297 lines
6.6 KiB
C++
297 lines
6.6 KiB
C++
/*
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* Copyright (C) 2013-2018 Max Kellermann <max.kellermann@gmail.com>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef WRITABLE_BUFFER_HXX
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#define WRITABLE_BUFFER_HXX
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#include "ConstBuffer.hxx"
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#include "Compiler.h"
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#include <cstddef>
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#ifndef NDEBUG
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#include <assert.h>
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#endif
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template<typename T>
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struct WritableBuffer;
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template<>
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struct WritableBuffer<void> {
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typedef size_t size_type;
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typedef void value_type;
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typedef void *pointer_type;
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typedef const void *const_pointer_type;
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typedef pointer_type iterator;
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typedef const_pointer_type const_iterator;
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pointer_type data;
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size_type size;
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WritableBuffer() = default;
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constexpr WritableBuffer(std::nullptr_t):data(nullptr), size(0) {}
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constexpr WritableBuffer(pointer_type _data, size_type _size)
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:data(_data), size(_size) {}
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constexpr operator ConstBuffer<void>() const noexcept {
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return {data, size};
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}
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constexpr bool IsNull() const {
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return data == nullptr;
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}
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constexpr bool operator==(std::nullptr_t) const {
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return data == nullptr;
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}
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constexpr bool operator!=(std::nullptr_t) const {
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return data != nullptr;
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}
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constexpr bool empty() const {
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return size == 0;
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}
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};
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/**
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* A reference to a memory area that is writable.
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*
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* @see ConstBuffer
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*/
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template<typename T>
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struct WritableBuffer {
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typedef size_t size_type;
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typedef T value_type;
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typedef T &reference_type;
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typedef const T &const_reference_type;
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typedef T *pointer_type;
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typedef const T *const_pointer_type;
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typedef pointer_type iterator;
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typedef const_pointer_type const_iterator;
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pointer_type data;
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size_type size;
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WritableBuffer() = default;
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constexpr WritableBuffer(std::nullptr_t):data(nullptr), size(0) {}
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constexpr WritableBuffer(pointer_type _data, size_type _size)
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:data(_data), size(_size) {}
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constexpr WritableBuffer(pointer_type _data, pointer_type _end)
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:data(_data), size(_end - _data) {}
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/**
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* Convert array to WritableBuffer instance.
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*/
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template<size_type _size>
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constexpr WritableBuffer(T (&_data)[_size])
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:data(_data), size(_size) {}
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constexpr operator ConstBuffer<T>() const noexcept {
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return {data, size};
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}
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/**
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* Cast a WritableBuffer<void> to a WritableBuffer<T>,
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* rounding down to the next multiple of T's size.
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*/
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static constexpr WritableBuffer<T> FromVoidFloor(WritableBuffer<void> other) {
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static_assert(sizeof(T) > 0, "Empty base type");
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return WritableBuffer<T>(pointer_type(other.data),
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other.size / sizeof(T));
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}
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/**
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* Cast a WritableBuffer<void> to a WritableBuffer<T>. A "void"
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* buffer records its size in bytes, and when casting to "T",
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* the assertion below ensures that the size is a multiple of
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* sizeof(T).
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*/
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#ifdef NDEBUG
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constexpr
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#endif
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static WritableBuffer<T> FromVoid(WritableBuffer<void> other) {
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static_assert(sizeof(T) > 0, "Empty base type");
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#ifndef NDEBUG
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assert(other.size % sizeof(T) == 0);
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#endif
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return FromVoidFloor(other);
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}
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constexpr WritableBuffer<void> ToVoid() const {
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static_assert(sizeof(T) > 0, "Empty base type");
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return WritableBuffer<void>(data, size * sizeof(T));
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}
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constexpr bool IsNull() const {
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return data == nullptr;
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}
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constexpr bool operator==(std::nullptr_t) const {
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return data == nullptr;
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}
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constexpr bool operator!=(std::nullptr_t) const {
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return data != nullptr;
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}
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constexpr bool empty() const {
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return size == 0;
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}
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constexpr iterator begin() const {
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return data;
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}
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constexpr iterator end() const {
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return data + size;
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}
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constexpr const_iterator cbegin() const {
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return data;
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}
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constexpr const_iterator cend() const {
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return data + size;
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}
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#ifdef NDEBUG
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constexpr
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#endif
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reference_type operator[](size_type i) const {
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#ifndef NDEBUG
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assert(i < size);
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#endif
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return data[i];
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}
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/**
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* Returns a reference to the first element. Buffer must not
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* be empty.
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*/
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#ifdef NDEBUG
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constexpr
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#endif
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reference_type front() const {
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#ifndef NDEBUG
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assert(!empty());
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#endif
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return data[0];
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}
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/**
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* Returns a reference to the last element. Buffer must not
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* be empty.
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*/
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#ifdef NDEBUG
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constexpr
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#endif
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reference_type back() const {
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#ifndef NDEBUG
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assert(!empty());
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#endif
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return data[size - 1];
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}
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/**
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* Remove the first element (by moving the head pointer, does
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* not actually modify the buffer). Buffer must not be empty.
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*/
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void pop_front() {
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assert(!empty());
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++data;
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--size;
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}
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/**
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* Remove the last element (by moving the tail pointer, does
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* not actually modify the buffer). Buffer must not be empty.
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*/
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void pop_back() {
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assert(!empty());
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--size;
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}
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/**
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* Remove the first element and return a reference to it.
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* Buffer must not be empty.
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*/
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reference_type shift() {
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reference_type result = front();
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pop_front();
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return result;
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}
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void skip_front(size_type n) {
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#ifndef NDEBUG
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assert(size >= n);
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#endif
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data += n;
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size -= n;
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}
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/**
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* Move the front pointer to the given address, and adjust the
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* size attribute to retain the old end address.
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*/
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void MoveFront(pointer_type new_data) {
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#ifndef NDEBUG
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assert(IsNull() == (new_data == nullptr));
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assert(new_data <= end());
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#endif
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size = end() - new_data;
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data = new_data;
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}
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/**
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* Move the end pointer to the given address (by adjusting the
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* size).
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*/
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void SetEnd(pointer_type new_end) {
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#ifndef NDEBUG
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assert(IsNull() == (new_end == nullptr));
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assert(new_end >= begin());
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#endif
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size = new_end - data;
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}
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};
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#endif
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