import asyncio
import sys
import zlib
from abc import ABC, abstractmethod
from concurrent.futures import Executor
from typing import Any, Final, Protocol, TypedDict, cast
if sys.version_info >= (3, 12):
from collections.abc import Buffer
else:
from typing import Union
Buffer = Union[bytes, bytearray, "memoryview[int]", "memoryview[bytes]"]
try:
try:
import brotlicffi as brotli
except ImportError:
import brotli
HAS_BROTLI = True
except ImportError: # pragma: no cover
HAS_BROTLI = False
try:
if sys.version_info >= (3, 14):
from compression.zstd import ZstdDecompressor # noqa: I900
else: # TODO(PY314): Remove mentions of backports.zstd across codebase
from backports.zstd import ZstdDecompressor
HAS_ZSTD = True
except ImportError:
HAS_ZSTD = False
MAX_SYNC_CHUNK_SIZE = 4096
# Unlimited decompression constants - different libraries use different conventions
ZLIB_MAX_LENGTH_UNLIMITED = 0 # zlib uses 0 to mean unlimited
ZSTD_MAX_LENGTH_UNLIMITED = -1 # zstd uses -1 to mean unlimited
class ZLibCompressObjProtocol(Protocol):
def compress(self, data: Buffer) -> bytes: ...
def flush(self, mode: int = ..., /) -> bytes: ...
class ZLibDecompressObjProtocol(Protocol):
def decompress(self, data: Buffer, max_length: int = ...) -> bytes: ...
def flush(self, length: int = ..., /) -> bytes: ...
@property
def eof(self) -> bool: ...
@property
def unconsumed_tail(self) -> bytes: ...
@property
def unused_data(self) -> bytes: ...
class ZLibBackendProtocol(Protocol):
MAX_WBITS: int
Z_FULL_FLUSH: int
Z_SYNC_FLUSH: int
Z_BEST_SPEED: int
Z_FINISH: int
def compressobj(
self,
level: int = ...,
method: int = ...,
wbits: int = ...,
memLevel: int = ...,
strategy: int = ...,
zdict: Buffer | None = ...,
) -> ZLibCompressObjProtocol: ...
def decompressobj(
self, wbits: int = ..., zdict: Buffer = ...
) -> ZLibDecompressObjProtocol: ...
def compress(
self, data: Buffer, /, level: int = ..., wbits: int = ...
) -> bytes: ...
def decompress(
self, data: Buffer, /, wbits: int = ..., bufsize: int = ...
) -> bytes: ...
class CompressObjArgs(TypedDict, total=False):
wbits: int
strategy: int
level: int
class ZLibBackendWrapper:
def __init__(self, _zlib_backend: ZLibBackendProtocol):
self._zlib_backend: ZLibBackendProtocol = _zlib_backend
@property
def name(self) -> str:
return getattr(self._zlib_backend, "__name__", "undefined")
@property
def MAX_WBITS(self) -> int:
return self._zlib_backend.MAX_WBITS
@property
def Z_FULL_FLUSH(self) -> int:
return self._zlib_backend.Z_FULL_FLUSH
@property
def Z_SYNC_FLUSH(self) -> int:
return self._zlib_backend.Z_SYNC_FLUSH
@property
def Z_BEST_SPEED(self) -> int:
return self._zlib_backend.Z_BEST_SPEED
@property
def Z_FINISH(self) -> int:
return self._zlib_backend.Z_FINISH
def compressobj(self, *args: Any, **kwargs: Any) -> ZLibCompressObjProtocol:
return self._zlib_backend.compressobj(*args, **kwargs)
def decompressobj(self, *args: Any, **kwargs: Any) -> ZLibDecompressObjProtocol:
return self._zlib_backend.decompressobj(*args, **kwargs)
def compress(self, data: Buffer, *args: Any, **kwargs: Any) -> bytes:
return self._zlib_backend.compress(data, *args, **kwargs)
def decompress(self, data: Buffer, *args: Any, **kwargs: Any) -> bytes:
return self._zlib_backend.decompress(data, *args, **kwargs)
# Everything not explicitly listed in the Protocol we just pass through
def __getattr__(self, attrname: str) -> Any:
return getattr(self._zlib_backend, attrname)
ZLibBackend: ZLibBackendWrapper = ZLibBackendWrapper(zlib)
[docs]
def set_zlib_backend(new_zlib_backend: ZLibBackendProtocol) -> None:
ZLibBackend._zlib_backend = new_zlib_backend
def encoding_to_mode(
encoding: str | None = None,
suppress_deflate_header: bool = False,
) -> int:
if encoding == "gzip":
return 16 + ZLibBackend.MAX_WBITS
return -ZLibBackend.MAX_WBITS if suppress_deflate_header else ZLibBackend.MAX_WBITS
class DecompressionBaseHandler(ABC):
def __init__(
self,
executor: Executor | None = None,
max_sync_chunk_size: int | None = MAX_SYNC_CHUNK_SIZE,
):
"""Base class for decompression handlers."""
