup * (M + 4);
+ main->xbuffer[1][ci] = xbuf;
+ }
+}
+
+
+LOCAL(void)
+make_funny_pointers (j_decompress_ptr cinfo)
+/* Create the funny pointer lists discussed in the comments above.
+ * The actual workspace is already allocated (in main->buffer),
+ * and the space for the pointer lists is allocated too.
+ * This routine just fills in the curiously ordered lists.
+ * This will be repeated at the beginning of each pass.
+ */
+{
+ my_main_ptr main = (my_main_ptr) cinfo->main;
+ int ci, i, rgroup;
+ int M = cinfo->min_DCT_scaled_size;
+ jpeg_component_info *compptr;
+ JSAMPARRAY buf, xbuf0, xbuf1;
+
+ for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+ ci++, compptr++) {
+ rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
+ cinfo->min_DCT_scaled_size; /* height of a row group of component */
+ xbuf0 = main->xbuffer[0][ci];
+ xbuf1 = main->xbuffer[1][ci];
+ /* First copy the workspace pointers as-is */
+ buf = main->buffer[ci];
+ for (i = 0; i < rgroup * (M + 2); i++) {
+ xbuf0[i] = xbuf1[i] = buf[i];
+ }
+ /* In the second list, put the last four row groups in swapped order */
+ for (i = 0; i < rgroup * 2; i++) {
+ xbuf1[rgroup*(M-2) + i] = buf[rgroup*M + i];
+ xbuf1[rgroup*M + i] = buf[rgroup*(M-2) + i];
+ }
+ /* The wraparound pointers at top and bottom will be filled later
+ * (see set_wraparound_pointers, below). Initially we want the "above"
+ * pointers to duplicate the first actual data line. This only needs
+ * to happen in xbuffer[0].
+ */
+ for (i = 0; i < rgroup; i++) {
+ xbuf0[i - rgroup] = xbuf0[0];
+ }
+ }
+}
+
+
+LOCAL(void)
+set_wraparound_pointers (j_decompress_ptr cinfo)
+/* Set up the "wraparound" pointers at top and bottom of the pointer lists.
+ * This changes the pointer list state from top-of-image to the normal state.
+ */
+{
+ my_main_ptr main = (my_main_ptr) cinfo->main;
+ int ci, i, rgroup;
+ int M = cinfo->min_DCT_scaled_size;
+ jpeg_component_info *compptr;
+ JSAMPARRAY xbuf0, xbuf1;
+
+ for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+ ci++, compptr++) {
+ rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
+ cinfo->min_DCT_scaled_size; /* height of a row group of component */
+ xbuf0 = main->xbuffer[0][ci];
+ xbuf1 = main->xbuffer[1][ci];
+ for (i = 0; i < rgroup; i++) {
+ xbuf0[i - rgroup] = xbuf0[rgroup*(M+1) + i];
+ xbuf1[i - rgroup] = xbuf1[rgroup*(M+1) + i];
+ xbuf0[rgroup*(M+2) + i] = xbuf0[i];
+ xbuf1[rgroup*(M+2) + i] = xbuf1[i];
+ }
+ }
+}
+
+
+LOCAL(void)
+set_bottom_pointers (j_decompress_ptr cinfo)
+/* Change the pointer lists to duplicate the last sample row at the bottom
+ * of the image. whichptr indicates which xbuffer holds the final iMCU row.
+ * Also sets rowgroups_avail to indicate number of nondummy row groups in row.
+ */
+{
+ my_main_ptr main = (my_main_ptr) cinfo->main;
+ int ci, i, rgroup, iMCUheight, rows_left;
+ jpeg_component_info *compptr;
+ JSAMPARRAY xbuf;
+
+ for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+ ci++, compptr++) {
+ /* Count sample rows in one iMCU row and in one row group */
+ iMCUheight = compptr->v_samp_factor * compptr->DCT_scaled_size;
+ rgroup = iMCUheight / cinfo->min_DCT_scaled_size;
+ /* Count nondummy sample rows remaining for this component */
+ rows_left = (int) (compptr->downsampled_height % (JDIMENSION) iMCUheight);
+ if (rows_left == 0) rows_left = iMCUheight;
+ /* Count nondummy row groups. Should get same answer for each component,
+ * so we need only do it once.
+ */
+ if (ci == 0) {
+ main->rowgroups_avail = (JDIMENSION) ((rows_left-1) / rgroup + 1);
+ }
+ /* Duplicate the last real sample row rgroup*2 times; this pads out the
+ * last partial rowgroup and ensures at least one full rowgroup of context.
