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cdcc09096a
The modified CRC8 implementation didn't detect some errors. For example, using the modified CRC8: CC5QQLALU and DC5QQLALU calculates to the same value. BUG=b:37952913 BRANCH=none TEST=make buildall Used online CRC-5-USB calculator to test several values against this implementation. Signed-off-by: Sam Hurst <shurst@chromium.org> Change-Id: I5a17941e25691872a25b41525f65f36e2ed1d4fa Reviewed-on: https://chromium-review.googlesource.com/660812 Commit-Ready: Sam Hurst <shurst@google.com> Tested-by: Sam Hurst <shurst@google.com> Reviewed-by: Randall Spangler <rspangler@chromium.org> Reviewed-by: Michael Tang <ntang@chromium.org>
74 lines
2.7 KiB
C
74 lines
2.7 KiB
C
/* Copyright 2017 The Chromium OS Authors. All rights reserved.
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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/* Base-32 encoding/decoding, designed for manual operator entry. */
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#ifndef __CROS_EC_BASE32_H
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#define __CROS_EC_BASE32_H
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/* Symbol map for base32 encoding */
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extern const char base32_map[33];
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/**
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* CRC-5-USB Initially created for USB Token Packets. It uses
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* the generator polynomial X^5 + X^2 + X^0 and is 5-bits.
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*
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* @param sym New symbol to update CRC with
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* @param previous_crc Existing CRC value
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* @return The updated CRC.
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*/
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uint8_t crc5_sym(uint8_t sym, uint8_t previous_crc);
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/**
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* base32-encode data into a null-terminated string
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*
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* Uses A-Z0-9 encoding, skipping I,O,0,1 since they're easy to get mixed up.
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*
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* @param dest Destination buffer; set to empty string on
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* error
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* @param destlen_chars Length of destination buffer in characters
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* @param src Source binary data
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* @param srclen_bits Length of source *in bits*. If this is not a
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* multiple of 8, the *most significant* bits of
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* the last byte will be used. If this is not a
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* multiple of 5, the least significant bits of
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* the last symbol will be padded with 0 bits.
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* @param add_crc_every If non-zero, add a CRC symbol after each group
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* of this many symbols. There must be an exact
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* number of groups; that is, ceil(srclen_bits/5)
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* must be a multiple of add_crc_every.
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* @return EC_SUCCESS, or non-zero error code.
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*/
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int base32_encode(char *dest, int destlen_chars,
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const void *srcbits, int srclen_bits,
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int add_crc_every);
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/**
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* base32-decode data from a null-terminated string
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*
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* Ignores whitespace and '-' dashes in the source string.
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*
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* If the destination is smaller than the decoded bitstream, only that many
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* bits will be decoded. This is useful for decoding the first part of a
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* bitstream to look for a struct version.
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*
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* If the destination is larger than the decoded bitstream, check the return
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* value to determine how many bits were decoded from the source. Note that if
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* padding was added by base32_encode (that is, the input length was not a
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* multiple of 5 bits), the padding will be included in the count.
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*
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* @param dest Destination; must be at least
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* ceil(destlen_bits/8) bytes.
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* @param destlen_bits Length of destination *in bits*.
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* @param src Source string (null-terminated)
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* @param crc_after_every If non-zero, expect CRC symbol after every
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* group of this many symbols.
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* @return Number of decoded *bits*, or -1 if error.
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*/
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int base32_decode(uint8_t *dest, int destlen_bits, const char *src,
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int crc_after_every);
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#endif
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