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-rw-r--r--media/libjpeg/jchuff.c1137
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+/*
+ * jchuff.c
+ *
+ * This file was part of the Independent JPEG Group's software:
+ * Copyright (C) 1991-1997, Thomas G. Lane.
+ * libjpeg-turbo Modifications:
+ * Copyright (C) 2009-2011, 2014-2016, 2018-2022, D. R. Commander.
+ * Copyright (C) 2015, Matthieu Darbois.
+ * Copyright (C) 2018, Matthias Räncker.
+ * Copyright (C) 2020, Arm Limited.
+ * For conditions of distribution and use, see the accompanying README.ijg
+ * file.
+ *
+ * This file contains Huffman entropy encoding routines.
+ *
+ * Much of the complexity here has to do with supporting output suspension.
+ * If the data destination module demands suspension, we want to be able to
+ * back up to the start of the current MCU. To do this, we copy state
+ * variables into local working storage, and update them back to the
+ * permanent JPEG objects only upon successful completion of an MCU.
+ *
+ * NOTE: All referenced figures are from
+ * Recommendation ITU-T T.81 (1992) | ISO/IEC 10918-1:1994.
+ */
+
+#define JPEG_INTERNALS
+#include "jinclude.h"
+#include "jpeglib.h"
+#include "jsimd.h"
+#include "jconfigint.h"
+#include <limits.h>
+
+/*
+ * NOTE: If USE_CLZ_INTRINSIC is defined, then clz/bsr instructions will be
+ * used for bit counting rather than the lookup table. This will reduce the
+ * memory footprint by 64k, which is important for some mobile applications
+ * that create many isolated instances of libjpeg-turbo (web browsers, for
+ * instance.) This may improve performance on some mobile platforms as well.
+ * This feature is enabled by default only on Arm processors, because some x86
+ * chips have a slow implementation of bsr, and the use of clz/bsr cannot be
+ * shown to have a significant performance impact even on the x86 chips that
+ * have a fast implementation of it. When building for Armv6, you can
+ * explicitly disable the use of clz/bsr by adding -mthumb to the compiler
+ * flags (this defines __thumb__).
+ */
+
+/* NOTE: Both GCC and Clang define __GNUC__ */
+#if (defined(__GNUC__) && (defined(__arm__) || defined(__aarch64__))) || \
+ defined(_M_ARM) || defined(_M_ARM64)
+#if !defined(__thumb__) || defined(__thumb2__)
+#define USE_CLZ_INTRINSIC
+#endif
+#endif
+
+#ifdef USE_CLZ_INTRINSIC
+#if defined(_MSC_VER) && !defined(__clang__)
+#define JPEG_NBITS_NONZERO(x) (32 - _CountLeadingZeros(x))
+#else
+#define JPEG_NBITS_NONZERO(x) (32 - __builtin_clz(x))
+#endif
+#define JPEG_NBITS(x) (x ? JPEG_NBITS_NONZERO(x) : 0)
+#else
+#include "jpeg_nbits_table.h"
+#define JPEG_NBITS(x) (jpeg_nbits_table[x])
+#define JPEG_NBITS_NONZERO(x) JPEG_NBITS(x)
+#endif
+
+
+/* Expanded entropy encoder object for Huffman encoding.
+ *
+ * The savable_state subrecord contains fields that change within an MCU,
+ * but must not be updated permanently until we complete the MCU.
+ */
+
+#if defined(__x86_64__) && defined(__ILP32__)
+typedef unsigned long long bit_buf_type;
+#else
+typedef size_t bit_buf_type;
+#endif
+
+/* NOTE: The more optimal Huffman encoding algorithm is only used by the
+ * intrinsics implementation of the Arm Neon SIMD extensions, which is why we
+ * retain the old Huffman encoder behavior when using the GAS implementation.
+ */
+#if defined(WITH_SIMD) && !(defined(__arm__) || defined(__aarch64__) || \
+ defined(_M_ARM) || defined(_M_ARM64))
+typedef unsigned long long simd_bit_buf_type;
+#else
+typedef bit_buf_type simd_bit_buf_type;
+#endif
+
+#if (defined(SIZEOF_SIZE_T) && SIZEOF_SIZE_T == 8) || defined(_WIN64) || \
+ (defined(__x86_64__) && defined(__ILP32__))
+#define BIT_BUF_SIZE 64
+#elif (defined(SIZEOF_SIZE_T) && SIZEOF_SIZE_T == 4) || defined(_WIN32)
+#define BIT_BUF_SIZE 32
+#else
+#error Cannot determine word size
+#endif
+#define SIMD_BIT_BUF_SIZE (sizeof(simd_bit_buf_type) * 8)
+
+typedef struct {
+ union {
+ bit_buf_type c;
+ simd_bit_buf_type simd;
+ } put_buffer; /* current bit accumulation buffer */
+ int free_bits; /* # of bits available in it */
+ /* (Neon GAS: # of bits now in it) */
+ int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
+} savable_state;
+
+typedef struct {
+ struct jpeg_entropy_encoder pub; /* public fields */
+
+ savable_state saved; /* Bit buffer & DC state at start of MCU */
+
+ /* These fields are NOT loaded into local working state. */
+ unsigned int restarts_to_go; /* MCUs left in this restart interval */
+ int next_restart_num; /* next restart number to write (0-7) */
+
+ /* Pointers to derived tables (these workspaces have image lifespan) */
+ c_derived_tbl *dc_derived_tbls[NUM_HUFF_TBLS];
+ c_derived_tbl *ac_derived_tbls[NUM_HUFF_TBLS];
+
+#ifdef ENTROPY_OPT_SUPPORTED /* Statistics tables for optimization */
+ long *dc_count_ptrs[NUM_HUFF_TBLS];
+ long *ac_count_ptrs[NUM_HUFF_TBLS];
+#endif
+
+ int simd;
+} huff_entropy_encoder;
+
+typedef huff_entropy_encoder *huff_entropy_ptr;
+
+/* Working state while writing an MCU.
