: Signed LEB128 (SLEB128) requires sign-extension logic during decoding and checking the sign bit of the last 7-bit chunk during encoding. Performance : For high-performance needs, consider using the library available on , which handles signed integers and edge cases efficiently.
This is perfect for metadata like:
# Encoding a negative integer encoded_signed = leb128.i.encode(-12345) print(list(encoded_signed)) # Output: [199, 159, 127] (0xc7, 0x9f, 0x7f) # Decoding back decoded_signed = leb128.i.decode(encoded_signed) print(decoded_signed) # Output: -12345 Use code with caution. Copied to clipboard Why Use LEB128? Small numbers (0–127) take only 1 byte .
LEB128, short for Little Endian Base 128, is a variable-length encoding used to represent integers in a compact binary format. This encoding scheme is widely used in various file formats, network protocols, and programming languages, including Java, .NET, and Google's Protocol Buffers. In this article, we will explore the basics of LEB128 encoding, its advantages, and provide a comprehensive guide to implementing LEB128 in Python. leb128 python
data = leb128.encode_uleb128(300) print(data.hex()) # 'ac02'
Pure Python loops over bytes are fine for thousands of values. But for parsing large WASM files (megabytes), consider:
import leb128 # Encoding an unsigned integer encoded = leb128.u.encode(624485) print(list(encoded)) # Output: [229, 142, 38] (0xe5, 0x8e, 0x26) # Decoding back decoded = leb128.u.decode(encoded) print(decoded) # Output: 624485 Use code with caution. Copied to clipboard Signed LEB128 (SLEB128) Copied to clipboard Why Use LEB128
Args: bytes_data (bytes): The LEB128-encoded bytes.
Decoding requires shifting the 7-bit payloads back into position based on their index.
neg_data = leb128.encode_sleb128(-42) val2, _ = leb128.decode_sleb128(neg_data) print(val2) # -42 This encoding scheme is widely used in various
return result, pos - offset
def encode_uleb128(value: int) -> bytes: if value < 0: raise ValueError("ULEB128 cannot encode negative numbers") result = bytearray() while True: byte = value & 0x7F value >>= 7 if value != 0: byte |= 0x80 result.append(byte) if value == 0: break return bytes(result)