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*
* Copyright (C) 2013 PX4 Development Team. All rights reserved.
*
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* modification, are permitted provided that the following conditions
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*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
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* used to endorse or promote products derived from this software
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*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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****************************************************************************/
/**
* @file ringbuffer.h
*
* A flexible ringbuffer class.
*/
#pragma once
class RingBuffer {
public:
RingBuffer(unsigned ring_size, size_t entry_size);
virtual ~RingBuffer();
/**
* Put an item into the buffer.
*
* @param val Item to put
* @return true if the item was put, false if the buffer is full
*/
bool put(const void *val, size_t val_size = 0);
bool put(int8_t val);
bool put(uint8_t val);
bool put(int16_t val);
bool put(uint16_t val);
bool put(int32_t val);
bool put(uint32_t val);
bool put(int64_t val);
bool put(uint64_t val);
bool put(float val);
bool put(double val);
/**
* Force an item into the buffer, discarding an older item if there is not space.
*
* @param val Item to put
* @return true if an item was discarded to make space
*/
bool force(const void *val, size_t val_size = 0);
bool force(int8_t val);
bool force(uint8_t val);
bool force(int16_t val);
bool force(uint16_t val);
bool force(int32_t val);
bool force(uint32_t val);
bool force(int64_t val);
bool force(uint64_t val);
bool force(float val);
bool force(double val);
/**
* Get an item from the buffer.
*
* @param val Item that was gotten
* @return true if an item was got, false if the buffer was empty.
*/
bool get(void *val, size_t val_size = 0);
bool get(int8_t &val);
bool get(uint8_t &val);
bool get(int16_t &val);
bool get(uint16_t &val);
bool get(int32_t &val);
bool get(uint32_t &val);
bool get(int64_t &val);
bool get(uint64_t &val);
bool get(float &val);
bool get(double &val);
/*
* Get the number of slots free in the buffer.
*
* @return The number of items that can be put into the buffer before
* it becomes full.
*/
unsigned space(void);
/*
* Get the number of items in the buffer.
*
* @return The number of items that can be got from the buffer before
* it becomes empty.
*/
unsigned count(void);
/*
* Returns true if the buffer is empty.
*/
bool empty();
/*
* Returns true if the buffer is full.
*/
bool full();
/*
* Returns the capacity of the buffer, or zero if the buffer could
* not be allocated.
*/
unsigned size();
/*
* Empties the buffer.
*/
void flush();
/*
* resize the buffer. This is unsafe to be called while
* a producer or consuming is running. Caller is responsible
* for any locking needed
*
* @param new_size new size for buffer
* @return true if the resize succeeds, false if
* not (allocation error)
*/
bool resize(unsigned new_size);
/*
* printf() some info on the buffer
*/
void print_info(const char *name);
private:
unsigned _num_items;
const size_t _item_size;
char *_buf;
volatile unsigned _head; /**< insertion point in _item_size units */
volatile unsigned _tail; /**< removal point in _item_size units */
unsigned _next(unsigned index);
/* we don't want this class to be copied */
RingBuffer(const RingBuffer&);
RingBuffer operator=(const RingBuffer&);
};
RingBuffer::RingBuffer(unsigned num_items, size_t item_size) :
_num_items(num_items),
_item_size(item_size),
_buf(new char[(_num_items+1) * item_size]),
_head(_num_items),
_tail(_num_items)
{}
RingBuffer::~RingBuffer()
{
if (_buf != nullptr)
delete[] _buf;
}
unsigned
RingBuffer::_next(unsigned index)
{
return (0 == index) ? _num_items : (index - 1);
}
bool
RingBuffer::empty()
{
return _tail == _head;
}
bool
RingBuffer::full()
{
return _next(_head) == _tail;
}
unsigned
RingBuffer::size()
{
return (_buf != nullptr) ? _num_items : 0;
}
void
RingBuffer::flush()
{
while (!empty())
get(NULL);
}
bool
RingBuffer::put(const void *val, size_t val_size)
{
unsigned next = _next(_head);
if (next != _tail) {