+ * This struct contains all the fields that are needed by subroutines.
+ */
+
+typedef struct {
+ JOCTET *next_output_byte; /* => next byte to write in buffer */
+ size_t free_in_buffer; /* # of byte spaces remaining in buffer */
+ savable_state cur; /* Current bit buffer & DC state */
+ j_compress_ptr cinfo; /* dump_buffer needs access to this */
+ int simd;
+} working_state;
+
+
+/* Forward declarations */
+METHODDEF(boolean) encode_mcu_huff(j_compress_ptr cinfo, JBLOCKROW *MCU_data);
+METHODDEF(void) finish_pass_huff(j_compress_ptr cinfo);
+#ifdef ENTROPY_OPT_SUPPORTED
+METHODDEF(boolean) encode_mcu_gather(j_compress_ptr cinfo,
+ JBLOCKROW *MCU_data);
+METHODDEF(void) finish_pass_gather(j_compress_ptr cinfo);
+#endif
+
+
+/*
+ * Initialize for a Huffman-compressed scan.
+ * If gather_statistics is TRUE, we do not output anything during the scan,
+ * just count the Huffman symbols used and generate Huffman code tables.
+ */
+
+METHODDEF(void)
+start_pass_huff(j_compress_ptr cinfo, boolean gather_statistics)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
+ int ci, dctbl, actbl;
+ jpeg_component_info *compptr;
+
+ if (gather_statistics) {
+#ifdef ENTROPY_OPT_SUPPORTED
+ entropy->pub.encode_mcu = encode_mcu_gather;
+ entropy->pub.finish_pass = finish_pass_gather;
+#else
+ ERREXIT(cinfo, JERR_NOT_COMPILED);
+#endif
+ } else {
+ entropy->pub.encode_mcu = encode_mcu_huff;
+ entropy->pub.finish_pass = finish_pass_huff;
+ }
+
+ entropy->simd = jsimd_can_huff_encode_one_block();
+
+ for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
+ compptr = cinfo->cur_comp_info[ci];
+ dctbl = compptr->dc_tbl_no;
+ actbl = compptr->ac_tbl_no;
+ if (gather_statistics) {
+#ifdef ENTROPY_OPT_SUPPORTED
+ /* Check for invalid table indexes */
+ /* (make_c_derived_tbl does this in the other path) */
+ if (dctbl < 0 || dctbl >= NUM_HUFF_TBLS)
+ ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, dctbl);
+ if (actbl < 0 || actbl >= NUM_HUFF_TBLS)
+ ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, actbl);
+ /* Allocate and zero the statistics tables */
+ /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */
+ if (entropy->dc_count_ptrs[dctbl] == NULL)
+ entropy->dc_count_ptrs[dctbl] = (long *)
+ (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
+ 257 * sizeof(long));
+ memset(entropy->dc_count_ptrs[dctbl], 0, 257 * sizeof(long));
+ if (entropy->ac_count_ptrs[actbl] == NULL)
+ entropy->ac_count_ptrs[actbl] = (long *)
+ (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
+ 257 * sizeof(long));
+ memset(entropy->ac_count_ptrs[actbl], 0, 257 * sizeof(long));
+#endif
+ } else {
+ /* Compute derived values for Huffman tables */
+ /* We may do this more than once for a table, but it's not expensive */
+ jpeg_make_c_derived_tbl(cinfo, TRUE, dctbl,
+ &entropy->dc_derived_tbls[dctbl]);
+ jpeg_make_c_derived_tbl(cinfo, FALSE, actbl,
+ &entropy->ac_derived_tbls[actbl]);
+ }
+ /* Initialize DC predictions to 0 */
+ entropy->saved.last_dc_val[ci] = 0;
+ }
+
+ /* Initialize bit buffer to empty */
+ if (entropy->simd) {
+ entropy->saved.put_buffer.simd = 0;
+#if defined(__aarch64__) && !defined(NEON_INTRINSICS)
+ entropy->saved.free_bits = 0;
+#else
+ entropy->saved.free_bits = SIMD_BIT_BUF_SIZE;
+#endif
+ } else {
+ entropy->saved.put_buffer.c = 0;
+ entropy->saved.free_bits = BIT_BUF_SIZE;
+ }
+
+ /* Initialize restart stuff */
+ entropy->restarts_to_go = cinfo->restart_interval;
+ entropy->next_restart_num = 0;
+}
+
+
+/*
+ * Compute the derived values for a Huffman table.
+ * This routine also performs some validation checks on the table.
+ *
+ * Note this is also used by jcphuff.c.
+ */
+
+GLOBAL(void)
+jpeg_make_c_derived_tbl(j_compress_ptr cinfo, boolean isDC, int tblno,
+ c_derived_tbl **pdtbl)
+{
+ JHUFF_TBL *htbl;
+ c_derived_tbl *dtbl;
+ int p, i, l, lastp, si, maxsymbol;
+ char huffsize[257];
+ unsigned int huffcode[257];
+ unsigned int code;
+
+ /* Note that huffsize[] and huffcode[] are filled in code-length order,
+ * paralleling the order of the symbols themselves in htbl->huffval[].
