media/libjpeg/jchuff.h
author Jan de Mooij <jdemooij@mozilla.com>
Sat, 12 Jan 2019 10:50:04 +0000
changeset 453631 cfa1c48c717048f00eb4811b5719cd716eb1e5b3
parent 440267 a3fa8bb51b3c4a1d3751fddf3db69bc770eb8aae
permissions -rw-r--r--
Bug 1518753 part 5 - Stop using JSProtoKey for initial shapes. r=tcampbell I added this optimization in bug 1299107 to share more shapes across compartments. Unfortunately this doesn't play well with same-compartment realms (ICs can misbehave) because it relies on compartments being isolated from each other. I think we should remove this optimization: * Fixing the IC issue is impossible without deoptimizing everything. * I added it mainly for chrome globals. The shared-JSM-global work has eliminated the need for this there. * Same-compartment realms win memory back by eliminating CCWs etc. * It's quite a lot of complicated code. Differential Revision: https://phabricator.services.mozilla.com/D16170

/*
 * jchuff.h
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1991-1997, Thomas G. Lane.
 * It was modified by The libjpeg-turbo Project to include only code relevant
 * to libjpeg-turbo.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains declarations for Huffman entropy encoding routines
 * that are shared between the sequential encoder (jchuff.c) and the
 * progressive encoder (jcphuff.c).  No other modules need to see these.
 */

/* The legal range of a DCT coefficient is
 *  -1024 .. +1023  for 8-bit data;
 * -16384 .. +16383 for 12-bit data.
 * Hence the magnitude should always fit in 10 or 14 bits respectively.
 */

#if BITS_IN_JSAMPLE == 8
#define MAX_COEF_BITS  10
#else
#define MAX_COEF_BITS  14
#endif

/* Derived data constructed for each Huffman table */

typedef struct {
  unsigned int ehufco[256];     /* code for each symbol */
  char ehufsi[256];             /* length of code for each symbol */
  /* If no code has been allocated for a symbol S, ehufsi[S] contains 0 */
} c_derived_tbl;

/* Expand a Huffman table definition into the derived format */
EXTERN(void) jpeg_make_c_derived_tbl(j_compress_ptr cinfo, boolean isDC,
                                     int tblno, c_derived_tbl **pdtbl);

/* Generate an optimal table definition given the specified counts */
EXTERN(void) jpeg_gen_optimal_table(j_compress_ptr cinfo, JHUFF_TBL *htbl,
                                    long freq[]);