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67 lines
2.1 KiB
C
67 lines
2.1 KiB
C
/*
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* Copyright 2024 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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//! \file
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//! Calculate the CRC-32 checksum of data.
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//!
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//! The checksum is the standard CRC-32 used by zlib, PNG and others.
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//! The model parameters for the algorithm, as described in A Painless Guide to
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//! CRC Error Detection Algorithms (http://www.zlib.net/crc_v3.txt), are:
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//! Name: "CRC-32"
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//! Width: 32
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//! Poly: 04C11DB7
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//! Init: FFFFFFFF
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//! RefIn: True
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//! RefOut: True
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//! XorOut: FFFFFFFF
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//! Check: CBF43926
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#include <stdint.h>
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#include <string.h>
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//! Update a running CRC-32 checksum with the bytes of data and return the
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//! updated CRC-32. If data is NULL, the function returns the required initial
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//! value for the CRC.
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//!
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//! This function is drop-in compatible with zlib's crc32 function.
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//!
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//! \par Usage
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//! \code
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//! uint32_t crc = crc32(0, NULL, 0);
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//! while (read_buffer(data, length)) {
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//! crc = crc32(crc, data, length);
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//! }
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//! \endcode
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uint32_t crc32(uint32_t crc, const void * restrict data, size_t length);
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//! The initial CRC register value for a standard CRC-32 checksum.
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//!
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//! It is the same value as is returned by the `crc32` function when data is
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//! NULL.
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//!
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//! \code
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//! assert(CRC32_INIT == crc32(0, NULL, 0));
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//! \endcode
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#define CRC32_INIT (0)
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//! The residue constant of the CRC-32 algorithm.
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//!
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//! If the CRC-32 value of a message is appended (little-endian) onto the
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//! end of the message, the CRC-32 of the concatenated message and CRC will be
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//! equal to CRC32_RESIDUE if the message has not been corrupted in transit.
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#define CRC32_RESIDUE (0x2144DF1C)
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