self._executor = executor
self._max_sync_chunk_size = max_sync_chunk_size
@abstractmethod
def decompress_sync(
self, data: Buffer, max_length: int = ZLIB_MAX_LENGTH_UNLIMITED
) -> bytes:
"""Decompress the given data."""
async def decompress(
self, data: Buffer, max_length: int = ZLIB_MAX_LENGTH_UNLIMITED
) -> bytes:
"""Decompress the given data."""
if (
self._max_sync_chunk_size is not None
and len(data) > self._max_sync_chunk_size
):
return await asyncio.get_event_loop().run_in_executor(
self._executor, self.decompress_sync, data, max_length
)
return self.decompress_sync(data, max_length)
@property
@abstractmethod
def data_available(self) -> bool:
"""Return True if more output is available by passing b""."""
class ZLibCompressor:
def __init__(
self,
encoding: str | None = None,
suppress_deflate_header: bool = False,
level: int | None = None,
wbits: int | None = None,
strategy: int | None = None,
executor: Executor | None = None,
max_sync_chunk_size: int | None = MAX_SYNC_CHUNK_SIZE,
):
self._executor = executor
self._max_sync_chunk_size = max_sync_chunk_size
self._mode = (
encoding_to_mode(encoding, suppress_deflate_header)
if wbits is None
else wbits
)
self._zlib_backend: Final = ZLibBackendWrapper(ZLibBackend._zlib_backend)
kwargs: CompressObjArgs = {}
kwargs["wbits"] = self._mode
if strategy is not None:
kwargs["strategy"] = strategy
if level is not None:
kwargs["level"] = level
self._compressor = self._zlib_backend.compressobj(**kwargs)
def compress_sync(self, data: Buffer) -> bytes:
return self._compressor.compress(data)
async def compress(self, data: Buffer) -> bytes:
"""Compress the data and returned the compressed bytes.
Note that flush() must be called after the last call to compress()
If the data size is large than the max_sync_chunk_size, the compression
will be done in the executor. Otherwise, the compression will be done
in the event loop.
**WARNING: This method is NOT cancellation-safe when used with flush().**
If this operation is cancelled, the compressor state may be corrupted.
The connection MUST be closed after cancellation to avoid data corruption
in subsequent compress operations.
For cancellation-safe compression (e.g., WebSocket), the caller MUST wrap
compress() + flush() + send operations in a shield and lock to ensure atomicity.
"""
# For large payloads, offload compression to executor to avoid blocking event loop
should_use_executor = (
self._max_sync_chunk_size is not None
and len(data) > self._max_sync_chunk_size
)
if should_use_executor:
return await asyncio.get_running_loop().run_in_executor(
self._executor, self._compressor.compress, data
)
return self.compress_sync(data)
def flush(self, mode: int | None = None) -> bytes:
"""Flush the compressor synchronously.
**WARNING: This method is NOT cancellation-safe when called after compress().**
The flush() operation accesses shared compressor state. If compress() was
cancelled, calling flush() may result in corrupted data. The connection MUST
be closed after compress() cancellation.
For cancellation-safe compression (e.g., WebSocket), the caller MUST wrap
compress() + flush() + send operations in a shield and lock to ensure atomicity.
"""
return self._compressor.flush(
mode if mode is not None else self._zlib_backend.Z_FINISH
)
class ZLibDecompressor(DecompressionBaseHandler):
def __init__(
self,
encoding: str | None = None,
suppress_deflate_header: bool = False,
executor: Executor | None = None,
max_sync_chunk_size: int | None = MAX_SYNC_CHUNK_SIZE,
):
super().__init__(executor=executor, max_sync_chunk_size=max_sync_chunk_size)
self._mode = encoding_to_mode(encoding, suppress_deflate_header)
self._zlib_backend: Final = ZLibBackendWrapper(ZLibBackend._zlib_backend)
self._decompressor = self._zlib_backend.decompressobj(wbits=self._mode)
self._last_empty = False
self._pending_unused_data: bytes | None = None
def decompress_sync(
self, data: Buffer, max_length: int = ZLIB_MAX_LENGTH_UNLIMITED
) -> bytes:
if self._pending_unused_data is not None:
data = self._pending_unused_data + bytes(data)
self._pending_unused_data = None
result = self._decompressor.decompress(
self._decompressor.unconsumed_tail + data, max_length
)
# Only way to know that isal has no further data is checking we get no output
self._last_empty = result == b""
