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