148 lines
3.1 KiB
C
148 lines
3.1 KiB
C
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#include "libbb.h"
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#ifdef CONFIG_FEATURE_LZMA_FAST
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# define speed_inline ATTRIBUTE_ALWAYS_INLINE
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#else
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# define speed_inline
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#endif
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typedef struct {
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int fd;
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uint8_t *ptr;
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uint8_t *buffer;
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uint8_t *buffer_end;
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int buffer_size;
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uint32_t code;
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uint32_t range;
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uint32_t bound;
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} rc_t;
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#define RC_TOP_BITS 24
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#define RC_MOVE_BITS 5
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#define RC_MODEL_TOTAL_BITS 11
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/* Called twice: once at startup and once in rc_normalize() */
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static void rc_read(rc_t * rc)
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{
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rc->buffer_size = read(rc->fd, rc->buffer, rc->buffer_size);
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if (rc->buffer_size <= 0)
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bb_error_msg_and_die("unexpected EOF");
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rc->ptr = rc->buffer;
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rc->buffer_end = rc->buffer + rc->buffer_size;
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}
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/* Called once */
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static ATTRIBUTE_ALWAYS_INLINE void rc_init(rc_t * rc, int fd, int buffer_size)
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{
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int i;
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rc->fd = fd;
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rc->buffer = malloc(buffer_size);
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rc->buffer_size = buffer_size;
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rc->buffer_end = rc->buffer + rc->buffer_size;
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rc->ptr = rc->buffer_end;
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rc->code = 0;
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rc->range = 0xFFFFFFFF;
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for (i = 0; i < 5; i++) {
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if (rc->ptr >= rc->buffer_end)
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rc_read(rc);
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rc->code = (rc->code << 8) | *rc->ptr++;
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}
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}
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/* Called once. TODO: bb_maybe_free() */
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static ATTRIBUTE_ALWAYS_INLINE void rc_free(rc_t * rc)
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{
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if (ENABLE_FEATURE_CLEAN_UP)
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free(rc->buffer);
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}
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/* Called twice, but one callsite is in speed_inline'd rc_is_bit_0_helper() */
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static void rc_do_normalize(rc_t * rc)
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{
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if (rc->ptr >= rc->buffer_end)
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rc_read(rc);
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rc->range <<= 8;
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rc->code = (rc->code << 8) | *rc->ptr++;
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}
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static ATTRIBUTE_ALWAYS_INLINE void rc_normalize(rc_t * rc)
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{
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if (rc->range < (1 << RC_TOP_BITS)) {
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rc_do_normalize(rc);
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}
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}
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/* Called 9 times */
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/* Why rc_is_bit_0_helper exists?
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* Because we want to always expose (rc->code < rc->bound) to optimizer
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*/
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static speed_inline uint32_t rc_is_bit_0_helper(rc_t * rc, uint16_t * p)
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{
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rc_normalize(rc);
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rc->bound = *p * (rc->range >> RC_MODEL_TOTAL_BITS);
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return rc->bound;
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}
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static ATTRIBUTE_ALWAYS_INLINE int rc_is_bit_0(rc_t * rc, uint16_t * p)
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{
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uint32_t t = rc_is_bit_0_helper(rc, p);
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return rc->code < t;
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}
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/* Called ~10 times, but very small, thus inlined */
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static speed_inline void rc_update_bit_0(rc_t * rc, uint16_t * p)
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{
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rc->range = rc->bound;
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*p += ((1 << RC_MODEL_TOTAL_BITS) - *p) >> RC_MOVE_BITS;
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}
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static speed_inline void rc_update_bit_1(rc_t * rc, uint16_t * p)
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{
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rc->range -= rc->bound;
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rc->code -= rc->bound;
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*p -= *p >> RC_MOVE_BITS;
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}
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/* Called 4 times in unlzma loop */
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static int rc_get_bit(rc_t * rc, uint16_t * p, int *symbol)
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{
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if (rc_is_bit_0(rc, p)) {
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rc_update_bit_0(rc, p);
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*symbol *= 2;
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return 0;
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} else {
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rc_update_bit_1(rc, p);
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*symbol = *symbol * 2 + 1;
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return 1;
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}
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}
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/* Called once */
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static ATTRIBUTE_ALWAYS_INLINE int rc_direct_bit(rc_t * rc)
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{
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rc_normalize(rc);
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rc->range >>= 1;
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if (rc->code >= rc->range) {
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rc->code -= rc->range;
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return 1;
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}
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return 0;
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}
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/* Called twice */
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static speed_inline void
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rc_bit_tree_decode(rc_t * rc, uint16_t * p, int num_levels, int *symbol)
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{
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int i = num_levels;
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*symbol = 1;
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while (i--)
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rc_get_bit(rc, p + *symbol, symbol);
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*symbol -= 1 << num_levels;
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}
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/* vi:set ts=4: */
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