[POWERPC] Add documentation for the zImage's gunzip convenience functions

#include "ops.h"

#include "gunzip_util.h"

struct gunzip_state state;

#define HEAD_CRC	2

#define EXTRA_FIELD	4

#define ORIG_NAME	8

#define COMMENT		0x10

#define RESERVED	0xe0

/**

 * gunzip_start - prepare to decompress gzip data

 * @state:     decompressor state structure to be initialized

 * @src:       buffer containing gzip compressed or uncompressed data

 * @srclen:    size in bytes of the buffer at src

 *

 * If the buffer at @src contains a gzip header, this function

 * initializes zlib to decompress the data, storing the decompression

 * state in @state.  The other functions in this file can then be used

 * to decompress data from the gzipped stream.

 *

 * If the buffer at @src does not contain a gzip header, it is assumed

 * to contain uncompressed data.  The buffer information is recorded

 * in @state and the other functions in this file will simply copy

 * data from the uncompressed data stream at @src.

 *

 * Any errors, such as bad compressed data, cause an error to be

 * printed an the platform's exit() function to be called.

 */

void gunzip_start(struct gunzip_state *state, void *src, int srclen)

{

	char *hdr = src;

	state->s.avail_in = srclen - hdrlen;

}

/**

 * gunzip_partial - extract bytes from a gzip data stream

 * @state:     gzip state structure previously initialized by gunzip_start()

 * @dst:       buffer to store extracted data

 * @dstlen:    maximum number of bytes to extract

 *

 * This function extracts at most @dstlen bytes from the data stream

 * previously associated with @state by gunzip_start(), decompressing

 * if necessary.  Exactly @dstlen bytes are extracted unless the data

 * stream doesn't contain enough bytes, in which case the entire

 * remainder of the stream is decompressed.

 *

 * Returns the actual number of bytes extracted.  If any errors occur,

 * such as a corrupted compressed stream, an error is printed an the

 * platform's exit() function is called.

 */

int gunzip_partial(struct gunzip_state *state, void *dst, int dstlen)

{

	int len;

	return len;

}

/**

 * gunzip_exactly - extract a fixed number of bytes from a gzip data stream

 * @state:     gzip state structure previously initialized by gunzip_start()

 * @dst:       buffer to store extracted data

 * @dstlen:    number of bytes to extract

 *

 * This function extracts exactly @dstlen bytes from the data stream

 * previously associated with @state by gunzip_start(), decompressing

 * if necessary.

 *

 * If there are less @dstlen bytes available in the data stream, or if

 * any other errors occur, such as a corrupted compressed stream, an

 * error is printed an the platform's exit() function is called.

 */

void gunzip_exactly(struct gunzip_state *state, void *dst, int dstlen)

{

	int len;

	}

}

/**

 * gunzip_discard - discard bytes from a gzip data stream

 * @state:     gzip state structure previously initialized by gunzip_start()

 * @len:       number of bytes to discard

 *

 * This function extracts, then discards exactly @len bytes from the

 * data stream previously associated with @state by gunzip_start().

 * Subsequent gunzip_partial(), gunzip_exactly() or gunzip_finish()

 * calls will extract the data following the discarded bytes in the

 * data stream.

 *

 * If there are less @len bytes available in the data stream, or if

 * any other errors occur, such as a corrupted compressed stream, an

 * error is printed an the platform's exit() function is called.

 */

void gunzip_discard(struct gunzip_state *state, int len)

{

	static char discard_buf[128];

		gunzip_exactly(state, discard_buf, len);

}

/**

 * gunzip_finish - extract all remaining bytes from a gzip data stream

 * @state:     gzip state structure previously initialized by gunzip_start()

 * @dst:       buffer to store extracted data

 * @dstlen:    maximum number of bytes to extract

 *

 * This function extracts all remaining data, or at most @dstlen

 * bytes, from the stream previously associated with @state by

 * gunzip_start().  zlib is then shut down, so it is an error to use

 * any of the functions in this file on @state until it is

 * re-initialized with another call to gunzip_start().

 *

 * If any errors occur, such as a corrupted compressed stream, an

 * error is printed an the platform's exit() function is called.

 */

int gunzip_finish(struct gunzip_state *state, void *dst, int dstlen)

{

	int len;

#include "zlib.h"

/*

 * These functions are designed to make life easy for decompressing

 * kernel images, initrd images or any other gzip compressed image,

 * particularly if its useful to decompress part of the image (e.g. to

 * examine headers) before decompressing the remainder.

 *

 * To use:

 *     - declare a gunzip_state structure

 *     - use gunzip_start() to initialize the state, associating it

 *       with a stream of compressed data

 *     - use gunzip_partial(), gunzip_exactly() and gunzip_discard()

 *       in any combination to extract pieces of data from the stream

 *     - Finally use gunzip_finish() to extract the tail of the

 *       compressed stream and wind up zlib

 */

/* scratch space for gunzip; 46912 is from zlib_inflate_workspacesize() */

#define GUNZIP_SCRATCH_SIZE	46912

int gunzip_finish(struct gunzip_state *state, void *dst, int len);

#endif /* _PPC_BOOT_GUNZIP_UTIL_H_ */