+ */
+ xbuf = main->xbuffer[main->whichptr][ci];
+ for (i = 0; i < rgroup * 2; i++) {
+ xbuf[rows_left + i] = xbuf[rows_left-1];
+ }
+ }
+}
+
+
+/*
+ * Initialize for a processing pass.
+ */
+
+METHODDEF(void)
+start_pass_main (j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
+{
+ my_main_ptr main = (my_main_ptr) cinfo->main;
+
+ switch (pass_mode) {
+ case JBUF_PASS_THRU:
+ if (cinfo->upsample->need_context_rows) {
+ main->pub.process_data = process_data_context_main;
+ make_funny_pointers(cinfo); /* Create the xbuffer[] lists */
+ main->whichptr = 0; /* Read first iMCU row into xbuffer[0] */
+ main->context_state = CTX_PREPARE_FOR_IMCU;
+ main->iMCU_row_ctr = 0;
+ } else {
+ /* Simple case with no context needed */
+ main->pub.process_data = process_data_simple_main;
+ }
+ main->buffer_full = FALSE; /* Mark buffer empty */
+ main->rowgroup_ctr = 0;
+ break;
+#ifdef QUANT_2PASS_SUPPORTED
+ case JBUF_CRANK_DEST:
+ /* For last pass of 2-pass quantization, just crank the postprocessor */
+ main->pub.process_data = process_data_crank_post;
+ break;
+#endif
+ default:
+ ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
+ break;
+ }
+}
+
+
+/*
+ * Process some data.
+ * This handles the simple case where no context is required.
+ */
+
+METHODDEF(void)
+process_data_simple_main (j_decompress_ptr cinfo,
+ JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
+ JDIMENSION out_rows_avail)
+{
+ my_main_ptr main = (my_main_ptr) cinfo->main;
+ JDIMENSION rowgroups_avail;
+
+ /* Read input data if we haven't filled the main buffer yet */
+ if (! main->buffer_full) {
+ if (! (*cinfo->coef->decompress_data) (cinfo, main->buffer))
+ return; /* suspension forced, can do nothing more */
+ main->buffer_full = TRUE; /* OK, we have an iMCU row to work with */
+ }
+
+ /* There are always min_DCT_scaled_size row groups in an iMCU row. */
+ rowgroups_avail = (JDIMENSION) cinfo->min_DCT_scaled_size;
+ /* Note: at the bottom of the image, we may pass extra garbage row groups
+ * to the postprocessor. The postprocessor has to check for bottom
+ * of image anyway (at row resolution), so no point in us doing it too.
+ */
+
+ /* Feed the postprocessor */
+ (*cinfo->post->post_process_data) (cinfo, main->buffer,
+ &main->rowgroup_ctr, rowgroups_avail,
+ output_buf, out_row_ctr, out_rows_avail);
+
+ /* Has postprocessor consumed all the data yet? If so, mark buffer empty */
+ if (main->rowgroup_ctr >= rowgroups_avail) {
+ main->buffer_full = FALSE;
+ main->rowgroup_ctr = 0;
+ }
+}
+
+
+/*
+ * Process some data.
+ * This handles the case where context rows must be provided.
+ */
+
+METHODDEF(void)
+process_data_context_main (j_decompress_ptr cinfo,
+ JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
+ JDIMENSION out_rows_avail)
+{
+ my_main_ptr main = (my_main_ptr) cinfo->main;
+
+ /* Read input data if we haven't filled the main buffer yet */
+ if (! main->buffer_full) {
+ if (! (*cinfo->coef->decompress_data) (cinfo,
+ main->xbuffer[main->whichptr]))
+ return; /* suspension forced, can do nothing more */
+ main->buffer_full = TRUE; /* OK, we have an iMCU row to work with */
+ main->iMCU_row_ctr++; /* count rows received */
+ }
+
+ /* Postprocessor typically will not swallow all the input data it is handed
+ * in one call (due to filling the output buffer first). Must be prepared
+ * to exit and restart. This switch lets us keep track of how far we got.
+ * Note that each case falls through to the next on successful completion.
