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Refactored reader requireents box to use just a single file read. #212

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jevans 2014-04-05 22:24:11 -04:00
commit f15913cee6
1 changed files with 38 additions and 35 deletions
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69
glymur/jp2box.py
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@ -2252,29 +2252,34 @@ class ReaderRequirementsBox(Jp2kBox):
------- -------
ReaderRequirementsBox instance ReaderRequirementsBox instance
""" """
read_buffer = fptr.read(1) num_bytes = length - 16 if box_is_XL else length - 8
mask_length, = struct.unpack('>B', read_buffer) read_buffer = fptr.read(num_bytes)
mask_length, = struct.unpack_from('>B', read_buffer, offset=0)
if mask_length == 3: if mask_length == 3:
return _parse_rreq3(fptr, length, offset) return _parse_rreq3(read_buffer, length, offset)
# Fully Understands Aspect Mask # Fully Understands Aspect Mask
# Decodes Completely Mask # Decodes Completely Mask
read_buffer = fptr.read(2 * mask_length)
fuam = dcm = standard_flag = standard_mask = [] fuam = dcm = standard_flag = standard_mask = []
vendor_feature = vendor_mask = [] vendor_feature = vendor_mask = []
# The mask length tells us the format string to use when unpacking # The mask length tells us the format string to use when unpacking
# from the buffer read from file. # from the buffer read from file.
try: try:
mask_format = {1: 'B', 2: 'H', 4: 'I', 8: 'Q'}[mask_length] mask_format = {1: 'B', 2: 'H', 4: 'I', 8: 'Q'}[mask_length]
fuam, dcm = struct.unpack('>' + mask_format * 2, read_buffer) fuam, dcm = struct.unpack_from('>' + mask_format * 2, read_buffer,
standard_flag, standard_mask = _parse_standard_flag(fptr, offset=1)
std_flg_offset = 1 + 2 * mask_length
data = _parse_standard_flag(read_buffer[std_flg_offset:],
mask_length) mask_length)
vendor_feature, vendor_mask = _parse_vendor_features(fptr, standard_flag, standard_mask = data
nflags = len(standard_flag)
vendor_offset = 1 + 2 * mask_length + 2 + (2 + mask_length) * nflags
data = _parse_vendor_features(read_buffer[vendor_offset:],
mask_length) mask_length)
vendor_feature, vendor_mask = data
except KeyError: except KeyError:
msg = 'The ReaderRequirements box (rreq) has a mask length of {0} ' msg = 'The ReaderRequirements box (rreq) has a mask length of {0} '
@ -2287,27 +2292,23 @@ class ReaderRequirementsBox(Jp2kBox):
length=length, offset=offset) length=length, offset=offset)
def _parse_rreq3(fptr, length, offset): def _parse_rreq3(read_buffer, length, offset):
"""Parse a reader requirements box. Special case when mask length is 3.""" """Parse a reader requirements box. Special case when mask length is 3."""
# Fully Understands Aspect Mask # Fully Understands Aspect Mask
# Decodes Completely Mask # Decodes Completely Mask
read_buffer = fptr.read(2 * 3)
fuam = dcm = standard_flag = standard_mask = [] fuam = dcm = standard_flag = standard_mask = []
vendor_feature = vendor_mask = [] vendor_feature = vendor_mask = []
# The mask length tells us the format string to use when unpacking # The mask length tells us the format string to use when unpacking
# from the buffer read from file. # from the buffer read from file.
lst = struct.unpack('>BBBBBB', read_buffer) lst = struct.unpack_from('>BBBBBB', read_buffer, offset=1)
fuam = lst[0] << 16 | lst[1] << 8 | lst[2] fuam = lst[0] << 16 | lst[1] << 8 | lst[2]
dcm = lst[3] << 16 | lst[4] << 8 | lst[5] dcm = lst[3] << 16 | lst[4] << 8 | lst[5]
read_buffer = fptr.read(2) num_standard_features, = struct.unpack_from('>H', read_buffer, offset=7)
num_standard_features, = struct.unpack('>H', read_buffer)
fmt = '>' + 'HBBB' * num_standard_features fmt = '>' + 'HBBB' * num_standard_features
read_buffer = fptr.read(num_standard_features * 5) lst = struct.unpack(fmt, read_buffer, offset=9)
lst = struct.unpack(fmt, read_buffer)
standard_flag = lst[0::4] standard_flag = lst[0::4]
standard_mask = [] standard_mask = []
@ -2316,21 +2317,23 @@ def _parse_rreq3(fptr, length, offset):
mask = items[0] << 16 | items[1] << 8 | items[2] mask = items[0] << 16 | items[1] << 8 | items[2]
standard_mask.append(mask) standard_mask.append(mask)
read_buffer = fptr.read(2) boffset = 9 + num_standard_features * 5
num_vendor_features, = struct.unpack('>H', read_buffer) num_vendor_features, = struct.unpack_from('>H', read_buffer,
offset=boffset)
fmt = '>' + 'HBBB' * num_vendor_features fmt = '>' + 'HBBB' * num_vendor_features
read_buffer = fptr.read(num_vendor_features * 5) buffer_offset = 11 + num_standard_features * 5
lst = struct.unpack(fmt, read_buffer) lst = struct.unpack_from(fmt, read_buffer, offset=buffer_offset)
# Each vendor feature consists of a 16-byte UUID plus a mask whose # Each vendor feature consists of a 16-byte UUID plus a mask whose
