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| -rw-r--r-- | src/util/DynamicFifoBuffer.hxx | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/src/util/DynamicFifoBuffer.hxx b/src/util/DynamicFifoBuffer.hxx new file mode 100644 index 000000000..ead7389e9 --- /dev/null +++ b/src/util/DynamicFifoBuffer.hxx @@ -0,0 +1,199 @@ +/* + * Copyright (C) 2003-2013 Max Kellermann <max@duempel.org> + * + * 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 FIFO_BUFFER_HPP +#define FIFO_BUFFER_HPP + +#include "WritableBuffer.hxx" + +#include <utility> +#include <algorithm> + +#include <assert.h> +#include <stddef.h> +#include <stdint.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<typename T> +class DynamicFifoBuffer { +public: + typedef size_t size_type; + typedef WritableBuffer<T> Range; + typedef typename Range::pointer_type pointer_type; + typedef typename Range::const_pointer_type const_pointer_type; + +protected: + size_type head, tail, capacity; + T *data; + +public: + DynamicFifoBuffer(size_type _capacity) + :head(0), tail(0), capacity(_capacity), + data(new T[capacity]) {} + ~DynamicFifoBuffer() { + delete[] data; + } + + DynamicFifoBuffer(const DynamicFifoBuffer &) = delete; + + size_type GetCapacity() { + return capacity; + } + + void Grow(size_type new_capacity) { + assert(new_capacity > capacity); + + T *new_data = new T[new_capacity]; + std::move(data + head, data + tail, new_data); + delete[] data; + data = new_data; + capacity = new_capacity; + tail -= head; + head = 0; + } + + void Clear() { + head = tail = 0; + } + + bool IsEmpty() const { + return head == tail; + } + + bool IsFull() const { + return head == 0 && tail == capacity; + } + + /** + * Prepares writing. Returns a buffer range which may be written. + * When you are finished, call append(). + */ + Range Write() { + Shift(); + return Range(data + tail, capacity - tail); + } + + /** + * Expands the tail of the buffer, after data has been written to + * the buffer returned by write(). + */ + void Append(size_type n) { + assert(tail <= capacity); + assert(n <= capacity); + assert(tail + n <= capacity); + + tail += n; + } + + void WantWrite(size_type n) { + if (tail + n <= capacity) + /* enough space after the tail */ + return; + + const size_type in_use = tail - head; + const size_type required_capacity = in_use + n; + if (capacity >= required_capacity) { + Shift(); + } else { + size_type new_capacity = capacity; + do { + new_capacity <<= 1; + } while (new_capacity < required_capacity); + + Grow(new_capacity); + } + } + + /** + * Write data to the bfufer, growing it as needed. Returns a + * writable pointer. + */ + pointer_type Write(size_type n) { + WantWrite(n); + return data + tail; + } + + /** + * Append data to the buffer, growing it as needed. + */ + void Append(const_pointer_type p, size_type n) { + std::copy_n(p, n, Write(n)); + Append(n); + } + + /** + * Return a buffer range which may be read. The buffer pointer is + * writable, to allow modifications while parsing. + */ + Range Read() { + return Range(data + head, tail - head); + } + + /** + * Marks a chunk as consumed. + */ + void Consume(size_type n) { + assert(tail <= capacity); + assert(head <= tail); + assert(n <= tail); + assert(head + n <= tail); + + head += n; + } + + size_type Read(pointer_type p, size_type n) { + auto range = Read(); + if (n > range.size) + n = range.size; + std::copy_n(range.data, n, p); + Consume(n); + return n; + } + +protected: + void Shift() { + if (head == 0) + return; + + assert(head <= capacity); + assert(tail <= capacity); + assert(tail >= head); + + std::move(data + head, data + tail, data); + + tail -= head; + head = 0; + } +}; + +#endif |