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deflate.h
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deflate.h
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/*
* Header file for my independent implementation of Deflate
* (RFC1951) compression.
*/
#ifndef DEFLATE_DEFLATE_H
#define DEFLATE_DEFLATE_H
/*
* Types of Deflate data stream.
*
* DEFLATE_TYPE_BARE represents the basic Deflate data format, as
* defined in RFC 1951. It has no checksum to detect errors and no
* magic-number header for ease of recognition, but it does have
* internal EOF indication.
*
* DEFLATE_TYPE_ZLIB represents the zlib container format, as
* defined in RFC 1950. It has a two-byte header, and a four-byte
* Adler32 checksum at the end to verify correct decoding, but
* apart from those six bytes it's exactly equivalent to
* DEFLATE_TYPE_BARE.
*
* DEFLATE_TYPE_GZIP represents the gzip compressed file format, as
* defined in RFC 1952. This is a more full-featured format, with a
* magic number, a CRC checksum of the compressed data, and various
* header features including storing the original filename. This
* implementation accepts but ignores all of those features on
* input except the checksum, and outputs them in the most trivial
* fashion. Also, this implementation will not decode multiple
* concatenated gzip members (permitted by the RFC).
*/
enum {
DEFLATE_TYPE_BARE,
DEFLATE_TYPE_ZLIB,
DEFLATE_TYPE_GZIP
};
/* ----------------------------------------------------------------------
* Compression functions. Create a compression context with
* deflate_compress_new(); feed it data with repeated calls to
* deflate_compress_data(); destroy it with
* deflate_compress_free().
*/
typedef struct deflate_compress_ctx deflate_compress_ctx;
/*
* Create a new compression context. `type' indicates whether it's
* bare Deflate (as used in, say, zip files) or Zlib (as used in,
* say, PDF).
*/
deflate_compress_ctx *deflate_compress_new(int type);
/*
* Free a compression context previously allocated by
* deflate_compress_new().
*/
void deflate_compress_free(deflate_compress_ctx *ctx);
/*
* Give the compression context some data to compress. The input
* data is passed in `inblock', and has length `inlen'. This
* function may or may not produce some output data; if so, it is
* written to a dynamically allocated chunk of memory, a pointer to
* that memory is stored in `outblock', and the length of output
* data is stored in `outlen'. It is common for no data to be
* output, if the input data has merely been stored in internal
* buffers.
*
* `flushtype' indicates whether you want to force buffered data to
* be output. It can be one of the following values:
*
* - DEFLATE_NO_FLUSH: nothing is output if the compressor would
* rather not. Use this when the best compression is desired
* (i.e. most of the time).
*
* - DEFLATE_SYNC_FLUSH: all the buffered data is output, but the
* compressed data stream remains open and ready to continue
* compressing data. Use this in interactive protocols when a
* single compressed data stream is split across several network
* packets.
*
* - DEFLATE_END_OF_DATA: all the buffered data is output and the
* compressed data stream is cleaned up. Any checksums required
* at the end of the stream are also output.
*/
void deflate_compress_data(deflate_compress_ctx *ctx,
const void *inblock, int inlen, int flushtype,
void **outblock, int *outlen);
enum {
DEFLATE_NO_FLUSH,
DEFLATE_SYNC_FLUSH,
DEFLATE_END_OF_DATA
};
/* ----------------------------------------------------------------------
* Decompression functions. Create a decompression context with
* deflate_decompress_new(); feed it data with repeated calls to
* deflate_decompress_data(); destroy it with
* deflate_decompress_free().
*/
typedef struct deflate_decompress_ctx deflate_decompress_ctx;
/*
* Create a new decompression context. `type' means the same as it
* does in deflate_compress_new().
*/
deflate_decompress_ctx *deflate_decompress_new(int type);
/*
* Free a decompression context previously allocated by
* deflate_decompress_new().
*/
void deflate_decompress_free(deflate_decompress_ctx *ctx);
/*
* Give the decompression context some data to decompress. The
* input data is passed in `inblock', and has length `inlen'. This
* function may or may not produce some output data; if so, it is
* written to a dynamically allocated chunk of memory, a pointer to
* that memory is stored in `outblock', and the length of output
* data is stored in `outlen'.
*
* Returns 0 on success, or a non-zero error code if there was a
* decoding error. In case of an error return, the data decoded
* before the error is still returned as well. The possible errors
* are listed below.
*
* If you want to check that the compressed data stream was
* correctly terminated, you can call this function with inlen==0
* to signal input EOF and see if an error comes back. If you don't
* care, don't bother.
*/
int deflate_decompress_data(deflate_decompress_ctx *ctx,
const void *inblock, int inlen,
void **outblock, int *outlen);
/*
* Enumeration of error codes. The strange macro is so that I can
* define description arrays in the accompanying source.
*/
#define DEFLATE_ERRORLIST(A) \
A(DEFLATE_NO_ERR, "success"), \
A(DEFLATE_ERR_ZLIB_HEADER, "invalid zlib header"), \
A(DEFLATE_ERR_ZLIB_WRONGCOMP, "zlib header specifies non-deflate compression"), \
A(DEFLATE_ERR_GZIP_HEADER, "invalid gzip header"), \
A(DEFLATE_ERR_GZIP_WRONGCOMP, "gzip header specifies non-deflate compression"), \
A(DEFLATE_ERR_GZIP_FHCRC, "gzip header specifies disputed FHCRC flag"), \
A(DEFLATE_ERR_SMALL_HUFTABLE, "under-committed Huffman code space"), \
A(DEFLATE_ERR_LARGE_HUFTABLE, "over-committed Huffman code space"), \
A(DEFLATE_ERR_UNCOMP_HDR, "wrongly formatted header in uncompressed block"), \
A(DEFLATE_ERR_NODISTTABLE, "backward copy encoded in block without distances table"), \
A(DEFLATE_ERR_BADDISTCODE, "invalid distance code 30 or 31 found in block"), \
A(DEFLATE_ERR_CHECKSUM, "incorrect data checksum"), \
A(DEFLATE_ERR_INLEN, "incorrect data length"), \
A(DEFLATE_ERR_UNEXPECTED_EOF, "unexpected end of data")
#define DEFLATE_ENUM_DEF(x,y) x
enum { DEFLATE_ERRORLIST(DEFLATE_ENUM_DEF), DEFLATE_NUM_ERRORS };
#undef DEFLATE_ENUM_DEF
/*
* Arrays mapping the above error codes to, respectively, a text
* error string and a textual representation of the symbolic error
* code.
*/
extern const char *const deflate_error_msg[DEFLATE_NUM_ERRORS];
extern const char *const deflate_error_sym[DEFLATE_NUM_ERRORS];
#endif /* DEFLATE_DEFLATE_H */