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 /*
  * XZ decompressor
  *
  * Authors: Lasse Collin <lasse.collin@tukaani.org>
  *          Igor Pavlov <http://7-zip.org/>
  *
  * This file has been put into the public domain.
  * You can do whatever you want with this file.
  */
 
 #ifndef XZ_H
 #define XZ_H
 
 #ifdef __KERNEL__
 #   include <linux/stddef.h>
 #   include <linux/types.h>
 #else
 #   include <stddef.h>
 #   include <stdint.h>
 #endif
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /* In Linux, this is used to make extern functions static when needed. */
 #ifndef XZ_EXTERN
 #   define XZ_EXTERN extern
 #endif
 
 /**
  * enum xz_mode - Operation mode
  *
  * @XZ_SINGLE:              Single-call mode. This uses less RAM than
  *                          than multi-call modes, because the LZMA2
  *                          dictionary doesn't need to be allocated as
  *                          part of the decoder state. All required data
  *                          structures are allocated at initialization,
  *                          so xz_dec_run() cannot return XZ_MEM_ERROR.
  * @XZ_PREALLOC:            Multi-call mode with preallocated LZMA2
  *                          dictionary buffer. All data structures are
  *                          allocated at initialization, so xz_dec_run()
  *                          cannot return XZ_MEM_ERROR.
  * @XZ_DYNALLOC:            Multi-call mode. The LZMA2 dictionary is
  *                          allocated once the required size has been
  *                          parsed from the stream headers. If the
  *                          allocation fails, xz_dec_run() will return
  *                          XZ_MEM_ERROR.
  *
  * It is possible to enable support only for a subset of the above
  * modes at compile time by defining XZ_DEC_SINGLE, XZ_DEC_PREALLOC,
  * or XZ_DEC_DYNALLOC. The xz_dec kernel module is always compiled
  * with support for all operation modes, but the preboot code may
  * be built with fewer features to minimize code size.
  */
 enum xz_mode {
     XZ_SINGLE,
     XZ_PREALLOC,
     XZ_DYNALLOC
 };
 
 /**
  * enum xz_ret - Return codes
  * @XZ_OK:                  Everything is OK so far. More input or more
  *                          output space is required to continue. This
  *                          return code is possible only in multi-call mode
  *                          (XZ_PREALLOC or XZ_DYNALLOC).
  * @XZ_STREAM_END:          Operation finished successfully.
  * @XZ_UNSUPPORTED_CHECK:   Integrity check type is not supported. Decoding
  *                          is still possible in multi-call mode by simply
  *                          calling xz_dec_run() again.
  *                          Note that this return value is used only if
  *                          XZ_DEC_ANY_CHECK was defined at build time,
  *                          which is not used in the kernel. Unsupported
  *                          check types return XZ_OPTIONS_ERROR if
  *                          XZ_DEC_ANY_CHECK was not defined at build time.
  * @XZ_MEM_ERROR:           Allocating memory failed. This return code is
  *                          possible only if the decoder was initialized
  *                          with XZ_DYNALLOC. The amount of memory that was
  *                          tried to be allocated was no more than the
  *                          dict_max argument given to xz_dec_init().
  * @XZ_MEMLIMIT_ERROR:      A bigger LZMA2 dictionary would be needed than
  *                          allowed by the dict_max argument given to
  *                          xz_dec_init(). This return value is possible
  *                          only in multi-call mode (XZ_PREALLOC or
  *                          XZ_DYNALLOC); the single-call mode (XZ_SINGLE)
  *                          ignores the dict_max argument.
  * @XZ_FORMAT_ERROR:        File format was not recognized (wrong magic
  *                          bytes).
  * @XZ_OPTIONS_ERROR:       This implementation doesn't support the requested
  *                          compression options. In the decoder this means
  *                          that the header CRC32 matches, but the header
  *                          itself specifies something that we don't support.
  * @XZ_DATA_ERROR:          Compressed data is corrupt.
  * @XZ_BUF_ERROR:           Cannot make any progress. Details are slightly
  *                          different between multi-call and single-call
  *                          mode; more information below.
  *
  * In multi-call mode, XZ_BUF_ERROR is returned when two consecutive calls
  * to XZ code cannot consume any input and cannot produce any new output.
  * This happens when there is no new input available, or the output buffer
  * is full while at least one output byte is still pending. Assuming your
  * code is not buggy, you can get this error only when decoding a compressed
  * stream that is truncated or otherwise corrupt.
  *
  * In single-call mode, XZ_BUF_ERROR is returned only when the output buffer
  * is too small or the compressed input is corrupt in a way that makes the
  * decoder produce more output than the caller expected. When it is
  * (relatively) clear that the compressed input is truncated, XZ_DATA_ERROR
  * is used instead of XZ_BUF_ERROR.
  */
 enum xz_ret {
     XZ_OK,
     XZ_STREAM_END,
     XZ_UNSUPPORTED_CHECK,
     XZ_MEM_ERROR,
     XZ_MEMLIMIT_ERROR,
     XZ_FORMAT_ERROR,
     XZ_OPTIONS_ERROR,
     XZ_DATA_ERROR,
     XZ_BUF_ERROR
 };
 
