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Diffstat (limited to '')
-rw-r--r-- | src/util/SliceBuffer.hxx | 134 |
1 files changed, 134 insertions, 0 deletions
diff --git a/src/util/SliceBuffer.hxx b/src/util/SliceBuffer.hxx new file mode 100644 index 000000000..9ddad6b3d --- /dev/null +++ b/src/util/SliceBuffer.hxx @@ -0,0 +1,134 @@ +/* + * Copyright (C) 2003-2013 The Music Player Daemon Project + * http://www.musicpd.org + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#ifndef MPD_SLICE_BUFFER_HXX +#define MPD_SLICE_BUFFER_HXX + +#include "gcc.h" + +#include <glib.h> + +#include <utility> +#include <new> + +#include <assert.h> +#include <stddef.h> + +/** + * This class pre-allocates a certain number of objects, and allows + * callers to allocate and free these objects ("slices"). + */ +template<typename T> +class SliceBuffer { + union Slice { + Slice *next; + + T value; + }; + + /** + * The maximum number of slices in this container. + */ + const unsigned n_max; + + /** + * The number of slices currently allocated. + */ + unsigned n_allocated; + + Slice *const data; + + /** + * Pointer to the first free element in the chain. + */ + Slice *available; + +public: + SliceBuffer(unsigned _count) + :n_max(_count), n_allocated(0), + data(g_new(Slice, n_max)), available(data) { + assert(n_max > 0); + + Slice *const last = data + n_max - 1; + for (Slice *slice = data; slice != last; ++slice) + slice->next = slice + 1; + + last->next = nullptr; + } + + ~SliceBuffer() { + /* all slices must be freed explicitly, and this + assertion checks for leaks */ + assert(n_allocated == 0); + + g_free(data); + } + + SliceBuffer(const SliceBuffer &other) = delete; + SliceBuffer &operator=(const SliceBuffer &other) = delete; + + unsigned GetCapacity() const { + return n_max; + } + + bool IsEmpty() const { + return n_allocated == 0; + } + + bool IsFull() const { + return n_allocated == n_max; + } + + template<typename... Args> + T *Allocate(Args&&... args) { + assert(n_allocated <= n_max); + + if (available == nullptr) { + /* out of (internal) memory, buffer is full */ + assert(n_allocated == n_max); + return nullptr; + } + + /* allocate a slice */ + T *value = &available->value; + available = available->next; + ++n_allocated; + + /* construct the object */ + return ::new((void *)value) T(std::forward<Args>(args)...); + } + + void Free(T *value) { + assert(n_allocated > 0); + assert(n_allocated <= n_max); + + Slice *slice = reinterpret_cast<Slice *>(value); + assert(slice >= data && slice < data + n_max); + + /* destruct the object */ + value->~T(); + + /* insert the slice in the "available" linked list */ + slice->next = available; + available = slice; + --n_allocated; + } +}; + +#endif |