+ */
+
+ /* Find the input Huffman table */
+ if (tblno < 0 || tblno >= NUM_HUFF_TBLS)
+ ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
+ htbl =
+ isDC ? cinfo->dc_huff_tbl_ptrs[tblno] : cinfo->ac_huff_tbl_ptrs[tblno];
+ if (htbl == NULL)
+ ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tblno);
+
+ /* Allocate a workspace if we haven't already done so. */
+ if (*pdtbl == NULL)
+ *pdtbl = (c_derived_tbl *)
+ (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
+ sizeof(c_derived_tbl));
+ dtbl = *pdtbl;
+
+ /* Figure C.1: make table of Huffman code length for each symbol */
+
+ p = 0;
+ for (l = 1; l <= 16; l++) {
+ i = (int)htbl->bits[l];
+ if (i < 0 || p + i > 256) /* protect against table overrun */
+ ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
+ while (i--)
+ huffsize[p++] = (char)l;
+ }
+ huffsize[p] = 0;
+ lastp = p;
+
+ /* Figure C.2: generate the codes themselves */
+ /* We also validate that the counts represent a legal Huffman code tree. */
+
+ code = 0;
+ si = huffsize[0];
+ p = 0;
+ while (huffsize[p]) {
+ while (((int)huffsize[p]) == si) {
+ huffcode[p++] = code;
+ code++;
+ }
+ /* code is now 1 more than the last code used for codelength si; but
+ * it must still fit in si bits, since no code is allowed to be all ones.
+ */
+ if (((JLONG)code) >= (((JLONG)1) << si))
+ ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
+ code <<= 1;
+ si++;
+ }
+
+ /* Figure C.3: generate encoding tables */
+ /* These are code and size indexed by symbol value */
+
+ /* Set all codeless symbols to have code length 0;
+ * this lets us detect duplicate VAL entries here, and later
+ * allows emit_bits to detect any attempt to emit such symbols.
+ */
+ memset(dtbl->ehufco, 0, sizeof(dtbl->ehufco));
+ memset(dtbl->ehufsi, 0, sizeof(dtbl->ehufsi));
+
+ /* This is also a convenient place to check for out-of-range
+ * and duplicated VAL entries. We allow 0..255 for AC symbols
+ * but only 0..15 for DC. (We could constrain them further
+ * based on data depth and mode, but this seems enough.)
+ */
+ maxsymbol = isDC ? 15 : 255;
+
+ for (p = 0; p < lastp; p++) {
+ i = htbl->huffval[p];
+ if (i < 0 || i > maxsymbol || dtbl->ehufsi[i])
+ ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
+ dtbl->ehufco[i] = huffcode[p];
+ dtbl->ehufsi[i] = huffsize[p];
+ }
+}
+
+
+/* Outputting bytes to the file */
+
+/* Emit a byte, taking 'action' if must suspend. */
+#define emit_byte(state, val, action) { \
+ *(state)->next_output_byte++ = (JOCTET)(val); \
+ if (--(state)->free_in_buffer == 0) \
+ if (!dump_buffer(state)) \
+ { action; } \
+}
+
+
+LOCAL(boolean)
+dump_buffer(working_state *state)
+/* Empty the output buffer; return TRUE if successful, FALSE if must suspend */
+{
+ struct jpeg_destination_mgr *dest = state->cinfo->dest;
+
+ if (!(*dest->empty_output_buffer) (state->cinfo))
+ return FALSE;
+ /* After a successful buffer dump, must reset buffer pointers */
+ state->next_output_byte = dest->next_output_byte;
+ state->free_in_buffer = dest->free_in_buffer;
+ return TRUE;
+}
+
+
+/* Outputting bits to the file */
+
+/* Output byte b and, speculatively, an additional 0 byte. 0xFF must be
+ * encoded as 0xFF 0x00, so the output buffer pointer is advanced by 2 if the
+ * byte is 0xFF. Otherwise, the output buffer pointer is advanced by 1, and
+ * the speculative 0 byte will be overwritten by the next byte.
+ */
+#define EMIT_BYTE(b) { \
+ buffer[0] = (JOCTET)(b); \
+ buffer[1] = 0; \
+ buffer -= -2 + ((JOCTET)(b) < 0xFF); \
+}
+
+/* Output the entire bit buffer. If there are no 0xFF bytes in it, then write
+ * directly to the output buffer. Otherwise, use the EMIT_BYTE() macro to
+ * encode 0xFF as 0xFF 0x00.
+ */
+#if BIT_BUF_SIZE == 64
+
+#define FLUSH() { \
+ if (put_buffer & 0x8080808080808080 & ~(put_buffer + 0x0101010101010101)) { \
+ EMIT_BYTE(put_buffer >> 56) \
+ EMIT_BYTE(put_buffer >> 48) \
+ EMIT_BYTE(put_buffer >> 40) \
+ EMIT_BYTE(put_buffer >> 32) \
+ EMIT_BYTE(put_buffer >> 24) \
+ EMIT_BYTE(put_buffer >> 16) \
+ EMIT_BYTE(put_buffer >> 8) \
+ EMIT_BYTE(put_buffer ) \
+ } else { \
+ buffer[0] = (JOCTET)(put_buffer >> 56); \
+ buffer[1] = (JOCTET)(put_buffer >> 48); \
+ buffer[2] = (JOCTET)(put_buffer >> 40); \
+ buffer[3] = (JOCTET)(put_buffer >> 32); \
+ buffer[4] = (JOCTET)(put_buffer >> 24); \
+ buffer[5] = (JOCTET)(put_buffer >> 16); \
+ buffer[6] = (JOCTET)(put_buffer >> 8); \
+ buffer[7] = (JOCTET)(put_buffer); \
+ buffer += 8; \
+ } \
+}
+
+#else
+
+#define FLUSH() { \
+ if (put_buffer & 0x80808080 & ~(put_buffer + 0x01010101)) { \
+ EMIT_BYTE(put_buffer >> 24) \
+ EMIT_BYTE(put_buffer >> 16) \
+ EMIT_BYTE(put_buffer >> 8) \
+ EMIT_BYTE(put_buffer ) \
+ } else { \
+ buffer[0] = (JOCTET)(put_buffer >> 24); \
+ buffer[1] = (JOCTET)(put_buffer >> 16); \
+ buffer[2] = (JOCTET)(put_buffer >> 8); \
+ buffer[3] = (JOCTET)(put_buffer); \
+ buffer += 4; \
+ } \
+}
+
+#endif
+
+/* Fill the bit buffer to capacity with the leading bits from code, then output
+ * the bit buffer and put the remaining bits from code into the bit buffer.
