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/*
* Copyright (C) 2003-2017 Max Kellermann <max.kellermann@gmail.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef STATIC_FIFO_BUFFER_HXX
#define STATIC_FIFO_BUFFER_HXX
#include "WritableBuffer.hxx"
#include <utility>
#include <algorithm>
#include <assert.h>
#include <stddef.h>
/**
* A first-in-first-out buffer: you can append data at the end, and
* read data from the beginning. This class automatically shifts the
* buffer as needed. It is not thread safe.
*/
template<class T, size_t size>
class StaticFifoBuffer {
public:
typedef size_t size_type;
public:
typedef WritableBuffer<T> Range;
protected:
size_type head = 0, tail = 0;
T data[size];
public:
constexpr size_type GetCapacity() const noexcept {
return size;
}
void Shift() noexcept {
if (head == 0)
return;
assert(head <= size);
assert(tail <= size);
assert(tail >= head);
std::move(data + head, data + tail, data);
tail -= head;
head = 0;
}
void Clear() noexcept {
head = tail = 0;
}
constexpr bool empty() const noexcept {
return head == tail;
}
constexpr bool IsFull() const noexcept {
return head == 0 && tail == size;
}
/**
* Prepares writing. Returns a buffer range which may be written.
* When you are finished, call Append().
*/
Range Write() noexcept {
if (empty())
Clear();
else if (tail == size)
Shift();
return Range(data + tail, size - tail);
}
/**
* Expands the tail of the buffer, after data has been written to
* the buffer returned by Write().
*/
void Append(size_type n) noexcept {
assert(tail <= size);
assert(n <= size);
assert(tail + n <= size);
tail += n;
}
constexpr size_type GetAvailable() const noexcept {
return tail - head;
}
/**
* Return a buffer range which may be read. The buffer pointer is
* writable, to allow modifications while parsing.
*/
constexpr Range Read() noexcept {
return Range(data + head, tail - head);
}
/**
* Marks a chunk as consumed.
*/
void Consume(size_type n) noexcept {
assert(tail <= size);
assert(head <= tail);
assert(n <= tail);
assert(head + n <= tail);
head += n;
}
};
#endif
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