# length is specified by, you guessed it, "mask_length". # length is specified by, you guessed it, "mask_length".
entry_length = 16 + 3 entry_length = 16 + 3
read_buffer = fptr.read(num_vendor_features * entry_length)
vendor_feature = [] vendor_feature = []
vendor_mask = [] vendor_mask = []
read_buffer = read_buffer[9 + num_standard_features * 10:]
for j in range(num_vendor_features): for j in range(num_vendor_features):
ubuffer = read_buffer[j * entry_length:(j + 1) * entry_length] uslice = slice(j * entry_length, (j + 1) * entry_length)
ubuffer = read_buffer[slice]
vendor_feature.append(uuid.UUID(bytes=ubuffer[0:16])) vendor_feature.append(uuid.UUID(bytes=ubuffer[0:16]))
lst = struct.unpack('>BBB', ubuffer[16:]) lst = struct.unpack('>BBB', ubuffer[16:])
@ -2343,7 +2346,7 @@ def _parse_rreq3(fptr, length, offset):
return box return box
def _parse_standard_flag(fptr, mask_length): def _parse_standard_flag(read_buffer, mask_length):
"""Construct standard flag, standard mask data from the file. """Construct standard flag, standard mask data from the file.
Specifically working on Reader Requirements box. Specifically working on Reader Requirements box.
@ -2359,16 +2362,16 @@ def _parse_standard_flag(fptr, mask_length):
# from the buffer read from file. # from the buffer read from file.
mask_format = {1: 'B', 2: 'H', 4: 'I'}[mask_length] mask_format = {1: 'B', 2: 'H', 4: 'I'}[mask_length]
read_buffer = fptr.read(2) #read_buffer = fptr.read(2)
num_standard_flags, = struct.unpack('>H', read_buffer) num_standard_flags, = struct.unpack_from('>H', read_buffer, offset=0)
# Read in standard flags and standard masks. Each standard flag should # Read in standard flags and standard masks. Each standard flag should
# be two bytes, but the standard mask flag is as long as specified by # be two bytes, but the standard mask flag is as long as specified by
# the mask length. # the mask length.
read_buffer = fptr.read(num_standard_flags * (2 + mask_length)) #read_buffer = fptr.read(num_standard_flags * (2 + mask_length))
fmt = '>' + ('H' + mask_format) * num_standard_flags fmt = '>' + ('H' + mask_format) * num_standard_flags
data = struct.unpack(fmt, read_buffer) data = struct.unpack_from(fmt, read_buffer, offset=2)
standard_flag = data[0:num_standard_flags * 2:2] standard_flag = data[0:num_standard_flags * 2:2]
standard_mask = data[1:num_standard_flags * 2:2] standard_mask = data[1:num_standard_flags * 2:2]
@ -2376,7 +2379,7 @@ def _parse_standard_flag(fptr, mask_length):
return standard_flag, standard_mask return standard_flag, standard_mask
def _parse_vendor_features(fptr, mask_length): def _parse_vendor_features(read_buffer, mask_length):
"""Construct vendor features, vendor mask data from the file. """Construct vendor features, vendor mask data from the file.
Specifically working on Reader Requirements box. Specifically working on Reader Requirements box.
@ -2392,17 +2395,17 @@ def _parse_vendor_features(fptr, mask_length):
# from the buffer read from file. # from the buffer read from file.
mask_format = {1: 'B', 2: 'H', 4: 'I'}[mask_length] mask_format = {1: 'B', 2: 'H', 4: 'I'}[mask_length]
read_buffer = fptr.read(2) num_vendor_features, = struct.unpack_from('>H', read_buffer)
num_vendor_features, = struct.unpack('>H', read_buffer)
# Each vendor feature consists of a 16-byte UUID plus a mask whose # Each vendor feature consists of a 16-byte UUID plus a mask whose
# length is specified by, you guessed it, "mask_length". # length is specified by, you guessed it, "mask_length".
entry_length = 16 + mask_length entry_length = 16 + mask_length
read_buffer = fptr.read(num_vendor_features * entry_length) #read_buffer = fptr.read(num_vendor_features * entry_length)
vendor_feature = [] vendor_feature = []
vendor_mask = [] vendor_mask = []
for j in range(num_vendor_features): for j in range(num_vendor_features):
ubuffer = read_buffer[j * entry_length:(j + 1) * entry_length] uslice = slice(2 + j * entry_length, 2 + (j + 1) * entry_length)
ubuffer = read_buffer[uslice]
vendor_feature.append(uuid.UUID(bytes=ubuffer[0:16])) vendor_feature.append(uuid.UUID(bytes=ubuffer[0:16]))
vmask = struct.unpack('>' + mask_format, ubuffer[16:]) vmask = struct.unpack('>' + mask_format, ubuffer[16:])