+ */
+#define PUT_AND_FLUSH(code, size) { \
+ put_buffer = (put_buffer << (size + free_bits)) | (code >> -free_bits); \
+ FLUSH() \
+ free_bits += BIT_BUF_SIZE; \
+ put_buffer = code; \
+}
+
+/* Insert code into the bit buffer and output the bit buffer if needed.
+ * NOTE: We can't flush with free_bits == 0, since the left shift in
+ * PUT_AND_FLUSH() would have undefined behavior.
+ */
+#define PUT_BITS(code, size) { \
+ free_bits -= size; \
+ if (free_bits < 0) \
+ PUT_AND_FLUSH(code, size) \
+ else \
+ put_buffer = (put_buffer << size) | code; \
+}
+
+#define PUT_CODE(code, size) { \
+ temp &= (((JLONG)1) << nbits) - 1; \
+ temp |= code << nbits; \
+ nbits += size; \
+ PUT_BITS(temp, nbits) \
+}
+
+
+/* Although it is exceedingly rare, it is possible for a Huffman-encoded
+ * coefficient block to be larger than the 128-byte unencoded block. For each
+ * of the 64 coefficients, PUT_BITS is invoked twice, and each invocation can
+ * theoretically store 16 bits (for a maximum of 2048 bits or 256 bytes per
+ * encoded block.) If, for instance, one artificially sets the AC
+ * coefficients to alternating values of 32767 and -32768 (using the JPEG
+ * scanning order-- 1, 8, 16, etc.), then this will produce an encoded block
+ * larger than 200 bytes.
+ */
+#define BUFSIZE (DCTSIZE2 * 8)
+
+#define LOAD_BUFFER() { \
+ if (state->free_in_buffer < BUFSIZE) { \
+ localbuf = 1; \
+ buffer = _buffer; \
+ } else \
+ buffer = state->next_output_byte; \
+}
+
+#define STORE_BUFFER() { \
+ if (localbuf) { \
+ size_t bytes, bytestocopy; \
+ bytes = buffer - _buffer; \
+ buffer = _buffer; \
+ while (bytes > 0) { \
+ bytestocopy = MIN(bytes, state->free_in_buffer); \
+ memcpy(state->next_output_byte, buffer, bytestocopy); \
+ state->next_output_byte += bytestocopy; \
+ buffer += bytestocopy; \
+ state->free_in_buffer -= bytestocopy; \
+ if (state->free_in_buffer == 0) \
+ if (!dump_buffer(state)) return FALSE; \
+ bytes -= bytestocopy; \
+ } \
+ } else { \
+ state->free_in_buffer -= (buffer - state->next_output_byte); \
+ state->next_output_byte = buffer; \
+ } \
+}
+
+
+LOCAL(boolean)
+flush_bits(working_state *state)
+{
+ JOCTET _buffer[BUFSIZE], *buffer, temp;
+ simd_bit_buf_type put_buffer; int put_bits;
+ int localbuf = 0;
+
+ if (state->simd) {
+#if defined(__aarch64__) && !defined(NEON_INTRINSICS)
+ put_bits = state->cur.free_bits;
+#else
+ put_bits = SIMD_BIT_BUF_SIZE - state->cur.free_bits;
+#endif
+ put_buffer = state->cur.put_buffer.simd;
+ } else {
+ put_bits = BIT_BUF_SIZE - state->cur.free_bits;
+ put_buffer = state->cur.put_buffer.c;
+ }
+
+ LOAD_BUFFER()
+
+ while (put_bits >= 8) {
+ put_bits -= 8;
+ temp = (JOCTET)(put_buffer >> put_bits);
+ EMIT_BYTE(temp)
+ }
+ if (put_bits) {
+ /* fill partial byte with ones */
+ temp = (JOCTET)((put_buffer << (8 - put_bits)) | (0xFF >> put_bits));
+ EMIT_BYTE(temp)
+ }
+
+ if (state->simd) { /* and reset bit buffer to empty */
+ state->cur.put_buffer.simd = 0;
+#if defined(__aarch64__) && !defined(NEON_INTRINSICS)
+ state->cur.free_bits = 0;
+#else
+ state->cur.free_bits = SIMD_BIT_BUF_SIZE;
+#endif
+ } else {
+ state->cur.put_buffer.c = 0;
+ state->cur.free_bits = BIT_BUF_SIZE;
+ }
+ STORE_BUFFER()
+
+ return TRUE;
+}
+
+
+/* Encode a single block's worth of coefficients */
+
+LOCAL(boolean)
+encode_one_block_simd(working_state *state, JCOEFPTR block, int last_dc_val,
+ c_derived_tbl *dctbl, c_derived_tbl *actbl)
+{
+ JOCTET _buffer[BUFSIZE], *buffer;
+ int localbuf = 0;
+
+ LOAD_BUFFER()
+
+ buffer = jsimd_huff_encode_one_block(state, buffer, block, last_dc_val,
+ dctbl, actbl);
+
+ STORE_BUFFER()
+
+ return TRUE;
+}
+
+LOCAL(boolean)
+encode_one_block(working_state *state, JCOEFPTR block, int last_dc_val,
+ c_derived_tbl *dctbl, c_derived_tbl *actbl)
+{
+ int temp, nbits, free_bits;
+ bit_buf_type put_buffer;
+ JOCTET _buffer[BUFSIZE], *buffer;
+ int localbuf = 0;
+
+ free_bits = state->cur.free_bits;
+ put_buffer = state->cur.put_buffer.c;
+ LOAD_BUFFER()
+
+ /* Encode the DC coefficient difference per section F.1.2.1 */
+
+ temp = block[0] - last_dc_val;
+
+ /* This is a well-known technique for obtaining the absolute value without a
+ * branch. It is derived from an assembly language technique presented in
+ * "How to Optimize for the Pentium Processors", Copyright (c) 1996, 1997 by
+ * Agner Fog. This code assumes we are on a two's complement machine.
