Refactored reader requireents box to use just a single file read. #212
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jevans
parent
578470e149
commit
f15913cee6
1 changed files with 38 additions and 35 deletions
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@ -2252,29 +2252,34 @@ class ReaderRequirementsBox(Jp2kBox):
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-------
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ReaderRequirementsBox instance
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"""
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read_buffer = fptr.read(1)
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mask_length, = struct.unpack('>B', read_buffer)
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num_bytes = length - 16 if box_is_XL else length - 8
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read_buffer = fptr.read(num_bytes)
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mask_length, = struct.unpack_from('>B', read_buffer, offset=0)
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if mask_length == 3:
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return _parse_rreq3(fptr, length, offset)
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return _parse_rreq3(read_buffer, length, offset)
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# Fully Understands Aspect Mask
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# Decodes Completely Mask
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read_buffer = fptr.read(2 * mask_length)
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fuam = dcm = standard_flag = standard_mask = []
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vendor_feature = vendor_mask = []
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# The mask length tells us the format string to use when unpacking
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# from the buffer read from file.
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try:
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mask_format = {1: 'B', 2: 'H', 4: 'I', 8: 'Q'}[mask_length]
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fuam, dcm = struct.unpack('>' + mask_format * 2, read_buffer)
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standard_flag, standard_mask = _parse_standard_flag(fptr,
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mask_length)
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vendor_feature, vendor_mask = _parse_vendor_features(fptr,
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mask_length)
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fuam, dcm = struct.unpack_from('>' + mask_format * 2, read_buffer,
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offset=1)
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std_flg_offset = 1 + 2 * mask_length
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data = _parse_standard_flag(read_buffer[std_flg_offset:],
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mask_length)
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standard_flag, standard_mask = data
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nflags = len(standard_flag)
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vendor_offset = 1 + 2 * mask_length + 2 + (2 + mask_length) * nflags
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data = _parse_vendor_features(read_buffer[vendor_offset:],
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mask_length)
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vendor_feature, vendor_mask = data
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except KeyError:
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msg = 'The ReaderRequirements box (rreq) has a mask length of {0} '
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@ -2287,27 +2292,23 @@ class ReaderRequirementsBox(Jp2kBox):
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length=length, offset=offset)
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def _parse_rreq3(fptr, length, offset):
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def _parse_rreq3(read_buffer, length, offset):
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"""Parse a reader requirements box. Special case when mask length is 3."""
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# Fully Understands Aspect Mask
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# Decodes Completely Mask
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read_buffer = fptr.read(2 * 3)
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fuam = dcm = standard_flag = standard_mask = []
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vendor_feature = vendor_mask = []
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# The mask length tells us the format string to use when unpacking
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# from the buffer read from file.
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lst = struct.unpack('>BBBBBB', read_buffer)
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lst = struct.unpack_from('>BBBBBB', read_buffer, offset=1)
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fuam = lst[0] << 16 | lst[1] << 8 | lst[2]
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dcm = lst[3] << 16 | lst[4] << 8 | lst[5]
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read_buffer = fptr.read(2)
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num_standard_features, = struct.unpack('>H', read_buffer)
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num_standard_features, = struct.unpack_from('>H', read_buffer, offset=7)
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fmt = '>' + 'HBBB' * num_standard_features
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read_buffer = fptr.read(num_standard_features * 5)
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lst = struct.unpack(fmt, read_buffer)
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lst = struct.unpack(fmt, read_buffer, offset=9)
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standard_flag = lst[0::4]
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standard_mask = []
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@ -2316,21 +2317,23 @@ def _parse_rreq3(fptr, length, offset):
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mask = items[0] << 16 | items[1] << 8 | items[2]
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standard_mask.append(mask)
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read_buffer = fptr.read(2)
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num_vendor_features, = struct.unpack('>H', read_buffer)
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boffset = 9 + num_standard_features * 5
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num_vendor_features, = struct.unpack_from('>H', read_buffer,
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offset=boffset)
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fmt = '>' + 'HBBB' * num_vendor_features
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read_buffer = fptr.read(num_vendor_features * 5)
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lst = struct.unpack(fmt, read_buffer)
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buffer_offset = 11 + num_standard_features * 5
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lst = struct.unpack_from(fmt, read_buffer, offset=buffer_offset)
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# Each vendor feature consists of a 16-byte UUID plus a mask whose
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# length is specified by, you guessed it, "mask_length".
