LZMA源码的神秘面纱，它是如何压缩数据的？

LZMA（LempelZivMarkov chain Algorithm）是一种无损数据压缩算法，它是由Igor Pavlovic和Abraham Lempel在1977年发明的，LZMA源码涉及到很多细节，这里给出一个简化版的Python实现，仅供参考：

import sys
import struct
def compress(data):
    # 初始化字典
    dictionary = {bytes([i]): i for i in range(256)}
    next_code = 256
    output = []
    # 当前处理的数据块
    current_block = b''
    for byte in data:
        # 尝试将当前字节与已有字典中的条目组合
        pair = current_block + bytes([byte])
        if pair in dictionary:
            current_block = pair
        else:
            # 输出当前字典中的条目对应的编码
            output.append(dictionary[current_block])
            # 将新的字节添加到字典中
            dictionary[pair] = next_code
            next_code += 1
            current_block = bytes([byte])
    # 输出最后一个数据块的编码
    if current_block:
        output.append(dictionary[current_block])
    return output
def decompress(encoded_data):
    # 初始化字典
    dictionary = {i: bytes([i]) for i in range(256)}
    next_code = 256
    output = []
    # 当前处理的数据块
    current_block = b''
    for code in encoded_data:
        if code in dictionary:
            entry = dictionary[code]
        elif code == next_code:
            entry = current_block + current_block[0:1]
        else:
            raise ValueError("Invalid compressed data")
        output.append(entry)
        # 添加新的字典条目
        if not current_block:
            current_block = entry
        else:
            new_entry = current_block + entry[0:1]
            dictionary[next_code] = new_entry
            next_code += 1
            current_block = entry
    return b''.join(output)
if __name__ == "__main__":
    if len(sys.argv) != 3:
        print("Usage: python lzma.py <compress|decompress> <input_file>")
        sys.exit(1)
    operation = sys.argv[1]
    input_file = sys.argv[2]
    with open(input_file, "rb") as f:
        data = f.read()
    if operation == "compress":
        compressed_data = compress(data)
        with open(input_file + ".lzma", "wb") as f:
            for code in compressed_data:
                f.write(struct.pack("<H", code))
    elif operation == "decompress":
        compressed_data = [struct.unpack("<H", data[i:i+2])[0] for i in range(0, len(data), 2)]
        decompressed_data = decompress(compressed_data)
        with open(input_file[:5], "wb") as f:
            f.write(decompressed_data)
    else:
        print("Invalid operation. Use 'compress' or 'decompress'.")

这个简化版的LZMA实现仅支持单个字节的编码，实际应用中的LZMA算法会使用更复杂的编码方式，如多字节编码、重复计数等，以提高压缩效率，实际的LZMA实现还会包括更多的优化和错误检测功能。

小伙伴们，上文介绍了“lzma 源码”的内容，你了解清楚吗？希望对你有所帮助，任何问题可以给我留言，让我们下期再见吧。