+ */
+ nbits = temp >> (CHAR_BIT * sizeof(int) - 1);
+ temp += nbits;
+ nbits ^= temp;
+
+ /* Find the number of bits needed for the magnitude of the coefficient */
+ nbits = JPEG_NBITS(nbits);
+
+ /* Emit the Huffman-coded symbol for the number of bits.
+ * Emit that number of bits of the value, if positive,
+ * or the complement of its magnitude, if negative.
+ */
+ PUT_CODE(dctbl->ehufco[nbits], dctbl->ehufsi[nbits])
+
+ /* Encode the AC coefficients per section F.1.2.2 */
+
+ {
+ int r = 0; /* r = run length of zeros */
+
+/* Manually unroll the k loop to eliminate the counter variable. This
+ * improves performance greatly on systems with a limited number of
+ * registers (such as x86.)
+ */
+#define kloop(jpeg_natural_order_of_k) { \
+ if ((temp = block[jpeg_natural_order_of_k]) == 0) { \
+ r += 16; \
+ } else { \
+ /* Branch-less absolute value, bitwise complement, etc., same as above */ \
+ nbits = temp >> (CHAR_BIT * sizeof(int) - 1); \
+ temp += nbits; \
+ nbits ^= temp; \
+ nbits = JPEG_NBITS_NONZERO(nbits); \
+ /* if run length > 15, must emit special run-length-16 codes (0xF0) */ \
+ while (r >= 16 * 16) { \
+ r -= 16 * 16; \
+ PUT_BITS(actbl->ehufco[0xf0], actbl->ehufsi[0xf0]) \
+ } \
+ /* Emit Huffman symbol for run length / number of bits */ \
+ r += nbits; \
+ PUT_CODE(actbl->ehufco[r], actbl->ehufsi[r]) \
+ r = 0; \
+ } \
+}
+
+ /* One iteration for each value in jpeg_natural_order[] */
+ kloop(1); kloop(8); kloop(16); kloop(9); kloop(2); kloop(3);
+ kloop(10); kloop(17); kloop(24); kloop(32); kloop(25); kloop(18);
+ kloop(11); kloop(4); kloop(5); kloop(12); kloop(19); kloop(26);
+ kloop(33); kloop(40); kloop(48); kloop(41); kloop(34); kloop(27);
+ kloop(20); kloop(13); kloop(6); kloop(7); kloop(14); kloop(21);
+ kloop(28); kloop(35); kloop(42); kloop(49); kloop(56); kloop(57);
+ kloop(50); kloop(43); kloop(36); kloop(29); kloop(22); kloop(15);
+ kloop(23); kloop(30); kloop(37); kloop(44); kloop(51); kloop(58);
+ kloop(59); kloop(52); kloop(45); kloop(38); kloop(31); kloop(39);
+ kloop(46); kloop(53); kloop(60); kloop(61); kloop(54); kloop(47);
+ kloop(55); kloop(62); kloop(63);
+
+ /* If the last coef(s) were zero, emit an end-of-block code */
+ if (r > 0) {
+ PUT_BITS(actbl->ehufco[0], actbl->ehufsi[0])
+ }
+ }
+
+ state->cur.put_buffer.c = put_buffer;
+ state->cur.free_bits = free_bits;
+ STORE_BUFFER()
+
+ return TRUE;
+}
+
+
+/*
+ * Emit a restart marker & resynchronize predictions.
+ */
+
+LOCAL(boolean)
+emit_restart(working_state *state, int restart_num)
+{
+ int ci;
+
+ if (!flush_bits(state))
+ return FALSE;
+
+ emit_byte(state, 0xFF, return FALSE);
+ emit_byte(state, JPEG_RST0 + restart_num, return FALSE);
+
+ /* Re-initialize DC predictions to 0 */
+ for (ci = 0; ci < state->cinfo->comps_in_scan; ci++)
+ state->cur.last_dc_val[ci] = 0;
+
+ /* The restart counter is not updated until we successfully write the MCU. */
+
+ return TRUE;
+}
+
+
+/*
+ * Encode and output one MCU's worth of Huffman-compressed coefficients.
