jchuff.h (3950B)
1 /* 2 * jchuff.h 3 * 4 * This file was part of the Independent JPEG Group's software: 5 * Copyright (C) 1991-1997, Thomas G. Lane. 6 * libjpeg-turbo Modifications: 7 * Copyright (C) 2009, 2018, 2021, D. R. Commander. 8 * Copyright (C) 2018, Matthias Räncker. 9 * Copyright (C) 2020-2021, Arm Limited. 10 * For conditions of distribution and use, see the accompanying README.ijg 11 * file. 12 */ 13 14 /* Expanded entropy encoder object for Huffman encoding. 15 * 16 * The savable_state subrecord contains fields that change within an MCU, 17 * but must not be updated permanently until we complete the MCU. 18 */ 19 20 #if defined(__aarch64__) || defined(_M_ARM64) 21 #define BIT_BUF_SIZE 64 22 #else 23 #define BIT_BUF_SIZE 32 24 #endif 25 26 typedef struct { 27 size_t put_buffer; /* current bit accumulation buffer */ 28 int free_bits; /* # of bits available in it */ 29 int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */ 30 } savable_state; 31 32 typedef struct { 33 JOCTET *next_output_byte; /* => next byte to write in buffer */ 34 size_t free_in_buffer; /* # of byte spaces remaining in buffer */ 35 savable_state cur; /* Current bit buffer & DC state */ 36 j_compress_ptr cinfo; /* dump_buffer needs access to this */ 37 int simd; 38 } working_state; 39 40 /* Outputting bits to the file */ 41 42 /* Output byte b and, speculatively, an additional 0 byte. 0xFF must be encoded 43 * as 0xFF 0x00, so the output buffer pointer is advanced by 2 if the byte is 44 * 0xFF. Otherwise, the output buffer pointer is advanced by 1, and the 45 * speculative 0 byte will be overwritten by the next byte. 46 */ 47 #define EMIT_BYTE(b) { \ 48 buffer[0] = (JOCTET)(b); \ 49 buffer[1] = 0; \ 50 buffer -= -2 + ((JOCTET)(b) < 0xFF); \ 51 } 52 53 /* Output the entire bit buffer. If there are no 0xFF bytes in it, then write 54 * directly to the output buffer. Otherwise, use the EMIT_BYTE() macro to 55 * encode 0xFF as 0xFF 0x00. 56 */ 57 #if defined(__aarch64__) || defined(_M_ARM64) 58 59 #define FLUSH() { \ 60 if (put_buffer & 0x8080808080808080 & ~(put_buffer + 0x0101010101010101)) { \ 61 EMIT_BYTE(put_buffer >> 56) \ 62 EMIT_BYTE(put_buffer >> 48) \ 63 EMIT_BYTE(put_buffer >> 40) \ 64 EMIT_BYTE(put_buffer >> 32) \ 65 EMIT_BYTE(put_buffer >> 24) \ 66 EMIT_BYTE(put_buffer >> 16) \ 67 EMIT_BYTE(put_buffer >> 8) \ 68 EMIT_BYTE(put_buffer ) \ 69 } else { \ 70 *((uint64_t *)buffer) = BUILTIN_BSWAP64(put_buffer); \ 71 buffer += 8; \ 72 } \ 73 } 74 75 #else 76 77 #if defined(_MSC_VER) && !defined(__clang__) 78 #define SPLAT() { \ 79 buffer[0] = (JOCTET)(put_buffer >> 24); \ 80 buffer[1] = (JOCTET)(put_buffer >> 16); \ 81 buffer[2] = (JOCTET)(put_buffer >> 8); \ 82 buffer[3] = (JOCTET)(put_buffer ); \ 83 buffer += 4; \ 84 } 85 #else 86 #define SPLAT() { \ 87 put_buffer = __builtin_bswap32(put_buffer); \ 88 __asm__("str %1, [%0], #4" : "+r" (buffer) : "r" (put_buffer)); \ 89 } 90 #endif 91 92 #define FLUSH() { \ 93 if (put_buffer & 0x80808080 & ~(put_buffer + 0x01010101)) { \ 94 EMIT_BYTE(put_buffer >> 24) \ 95 EMIT_BYTE(put_buffer >> 16) \ 96 EMIT_BYTE(put_buffer >> 8) \ 97 EMIT_BYTE(put_buffer ) \ 98 } else { \ 99 SPLAT(); \ 100 } \ 101 } 102 103 #endif 104 105 /* Fill the bit buffer to capacity with the leading bits from code, then output 106 * the bit buffer and put the remaining bits from code into the bit buffer. 107 */ 108 #define PUT_AND_FLUSH(code, size) { \ 109 put_buffer = (put_buffer << (size + free_bits)) | (code >> -free_bits); \ 110 FLUSH() \ 111 free_bits += BIT_BUF_SIZE; \ 112 put_buffer = code; \ 113 } 114 115 /* Insert code into the bit buffer and output the bit buffer if needed. 116 * NOTE: We can't flush with free_bits == 0, since the left shift in 117 * PUT_AND_FLUSH() would have undefined behavior. 118 */ 119 #define PUT_BITS(code, size) { \ 120 free_bits -= size; \ 121 if (free_bits < 0) \ 122 PUT_AND_FLUSH(code, size) \ 123 else \ 124 put_buffer = (put_buffer << size) | code; \ 125 } 126 127 #define PUT_CODE(code, size, diff) { \ 128 diff |= code << nbits; \ 129 nbits += size; \ 130 PUT_BITS(diff, nbits) \ 131 }