#endif
#include "wimlib/endianness.h"
-#include "wimlib/error.h"
#include "wimlib/lzms.h"
#include "wimlib/util.h"
#include <pthread.h>
-/* A table that maps position slots to their base values. These are constants
- * computed at runtime by lzms_compute_slot_bases(). */
+/***************************************************************
+ * Constant tables initialized by lzms_compute_slots(): *
+ ***************************************************************/
+
+/* Table: position slot => position slot base value */
u32 lzms_position_slot_base[LZMS_MAX_NUM_OFFSET_SYMS + 1];
-/* A table that maps length slots to their base values. These are constants
- * computed at runtime by lzms_compute_slot_bases(). */
+/* Table: position slot => number of extra position bits */
+u8 lzms_extra_position_bits[LZMS_MAX_NUM_OFFSET_SYMS];
+
+/* Table: log2(position) => [lower bound, upper bound] on position slot */
+u16 lzms_order_to_position_slot_bounds[30][2];
+
+/* Table: length slot => length slot base value */
u32 lzms_length_slot_base[LZMS_NUM_LEN_SYMS + 1];
-/* Return the slot for the specified value. */
-unsigned
-lzms_get_slot(u32 value, const u32 slot_base_tab[], unsigned num_slots)
-{
- unsigned slot = 0;
+/* Table: length slot => number of extra length bits */
+u8 lzms_extra_length_bits[LZMS_NUM_LEN_SYMS];
- while (slot_base_tab[slot + 1] <= value)
- slot++;
+/* Table: length (< LZMS_NUM_FAST_LENGTHS only) => length slot */
+u8 lzms_length_slot_fast[LZMS_NUM_FAST_LENGTHS];
- return slot;
+u32
+lzms_get_slot(u32 value, const u32 slot_base_tab[], unsigned num_slots)
+{
+ u32 l = 0;
+ u32 r = num_slots - 1;
+ for (;;) {
+ LZMS_ASSERT(r >= l);
+ u32 slot = (l + r) / 2;
+ if (value >= slot_base_tab[slot]) {
+ if (value < slot_base_tab[slot + 1])
+ return slot;
+ else
+ l = slot + 1;
+ } else {
+ r = slot - 1;
+ }
+ }
}
-
static void
lzms_decode_delta_rle_slot_bases(u32 slot_bases[],
- const u8 delta_run_lens[], size_t num_run_lens)
+ u8 extra_bits[],
+ const u8 delta_run_lens[],
+ u32 num_run_lens,
+ u32 final,
+ u32 expected_num_slots)
{
+ u32 order = 0;
u32 delta = 1;
u32 base = 0;
- size_t slot = 0;
- for (size_t i = 0; i < num_run_lens; i++) {
+ u32 slot = 0;
+ for (u32 i = 0; i < num_run_lens; i++) {
u8 run_len = delta_run_lens[i];
while (run_len--) {
base += delta;
- slot_bases[slot++] = base;
+ if (slot > 0)
+ extra_bits[slot - 1] = order;
+ slot_bases[slot] = base;
+ slot++;
}
delta <<= 1;
+ order++;
}
+ LZMS_ASSERT(slot == expected_num_slots);
+
+ slot_bases[slot] = final;
+ extra_bits[slot - 1] = bsr32(slot_bases[slot] - slot_bases[slot - 1]);
}
/* Initialize the global position and length slot tables. */
static void
-lzms_compute_slot_bases(void)
+lzms_compute_slots(void)
{
/* If an explicit formula that maps LZMS position and length slots to
* slot bases exists, then it could be used here. But until one is
1,
};
+ /* Position slots */
lzms_decode_delta_rle_slot_bases(lzms_position_slot_base,
+ lzms_extra_position_bits,
position_slot_delta_run_lens,
- ARRAY_LEN(position_slot_delta_run_lens));
-
- lzms_position_slot_base[LZMS_MAX_NUM_OFFSET_SYMS] = 0x7fffffff;
+ ARRAY_LEN(position_slot_delta_run_lens),
+ 0x7fffffff,
+ LZMS_MAX_NUM_OFFSET_SYMS);
+
+ for (u32 order = 0; order < 30; order++) {
+ lzms_order_to_position_slot_bounds[order][0] =
+ lzms_get_slot(1U << order, lzms_position_slot_base,
+ LZMS_MAX_NUM_OFFSET_SYMS);
+ lzms_order_to_position_slot_bounds[order][1] =
+ lzms_get_slot((1U << (order + 1)) - 1, lzms_position_slot_base,
+ LZMS_MAX_NUM_OFFSET_SYMS);
+ }
+ /* Length slots */
lzms_decode_delta_rle_slot_bases(lzms_length_slot_base,
+ lzms_extra_length_bits,
length_slot_delta_run_lens,
- ARRAY_LEN(length_slot_delta_run_lens));
-
- lzms_length_slot_base[LZMS_NUM_LEN_SYMS] = 0x400108ab;
+ ARRAY_LEN(length_slot_delta_run_lens),
+ 0x400108ab,
+ LZMS_NUM_LEN_SYMS);
+
+ /* Create table mapping short lengths to length slots. */
+ for (u32 slot = 0, i = 0; i < LZMS_NUM_FAST_LENGTHS; i++) {
+ if (i >= lzms_length_slot_base[slot + 1])
+ slot++;
+ lzms_length_slot_fast[i] = slot;
+ }
}
-/* Initialize the global position length slot tables if not done so already. */
+/* Initialize the global position and length slot tables if not done so already.
