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/*
* jchuff.h
*
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1991-1997, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 2009, 2018, 2021, D. R. Commander.
* Copyright (C) 2018, Matthias Räncker.
* Copyright (C) 2020-2021, Arm Limited.
* For conditions of distribution and use, see the accompanying README.ijg
* file.
*/
/* 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(__aarch64__) || defined(_M_ARM64)
#define BIT_BUF_SIZE 64
#else
#define BIT_BUF_SIZE 32
#endif
typedef struct {
size_t put_buffer; /* current bit accumulation buffer */
int free_bits; /* # of bits available in it */
int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
} savable_state;
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;
/* 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 defined(__aarch64__) || defined(_M_ARM64)
#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 { \
*((uint64_t *)buffer) = BUILTIN_BSWAP64(put_buffer); \
buffer += 8; \
} \
}
#else
#if defined(_MSC_VER) && !defined(__clang__)
#define SPLAT() { \
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; \
}
#else
#define SPLAT() { \
put_buffer = __builtin_bswap32(put_buffer); \
__asm__("str %1, [%0], #4" : "+r" (buffer) : "r" (put_buffer)); \
}
#endif
#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 { \
SPLAT(); \
} \
}
#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, diff) { \
diff |= code << nbits; \
nbits += size; \
PUT_BITS(diff, nbits) \
}