+ */
+
+METHODDEF(boolean)
+encode_mcu_huff(j_compress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
+ working_state state;
+ int blkn, ci;
+ jpeg_component_info *compptr;
+
+ /* Load up working state */
+ state.next_output_byte = cinfo->dest->next_output_byte;
+ state.free_in_buffer = cinfo->dest->free_in_buffer;
+ state.cur = entropy->saved;
+ state.cinfo = cinfo;
+ state.simd = entropy->simd;
+
+ /* Emit restart marker if needed */
+ if (cinfo->restart_interval) {
+ if (entropy->restarts_to_go == 0)
+ if (!emit_restart(&state, entropy->next_restart_num))
+ return FALSE;
+ }
+
+ /* Encode the MCU data blocks */
+ if (entropy->simd) {
+ for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
+ ci = cinfo->MCU_membership[blkn];
+ compptr = cinfo->cur_comp_info[ci];
+ if (!encode_one_block_simd(&state,
+ MCU_data[blkn][0], state.cur.last_dc_val[ci],
+ entropy->dc_derived_tbls[compptr->dc_tbl_no],
+ entropy->ac_derived_tbls[compptr->ac_tbl_no]))
+ return FALSE;
+ /* Update last_dc_val */
+ state.cur.last_dc_val[ci] = MCU_data[blkn][0][0];
+ }
+ } else {
+ for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
+ ci = cinfo->MCU_membership[blkn];
+ compptr = cinfo->cur_comp_info[ci];
+ if (!encode_one_block(&state,
+ MCU_data[blkn][0], state.cur.last_dc_val[ci],
+ entropy->dc_derived_tbls[compptr->dc_tbl_no],
+ entropy->ac_derived_tbls[compptr->ac_tbl_no]))
+ return FALSE;
+ /* Update last_dc_val */
+ state.cur.last_dc_val[ci] = MCU_data[blkn][0][0];
+ }
+ }
+
+ /* Completed MCU, so update state */
+ cinfo->dest->next_output_byte = state.next_output_byte;
+ cinfo->dest->free_in_buffer = state.free_in_buffer;
+ entropy->saved = state.cur;
+
+ /* Update restart-interval state too */
+ if (cinfo->restart_interval) {
+ if (entropy->restarts_to_go == 0) {
+ entropy->restarts_to_go = cinfo->restart_interval;
+ entropy->next_restart_num++;
+ entropy->next_restart_num &= 7;
+ }
+ entropy->restarts_to_go--;
+ }
+
+ return TRUE;
+}
+
+
+/*
+ * Finish up at the end of a Huffman-compressed scan.
+ */
+
+METHODDEF(void)
+finish_pass_huff(j_compress_ptr cinfo)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
+ working_state state;
+
+ /* Load up working state ... flush_bits needs it */
+ state.next_output_byte = cinfo->dest->next_output_byte;
+ state.free_in_buffer = cinfo->dest->free_in_buffer;
+ state.cur = entropy->saved;
+ state.cinfo = cinfo;
+ state.simd = entropy->simd;
+
+ /* Flush out the last data */
+ if (!flush_bits(&state))
+ ERREXIT(cinfo, JERR_CANT_SUSPEND);
+
+ /* Update state */
+ cinfo->dest->next_output_byte = state.next_output_byte;
+ cinfo->dest->free_in_buffer = state.free_in_buffer;
+ entropy->saved = state.cur;
+}
+
+
+/*
+ * Huffman coding optimization.
+ *
+ * We first scan the supplied data and count the number of uses of each symbol
+ * that is to be Huffman-coded. (This process MUST agree with the code above.)
+ * Then we build a Huffman coding tree for the observed counts.
+ * Symbols which are not needed at all for the particular image are not
+ * assigned any code, which saves space in the DHT marker as well as in
+ * the compressed data.
+ */
+
+#ifdef ENTROPY_OPT_SUPPORTED
+
+
+/* Process a single block's worth of coefficients */
+
+LOCAL(void)
+htest_one_block(j_compress_ptr cinfo, JCOEFPTR block, int last_dc_val,
+ long dc_counts[], long ac_counts[])
+{
+ register int temp;
+ register int nbits;
+ register int k, r;
+
+ /* Encode the DC coefficient difference per section F.1.2.1 */
+
+ temp = block[0] - last_dc_val;
+ if (temp < 0)
+ temp = -temp;
+
+ /* Find the number of bits needed for the magnitude of the coefficient */
+ nbits = 0;
+ while (temp) {
+ nbits++;
+ temp >>= 1;
+ }
+ /* Check for out-of-range coefficient values.
+ * Since we're encoding a difference, the range limit is twice as much.
+ */
+ if (nbits > MAX_COEF_BITS + 1)
+ ERREXIT(cinfo, JERR_BAD_DCT_COEF);
+
+ /* Count the Huffman symbol for the number of bits */
+ dc_counts[nbits]++;
+
+ /* Encode the AC coefficients per section F.1.2.2 */
+
+ r = 0; /* r = run length of zeros */
+
+ for (k = 1; k < DCTSIZE2; k++) {
+ if ((temp = block[jpeg_natural_order[k]]) == 0) {
+ r++;
+ } else {
+ /* if run length > 15, must emit special run-length-16 codes (0xF0) */
+ while (r > 15) {
+ ac_counts[0xF0]++;
+ r -= 16;
+ }
+
+ /* Find the number of bits needed for the magnitude of the coefficient */
+ if (temp < 0)
+ temp = -temp;
+
+ /* Find the number of bits needed for the magnitude of the coefficient */
+ nbits = 1; /* there must be at least one 1 bit */
+ while ((temp >>= 1))
+ nbits++;
+ /* Check for out-of-range coefficient values */
+ if (nbits > MAX_COEF_BITS)
+ ERREXIT(cinfo, JERR_BAD_DCT_COEF);
+
+ /* Count Huffman symbol for run length / number of bits */
+ ac_counts[(r << 4) + nbits]++;
+
+ r = 0;
+ }
+ }
+
+ /* If the last coef(s) were zero, emit an end-of-block code */
+ if (r > 0)
+ ac_counts[0]++;
+}
+
+
+/*
+ * Trial-encode one MCU's worth of Huffman-compressed coefficients.
