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50 lines
3.5 KiB
C++
50 lines
3.5 KiB
C++
/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
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// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
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#ident "$Id$"
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#ident "Copyright (c) 2007-2012 Tokutek Inc. All rights reserved."
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#ident "The technology is licensed by the Massachusetts Institute of Technology, Rutgers State University of New Jersey, and the Research Foundation of State University of New York at Stony Brook under United States of America Serial No. 11/760379 and to the patents and/or patent applications resulting from it."
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#ifndef TOKU_COMPRESS_H
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#define TOKU_COMPRESS_H
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#include <zlib.h>
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#include <db.h>
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// The following provides an abstraction of quicklz and zlib.
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// We offer three compression methods: ZLIB, QUICKLZ, and LZMA, as well as a "no compression" option. These options are declared in make_tdb.c.
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// The resulting byte string includes enough information for us to decompress it. That is, we can tell whether it's z-compressed or qz-compressed or xz-compressed.
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size_t toku_compress_bound (enum toku_compression_method a, size_t size);
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// Effect: Return the number of bytes needed to compress a buffer of size SIZE using compression method A.
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// Typically, the result is a little bit larger than SIZE, since some data cannot be compressed.
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// Usage note: It may help to know roughly how much space is involved.
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// zlib's bound is something like (size + (size>>12) + (size>>14) + (size>>25) + 13.
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// quicklz's bound is something like size+400.
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void toku_compress (enum toku_compression_method a,
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// the following types and naming conventions come from zlib.h
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Bytef *dest, uLongf *destLen,
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const Bytef *source, uLong sourceLen);
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// Effect: Using compression method A, compress SOURCE into DEST. The number of bytes to compress is passed in SOURCELEN.
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// On input: *destLen is the size of the buffer.
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// On output: *destLen is the size of the actual compressed data.
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// Usage note: sourceLen may be be zero (unlike for quicklz, which requires sourceLen>0).
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// Requires: The buffer must be big enough to hold the compressed data. (That is *destLen >= compressBound(a, sourceLen))
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// Requires: sourceLen < 2^32.
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// Usage note: Although we *try* to assert if the DESTLEN isn't big enough, it's possible that it's too late by then (in the case of quicklz which offers
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// no way to avoid a buffer overrun.) So we require that that DESTLEN is big enough.
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// Rationale: zlib's argument order is DEST then SOURCE with the size of the buffer passed in *destLen, and the size of the result returned in *destLen.
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// quicklz's argument order is SOURCE then DEST with the size returned (and it has no way to verify that an overright didn't happen).
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// We use zlib's calling conventions partly because it is safer, and partly because it is more established.
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// We also use zlib's ugly camel case convention for destLen and sourceLen.
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// Unlike zlib, we return no error codes. Instead, we require that the data be OK and the size of the buffers is OK, and assert if there's a problem.
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void toku_decompress (Bytef *dest, uLongf destLen,
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const Bytef *source, uLongf sourceLen);
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// Effect: Decompress source (length sourceLen) into dest (length destLen)
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// This function can decompress data compressed with either zlib or quicklz compression methods (calling toku_compress(), which puts an appropriate header on so we know which it is.)
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// Requires: destLen is equal to the actual decompressed size of the data.
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// Requires: The source must have been properly compressed.
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#endif
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