mirror of
https://github.com/Sneed-Group/pypush-plus-plus
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73 lines
2 KiB
Python
73 lines
2 KiB
Python
# https://en.wikipedia.org/wiki/LEB128
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#
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# LEB128 or Little Endian Base 128 is a form of variable-length code
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# compression used to store an arbitrarily large integer in a small number of
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# bytes. LEB128 is used in the DWARF debug file format and the WebAssembly
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# binary encoding for all integer literals.
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# Taken from https://github.com/mohanson/pywasm/blob/master/pywasm/leb128.py under the MIT license
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import typing
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class ULEB128:
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@staticmethod
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def encode(i: int) -> bytearray:
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assert i >= 0
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r = []
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while True:
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byte = i & 0x7F
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i = i >> 7
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if i == 0:
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r.append(byte)
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return bytearray(r)
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r.append(0x80 | byte)
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@staticmethod
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def decode(b: bytearray) -> int:
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r = 0
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for i, e in enumerate(b):
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r = r + ((e & 0x7F) << (i * 7))
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return r
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@staticmethod
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def decode_reader(r: typing.BinaryIO) -> (int, int):
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a = bytearray()
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while True:
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b = ord(r.read(1))
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a.append(b)
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if (b & 0x80) == 0:
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break
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return ULEB128.decode(a), len(a)
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class ILEB128:
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@staticmethod
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def encode(i: int) -> bytearray:
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r = []
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while True:
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byte = i & 0x7F
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i = i >> 7
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if (i == 0 and byte & 0x40 == 0) or (i == -1 and byte & 0x40 != 0):
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r.append(byte)
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return bytearray(r)
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r.append(0x80 | byte)
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@staticmethod
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def decode(b: bytearray) -> int:
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r = 0
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for i, e in enumerate(b):
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r = r + ((e & 0x7F) << (i * 7))
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if e & 0x40 != 0:
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r |= -(1 << (i * 7) + 7)
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return r
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@staticmethod
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def decode_reader(r: typing.BinaryIO) -> (int, int):
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a = bytearray()
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while True:
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b = ord(r.read(1))
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a.append(b)
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if (b & 0x80) == 0:
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break
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return ILEB128.decode(a), len(a)
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