+ * */
void
-lzms_init_slot_bases(void)
+lzms_init_slots(void)
{
- static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
- static bool already_computed = false;
-
- if (unlikely(!already_computed)) {
- pthread_mutex_lock(&mutex);
- if (!already_computed) {
- lzms_compute_slot_bases();
- already_computed = true;
- }
- pthread_mutex_unlock(&mutex);
- }
+ static pthread_once_t once = PTHREAD_ONCE_INIT;
+
+ pthread_once(&once, lzms_compute_slots);
}
static s32
return i + 1;
}
-static s32
-lzms_may_x86_translate(const u8 p[restrict],
- s32 *restrict max_offset_ret)
+static inline s32
+lzms_may_x86_translate(const u8 p[restrict], s32 *restrict max_offset_ret)
{
/* Switch on first byte of the opcode, assuming it is really an x86
* instruction. */
* Translate relative addresses embedded in x86 instructions into absolute
* addresses (@undo == %false), or undo this translation (@undo == %true).
*
- * @last_target_usages is a temporary array of length >= 65536.
+ * Absolute addresses are usually more compressible by LZ factorization.
+ *
+ * @last_target_usages must be a temporary array of length >= 65536.
*/
void
-lzms_x86_filter(u8 data[restrict],
- s32 size,
- s32 last_target_usages[restrict],
- bool undo)
+lzms_x86_filter(u8 data[restrict], s32 size,
+ s32 last_target_usages[restrict], bool undo)
{
+ /*
+ * Note: this filter runs unconditionally and uses a custom algorithm to
+ * detect data regions that probably contain x86 code.
+ *
+ * 'closest_target_usage' tracks the most recent position that has a
+ * good chance of being an x86 instruction. When the filter detects a
+ * likely x86 instruction, it updates this variable and considers the
+ * next 1023 bytes of data as valid for x86 translations.
+ *
+ * If part of the data does not, in fact, contain x86 machine code, then
+ * 'closest_target_usage' will, very likely, eventually fall more than
+ * 1023 bytes behind the current position. This results in x86
+ * translations being disabled until the next likely x86 instruction is
+ * detected.
+ *
+ * Translations on relative call (e8 opcode) instructions are slightly
+ * more restricted. They require that the most recent likely x86
+ * instruction was in the last 511 bytes, rather than the last 1023
+ * bytes.
+ *
+ * To identify "likely x86 instructions", the algorithm attempts to
+ * track the position of the most recent potential relative-addressing
+ * instruction that referenced each possible memory address. If it
+ * finds two references to the same memory address within a 65535 byte
+ * window, the second reference is flagged as a likely x86 instruction.
+ * Since the instructions considered for translation necessarily use
+ * relative addressing, the algorithm does a tentative translation into
+ * absolute addresses. In addition, so that memory addresses can be
+ * looked up in an array of reasonable size (in this code,
+ * 'last_target_usages'), only the low-order 2 bytes of each address are
+ * considered significant.
+ */
+
s32 closest_target_usage = -LZMS_X86_MAX_TRANSLATION_OFFSET - 1;
for (s32 i = 0; i < 65536; i++)
last_target_usages[i] = -LZMS_X86_MAX_GOOD_TARGET_OFFSET - 1;
- for (s32 i = 0; i < size - 11; ) {
+ for (s32 i = 1; i < size - 16; ) {
s32 max_trans_offset;
s32 n;
n = lzms_may_x86_translate(data + i, &max_trans_offset);
+
if (max_trans_offset) {
+ /* Recognized opcode. */
i = lzms_maybe_do_x86_translation(data, i, n,
&closest_target_usage,
last_target_usages,
max_trans_offset,
undo);
} else {
+ /* Not a recognized opcode. */
i += n;
}
}
static void
lzms_init_lz_lru_queues(struct lzms_lz_lru_queues *lz)
{
- /* Recent offsets for LZ matches */
+ /* Recent offsets for LZ matches */
for (u32 i = 0; i < LZMS_NUM_RECENT_OFFSETS + 1; i++)
lz->recent_offsets[i] = i + 1;
static void
lzms_init_delta_lru_queues(struct lzms_delta_lru_queues *delta)
{
- /* Recent offsets and powers for LZ matches */
+ /* Recent offsets and powers for LZ matches */
for (u32 i = 0; i < LZMS_NUM_RECENT_OFFSETS + 1; i++) {
delta->recent_offsets[i] = i + 1;
delta->recent_powers[i] = 0;
void
lzms_init_lru_queues(struct lzms_lru_queues *lru)
{
- lzms_init_lz_lru_queues(&lru->lz);
- lzms_init_delta_lru_queues(&lru->delta);
+ lzms_init_lz_lru_queues(&lru->lz);
+ lzms_init_delta_lru_queues(&lru->delta);
}
void
void
lzms_update_lru_queues(struct lzms_lru_queues *lru)
{
- lzms_update_lz_lru_queues(&lru->lz);
- lzms_update_delta_lru_queues(&lru->delta);
+ lzms_update_lz_lru_queues(&lru->lz);
+ lzms_update_delta_lru_queues(&lru->delta);
}
git://wimlib.net / wimlib / blobdiff