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fix the bit-writer for lossless in 32bit mode

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Sometimes, we can write 18bit or more at time, and it would
overflow the 32bit accumulator.

Also clarified the num-bits limitations (and exposed
VP8L_MAX_NUM_BIT_READ in bit_reader.h)

fixes http://code.google.com/p/webp/issues/detail?id=200

Seems a bit faster (use of local fields for bits_ / used_)

also: added the __QNX__ bswap while at it.

Change-Id: I876db93a931db15b083cf1d838c70105effa7167
This commit is contained in:
skal
2014-05-22 07:17:24 +02:00
parent 541784c710
commit 176fda2650
4 changed files with 50 additions and 23 deletions
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10
src/utils/bit_reader.h
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@ -316,6 +316,9 @@ static WEBP_INLINE int VP8GetSigned(VP8BitReader* const br, int v) {
// -----------------------------------------------------------------------------
// Bitreader for lossless format
// maximum number of bits (inclusive) the bit-reader can handle:
#define VP8L_MAX_NUM_BIT_READ 24
typedef uint64_t vp8l_val_t; // right now, this bit-reader can only use 64bit.
typedef struct {
@ -336,9 +339,10 @@ void VP8LInitBitReader(VP8LBitReader* const br,
void VP8LBitReaderSetBuffer(VP8LBitReader* const br,
const uint8_t* const buffer, size_t length);
// Reads the specified number of bits from Read Buffer.
// Flags an error in case end_of_stream or n_bits is more than allowed limit.
// Flags eos if this read attempt is going to cross the read buffer.
// Reads the specified number of bits from read buffer.
// Flags an error in case end_of_stream or n_bits is more than the allowed limit
// of VP8L_MAX_NUM_BIT_READ (inclusive).
// Flags eos_ if this read attempt is going to cross the read buffer.
uint32_t VP8LReadBits(VP8LBitReader* const br, int n_bits);
// Return the prefetched bits, so they can be looked up.