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Diffstat (limited to 'c/dec/bit_reader.h')
-rw-r--r--c/dec/bit_reader.h68
1 files changed, 43 insertions, 25 deletions
diff --git a/c/dec/bit_reader.h b/c/dec/bit_reader.h
index 5f48711..b3fddea 100644
--- a/c/dec/bit_reader.h
+++ b/c/dec/bit_reader.h
@@ -22,6 +22,9 @@ extern "C" {
#define BROTLI_SHORT_FILL_BIT_WINDOW_READ (sizeof(brotli_reg_t) >> 1)
+/* 162 bits + 7 bytes */
+#define BROTLI_FAST_INPUT_SLACK 28
+
BROTLI_INTERNAL extern const brotli_reg_t kBrotliBitMask[33];
static BROTLI_INLINE brotli_reg_t BitMask(brotli_reg_t n) {
@@ -38,7 +41,8 @@ typedef struct {
brotli_reg_t val_; /* pre-fetched bits */
brotli_reg_t bit_pos_; /* current bit-reading position in val_ */
const uint8_t* next_in; /* the byte we're reading from */
- size_t avail_in;
+ const uint8_t* guard_in; /* position from which "fast-path" is prohibited */
+ const uint8_t* last_in; /* == next_in + avail_in */
} BrotliBitReader;
typedef struct {
@@ -64,12 +68,28 @@ BROTLI_INTERNAL BROTLI_BOOL BrotliWarmupBitReader(BrotliBitReader* br);
BROTLI_INTERNAL BROTLI_NOINLINE BROTLI_BOOL BrotliSafeReadBits32Slow(
BrotliBitReader* br, brotli_reg_t n_bits, brotli_reg_t* val);
+static BROTLI_INLINE size_t
+BrotliBitReaderGetAvailIn(BrotliBitReader* const br) {
+ return (size_t)(br->last_in - br->next_in);
+}
+
static BROTLI_INLINE void BrotliBitReaderSaveState(
BrotliBitReader* const from, BrotliBitReaderState* to) {
to->val_ = from->val_;
to->bit_pos_ = from->bit_pos_;
to->next_in = from->next_in;
- to->avail_in = from->avail_in;
+ to->avail_in = BrotliBitReaderGetAvailIn(from);
+}
+
+static BROTLI_INLINE void BrotliBitReaderSetInput(
+ BrotliBitReader* const br, const uint8_t* next_in, size_t avail_in) {
+ br->next_in = next_in;
+ br->last_in = next_in + avail_in;
+ if (avail_in + 1 > BROTLI_FAST_INPUT_SLACK) {
+ br->guard_in = next_in + (avail_in + 1 - BROTLI_FAST_INPUT_SLACK);
+ } else {
+ br->guard_in = next_in;
+ }
}
static BROTLI_INLINE void BrotliBitReaderRestoreState(
@@ -77,7 +97,7 @@ static BROTLI_INLINE void BrotliBitReaderRestoreState(
to->val_ = from->val_;
to->bit_pos_ = from->bit_pos_;
to->next_in = from->next_in;
- to->avail_in = from->avail_in;
+ BrotliBitReaderSetInput(to, from->next_in, from->avail_in);
}
static BROTLI_INLINE brotli_reg_t BrotliGetAvailableBits(
@@ -90,15 +110,16 @@ static BROTLI_INLINE brotli_reg_t BrotliGetAvailableBits(
maximal ring-buffer size (larger number won't be utilized anyway). */
static BROTLI_INLINE size_t BrotliGetRemainingBytes(BrotliBitReader* br) {
static const size_t kCap = (size_t)1 << BROTLI_LARGE_MAX_WBITS;
- if (br->avail_in > kCap) return kCap;
- return br->avail_in + (BrotliGetAvailableBits(br) >> 3);
+ size_t avail_in = BrotliBitReaderGetAvailIn(br);
+ if (avail_in > kCap) return kCap;
+ return avail_in + (BrotliGetAvailableBits(br) >> 3);
}
/* Checks if there is at least |num| bytes left in the input ring-buffer
(excluding the bits remaining in br->val_). */
static BROTLI_INLINE BROTLI_BOOL BrotliCheckInputAmount(
- BrotliBitReader* const br, size_t num) {
- return TO_BROTLI_BOOL(br->avail_in >= num);
+ BrotliBitReader* const br) {
+ return TO_BROTLI_BOOL(br->next_in < br->guard_in);
}
/* Guarantees that there are at least |n_bits| + 1 bits in accumulator.