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entry_length = 16 + 3
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read_buffer = fptr.read(num_vendor_features * entry_length)
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vendor_feature = []
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vendor_mask = []
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read_buffer = read_buffer[9 + num_standard_features * 10:]
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for j in range(num_vendor_features):
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ubuffer = read_buffer[j * entry_length:(j + 1) * entry_length]
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uslice = slice(j * entry_length, (j + 1) * entry_length)
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ubuffer = read_buffer[slice]
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vendor_feature.append(uuid.UUID(bytes=ubuffer[0:16]))
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lst = struct.unpack('>BBB', ubuffer[16:])
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@ -2343,7 +2346,7 @@ def _parse_rreq3(fptr, length, offset):
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return box
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def _parse_standard_flag(fptr, mask_length):
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def _parse_standard_flag(read_buffer, mask_length):
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"""Construct standard flag, standard mask data from the file.
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Specifically working on Reader Requirements box.
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@ -2359,16 +2362,16 @@ def _parse_standard_flag(fptr, mask_length):
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# from the buffer read from file.
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mask_format = {1: 'B', 2: 'H', 4: 'I'}[mask_length]
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read_buffer = fptr.read(2)
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num_standard_flags, = struct.unpack('>H', read_buffer)
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#read_buffer = fptr.read(2)
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num_standard_flags, = struct.unpack_from('>H', read_buffer, offset=0)
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# Read in standard flags and standard masks. Each standard flag should
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# be two bytes, but the standard mask flag is as long as specified by
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# the mask length.
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read_buffer = fptr.read(num_standard_flags * (2 + mask_length))
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#read_buffer = fptr.read(num_standard_flags * (2 + mask_length))
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fmt = '>' + ('H' + mask_format) * num_standard_flags
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data = struct.unpack(fmt, read_buffer)
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data = struct.unpack_from(fmt, read_buffer, offset=2)
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standard_flag = data[0:num_standard_flags * 2:2]
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standard_mask = data[1:num_standard_flags * 2:2]
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@ -2376,7 +2379,7 @@ def _parse_standard_flag(fptr, mask_length):
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return standard_flag, standard_mask
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def _parse_vendor_features(fptr, mask_length):
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def _parse_vendor_features(read_buffer, mask_length):
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"""Construct vendor features, vendor mask data from the file.
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Specifically working on Reader Requirements box.
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@ -2392,17 +2395,17 @@ def _parse_vendor_features(fptr, mask_length):
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# from the buffer read from file.
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mask_format = {1: 'B', 2: 'H', 4: 'I'}[mask_length]
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read_buffer = fptr.read(2)
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num_vendor_features, = struct.unpack('>H', read_buffer)
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num_vendor_features, = struct.unpack_from('>H', read_buffer)
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# Each vendor feature consists of a 16-byte UUID plus a mask whose
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# length is specified by, you guessed it, "mask_length".
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entry_length = 16 + mask_length
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read_buffer = fptr.read(num_vendor_features * entry_length)
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#read_buffer = fptr.read(num_vendor_features * entry_length)
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vendor_feature = []
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vendor_mask = []
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for j in range(num_vendor_features):
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ubuffer = read_buffer[j * entry_length:(j + 1) * entry_length]
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uslice = slice(2 + j * entry_length, 2 + (j + 1) * entry_length)
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ubuffer = read_buffer[uslice]
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vendor_feature.append(uuid.UUID(bytes=ubuffer[0:16]))
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vmask = struct.unpack('>' + mask_format, ubuffer[16:])
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