| /* |
| * 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, 2018-2020, 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__)) |
| #if !defined(__thumb__) || defined(__thumb2__) |
| #define USE_CLZ_INTRINSIC |
| #endif |
| #endif |
| |
| #ifdef USE_CLZ_INTRINSIC |
| #define JPEG_NBITS_NONZERO(x) (32 - __builtin_clz(x)) |
| #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)); |
| MEMZERO(entropy->dc_count_ptrs[dctbl], 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)); |
| MEMZERO(entropy->ac_count_ptrs[actbl], 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. |
| */ |
| MEMZERO(dtbl->ehufsi, 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); \ |
| MEMCOPY(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 */ |
| |
| MEMZERO(bits, sizeof(bits)); |
| MEMZERO(codesize, 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) */ |
| MEMCOPY(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! |
| */ |
| MEMZERO(did_dc, sizeof(did_dc)); |
| MEMZERO(did_ac, 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 |
| } |
| } |