@@ -116,7 +137,6 @@ static BROTLI_INLINE void BrotliFillBitWindow(
(br->val_ >> 56) | (BROTLI_UNALIGNED_LOAD64LE(br->next_in) << 8);
br->bit_pos_ =
bit_pos ^ 56; /* here same as -= 56 because of the if condition */
- br->avail_in -= 7;
br->next_in += 7;
}
} else if (BROTLI_UNALIGNED_READ_FAST && BROTLI_IS_CONSTANT(n_bits) &&
@@ -127,7 +147,6 @@ static BROTLI_INLINE void BrotliFillBitWindow(
(br->val_ >> 48) | (BROTLI_UNALIGNED_LOAD64LE(br->next_in) << 16);
br->bit_pos_ =
bit_pos ^ 48; /* here same as -= 48 because of the if condition */
- br->avail_in -= 6;
br->next_in += 6;
}
} else {
@@ -137,7 +156,6 @@ static BROTLI_INLINE void BrotliFillBitWindow(
(((uint64_t)BROTLI_UNALIGNED_LOAD32LE(br->next_in)) << 32);
br->bit_pos_ =
bit_pos ^ 32; /* here same as -= 32 because of the if condition */
- br->avail_in -= BROTLI_SHORT_FILL_BIT_WINDOW_READ;
br->next_in += BROTLI_SHORT_FILL_BIT_WINDOW_READ;
}
}
@@ -150,7 +168,6 @@ static BROTLI_INLINE void BrotliFillBitWindow(
(br->val_ >> 24) | (BROTLI_UNALIGNED_LOAD32LE(br->next_in) << 8);
br->bit_pos_ =
bit_pos ^ 24; /* here same as -= 24 because of the if condition */
- br->avail_in -= 3;
br->next_in += 3;
}
} else {
@@ -160,7 +177,6 @@ static BROTLI_INLINE void BrotliFillBitWindow(
(((brotli_reg_t)BROTLI_UNALIGNED_LOAD16LE(br->next_in)) << 16);
br->bit_pos_ =
bit_pos ^ 16; /* here same as -= 16 because of the if condition */
- br->avail_in -= BROTLI_SHORT_FILL_BIT_WINDOW_READ;
br->next_in += BROTLI_SHORT_FILL_BIT_WINDOW_READ;
}
}
@@ -176,7 +192,7 @@ static BROTLI_INLINE void BrotliFillBitWindow16(BrotliBitReader* const br) {
/* Tries to pull one byte of input to accumulator.
Returns BROTLI_FALSE if there is no input available. */
static BROTLI_INLINE BROTLI_BOOL BrotliPullByte(BrotliBitReader* const br) {
- if (br->avail_in == 0) {
+ if (br->next_in == br->last_in) {
return BROTLI_FALSE;
}
br->val_ >>= 8;
@@ -186,7 +202,6 @@ static BROTLI_INLINE BROTLI_BOOL BrotliPullByte(BrotliBitReader* const br) {
br->val_ |= ((brotli_reg_t)*br->next_in) << 24;
#endif
br->bit_pos_ -= 8;
- --br->avail_in;
++br->next_in;
return BROTLI_TRUE;
}
@@ -236,7 +251,6 @@ static BROTLI_INLINE void BrotliDropBits(
static BROTLI_INLINE void BrotliBitReaderUnload(BrotliBitReader* br) {
brotli_reg_t unused_bytes = BrotliGetAvailableBits(br) >> 3;
brotli_reg_t unused_bits = unused_bytes << 3;
- br->avail_in += unused_bytes;
br->next_in -= unused_bytes;
if (unused_bits == sizeof(br->val_) << 3) {
br->val_ = 0;
@@ -248,11 +262,13 @@ static BROTLI_INLINE void BrotliBitReaderUnload(BrotliBitReader* br) {
/* Reads the specified number of bits from |br| and advances the bit pos.
