liblzma (XZ Utils): lzma/check.h File Reference

liblzma (XZ Utils) 5.4.2

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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.