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Ernesto A. Fernández
b4f0aef525
Introduce compression, using a modified version of Stan's code from the driver, plus my new implementation of LZBITMAP. This is mainly needed for sealed volumes, since for some reason Apple calculates hashes on the decompressed contents of files instead of the xattrs themselves. At this point, the hash checks are all passing. Very few checks on the compression metadata were put in place; I would like to revisit this in the future, at least to check the inode's reported decompressed size, but it's not a priority right now. These are a lot of messy changes and I was forced to interrupt the work halfway through to reverse engineer LZBITMAP, so I don't recall all the details and I'll keep the commit message brief. Signed-off-by: Ernesto A. Fernández <ernesto@corellium.com>
69 lines
2.7 KiB
C
69 lines
2.7 KiB
C
#ifndef _LIBZBITMAP_H
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#define _LIBZBITMAP_H
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#include <stddef.h>
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#define ZBM_NOMEM (-1) /* Failed to allocate memory */
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#define ZBM_INVAL (-2) /* Compressed input is invalid */
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#define ZBM_RANGE (-3) /* The destination buffer is too small */
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#define ZBM_OVERFLOW (-4) /* Integer overflow from size or index */
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/**
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* zbm_decompress - Decompress an LZBITMAP buffer
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* @dest: destination buffer (may be NULL)
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* @dest_size: size of the destination buffer
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* @src: source buffer
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* @src_size: size of the source buffer
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* @out_len: on return, the length of the decompressed output
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*
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* May be called with a NULL destination buffer to retrieve the expected length
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* of the decompressed data. Returns 0 on success, or a negative error code in
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* case of failure.
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*/
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int zbm_decompress(void *dest, size_t dest_size, const void *src, size_t src_size, size_t *out_len);
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/**
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* zbm_compress - Compress a whole buffer with LZBITMAP
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* @dest: destination buffer (may be NULL)
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* @dest_size: size of the destination buffer
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* @src: source buffer
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* @src_size: size of the source buffer
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* @out_len: on return, the length of the compressed output
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*
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* May be called with a NULL destination buffer to retrieve the maximum possible
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* length of the compressed output. Returns 0 on success, or a negative error
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* code in case of failure.
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*
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* This function just compresses the whole buffer sequentially, using a single
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* thread. For speed, the caller should consider using zbm_compress_chunk()
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* instead.
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*/
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int zbm_compress(void *dest, size_t dest_size, const void *src, size_t src_size, size_t *out_len);
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#define ZBM_MAX_CHUNK_SIZE 0x800A
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#define ZBM_LAST_CHUNK_SIZE 6
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/*
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* zbm_compress_chunk - Compress a single chunk in a buffer with LZBITMAP
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* @dest: destination buffer
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* @dest_size: size of the destination buffer
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* @src: source buffer
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* @src_size: size of the source buffer
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* @index: which chunk from @src to compress
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* @out_len: on return, the length of the compressed output
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*
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* Returns 0 on success, or a negative error code in case of failure.
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*
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* To compress a whole buffer, this function must be called repeatedly with the
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* same value of @src and a sequentially increasing value of @index. The process
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* concludes when @out_len returns ZBM_LAST_CHUNK_SIZE. The size of @dest must
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* always be ZBM_MAX_CHUNK_SIZE or more.
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*
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* The advantage of this over zbm_compress() is that the caller can compress
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* multiple chunks in parallel. For an example using pthreads, check the test
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* code in test/test.c.
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*/
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int zbm_compress_chunk(void *dest, size_t dest_size, const void *src, size_t src_size, size_t index, size_t *out_len);
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#endif /* _LIBZBITMAP_H */
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