Precondition: accumulator MUST contain at least |n_bits|. */
-static BROTLI_INLINE void BrotliTakeBits(
- BrotliBitReader* const br, brotli_reg_t n_bits, brotli_reg_t* val) {
+static BROTLI_INLINE void BrotliTakeBits(BrotliBitReader* const br,
+ brotli_reg_t n_bits,
+ brotli_reg_t* val) {
*val = BrotliGetBitsUnmasked(br) & BitMask(n_bits);
BROTLI_LOG(("[BrotliTakeBits] %d %d %d val: %6x\n",
- (int)br->avail_in, (int)br->bit_pos_, (int)n_bits, (int)*val));
+ (int)BrotliBitReaderGetAvailIn(br), (int)br->bit_pos_,
+ (int)n_bits, (int)*val));
BrotliDropBits(br, n_bits);
}
@@ -342,7 +358,6 @@ static BROTLI_INLINE BROTLI_BOOL BrotliJumpToByteBoundary(BrotliBitReader* br) {
}
static BROTLI_INLINE void BrotliDropBytes(BrotliBitReader* br, size_t num) {
- br->avail_in -= num;
br->next_in += num;
}
@@ -365,21 +380,24 @@ static BROTLI_INLINE void BrotliCopyBytes(uint8_t* dest,
BROTLI_UNUSED_FUNCTION void BrotliBitReaderSuppressUnusedFunctions(void) {
BROTLI_UNUSED(&BrotliBitReaderSuppressUnusedFunctions);
- BROTLI_UNUSED(&BrotliBitReaderSaveState);
+
+ BROTLI_UNUSED(&BrotliBitReaderGetAvailIn);
BROTLI_UNUSED(&BrotliBitReaderRestoreState);
- BROTLI_UNUSED(&BrotliGetRemainingBytes);
+ BROTLI_UNUSED(&BrotliBitReaderSaveState);
+ BROTLI_UNUSED(&BrotliBitReaderSetInput);
+ BROTLI_UNUSED(&BrotliBitReaderUnload);
BROTLI_UNUSED(&BrotliCheckInputAmount);
+ BROTLI_UNUSED(&BrotliCopyBytes);
BROTLI_UNUSED(&BrotliFillBitWindow16);
BROTLI_UNUSED(&BrotliGet16BitsUnmasked);
BROTLI_UNUSED(&BrotliGetBits);
- BROTLI_UNUSED(&BrotliSafeGetBits);
- BROTLI_UNUSED(&BrotliBitReaderUnload);
+ BROTLI_UNUSED(&BrotliGetRemainingBytes);
+ BROTLI_UNUSED(&BrotliJumpToByteBoundary);
BROTLI_UNUSED(&BrotliReadBits24);
BROTLI_UNUSED(&BrotliReadBits32);
+ BROTLI_UNUSED(&BrotliSafeGetBits);
BROTLI_UNUSED(&BrotliSafeReadBits);
BROTLI_UNUSED(&BrotliSafeReadBits32);
- BROTLI_UNUSED(&BrotliJumpToByteBoundary);
- BROTLI_UNUSED(&BrotliCopyBytes);
}
#if defined(__cplusplus) || defined(c_plusplus)
generated by cgit v1.1 at 2024-10-19 21:56:13 +0000