check.h File Reference

Integrity checks. More...

Macros
#define	LZMA_CHECK_ID_MAX   15
	Maximum valid Check ID.
#define	LZMA_CHECK_SIZE_MAX   64
	Maximum size of a Check field.

Enumerations
enum	lzma_check { LZMA_CHECK_NONE = 0 , LZMA_CHECK_CRC32 = 1 , LZMA_CHECK_CRC64 = 4 , LZMA_CHECK_SHA256 = 10 }
	Type of the integrity check (Check ID) More...

Functions
lzma_bool	lzma_check_is_supported (lzma_check check) lzma_nothrow lzma_attr_const
	Test if the given Check ID is supported.
uint32_t	lzma_check_size (lzma_check check) lzma_nothrow lzma_attr_const
	Get the size of the Check field with the given Check ID.
uint32_t	lzma_crc32 (const uint8_t *buf, size_t size, uint32_t crc) lzma_nothrow lzma_attr_pure
	Calculate CRC32.
uint64_t	lzma_crc64 (const uint8_t *buf, size_t size, uint64_t crc) lzma_nothrow lzma_attr_pure
	Calculate CRC64.
lzma_check	lzma_get_check (const lzma_stream *strm) lzma_nothrow
	Get the type of the integrity check.

Detailed Description

Integrity checks.

Note

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

Macro Definition Documentation

LZMA_CHECK_ID_MAX

#define LZMA_CHECK_ID_MAX   15

Maximum valid Check ID.

The .xz file format specification specifies 16 Check IDs (0-15). Some of them are only reserved, that is, no actual Check algorithm has been assigned. When decoding, liblzma still accepts unknown Check IDs for future compatibility. If a valid but unsupported Check ID is detected, liblzma can indicate a warning; see the flags LZMA_TELL_NO_CHECK, LZMA_TELL_UNSUPPORTED_CHECK, and LZMA_TELL_ANY_CHECK in container.h.

Enumeration Type Documentation

lzma_check

enum lzma_check

Type of the integrity check (Check ID)

The .xz format supports multiple types of checks that are calculated from the uncompressed data. They vary in both speed and ability to detect errors.

Enumerator
LZMA_CHECK_NONE	No Check is calculated. Size of the Check field: 0 bytes
LZMA_CHECK_CRC32	CRC32 using the polynomial from the IEEE 802.3 standard Size of the Check field: 4 bytes
LZMA_CHECK_CRC64	CRC64 using the polynomial from the ECMA-182 standard Size of the Check field: 8 bytes
LZMA_CHECK_SHA256	SHA-256 Size of the Check field: 32 bytes

Function Documentation

lzma_check_is_supported()

lzma_bool lzma_check_is_supported

(

lzma_check

check

)

const

Test if the given Check ID is supported.

LZMA_CHECK_NONE and LZMA_CHECK_CRC32 are always supported (even if liblzma is built with limited features).

Note

It is safe to call this with a value that is not in the range [0, 15]; in that case the return value is always false.

Parameters

check

Check ID

Returns

lzma_bool:

• true if Check ID is supported by this liblzma build.
• false otherwise.

lzma_check_size()

uint32_t lzma_check_size

(

lzma_check

check

)

const

Get the size of the Check field with the given Check ID.

Although not all Check IDs have a check algorithm associated, the size of every Check is already frozen. This function returns the size (in bytes) of the Check field with the specified Check ID. The values are: { 0, 4, 4, 4, 8, 8, 8, 16, 16, 16, 32, 32, 32, 64, 64, 64 }

Parameters

check

Check ID

Returns

Size of the Check field in bytes. If the argument is not in the range [0, 15], UINT32_MAX is returned.

lzma_crc32()

uint32_t lzma_crc32	(	const uint8_t *	buf,
		size_t	size,
		uint32_t	crc
	)

Calculate CRC32.

Calculate CRC32 using the polynomial from the IEEE 802.3 standard.

Parameters

buf	Pointer to the input buffer
size	Size of the input buffer
crc	Previously returned CRC value. This is used to calculate the CRC of a big buffer in smaller chunks. Set to zero when starting a new calculation.

Returns

Updated CRC value, which can be passed to this function again to continue CRC calculation.

lzma_crc64()

uint64_t lzma_crc64	(	const uint8_t *	buf,
		size_t	size,
		uint64_t	crc
	)

Calculate CRC64.

Calculate CRC64 using the polynomial from the ECMA-182 standard.

This function is used similarly to lzma_crc32().

Parameters

buf	Pointer to the input buffer
size	Size of the input buffer
crc	Previously returned CRC value. This is used to calculate the CRC of a big buffer in smaller chunks. Set to zero when starting a new calculation.

Returns

Updated CRC value, which can be passed to this function again to continue CRC calculation.

lzma_get_check()

lzma_check lzma_get_check

(

const lzma_stream *

strm

)

Get the type of the integrity check.

This function can be called only immediately after lzma_code() has returned LZMA_NO_CHECK, LZMA_UNSUPPORTED_CHECK, or LZMA_GET_CHECK. Calling this function in any other situation has undefined behavior.

Parameters

strm	Pointer to lzma_stream meeting the above conditions.

Returns

Check ID in the lzma_stream, or undefined if called improperly.