pebble/platform/snowy/boot/src/util/cobs.h
2025-01-27 11:38:16 -08:00

40 lines
1.4 KiB
C

/*
* Copyright 2024 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <stddef.h>
#include <stdint.h>
//! An implementation of Consistent Overhead Byte Stuffing
//!
//! http://conferences.sigcomm.org/sigcomm/1997/papers/p062.pdf
//! http://en.wikipedia.org/wiki/Consistent_Overhead_Byte_Stuffing
//! Evaluates to the offset required when encoding in-place
#define COBS_OVERHEAD(n) (((n) + 253) / 254)
//! Evaluates to the maximum buffer size required to hold n bytes of data
//! after COBS encoding.
#define MAX_SIZE_AFTER_COBS_ENCODING(n) ((n) + COBS_OVERHEAD(n))
//! COBS-encode a buffer out to another buffer.
//!
//! @param [out] dst destination buffer. The buffer must be at least
//! MAX_SIZE_AFTER_COBS_ENCODING(length) bytes long.
//! @param [in] src source buffer
//! @param length length of src
size_t cobs_encode(void * restrict dst, const void * restrict src,
size_t length);