+ * No data is actually output, so no suspension return is possible.
+ */
+
+METHODDEF(boolean)
+encode_mcu_gather(j_compress_ptr cinfo, JBLOCKROW *MCU_data)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
+ int blkn, ci;
+ jpeg_component_info *compptr;
+
+ /* Take care of restart intervals if needed */
+ if (cinfo->restart_interval) {
+ if (entropy->restarts_to_go == 0) {
+ /* Re-initialize DC predictions to 0 */
+ for (ci = 0; ci < cinfo->comps_in_scan; ci++)
+ entropy->saved.last_dc_val[ci] = 0;
+ /* Update restart state */
+ entropy->restarts_to_go = cinfo->restart_interval;
+ }
+ entropy->restarts_to_go--;
+ }
+
+ for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
+ ci = cinfo->MCU_membership[blkn];
+ compptr = cinfo->cur_comp_info[ci];
+ htest_one_block(cinfo, MCU_data[blkn][0], entropy->saved.last_dc_val[ci],
+ entropy->dc_count_ptrs[compptr->dc_tbl_no],
+ entropy->ac_count_ptrs[compptr->ac_tbl_no]);
+ entropy->saved.last_dc_val[ci] = MCU_data[blkn][0][0];
+ }
+
+ return TRUE;
+}
+
+
+/*
+ * Generate the best Huffman code table for the given counts, fill htbl.
+ * Note this is also used by jcphuff.c.
+ *
+ * The JPEG standard requires that no symbol be assigned a codeword of all
+ * one bits (so that padding bits added at the end of a compressed segment
+ * can't look like a valid code). Because of the canonical ordering of
+ * codewords, this just means that there must be an unused slot in the
+ * longest codeword length category. Annex K (Clause K.2) of
+ * Rec. ITU-T T.81 (1992) | ISO/IEC 10918-1:1994 suggests reserving such a slot
+ * by pretending that symbol 256 is a valid symbol with count 1. In theory
+ * that's not optimal; giving it count zero but including it in the symbol set
+ * anyway should give a better Huffman code. But the theoretically better code
+ * actually seems to come out worse in practice, because it produces more
+ * all-ones bytes (which incur stuffed zero bytes in the final file). In any
+ * case the difference is tiny.
+ *
+ * The JPEG standard requires Huffman codes to be no more than 16 bits long.
+ * If some symbols have a very small but nonzero probability, the Huffman tree
+ * must be adjusted to meet the code length restriction. We currently use
+ * the adjustment method suggested in JPEG section K.2. This method is *not*
+ * optimal; it may not choose the best possible limited-length code. But
+ * typically only very-low-frequency symbols will be given less-than-optimal
+ * lengths, so the code is almost optimal. Experimental comparisons against
+ * an optimal limited-length-code algorithm indicate that the difference is
+ * microscopic --- usually less than a hundredth of a percent of total size.
+ * So the extra complexity of an optimal algorithm doesn't seem worthwhile.
+ */
+
+GLOBAL(void)
+jpeg_gen_optimal_table(j_compress_ptr cinfo, JHUFF_TBL *htbl, long freq[])
+{
+#define MAX_CLEN 32 /* assumed maximum initial code length */
+ UINT8 bits[MAX_CLEN + 1]; /* bits[k] = # of symbols with code length k */
+ int codesize[257]; /* codesize[k] = code length of symbol k */
+ int others[257]; /* next symbol in current branch of tree */
+ int c1, c2;
+ int p, i, j;
+ long v;
+
+ /* This algorithm is explained in section K.2 of the JPEG standard */
+
+ memset(bits, 0, sizeof(bits));
+ memset(codesize, 0, sizeof(codesize));
+ for (i = 0; i < 257; i++)
+ others[i] = -1; /* init links to empty */
+
+ freq[256] = 1; /* make sure 256 has a nonzero count */
+ /* Including the pseudo-symbol 256 in the Huffman procedure guarantees
+ * that no real symbol is given code-value of all ones, because 256
+ * will be placed last in the largest codeword category.
+ */
+
+ /* Huffman's basic algorithm to assign optimal code lengths to symbols */
+
+ for (;;) {
+ /* Find the smallest nonzero frequency, set c1 = its symbol */
+ /* In case of ties, take the larger symbol number */
+ c1 = -1;
+ v = 1000000000L;
+ for (i = 0; i <= 256; i++) {
+ if (freq[i] && freq[i] <= v) {
+ v = freq[i];
+ c1 = i;
+ }
+ }
+
+ /* Find the next smallest nonzero frequency, set c2 = its symbol */
+ /* In case of ties, take the larger symbol number */
+ c2 = -1;
+ v = 1000000000L;
+ for (i = 0; i <= 256; i++) {
+ if (freq[i] && freq[i] <= v && i != c1) {
+ v = freq[i];
+ c2 = i;
+ }
+ }
+
+ /* Done if we've merged everything into one frequency */
+ if (c2 < 0)
+ break;
+
+ /* Else merge the two counts/trees */
+ freq[c1] += freq[c2];
+ freq[c2] = 0;
+
+ /* Increment the codesize of everything in c1's tree branch */
+ codesize[c1]++;
+ while (others[c1] >= 0) {
+ c1 = others[c1];
+ codesize[c1]++;
+ }
+
+ others[c1] = c2; /* chain c2 onto c1's tree branch */
+
+ /* Increment the codesize of everything in c2's tree branch */
+ codesize[c2]++;
+ while (others[c2] >= 0) {
+ c2 = others[c2];
+ codesize[c2]++;
+ }
+ }
+
+ /* Now count the number of symbols of each code length */
+ for (i = 0; i <= 256; i++) {
+ if (codesize[i]) {
+ /* The JPEG standard seems to think that this can't happen, */
+ /* but I'm paranoid... */
+ if (codesize[i] > MAX_CLEN)
+ ERREXIT(cinfo, JERR_HUFF_CLEN_OVERFLOW);
+
+ bits[codesize[i]]++;
+ }
+ }
+
+ /* JPEG doesn't allow symbols with code lengths over 16 bits, so if the pure
+ * Huffman procedure assigned any such lengths, we must adjust the coding.
