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import struct, warnings
try:
import lz4
except ImportError:
lz4 = None
else:
import lz4.block
# old scheme for VERSION < 0.9 otherwise use lz4.block
def decompress(data):
(compression,) = struct.unpack(">L", data[4:8])
scheme = compression >> 27
size = compression & 0x07FFFFFF
if scheme == 0:
pass
elif scheme == 1 and lz4:
res = lz4.block.decompress(struct.pack("<L", size) + data[8:])
if len(res) != size:
warnings.warn("Table decompression failed.")
else:
data = res
else:
warnings.warn("Table is compressed with an unsupported compression scheme")
return (data, scheme)
def compress(scheme, data):
hdr = data[:4] + struct.pack(">L", (scheme << 27) + (len(data) & 0x07FFFFFF))
if scheme == 0:
return data
elif scheme == 1 and lz4:
res = lz4.block.compress(
data, mode="high_compression", compression=16, store_size=False
)
return hdr + res
else:
warnings.warn("Table failed to compress by unsupported compression scheme")
return data
def _entries(attrs, sameval):
ak = 0
vals = []
lastv = 0
for k, v in attrs:
if len(vals) and (k != ak + 1 or (sameval and v != lastv)):
yield (ak - len(vals) + 1, len(vals), vals)
vals = []
ak = k
vals.append(v)
lastv = v
yield (ak - len(vals) + 1, len(vals), vals)
def entries(attributes, sameval=False):
g = _entries(sorted(attributes.items(), key=lambda x: int(x[0])), sameval)
return g
def bininfo(num, size=1):
if num == 0:
return struct.pack(">4H", 0, 0, 0, 0)
srange = 1
select = 0
while srange <= num:
srange *= 2
select += 1
select -= 1
srange //= 2
srange *= size
shift = num * size - srange
return struct.pack(">4H", num, srange, select, shift)
def num2tag(n):
if n < 0x200000:
return str(n)
else:
return (
struct.unpack("4s", struct.pack(">L", n))[0].replace(b"\000", b"").decode()
)
def tag2num(n):
try:
return int(n)
except ValueError:
n = (n + " ")[:4]
return struct.unpack(">L", n.encode("ascii"))[0]
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