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R2671/Firmware/src/lib/circular_buffer.c
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circular_buffer.c
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/*
* Copyright (C) 2017 EPFL-LSRO (Laboratoire de Systemes Robotiques).
*
* 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.
*/
#include "circular_buffer.h"
#include "utils.h"
/**
* @brief Initializes a cb_CircularBuffer structure.
* Initializes a cb_CircularBuffer structure with the given buffer. The buffer
* has to be provided by the user, to avoid dynamic memory allocation.
* @param cb the cb_CircularBuffer structure to initialize.
* @param buffer pointer to an existing array.
* @param bufferSize length of the circular buffer. The given buffer should have
* a size greater or equal to this value.
*/
void cb_Init(cb_CircularBuffer* cb, uint8_t *buffer, uint16_t bufferSize)
{
cb->buffer = buffer;
cb->bufferSize = bufferSize;
cb->readIndex = 0;
cb->writeIndex = 0;
}
/**
* @brief Gets the number of bytes stored in the queue.
* @param cb the cb_CircularBuffer to check.
* @return the number of bytes stored in the queue.
*/
uint16_t cb_ItemsCount(cb_CircularBuffer* cb)
{
if (cb->writeIndex >= cb->readIndex)
return cb->writeIndex - cb->readIndex;
else
return cb->bufferSize - cb->readIndex + cb->writeIndex;
}
/**
* @brief Check if the queue is empty.
* @param cb the cb_CircularBuffer to check.
* @return 1 if there are no bytes stored in the queue, 0 otherwise.
*/
bool cb_IsEmpty(cb_CircularBuffer* cb)
{
return cb->writeIndex == cb->readIndex;
}
/**
* @brief Check if the queue is full.
* @param cb the cb_CircularBuffer to check.
* @return 1 if the queue is full, 0 otherwise.
*/
bool cb_IsFull(cb_CircularBuffer* cb)
{
if (cb->writeIndex == cb->readIndex)
return false;
else if (cb->readIndex < cb->writeIndex)
return (cb->readIndex == 0 && cb->writeIndex == cb->bufferSize - 1);
else
return (cb->writeIndex == cb->readIndex-1);
}
/**
* @brief Add a item at the back of the queue.
* @param cb the cb_CircularBuffer to affect.
* @param newElem the byte to add to the back of the queue.
* @warning If the queue is already full, this function does nothing if
* CPU_TRAPS_ENABLED is 0. If CPU_TRAPS_ENABLED is 1, this function will block
* forever the program execution, so the problem can be found with the
* debugger.
*/
void cb_Push(cb_CircularBuffer* cb, uint8_t newElem)
{
if (!cb_IsFull(cb)) // Not full.
{
cb->buffer[cb->writeIndex] = newElem;
cb->writeIndex++;
if (cb->writeIndex >= cb->bufferSize)
cb->writeIndex = 0;
}
else // Error, can't push an item, because the queue is full.
utils_TrapCpu();
}
/**
* @brief Extract the item at the front of the queue.
* Returns the value of the item at the front of the queue, and remove this item
* from the queue.
* @param cb the cb_CircularBuffer to affect.
* @return the value of the byte that has been extracted from the queue.
* @warning If the queue is empty and CPU_TRAPS_ENABLED is 0, this function
* returns 0. If CPU_TRAPS_ENABLED is 1, this function will block forever the
* program execution, so the problem can be found with the debugger.
*/
uint8_t cb_Pull(cb_CircularBuffer* cb)
{
if (cb->writeIndex != cb->readIndex) // Not empty.
{
uint8_t pulled = cb->buffer[cb->readIndex];
cb->readIndex++;
if (cb->readIndex >= cb->bufferSize)
cb->readIndex = 0;
return pulled;
}
else // Error, can't pull an item, because the queue is empty.
{
utils_TrapCpu();
return 0;
}
}
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