if ((val_size == 0) || (val_size > _item_size))
val_size = _item_size;
memcpy(&_buf[_head * _item_size], val, val_size);
_head = next;
return true;
} else {
return false;
}
}
bool
RingBuffer::put(int8_t val)
{
return put(&val, sizeof(val));
}
bool
RingBuffer::put(uint8_t val)
{
return put(&val, sizeof(val));
}
bool
RingBuffer::put(int16_t val)
{
return put(&val, sizeof(val));
}
bool
RingBuffer::put(uint16_t val)
{
return put(&val, sizeof(val));
}
bool
RingBuffer::put(int32_t val)
{
return put(&val, sizeof(val));
}
bool
RingBuffer::put(uint32_t val)
{
return put(&val, sizeof(val));
}
bool
RingBuffer::put(int64_t val)
{
return put(&val, sizeof(val));
}
bool
RingBuffer::put(uint64_t val)
{
return put(&val, sizeof(val));
}
bool
RingBuffer::put(float val)
{
return put(&val, sizeof(val));
}
bool
RingBuffer::put(double val)
{
return put(&val, sizeof(val));
}
bool
RingBuffer::force(const void *val, size_t val_size)
{
bool overwrote = false;
for (;;) {
if (put(val, val_size))
break;
get(NULL);
overwrote = true;
}
return overwrote;
}
bool
RingBuffer::force(int8_t val)
{
return force(&val, sizeof(val));
}
bool
RingBuffer::force(uint8_t val)
{
return force(&val, sizeof(val));
}
bool
RingBuffer::force(int16_t val)
{
return force(&val, sizeof(val));
}
bool
RingBuffer::force(uint16_t val)
{
return force(&val, sizeof(val));
}
bool
RingBuffer::force(int32_t val)
{
return force(&val, sizeof(val));
}
bool
RingBuffer::force(uint32_t val)
{
return force(&val, sizeof(val));
}
bool
RingBuffer::force(int64_t val)
{
return force(&val, sizeof(val));
}
bool
RingBuffer::force(uint64_t val)
{
return force(&val, sizeof(val));
}
bool
RingBuffer::force(float val)
{
return force(&val, sizeof(val));
}
bool
RingBuffer::force(double val)
{
return force(&val, sizeof(val));
}
bool
RingBuffer::get(void *val, size_t val_size)
{
if (_tail != _head) {
unsigned candidate;
unsigned next;
if ((val_size == 0) || (val_size > _item_size))
val_size = _item_size;
do {
/* decide which element we think we're going to read */
candidate = _tail;
/* and what the corresponding next index will be */
next = _next(candidate);
/* go ahead and read from this index */
if (val != NULL)
memcpy(val, &_buf[candidate * _item_size], val_size);
/* if the tail pointer didn't change, we got our item */
} while (!__sync_bool_compare_and_swap(&_tail, candidate, next));
return true;
} else {
return false;
}
}
bool
RingBuffer::get(int8_t &val)
{
return get(&val, sizeof(val));
}
bool
RingBuffer::get(uint8_t &val)
{
return get(&val, sizeof(val));
}
bool
RingBuffer::get(int16_t &val)
{
return get(&val, sizeof(val));
}
bool
RingBuffer::get(uint16_t &val)
{
return get(&val, sizeof(val));
}
bool
RingBuffer::get(int32_t &val)
{
return get(&val, sizeof(val));
}
bool
RingBuffer::get(uint32_t &val)
{
return get(&val, sizeof(val));
}
bool
RingBuffer::get(int64_t &val)
{
return get(&val, sizeof(val));
}
bool
RingBuffer::get(uint64_t &val)
{
return get(&val, sizeof(val));
}
bool
RingBuffer::get(float &val)
{
return get(&val, sizeof(val));
}
bool
RingBuffer::get(double &val)
{
return get(&val, sizeof(val));
}
unsigned
RingBuffer::space(void)
{
unsigned tail, head;
/*
* Make a copy of the head/tail pointers in a fashion that
* may err on the side of under-estimating the free space
* in the buffer in the case that the buffer is being updated
* asynchronously with our check.
* If the head pointer changes (reducing space) while copying,
* re-try the copy.
*/
do {
head = _head;
tail = _tail;
} while (head != _head);
return (tail >= head) ? (_num_items - (tail - head)) : (head - tail - 1);
}
unsigned
RingBuffer::count(void)
{
/*
* Note that due to the conservative nature of space(), this may
* over-estimate the number of items in the buffer.
*/
return _num_items - space();
}
bool
RingBuffer::resize(unsigned new_size)
{
char *old_buffer;
char *new_buffer = new char [(new_size+1) * _item_size];
if (new_buffer == nullptr) {
return false;
}
old_buffer = _buf;
_buf = new_buffer;
_num_items = new_size;
_head = new_size;
_tail = new_size;
delete[] old_buffer;
return true;
}
void
RingBuffer::print_info(const char *name)
{
printf("%s %u/%lu (%u/%u @ %p)\n",
name,
_num_items,
(unsigned long)_num_items * _item_size,
_head,
_tail,
_buf);
}