 /**
  * struct xz_buf - Passing input and output buffers to XZ code
  * @in:         Beginning of the input buffer. This may be NULL if and only
  *              if in_pos is equal to in_size.
  * @in_pos:     Current position in the input buffer. This must not exceed
  *              in_size.
  * @in_size:    Size of the input buffer
  * @out:        Beginning of the output buffer. This may be NULL if and only
  *              if out_pos is equal to out_size.
  * @out_pos:    Current position in the output buffer. This must not exceed
  *              out_size.
  * @out_size:   Size of the output buffer
  *
  * Only the contents of the output buffer from out[out_pos] onward, and
  * the variables in_pos and out_pos are modified by the XZ code.
  */
 struct xz_buf {
     const uint8_t *in;
     size_t in_pos;
     size_t in_size;
 
     uint8_t *out;
     size_t out_pos;
     size_t out_size;
 };
 
 /**
  * struct xz_dec - Opaque type to hold the XZ decoder state
  */
 struct xz_dec;
 
 /**
  * xz_dec_init() - Allocate and initialize a XZ decoder state
  * @mode:       Operation mode
  * @dict_max:   Maximum size of the LZMA2 dictionary (history buffer) for
  *              multi-call decoding. This is ignored in single-call mode
  *              (mode == XZ_SINGLE). LZMA2 dictionary is always 2^n bytes
  *              or 2^n + 2^(n-1) bytes (the latter sizes are less common
  *              in practice), so other values for dict_max don't make sense.
  *              In the kernel, dictionary sizes of 64 KiB, 128 KiB, 256 KiB,
  *              512 KiB, and 1 MiB are probably the only reasonable values,
  *              except for kernel and initramfs images where a bigger
  *              dictionary can be fine and useful.
  *
  * Single-call mode (XZ_SINGLE): xz_dec_run() decodes the whole stream at
  * once. The caller must provide enough output space or the decoding will
  * fail. The output space is used as the dictionary buffer, which is why
  * there is no need to allocate the dictionary as part of the decoder's
  * internal state.
  *
  * Because the output buffer is used as the workspace, streams encoded using
  * a big dictionary are not a problem in single-call mode. It is enough that
  * the output buffer is big enough to hold the actual uncompressed data; it
  * can be smaller than the dictionary size stored in the stream headers.
  *
  * Multi-call mode with preallocated dictionary (XZ_PREALLOC): dict_max bytes
  * of memory is preallocated for the LZMA2 dictionary. This way there is no
  * risk that xz_dec_run() could run out of memory, since xz_dec_run() will
  * never allocate any memory. Instead, if the preallocated dictionary is too
  * small for decoding the given input stream, xz_dec_run() will return
  * XZ_MEMLIMIT_ERROR. Thus, it is important to know what kind of data will be
  * decoded to avoid allocating excessive amount of memory for the dictionary.
  *
  * Multi-call mode with dynamically allocated dictionary (XZ_DYNALLOC):
  * dict_max specifies the maximum allowed dictionary size that xz_dec_run()
  * may allocate once it has parsed the dictionary size from the stream
  * headers. This way excessive allocations can be avoided while still
  * limiting the maximum memory usage to a sane value to prevent running the
  * system out of memory when decompressing streams from untrusted sources.
  *
  * On success, xz_dec_init() returns a pointer to struct xz_dec, which is
  * ready to be used with xz_dec_run(). If memory allocation fails,
  * xz_dec_init() returns NULL.
  */
 XZ_EXTERN struct xz_dec *xz_dec_init(enum xz_mode mode, uint32_t dict_max);
 
