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#ifndef _CIRCULAR_BUFFER_H_
#define _CIRCULAR_BUFFER_H_
/**
* Sanguino 3rd Generation Firmware (S3G)
*
* Specification for this protocol is located at:
* http://docs.google.com/Doc?id=dd5prwmp_14ggw37mfp
*
* License: GPLv2
* Authors: Marius Kintel, Adam Mayer, and Zach Hoeken
*/
#include <stddef.h>
#include <stdint.h>
#include "Timer1.h"
/**
* This is an implementation of a simple in-memory circular
* buffer.
*
* Please note that this implementation is NOT thread/interrupt
* safe. Remember that 16-bit data access is not atomic on
* 8-bit platforms! Turn off interrupts before accessing the
* buffer.
*/
class CircularBuffer {
private:
uint8_t* buffer; // ptr to the in-memory buffer
uint16_t capacity; // size of the buffer
uint16_t head; // index of first element of data
uint16_t tail; // index of last element of data
uint16_t currentSize; // number of elements of valid data in buffer
public:
/**
* Create a circular buffer of the given size with a provided
* chunk of memory.
* This implementation does not claim ownership of the buffer!
*/
CircularBuffer(uint16_t capacity, uint8_t* pBuf) {
this->capacity = capacity;
buffer = pBuf;
clear();
}
~CircularBuffer() {
}
/**
* Reset the circular buffer to an empty state.
*/
void clear() {
head = tail = 0;
currentSize = 0;
}
/**
* Return a byte of data in the circular buffer specified by its index.
*/
uint8_t operator[](uint16_t i) {
uint16_t idx;
idx = (i + tail) % capacity;
return buffer[idx];
}
/**
* Return the remaining capacity of the circular buffer.
*/
uint16_t remainingCapacity()
{
uint16_t remaining;
remaining = (capacity - currentSize);
return remaining;
}
/**
* Return the current number of valid bytes in the buffer.
*/
uint16_t size() {
uint16_t csize;
csize = currentSize;
return csize;
}
private:
/**
* Internal: append a byte of data to the buffer's contents.
*/
void appendInternal(uint8_t datum)
{
if ((currentSize + 1) <= capacity)
{
buffer[head] = datum;
head = (head + 1) % capacity;
currentSize++;
}
}
public:
/**
* Append a single byte of data to the buffer.
*/
void append(uint8_t datum) {
appendInternal(datum);
}
/**
* Append a two-byte value to the buffer.
* The buffer stores values in little-endian format.
*/
void append_16(uint16_t datum) {
appendInternal(datum & 0xff);
appendInternal((datum >> 8) & 0xff);
}
/**
* Append a four-byte value to the buffer.
* The buffer stores values in little-endian format.
*/
void append_32(uint32_t datum) {
appendInternal(datum & 0xff);
appendInternal((datum >> 8) & 0xff);
appendInternal((datum >> 16) & 0xff);
appendInternal((datum >> 24) & 0xff);
}
private:
/**
* Internal: Remove the first byte of the buffer's data and return it.
*/
inline uint8_t removeInternal() {
if (currentSize == 0)
return 0;
else
{
uint8_t c = buffer[tail];
tail = (tail + 1) % capacity;
currentSize--;
return c;
}
}
public:
/**
* Remove and return a byte from the start of the circular buffer.
*/
uint8_t remove_8() {
return removeInternal();
}
/*
* Remove and return a two-byte value from the start of the circular
* buffer. The buffer stores values in little-endian format.
*/
uint16_t remove_16() {
uint8_t v[2];
v[0] = removeInternal();
v[1] = removeInternal();
return v[0] | ((uint16_t)v[1] << 8);
}
/*
* Remove and return a four-byte value from the start of the circular
* buffer. The buffer stores values in little-endian format.
*/
uint32_t remove_32() {
uint8_t v[4];
v[0] = removeInternal();
v[1] = removeInternal();
v[2] = removeInternal();
v[3] = removeInternal();
return v[0] |
((uint32_t)v[1] << 8) |
((uint32_t)v[2] << 16) |
((uint32_t)v[3] << 24);
}
void removeCount( uint16_t count ) {
if (currentSize < count)
count = currentSize;
tail = (tail + count) % capacity;
currentSize -= count;
}
class Cursor {
private:
CircularBuffer& buffer;
uint16_t idx;
public:
Cursor(CircularBuffer& src) : buffer(src), idx(0) {}
uint8_t read_8() {
return buffer[idx++];
}
uint16_t read_16() {
return
((uint16_t)read_8() << 0) |
((uint16_t)read_8() << 8);
}
uint32_t read_32() {
return
((uint32_t)read_8() << 0) |
((uint32_t)read_8() << 8) |
((uint32_t)read_8() << 16) |
((uint32_t)read_8() << 24);
}
void commit() {
buffer.removeCount(idx);
}
void rollback() {
idx = 0;
}
};
Cursor newCursor() {
return Cursor(*this);
}
};
#endif // _CIRCULAR_BUFFER_H_
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