folly::compression

Namespaces

Name	Description
contexts	Process-wide singleton ZSTD compression context pools.
instructions	CPU instruction-set backends for Elias-Fano bit operations.

Types

Name	Description
BitVectorCompressedListBase	Non-owning view over a bit-vector-encoded list and its sub-sections.
BitVectorEncoder	Encodes a strictly increasing sequence of unsigned integers as a bit vector.
BitVectorReader	Forward/random-access reader over a bit-vector-encoded integer sequence.
Codec	Base class for a compression/decompression codec.
CompressionContextPool	This implementation is slow under contention. Except under uncontended scenarios, you shouldn't use it directly. You likely want to use the CompressionCoreLocalContextPool instead, which, behind the fast cache slots, is backed by this implementation.
CompressionContextPoolDefaultCallback	Default no-op callback invoked periodically by CompressionContextPool.
CompressionCoreLocalContextPool	This class is intended to reduce contention on reserving a compression context and improve cache locality (but maybe not hotness) of the contexts it manages.
CompressionCoreLocalContextPoolBase	Non-templated base class which allows for generic interaction with context pool instances.
EliasFanoCompressedListBase	Non-owning view over an Elias-Fano-encoded list and its sub-sections.
EliasFanoEncoder	Encodes a sorted sequence of unsigned integers using Elias-Fano coding.
EliasFanoReader	Forward/random-access reader over an Elias-Fano-encoded, non-decreasing sequence of integers produced by EliasFanoEncoder.
StreamCodec	Base class for a codec that also supports a stateful streaming API.

Type Aliases

Name	Description
BitVectorCompressedList	Read-only bit-vector compressed list.
EliasFanoCompressedList	Read-only Elias-Fano compressed list.
MutableBitVectorCompressedList	Mutable bit-vector compressed list.
MutableEliasFanoCompressedList	Mutable Elias-Fano compressed list.

Enums

Name	Description
CodecType	Identifies a compression algorithm.

Functions

Name	Description
copyCompressedList	Returns a deep copy of a compressed list, owning a freshly allocated buffer.
getAutoUncompressionCodec	Returns a codec that can uncompress any of the given codec types as well as {LZ4_FRAME, ZSTD, ZLIB, GZIP, LZMA2, BZIP2}. Appends each default codec to customCodecs in order, so long as a codec with the same type() isn't already present in customCodecs or as the terminalCodec. When uncompress() is called, each codec's canUncompress() is called in the order that they are given. Appended default codecs are checked last. uncompress() is called on the first codec whose canUncompress() returns true.
getCodec	Return a codec for the given type. Throws on error. The level is a non-negative codec-dependent integer indicating the level of compression desired, or one of the following constants:
getStreamCodec	Return a codec for the given type. Throws on error. The level is a non-negative codec-dependent integer indicating the level of compression desired, or one of the following constants:
hasCodec	Check if a specified codec is supported.
hasStreamCodec	Check if a specified codec is supported and supports streaming.
zstdConvertLevel	Convert a folly abstract compression level (COMPRESSION_LEVEL_FASTEST, COMPRESSION_LEVEL_DEFAULT, COMPRESSION_LEVEL_BEST) to a raw ZSTD compression level (1-22). Passes through raw levels in [1, ZSTD_maxCLevel()] unchanged. Throws std::invalid_argument for out-of-range levels.

Variables

Name	Description
COMPRESSION_CONTEXT_POOL_CALLBACK_INTERVAL	Number of pool checkouts between successive callback invocations.
COMPRESSION_LEVEL_BEST	Abstract level selecting the best compression.
COMPRESSION_LEVEL_DEFAULT	Abstract level selecting the codec's default compression.
COMPRESSION_LEVEL_FASTEST	Abstract level selecting the fastest compression.
kCacheLineSize	Size in bytes of a cache line, used to size prefetches.
kLowerTrailingBytes	Trailing bytes that must be readable past the end of the lower bit sequence, required by loadUnaligned<uint64_t> reads in the lower accessor.
kUpperTrailingBytes	Trailing bytes that must be readable past the end of the upper bit sequence, required by loadUnaligned<uint64_t> reads in the upper accessor.