+ */
+ switch (main->context_state) {
+ case CTX_POSTPONED_ROW:
+ /* Call postprocessor using previously set pointers for postponed row */
+ (*cinfo->post->post_process_data) (cinfo, main->xbuffer[main->whichptr],
+ &main->rowgroup_ctr, main->rowgroups_avail,
+ output_buf, out_row_ctr, out_rows_avail);
+ if (main->rowgroup_ctr < main->rowgroups_avail)
+ return; /* Need to suspend */
+ main->context_state = CTX_PREPARE_FOR_IMCU;
+ if (*out_row_ctr >= out_rows_avail)
+ return; /* Postprocessor exactly filled output buf */
+ /*FALLTHROUGH*/
+ case CTX_PREPARE_FOR_IMCU:
+ /* Prepare to process first M-1 row groups of this iMCU row */
+ main->rowgroup_ctr = 0;
+ main->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size - 1);
+ /* Check for bottom of image: if so, tweak pointers to "duplicate"
+ * the last sample row, and adjust rowgroups_avail to ignore padding rows.
+ */
+ if (main->iMCU_row_ctr == cinfo->total_iMCU_rows)
+ set_bottom_pointers(cinfo);
+ main->context_state = CTX_PROCESS_IMCU;
+ /*FALLTHROUGH*/
+ case CTX_PROCESS_IMCU:
+ /* Call postprocessor using previously set pointers */
+ (*cinfo->post->post_process_data) (cinfo, main->xbuffer[main->whichptr],
+ &main->rowgroup_ctr, main->rowgroups_avail,
+ output_buf, out_row_ctr, out_rows_avail);
+ if (main->rowgroup_ctr < main->rowgroups_avail)
+ return; /* Need to suspend */
+ /* After the first iMCU, change wraparound pointers to normal state */
+ if (main->iMCU_row_ctr == 1)
+ set_wraparound_pointers(cinfo);
+ /* Prepare to load new iMCU row using other xbuffer list */
+ main->whichptr ^= 1; /* 0=>1 or 1=>0 */
+ main->buffer_full = FALSE;
+ /* Still need to process last row group of this iMCU row, */
+ /* which is saved at index M+1 of the other xbuffer */
+ main->rowgroup_ctr = (JDIMENSION) (cinfo->min_DCT_scaled_size + 1);
+ main->rowgroups_avail = (JDIMENSION) (cinfo->min_DCT_scaled_size + 2);
+ main->context_state = CTX_POSTPONED_ROW;
+ }
+}
+
+
+/*
+ * Process some data.
+ * Final pass of two-pass quantization: just call the postprocessor.
+ * Source data will be the postprocessor controller's internal buffer.
+ */
+
+#ifdef QUANT_2PASS_SUPPORTED
+
+METHODDEF(void)
+process_data_crank_post (j_decompress_ptr cinfo,
+ JSAMPARRAY output_buf, JDIMENSION *out_row_ctr,
+ JDIMENSION out_rows_avail)
+{
+ (*cinfo->post->post_process_data) (cinfo, (JSAMPIMAGE) NULL,
+ (JDIMENSION *) NULL, (JDIMENSION) 0,
+ output_buf, out_row_ctr, out_rows_avail);
+}
+
+#endif /* QUANT_2PASS_SUPPORTED */
+
+
+/*
+ * Initialize main buffer controller.
+ */
+
+GLOBAL(void)
+jinit_d_main_controller (j_decompress_ptr cinfo, boolean need_full_buffer)
+{
+ my_main_ptr main;
+ int ci, rgroup, ngroups;
+ jpeg_component_info *compptr;
+
+ main = (my_main_ptr)
+ (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
+ SIZEOF(my_main_controller));
+ cinfo->main = (struct jpeg_d_main_controller *) main;
+ main->pub.start_pass = start_pass_main;
+
+ if (need_full_buffer) /* shouldn't happen */
+ ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
+
+ /* Allocate the workspace.
+ * ngroups is the number of row groups we need.
+ */
+ if (cinfo->upsample->need_context_rows) {
+ if (cinfo->min_DCT_scaled_size < 2) /* unsupported, see comments above */
+ ERREXIT(cinfo, JERR_NOTIMPL);
+ alloc_funny_pointers(cinfo); /* Alloc space for xbuffer[] lists */
+ ngroups = cinfo->min_DCT_scaled_size + 2;
+ } else {
+ ngroups = cinfo->min_DCT_scaled_size;
+ }
+
+ for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
+ ci++, compptr++) {
+ rgroup = (compptr->v_samp_factor * compptr->DCT_scaled_size) /
+ cinfo->min_DCT_scaled_size; /* height of a row group of component */
+ main->buffer[ci] = (*cinfo->mem->alloc_sarray)
+ ((j_common_ptr) cinfo, JPOOL_IMAGE,
+ compptr->width_in_blocks * compptr->DCT_scaled_size,
+ (JDIMENSION) (rgroup * ngroups));
+ }
+}
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