aboutsummaryrefslogtreecommitdiffstats
path: root/src/util
diff options
context:
space:
mode:
authorMax Kellermann <max@duempel.org>2013-01-04 16:26:41 +0100
committerMax Kellermann <max@duempel.org>2013-01-04 17:12:21 +0100
commite3a2bd3a1ee935e40ba2d5a58bc3992b6ee2deab (patch)
tree2b04bdd9745699a8fca6c84f50b9ed71703a9833 /src/util
parentf0be6a4b9edf193a018f0e671106616f6f8dd30c (diff)
downloadmpd-e3a2bd3a1ee935e40ba2d5a58bc3992b6ee2deab.tar.gz
mpd-e3a2bd3a1ee935e40ba2d5a58bc3992b6ee2deab.tar.xz
mpd-e3a2bd3a1ee935e40ba2d5a58bc3992b6ee2deab.zip
MusicBuffer: move code to template class SliceBuffer
Diffstat (limited to 'src/util')
-rw-r--r--src/util/SliceBuffer.hxx134
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