 /**
  * xz_dec_run() - Run the XZ decoder
  * @s:          Decoder state allocated using xz_dec_init()
  * @b:          Input and output buffers
  *
  * The possible return values depend on build options and operation mode.
  * See enum xz_ret for details.
  *
  * Note that if an error occurs in single-call mode (return value is not
  * XZ_STREAM_END), b->in_pos and b->out_pos are not modified and the
  * contents of the output buffer from b->out[b->out_pos] onward are
  * undefined. This is true even after XZ_BUF_ERROR, because with some filter
  * chains, there may be a second pass over the output buffer, and this pass
  * cannot be properly done if the output buffer is truncated. Thus, you
  * cannot give the single-call decoder a too small buffer and then expect to
  * get that amount valid data from the beginning of the stream. You must use
  * the multi-call decoder if you don't want to uncompress the whole stream.
  */
 XZ_EXTERN enum xz_ret xz_dec_run(struct xz_dec *s, struct xz_buf *b);
 
 /**
  * xz_dec_reset() - Reset an already allocated decoder state
  * @s:          Decoder state allocated using xz_dec_init()
  *
  * This function can be used to reset the multi-call decoder state without
  * freeing and reallocating memory with xz_dec_end() and xz_dec_init().
  *
  * In single-call mode, xz_dec_reset() is always called in the beginning of
  * xz_dec_run(). Thus, explicit call to xz_dec_reset() is useful only in
  * multi-call mode.
  */
 XZ_EXTERN void xz_dec_reset(struct xz_dec *s);
 
 /**
  * xz_dec_end() - Free the memory allocated for the decoder state
  * @s:          Decoder state allocated using xz_dec_init(). If s is NULL,
  *              this function does nothing.
  */
 XZ_EXTERN void xz_dec_end(struct xz_dec *s);
 
 /*
  * Standalone build (userspace build or in-kernel build for boot time use)
  * needs a CRC32 implementation. For normal in-kernel use, kernel's own
  * CRC32 module is used instead, and users of this module don't need to
  * care about the functions below.
  */
 #ifndef XZ_INTERNAL_CRC32
 #   ifdef __KERNEL__
 #       define XZ_INTERNAL_CRC32 0
 #   else
 #       define XZ_INTERNAL_CRC32 1
 #   endif
 #endif
 
 /*
  * If CRC64 support has been enabled with XZ_USE_CRC64, a CRC64
  * implementation is needed too.
  */
 #ifndef XZ_USE_CRC64
 #   undef XZ_INTERNAL_CRC64
 #   define XZ_INTERNAL_CRC64 0
 #endif
 #ifndef XZ_INTERNAL_CRC64
 #   ifdef __KERNEL__
 #       error Using CRC64 in the kernel has not been implemented.
 #   else
 #       define XZ_INTERNAL_CRC64 1
 #   endif
 #endif
 
 #if XZ_INTERNAL_CRC32
 /*
  * This must be called before any other xz_* function to initialize
  * the CRC32 lookup table.
  */
 XZ_EXTERN void xz_crc32_init(void);
 
 /*
  * Update CRC32 value using the polynomial from IEEE-802.3. To start a new
  * calculation, the third argument must be zero. To continue the calculation,
  * the previously returned value is passed as the third argument.
  */
 XZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc);
 #endif
 
 #if XZ_INTERNAL_CRC64
 /*
  * This must be called before any other xz_* function (except xz_crc32_init())
  * to initialize the CRC64 lookup table.
  */
 XZ_EXTERN void xz_crc64_init(void);
 
 /*
  * Update CRC64 value using the polynomial from ECMA-182. To start a new
  * calculation, the third argument must be zero. To continue the calculation,
  * the previously returned value is passed as the third argument.
  */
 XZ_EXTERN uint64_t xz_crc64(const uint8_t *buf, size_t size, uint64_t crc);
 #endif
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif

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