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Variable-length integer handling. -More...

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-Macros
-#define	LZMA_VLI_MAX (UINT64_MAX / 2)
	Maximum supported value of a variable-length integer.

-#define	LZMA_VLI_UNKNOWN UINT64_MAX
	VLI value to denote that the value is unknown.

-#define	LZMA_VLI_BYTES_MAX 9
	Maximum supported encoded length of variable length integers.

-#define	LZMA_VLI_C(n) UINT64_C(n)
	VLI constant suffix.

#define	lzma_vli_is_valid(vli) ((vli) <= LZMA_VLI_MAX \|\| (vli) == LZMA_VLI_UNKNOWN)
	Validate a variable-length integer.

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-Typedefs
typedef uint64_t	lzma_vli
	Variable-length integer type.

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-Functions
lzma_ret	lzma_vli_encode (lzma_vli vli, size_t vli_pos, uint8_t out, size_t *out_pos, size_t out_size) lzma_nothrow
	Encode a variable-length integer.

lzma_ret	lzma_vli_decode (lzma_vli vli, size_t vli_pos, const uint8_t in, size_t in_pos, size_t in_size) lzma_nothrow
	Decode a variable-length integer.

uint32_t	lzma_vli_size (lzma_vli vli) lzma_nothrow lzma_attr_pure
	Get the number of bytes required to encode a VLI.

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Detailed Description

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Variable-length integer handling.

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Note: Never include this file directly. Use <lzma.h> instead.

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In the .xz format, most integers are encoded in a variable-length representation, which is sometimes called little endian base-128 encoding. This saves space when smaller values are more likely than bigger values.

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The encoding scheme encodes seven bits to every byte, using minimum number of bytes required to represent the given value. Encodings that use non-minimum number of bytes are invalid, thus every integer has exactly one encoded representation. The maximum number of bits in a VLI is 63, thus the vli argument must be less than or equal to UINT64_MAX / 2. You should use LZMA_VLI_MAX for clarity.

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Macro Definition Documentation

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◆ lzma_vli_is_valid

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#define lzma_vli_is_valid ( vli ) ((vli) <= LZMA_VLI_MAX || (vli) == LZMA_VLI_UNKNOWN)

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Validate a variable-length integer.

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This is useful to test that application has given acceptable values for example in the uncompressed_size and compressed_size variables.

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Returns: True if the integer is representable as VLI or if it indicates unknown value. False if the integer cannot be represented as VLI.

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Typedef Documentation

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◆ lzma_vli

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typedef uint64_t lzma_vli

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Variable-length integer type.

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Valid VLI values are in the range [0, LZMA_VLI_MAX]. Unknown value is indicated with LZMA_VLI_UNKNOWN, which is the maximum value of the underlying integer type.

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lzma_vli will be uint64_t for the foreseeable future. If a bigger size is needed in the future, it is guaranteed that 2 * LZMA_VLI_MAX will not overflow lzma_vli. This simplifies integer overflow detection.

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Function Documentation

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◆ lzma_vli_encode()

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lzma_ret lzma_vli_encode	(	lzma_vli	vli,
		size_t *	vli_pos,
		uint8_t *	out,
		size_t *	out_pos,
		size_t	out_size
	)

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Encode a variable-length integer.

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This function has two modes: single-call and multi-call. Single-call mode encodes the whole integer at once; it is an error if the output buffer is too small. Multi-call mode saves the position in *vli_pos, and thus it is possible to continue encoding if the buffer becomes full before the whole integer has been encoded.

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Parameters

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	vli	Integer to be encoded
[out]	vli_pos	How many VLI-encoded bytes have already been written out. When starting to encode a new integer in multi-call mode, *vli_pos must be set to zero. To use single-call encoding, set vli_pos to NULL.
[out]	out	Beginning of the output buffer
[out]	out_pos	The next byte will be written to out[*out_pos].
	out_size	Size of the out buffer; the first byte into which no data is written to is out[out_size].

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Returns: Slightly different return values are used in multi-call and single-call modes.

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Single-call (vli_pos == NULL):

LZMA_OK: Integer successfully encoded.
LZMA_PROG_ERROR: Arguments are not sane. This can be due to too little output space; single-call mode doesn't use LZMA_BUF_ERROR, since the application should have checked the encoded size with lzma_vli_size().

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Multi-call (vli_pos != NULL):

LZMA_OK: So far all OK, but the integer is not completely written out yet.
LZMA_STREAM_END: Integer successfully encoded.
LZMA_BUF_ERROR: No output space was provided.
LZMA_PROG_ERROR: Arguments are not sane.

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◆ lzma_vli_decode()

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lzma_ret lzma_vli_decode	(	lzma_vli *	vli,
		size_t *	vli_pos,
		const uint8_t *	in,
		size_t *	in_pos,
		size_t	in_size
	)

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Decode a variable-length integer.

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Like lzma_vli_encode(), this function has single-call and multi-call modes.

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Parameters

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[out]	vli	Pointer to decoded integer. The decoder will initialize it to zero when vli_pos == 0, so application isn't required to initialize vli.
[out]	vli_pos	How many bytes have already been decoded. When starting to decode a new integer in multi-call mode, *vli_pos must be initialized to zero. To use single-call decoding, set vli_pos to NULL.
	in	Beginning of the input buffer
[out]	in_pos	The next byte will be read from in[*in_pos].
	in_size	Size of the input buffer; the first byte that won't be read is in[in_size].

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Returns: Slightly different return values are used in multi-call and single-call modes.

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Single-call (vli_pos == NULL):

LZMA_OK: Integer successfully decoded.
LZMA_DATA_ERROR: Integer is corrupt. This includes hitting the end of the input buffer before the whole integer was decoded; providing no input at all will use LZMA_DATA_ERROR.
LZMA_PROG_ERROR: Arguments are not sane.

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Multi-call (vli_pos != NULL):

LZMA_OK: So far all OK, but the integer is not completely decoded yet.
LZMA_STREAM_END: Integer successfully decoded.
LZMA_DATA_ERROR: Integer is corrupt.
LZMA_BUF_ERROR: No input was provided.
LZMA_PROG_ERROR: Arguments are not sane.

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◆ lzma_vli_size()

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uint32_t lzma_vli_size ( lzma_vli vli )

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Get the number of bytes required to encode a VLI.

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Parameters

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vli	Integer whose encoded size is to be determined

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Returns: Number of bytes on success (1-9). If vli isn't valid, zero is returned.

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-Macros

-Typedefs

-Functions

Detailed Description

Macro Definition Documentation

◆ lzma_vli_is_valid

Typedef Documentation

◆ lzma_vli

Function Documentation

◆ lzma_vli_encode()

◆ lzma_vli_decode()

◆ lzma_vli_size()