xnu-3248.60.10.tar.gz

[apple/xnu.git] / osfmk / vm / WKdm_new.h

/*
 * Copyright (c) 2000-2013 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
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 * may not be used to create, or enable the creation or redistribution of,
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/* direct-mapped partial matching compressor with simple 22/10 split
 *
 *  Compresses buffers using a dictionary based match and partial match
 *  (high bits only or full match) scheme.
 *
 *  Paul Wilson -- wilson@cs.utexas.edu
 *  Scott F. Kaplan -- sfkaplan@cs.utexas.edu
 *  September 1997
 */

/* compressed output format, in memory order
 *  1. a four-word HEADER containing four one-word values:
 *     i.   a one-word code saying what algorithm compressed the data
 *     ii.  an integer WORD offset into the page saying
 *          where the queue position area starts
 *     iii. an integer WORD offset into the page saying where
 *          the low-bits area starts
 *     iv.  an integer WORD offset into the page saying where the
 *          low-bits area ends
 *
 *  2. a 64-word TAGS AREA holding one two-bit tag for each word in 
 *     the original (1024-word) page, packed 16 per word
 *
 *  3. a variable-sized FULL WORDS AREA (always word aligned and an
 *     integral number of words) holding full-word patterns that
 *     were not in the dictionary when encoded (i.e., dictionary misses)
 *
 *  4. a variable-sized QUEUE POSITIONS AREA (always word aligned and
 *     an integral number of words) holding four-bit queue positions,
 *     packed eight per word.
 *
 *  5. a variable-sized LOW BITS AREA (always word aligned and an
 *     integral number of words) holding ten-bit low-bit patterns
 *     (from partial matches), packed three per word. 
 */

#ifdef __cplusplus
extern "C" {
#endif

#include <mach/vm_param.h>


#define	WKdm_SCRATCH_BUF_SIZE	PAGE_SIZE

typedef unsigned int WK_word;


void
WKdm_decompress_new (WK_word* src_buf,
		     WK_word* dest_buf,
		     WK_word* scratch,
		     unsigned int bytes);
int
WKdm_compress_new (const WK_word* src_buf,
		   WK_word* dest_buf,
		   WK_word* scratch,
		   unsigned int limit);

#ifdef __cplusplus
} /* extern "C" */
#endif