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Diffstat (limited to '.venv/lib/python3.12/site-packages/hpack/huffman.py')
-rw-r--r-- | .venv/lib/python3.12/site-packages/hpack/huffman.py | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/.venv/lib/python3.12/site-packages/hpack/huffman.py b/.venv/lib/python3.12/site-packages/hpack/huffman.py new file mode 100644 index 00000000..f5b06c5e --- /dev/null +++ b/.venv/lib/python3.12/site-packages/hpack/huffman.py @@ -0,0 +1,64 @@ +""" +An implementation of a bitwise prefix tree specially built for decoding +Huffman-coded content where we already know the Huffman table. +""" +from __future__ import annotations + + +class HuffmanEncoder: + """ + Encodes a string according to the Huffman encoding table defined in the + HPACK specification. + """ + + def __init__(self, huffman_code_list: list[int], huffman_code_list_lengths: list[int]) -> None: + self.huffman_code_list = huffman_code_list + self.huffman_code_list_lengths = huffman_code_list_lengths + + def encode(self, bytes_to_encode: bytes | None) -> bytes: + """ + Given a string of bytes, encodes them according to the HPACK Huffman + specification. + """ + # If handed the empty string, just immediately return. + if not bytes_to_encode: + return b"" + + final_num = 0 + final_int_len = 0 + + # Turn each byte into its huffman code. These codes aren't necessarily + # octet aligned, so keep track of how far through an octet we are. To + # handle this cleanly, just use a single giant integer. + for byte in bytes_to_encode: + bin_int_len = self.huffman_code_list_lengths[byte] + bin_int = self.huffman_code_list[byte] & ( + 2 ** (bin_int_len + 1) - 1 + ) + final_num <<= bin_int_len + final_num |= bin_int + final_int_len += bin_int_len + + # Pad out to an octet with ones. + bits_to_be_padded = (8 - (final_int_len % 8)) % 8 + final_num <<= bits_to_be_padded + final_num |= (1 << bits_to_be_padded) - 1 + + # Convert the number to hex and strip off the leading '0x' and the + # trailing 'L', if present. + s = hex(final_num)[2:].rstrip("L") + + # If this is odd, prepend a zero. + s = "0" + s if len(s) % 2 != 0 else s + + # This number should have twice as many digits as bytes. If not, we're + # missing some leading zeroes. Work out how many bytes we want and how + # many digits we have, then add the missing zero digits to the front. + total_bytes = (final_int_len + bits_to_be_padded) // 8 + expected_digits = total_bytes * 2 + + if len(s) != expected_digits: + missing_digits = expected_digits - len(s) + s = ("0" * missing_digits) + s + + return bytes.fromhex(s) |