+ * Here is what Rec. ITU-T T.81 | ISO/IEC 10918-1 says about how this next
+ * bit works: Since symbols are paired for the longest Huffman code, the
+ * symbols are removed from this length category two at a time. The prefix
+ * for the pair (which is one bit shorter) is allocated to one of the pair;
+ * then, skipping the BITS entry for that prefix length, a code word from the
+ * next shortest nonzero BITS entry is converted into a prefix for two code
+ * words one bit longer.
+ */
+
+ for (i = MAX_CLEN; i > 16; i--) {
+ while (bits[i] > 0) {
+ j = i - 2; /* find length of new prefix to be used */
+ while (bits[j] == 0)
+ j--;
+
+ bits[i] -= 2; /* remove two symbols */
+ bits[i - 1]++; /* one goes in this length */
+ bits[j + 1] += 2; /* two new symbols in this length */
+ bits[j]--; /* symbol of this length is now a prefix */
+ }
+ }
+
+ /* Remove the count for the pseudo-symbol 256 from the largest codelength */
+ while (bits[i] == 0) /* find largest codelength still in use */
+ i--;
+ bits[i]--;
+
+ /* Return final symbol counts (only for lengths 0..16) */
+ memcpy(htbl->bits, bits, sizeof(htbl->bits));
+
+ /* Return a list of the symbols sorted by code length */
+ /* It's not real clear to me why we don't need to consider the codelength
+ * changes made above, but Rec. ITU-T T.81 | ISO/IEC 10918-1 seems to think
+ * this works.
+ */
+ p = 0;
+ for (i = 1; i <= MAX_CLEN; i++) {
+ for (j = 0; j <= 255; j++) {
+ if (codesize[j] == i) {
+ htbl->huffval[p] = (UINT8)j;
+ p++;
+ }
+ }
+ }
+
+ /* Set sent_table FALSE so updated table will be written to JPEG file. */
+ htbl->sent_table = FALSE;
+}
+
+
+/*
+ * Finish up a statistics-gathering pass and create the new Huffman tables.
+ */
+
+METHODDEF(void)
+finish_pass_gather(j_compress_ptr cinfo)
+{
+ huff_entropy_ptr entropy = (huff_entropy_ptr)cinfo->entropy;
+ int ci, dctbl, actbl;
+ jpeg_component_info *compptr;
+ JHUFF_TBL **htblptr;
+ boolean did_dc[NUM_HUFF_TBLS];
+ boolean did_ac[NUM_HUFF_TBLS];
+
+ /* It's important not to apply jpeg_gen_optimal_table more than once
+ * per table, because it clobbers the input frequency counts!
+ */
+ memset(did_dc, 0, sizeof(did_dc));
+ memset(did_ac, 0, sizeof(did_ac));
+
+ for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
+ compptr = cinfo->cur_comp_info[ci];
+ dctbl = compptr->dc_tbl_no;
+ actbl = compptr->ac_tbl_no;
+ if (!did_dc[dctbl]) {
+ htblptr = &cinfo->dc_huff_tbl_ptrs[dctbl];
+ if (*htblptr == NULL)
+ *htblptr = jpeg_alloc_huff_table((j_common_ptr)cinfo);
+ jpeg_gen_optimal_table(cinfo, *htblptr, entropy->dc_count_ptrs[dctbl]);
+ did_dc[dctbl] = TRUE;
+ }
+ if (!did_ac[actbl]) {
+ htblptr = &cinfo->ac_huff_tbl_ptrs[actbl];
+ if (*htblptr == NULL)
+ *htblptr = jpeg_alloc_huff_table((j_common_ptr)cinfo);
+ jpeg_gen_optimal_table(cinfo, *htblptr, entropy->ac_count_ptrs[actbl]);
+ did_ac[actbl] = TRUE;
+ }
+ }
+}
+
+
+#endif /* ENTROPY_OPT_SUPPORTED */
+
+
+/*
+ * Module initialization routine for Huffman entropy encoding.
+ */
+
+GLOBAL(void)
+jinit_huff_encoder(j_compress_ptr cinfo)
+{
+ huff_entropy_ptr entropy;
+ int i;
+
+ entropy = (huff_entropy_ptr)
+ (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
+ sizeof(huff_entropy_encoder));
+ cinfo->entropy = (struct jpeg_entropy_encoder *)entropy;
+ entropy->pub.start_pass = start_pass_huff;
+
+ /* Mark tables unallocated */
+ for (i = 0; i < NUM_HUFF_TBLS; i++) {
+ entropy->dc_derived_tbls[i] = entropy->ac_derived_tbls[i] = NULL;
+#ifdef ENTROPY_OPT_SUPPORTED
+ entropy->dc_count_ptrs[i] = entropy->ac_count_ptrs[i] = NULL;
+#endif
+ }
+}