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circularbuffer.c
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circularbuffer.c
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/**
* @file circularbuffer.c
* @author Atakan S.
* @date 01/01/2019
* @version 1.0
* @brief Lightweight Circular Buffer implementation for ARM Cortex-M.
*
* @copyright Copyright (c) 2018 Atakan SARIOGLU ~ www.atakansarioglu.com
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include "circularbuffer.h"
#include <string.h>
#include <assert.h>
/*
* @brief Initializes a circular buffer object using the provided memory space.
* @param bufferObject The buffer object handler.
* @param bufferMemory The memory sppace for the buffer.
* @param length_2N Size of the buffer memory, i.e. 8 indicates 2^8=256 bytes.
*/
void CircularBuffer_init(CircularBufferObject_t * const bufferObject, uint8_t * const bufferMemory, const uint8_t length_2N) {
// Buffer check.
assert(bufferObject);
// Size is limited to 2^16.
assert(length_2N <= 16);
// Initialize the struct.
bufferObject->memory = (uint8_t *)bufferMemory;
bufferObject->lengthMask = (0x0001UL << length_2N) - 1;
bufferObject->length = length_2N ? (uint32_t)bufferObject->lengthMask + 1 : 0;
bufferObject->faultFlag = false;
bufferObject->front = 0;
bufferObject->back = 0;
}
/*
* @brief Gets the size of available data in the buffer.
* @param bufferObject The buffer object handler.
* @return Unread data size in bytes.
*/
uint16_t CircularBuffer_getUnreadSize(const CircularBufferObject_t * const bufferObject) {
// Buffer check.
assert(bufferObject && bufferObject->memory);
// Get snapshot.
CircularBufferPointers_t cachedPointers;
*((uint32_t *)&cachedPointers) = *((uint32_t *)bufferObject);
// Return the difference.
return (cachedPointers.back - cachedPointers.front) & bufferObject->lengthMask;
}
/*
* @brief Checks for fault (i.e. data loss) and clears the buffer on request.
* @param bufferObject The buffer object handler.
* @param clearBuffer Set true to clear/discard the buffer.
* @return Returns true if a fault occured and clears the fault before return.
*/
bool CircularBuffer_checkAndClearFault(CircularBufferObject_t * const bufferObject, const bool clearBuffer) {
// Buffer check.
assert(bufferObject && bufferObject->memory);
// Clear the buffer.
if(clearBuffer){
// New front is back.
bufferObject->front = bufferObject->back;
}
// Check fault.
if (bufferObject->faultFlag) {
// Clear the flag.
bufferObject->faultFlag = false;
// There was fault.
return true;
}
// No fault.
return false;
}
/*
* @brief Push-back a byte into the buffer.
* @param bufferObject The buffer object handler.
* @param data The byte data to be pushed.
* @return Returns true on success, false if no space is left.
*/
bool CircularBuffer_pushBackByte(CircularBufferObject_t * const bufferObject, const uint8_t data) {
// Buffer check.
assert(bufferObject && bufferObject->memory);
// Get unread byte count.
uint16_t unread = CircularBuffer_getUnreadSize(bufferObject);
// Buffer space is available.
if (unread < bufferObject->lengthMask) {
// Write to back.
bufferObject->memory[bufferObject->back] = data;
// Advance the back pointer.
bufferObject->back = (bufferObject->back + 1) & bufferObject->lengthMask;
// Success.
return true;
}
// No space left.
else {
// Set fault flag and result.
bufferObject->faultFlag = true;
}
// Failure.
return false;
}
/*
* @brief Pop-front a byte from buffer .
* @param bufferObject The buffer object handler.
* @param data Pointer to byte to write the popped data.
* @return Returns true if data was popped, false if no data available.
*/
bool CircularBuffer_popFrontByte(CircularBufferObject_t * const bufferObject, uint8_t * const data) {
// Buffer check.
assert(bufferObject && bufferObject->memory);
// Check data availability.
if(bufferObject->back != bufferObject->front){
// Read from front.
*data = bufferObject->memory[bufferObject->front];
// Advance the back pointer.
bufferObject->front = (bufferObject->front + 1) & bufferObject->lengthMask;
// Success.
return true;
}
// Failure.
return false;
}
/*
* @brief Push-back multiple data to the buffer until maxlen is reached or the buffer is full.
* @param bufferObject The buffer object handler.
* @param data Pointer to the data source.
* @param maxlen Size of the source data.
* @return Actual bytes pushed to the buffer.
*/
uint16_t CircularBuffer_pushBack(CircularBufferObject_t * const bufferObject, const uint8_t * data, const uint16_t maxlen) {
// Buffer check.
assert(bufferObject && bufferObject->memory);
// Get the free size.
uint16_t lenTotal = bufferObject->lengthMask - CircularBuffer_getUnreadSize(bufferObject);
// Limit the total count by client buffer size.
if(lenTotal > maxlen){
lenTotal = maxlen;
}
// Actual number of bytes to write.
uint16_t actualLen = lenTotal;
// Copy in 1 or 2 parts [OOoooOOO] -> [oooooOOO] + [OOoooooo].
while(lenTotal > 0){
// Limit the transfer by the end of the buffer.
uint16_t partialLen = lenTotal;
if((bufferObject->length - bufferObject->back) < partialLen) {
partialLen = bufferObject->length - bufferObject->back;
}
// Copy actual bytes.
memcpy(&bufferObject->memory[bufferObject->back], data, partialLen);
// Move the back pointer forward.
bufferObject->back = (bufferObject->back + partialLen) & bufferObject->lengthMask;
// Substract the read bytes.
lenTotal -= partialLen;
// Iterate our buffer pointer;
data += partialLen;
}
// Return count of actual written bytes.
return actualLen;
}
/*
* @brief Pop-front multiple data from the buffer until maxlen is reached or the buffer is empty.
* @param bufferObject The buffer object handler.
* @param data Pointer to the output memory.
* @param maxlen Size of the output memory.
* @return Actual bytes popped from the buffer.
*/
uint16_t CircularBuffer_popFront(CircularBufferObject_t * const bufferObject, uint8_t * data, const uint16_t maxlen) {
// Buffer check.
assert(bufferObject && bufferObject->memory);
// Get available count.
uint16_t lenTotal = CircularBuffer_getUnreadSize(bufferObject);
// Limit the total count by client buffer size.
if(lenTotal > maxlen){
lenTotal = maxlen;
}
// Actual number of bytes to read.
uint16_t actualLen = lenTotal;
// Copy in 1 or 2 parts [OOoooOOO] -> [oooooOOO] + [OOoooooo].
while(lenTotal > 0){
// Limit the transfer by the end of the buffer.
uint16_t partialLen = lenTotal;
if((bufferObject->length - bufferObject->front) < partialLen) {
partialLen = bufferObject->length - bufferObject->front;
}
// Copy actual bytes.
memcpy(data, &bufferObject->memory[bufferObject->front], partialLen);
// Move the front pointer forward.
bufferObject->front = (bufferObject->front + partialLen) & bufferObject->lengthMask;
// Substract the read bytes.
lenTotal -= partialLen;
// Iterate our buffer pointer;
data += partialLen;
}
// Return count of actual read bytes.
return actualLen;
}