# Handle concatenated gzip/deflate streams (multi-member).
# After a member ends, unused_data holds the start of the next member.
# Create a fresh decompressor for each subsequent member.
while self._decompressor.eof and self._decompressor.unused_data:
unused = self._decompressor.unused_data
self._decompressor = self._zlib_backend.decompressobj(wbits=self._mode)
if max_length != ZLIB_MAX_LENGTH_UNLIMITED:
max_length -= len(result)
if max_length <= 0:
self._pending_unused_data = unused
break
chunk = self._decompressor.decompress(unused, max_length)
self._last_empty = chunk == b""
result += chunk
# Member ended exactly at chunk boundary — no unused_data, but the
# next feed_data() call would fail on the spent decompressor.
# Only reset for gzip; deflate's feed_eof() relies on eof=True to
# confirm the stream is complete.
if self._decompressor.eof and self._mode > self._zlib_backend.MAX_WBITS:
self._decompressor = self._zlib_backend.decompressobj(wbits=self._mode)
return result
def flush(self, length: int = 0) -> bytes:
return (
self._decompressor.flush(length)
if length > 0
else self._decompressor.flush()
)
@property
def data_available(self) -> bool:
return (
bool(self._decompressor.unconsumed_tail)
or not self._last_empty
or self._pending_unused_data is not None
)
@property
def eof(self) -> bool:
return self._decompressor.eof
class BrotliDecompressor(DecompressionBaseHandler):
# Supports both 'brotlipy' and 'Brotli' packages
# since they share an import name. The top branches
# are for 'brotlipy' and bottom branches for 'Brotli'
def __init__(
self,
executor: Executor | None = None,
max_sync_chunk_size: int | None = MAX_SYNC_CHUNK_SIZE,
) -> None:
"""Decompress data using the Brotli library."""
if not HAS_BROTLI:
raise RuntimeError(
"The brotli decompression is not available. "
"Please install `Brotli` module"
)
self._obj = brotli.Decompressor()
self._last_empty = False
super().__init__(executor=executor, max_sync_chunk_size=max_sync_chunk_size)
def decompress_sync(
self, data: Buffer, max_length: int = ZLIB_MAX_LENGTH_UNLIMITED
) -> bytes:
"""Decompress the given data."""
if hasattr(self._obj, "decompress"):
if max_length == ZLIB_MAX_LENGTH_UNLIMITED:
result = cast(bytes, self._obj.decompress(data))
else:
result = cast(bytes, self._obj.decompress(data, max_length))
else:
if max_length == ZLIB_MAX_LENGTH_UNLIMITED:
result = cast(bytes, self._obj.process(data))
else:
result = cast(bytes, self._obj.process(data, max_length))
# Only way to know that brotli has no further data is checking we get no output
self._last_empty = result == b""
return result
def flush(self) -> bytes:
"""Flush the decompressor."""
if hasattr(self._obj, "flush"):
return cast(bytes, self._obj.flush())
return b""
@property
def data_available(self) -> bool:
return not self._obj.is_finished() and not self._last_empty
class ZSTDDecompressor(DecompressionBaseHandler):
def __init__(
self,
executor: Executor | None = None,
max_sync_chunk_size: int | None = MAX_SYNC_CHUNK_SIZE,
) -> None:
if not HAS_ZSTD:
raise RuntimeError(
"The zstd decompression is not available. "
"Please install `backports.zstd` module"
)
self._obj = ZstdDecompressor()
self._pending_unused_data: bytes | None = None
super().__init__(executor=executor, max_sync_chunk_size=max_sync_chunk_size)
def decompress_sync(
self, data: Buffer, max_length: int = ZLIB_MAX_LENGTH_UNLIMITED
) -> bytes:
# zstd uses -1 for unlimited, while zlib uses 0 for unlimited
# Convert the zlib convention (0=unlimited) to zstd convention (-1=unlimited)
zstd_max_length = (
ZSTD_MAX_LENGTH_UNLIMITED
if max_length == ZLIB_MAX_LENGTH_UNLIMITED
else max_length
)
if self._pending_unused_data is not None:
data = self._pending_unused_data + data
self._pending_unused_data = None
result = self._obj.decompress(data, zstd_max_length)
# Handle multi-frame zstd streams.
# https://datatracker.ietf.org/doc/html/rfc8878#section-3.1.1
# ZstdDecompressor handles one frame only. When a frame ends,
# eof becomes True and any trailing data goes to unused_data.
# We create a fresh decompressor to continue with the next frame.
while self._obj.eof and self._obj.unused_data:
unused_data = self._obj.unused_data
self._obj = ZstdDecompressor()
if zstd_max_length != ZSTD_MAX_LENGTH_UNLIMITED:
zstd_max_length -= len(result)
if zstd_max_length <= 0:
self._pending_unused_data = unused_data
break
result += self._obj.decompress(unused_data, zstd_max_length)
# Frame ended exactly at chunk boundary — no unused_data, but the
# next feed_data() call would fail on the spent decompressor.
# Prepare a fresh one for the next chunk.
if self._obj.eof:
self._obj = ZstdDecompressor()
return result
def flush(self) -> bytes:
return b""
@property
def data_available(self) -> bool:
return (
not self._obj.needs_input and not self._obj.eof
) or self._pending_unused_data is not None
