diff options
Diffstat (limited to 'vp9/decoder/vp9_dboolhuff.c')
| -rw-r--r-- | vp9/decoder/vp9_dboolhuff.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/vp9/decoder/vp9_dboolhuff.c b/vp9/decoder/vp9_dboolhuff.c index df77d650d..31b1ae2b0 100644 --- a/vp9/decoder/vp9_dboolhuff.c +++ b/vp9/decoder/vp9_dboolhuff.c @@ -13,6 +13,12 @@ #include "vp9/decoder/vp9_dboolhuff.h" +// This is meant to be a large, positive constant that can still be efficiently +// loaded as an immediate (on platforms like ARM, for example). +// Even relatively modest values like 100 would work fine. +#define VP9_LOTS_OF_BITS 0x40000000 + + int vp9_reader_init(vp9_reader *r, const uint8_t *buffer, size_t size) { int marker_bit; @@ -67,3 +73,20 @@ const uint8_t *vp9_reader_find_end(vp9_reader *r) { return r->buffer; } +int vp9_reader_has_error(vp9_reader *r) { + // Check if we have reached the end of the buffer. + // + // Variable 'count' stores the number of bits in the 'value' buffer, minus + // 8. The top byte is part of the algorithm, and the remainder is buffered + // to be shifted into it. So if count == 8, the top 16 bits of 'value' are + // occupied, 8 for the algorithm and 8 in the buffer. + // + // When reading a byte from the user's buffer, count is filled with 8 and + // one byte is filled into the value buffer. When we reach the end of the + // data, count is additionally filled with VP9_LOTS_OF_BITS. So when + // count == VP9_LOTS_OF_BITS - 1, the user's data has been exhausted. + // + // 1 if we have tried to decode bits after the end of stream was encountered. + // 0 No error. + return r->count > VP9_BD_VALUE_SIZE && r->count < VP9_LOTS_OF_BITS; +} |