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Read the first two bytes of mini box directly #2408

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Read the first two bytes of mini box directly #2408

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61 changes: 43 additions & 18 deletions src/read.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3585,26 +3585,51 @@ static avifResult avifParseMinimizedImageBox(avifMeta * meta,

meta->fromMiniBox = AVIF_TRUE;

uint32_t version;
AVIF_CHECKERR(avifROStreamReadBits(&s, &version, 2), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(2) version = 0;
// Read and parse the first two bytes, which contain no conditional constructs.
uint8_t data[2];
AVIF_CHECKERR(avifROStreamRead(&s, data, 2), AVIF_RESULT_BMFF_PARSE_FAILED);

// bit(2) version = 0;
//
// // flags
// bit(1) explicit_codec_types_flag;
// bit(1) float_flag;
// bit(1) full_range_flag;
// bit(1) alpha_flag;
// bit(1) explicit_cicp_flag;
// bit(1) hdr_flag;
int byte = data[0];
const avifBool hasHdr = byte & 0x1;
byte >>= 1;
const avifBool hasExplicitCicp = byte & 0x1;
byte >>= 1;
const avifBool hasAlpha = byte & 0x1;
byte >>= 1;
const avifBool fullRange = byte & 0x1;
byte >>= 1;
const avifBool floatFlag = byte & 0x1;
byte >>= 1;
const avifBool hasExplicitCodecTypes = byte & 0x1;
byte >>= 1;
const uint32_t version = byte;
AVIF_CHECKERR(version == 0, AVIF_RESULT_BMFF_PARSE_FAILED);

// flags
uint32_t hasExplicitCodecTypes, floatFlag, fullRange, hasAlpha, hasExplicitCicp, hasHdr, hasIcc, hasExif, hasXmp;
AVIF_CHECKERR(avifROStreamReadBits(&s, &hasExplicitCodecTypes, 1), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(1) explicit_codec_types_flag;
AVIF_CHECKERR(avifROStreamReadBits(&s, &floatFlag, 1), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(1) float_flag;
AVIF_CHECKERR(avifROStreamReadBits(&s, &fullRange, 1), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(1) full_range_flag;
AVIF_CHECKERR(avifROStreamReadBits(&s, &hasAlpha, 1), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(1) alpha_flag;
AVIF_CHECKERR(avifROStreamReadBits(&s, &hasExplicitCicp, 1), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(1) explicit_cicp_flag;
AVIF_CHECKERR(avifROStreamReadBits(&s, &hasHdr, 1), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(1) hdr_flag;
AVIF_CHECKERR(avifROStreamReadBits(&s, &hasIcc, 1), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(1) icc_flag;
AVIF_CHECKERR(avifROStreamReadBits(&s, &hasExif, 1), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(1) exif_flag;
AVIF_CHECKERR(avifROStreamReadBits(&s, &hasXmp, 1), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(1) xmp_flag;

uint32_t chromaSubsampling, orientation;
AVIF_CHECKERR(avifROStreamReadBits(&s, &chromaSubsampling, 2), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(2) chroma_subsampling;
AVIF_CHECKERR(avifROStreamReadBits(&s, &orientation, 3), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(3) orientation_minus1;
++orientation;
// bit(1) icc_flag;
// bit(1) exif_flag;
// bit(1) xmp_flag;
//
// bit(2) chroma_subsampling;
// bit(3) orientation_minus1;
byte = data[1];
const uint32_t orientation = (byte & 0x7) + 1;
byte >>= 3;
const uint32_t chromaSubsampling = byte & 0x3;
byte >>= 2;
const avifBool hasXmp = byte & 0x1;
byte >>= 1;
const avifBool hasExif = byte & 0x1;
byte >>= 1;
const avifBool hasIcc = byte;

// Spatial extents
uint32_t smallDimensionsFlag, width, height;
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