Read the first three bytes of mini box directly

The first three bytes of the mini box can be read directly without checking any condition.
AOMediaCodec · Aug 10, 2024 · 273db56 · 273db56
1 parent d142df6
commit 273db56
Showing 1 changed file with 24 additions and 16 deletions.
diff --git a/src/read.c b/src/read.c
@@ -3571,32 +3571,40 @@ static avifResult avifParseMinimizedImageBox(avifMeta * meta, uint64_t rawOffset
 
  meta->fromMiniBox = AVIF_TRUE;
 
- uint32_t version;
- AVIF_CHECKERR(avifROStreamReadBits(&s, &version, 2), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(2) version;
+ uint8_t data[3];
+ AVIF_CHECKERR(avifROStreamRead(&s, data, 3), AVIF_RESULT_BMFF_PARSE_FAILED);
+
+ uint32_t version = (data[0] & 0xc0) >> 6; // bit(2) version;
  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;
+ hasExplicitCodecTypes = (data[0] & 0x20) != 0; // bit(1) explicit_codec_types_flag;
+ floatFlag = (data[0] & 0x10) != 0; // bit(1) float_flag;
+ fullRange = (data[0] & 0x8) != 0;  // bit(1) full_range_flag;
+ hasAlpha = (data[0] & 0x4) != 0;  // bit(1) alpha_flag;
+ hasExplicitCicp = (data[0] & 0x2) != 0;  // bit(1) explicit_cicp_flag;
+ hasHdr = (data[0] & 0x1) != 0;  // bit(1) hdr_flag;
+ hasIcc = (data[1] & 0x80) != 0;  // bit(1) icc_flag;
+ hasExif = (data[1] & 0x40) != 0;  // bit(1) exif_flag;
+ hasXmp = (data[1] & 0x20) != 0;  // 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;
+ chromaSubsampling = (data[1] & 0x18) >> 3; // bit(2) chroma_subsampling;
+ orientation = data[1] & 0x7;  // bit(3) orientation_minus1;
  ++orientation;
 
  // Spatial extents
  uint32_t smallDimensionsFlag, width, height;
- AVIF_CHECKERR(avifROStreamReadBits(&s, &smallDimensionsFlag, 1), AVIF_RESULT_BMFF_PARSE_FAILED); // bit(1) small_dimensions_flag;
- AVIF_CHECKERR(avifROStreamReadBits(&s, &width, smallDimensionsFlag ? 7 : 15),
- AVIF_RESULT_BMFF_PARSE_FAILED); // unsigned int(small_dimensions_flag ? 7 : 15) width_minus1;
+ smallDimensionsFlag = (data[2] & 0x80) != 0; // bit(1) small_dimensions_flag;
+ // unsigned int(small_dimensions_flag ? 7 : 15) width_minus1;
+ width = data[2];
+ if (smallDimensionsFlag) {
+ width &= 0x7f;
+ } else {
+ AVIF_CHECKERR(avifROStreamRead(&s, data, 1), AVIF_RESULT_BMFF_PARSE_FAILED);
+ width = (width << 8) + data[0];
+ }
  ++width;
  AVIF_CHECKERR(avifROStreamReadBits(&s, &height, smallDimensionsFlag ? 7 : 15),
  AVIF_RESULT_BMFF_PARSE_FAILED); // unsigned int(small_dimensions_flag ? 7 : 15) height_minus1;