CRC (Cyclic Redundancy Check) hash function implementation.
This module supports numerous CRC polynomials, in addition to the most widely used CRC-32-IEEE. See AVCRCId for a list of available polynomials.
Enumerator |
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AV_CRC_8_ATM |
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AV_CRC_16_ANSI |
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AV_CRC_16_CCITT |
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AV_CRC_32_IEEE |
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AV_CRC_32_IEEE_LE |
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AV_CRC_16_ANSI_LE |
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AV_CRC_24_IEEE |
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AV_CRC_MAX |
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uint32_t av_crc |
( |
const AVCRC * |
ctx, |
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uint32_t |
crc, |
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const uint8_t * |
buffer, |
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size_t |
length |
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) |
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Calculate the CRC of a block.
- Parameters
-
crc | CRC of previous blocks if any or initial value for CRC |
- Returns
- CRC updated with the data from the given block
- See also
- av_crc_init() "le" parameter
Get an initialized standard CRC table.
- Parameters
-
crc_id | ID of a standard CRC |
- Returns
- a pointer to the CRC table or NULL on failure
int av_crc_init |
( |
AVCRC * |
ctx, |
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int |
le, |
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int |
bits, |
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uint32_t |
poly, |
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int |
ctx_size |
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) |
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Initialize a CRC table.
- Parameters
-
ctx | must be an array of size sizeof(AVCRC)*257 or sizeof(AVCRC)*1024 |
le | If 1, the lowest bit represents the coefficient for the highest exponent of the corresponding polynomial (both for poly and actual CRC). If 0, you must swap the CRC parameter and the result of av_crc if you need the standard representation (can be simplified in most cases to e.g. bswap16): av_bswap32(crc << (32-bits)) |
bits | number of bits for the CRC |
poly | generator polynomial without the x**bits coefficient, in the representation as specified by le |
ctx_size | size of ctx in bytes |
- Returns
- <0 on failure