pcm_buffer: new library for temporary buffers

This library allocates temporary buffers for storing PCM conversion
results.  It should replace all those "static" buffer variables which
are racy and never freed.

src/pcm_buffer.h

@@ -0,0 +1,74 @@
+/*
+ * Copyright (C) 2003-2009 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef PCM_BUFFER_H
+#define PCM_BUFFER_H
+
+#include <glib.h>
+
+/**
+ * Manager for a temporary buffer which grows as needed.  We could
+ * allocate a new buffer every time pcm_convert() is called, but that
+ * would put too much stress on the allocator.
+ */
+struct pcm_buffer {
+	char *buffer;
+
+	size_t size;
+};
+
+/**
+ * Initialize the buffer, but don't allocate anything yet.
+ */
+static inline void
+pcm_buffer_init(struct pcm_buffer *buffer)
+{
+	buffer->buffer = NULL;
+	buffer->size = 0;
+}
+
+/**
+ * Free resources.  This function may be called more than once.
+ */
+static inline void
+pcm_buffer_deinit(struct pcm_buffer *buffer)
+{
+	g_free(buffer->buffer);
+
+	buffer->buffer = NULL;
+}
+
+/**
+ * Get the buffer, and guarantee a minimum size.  This buffer becomes
+ * invalid with the next pcm_buffer_get() call.
+ */
+static inline void *
+pcm_buffer_get(struct pcm_buffer *buffer, size_t size)
+{
+	if (buffer->size < size) {
+		/* free the old buffer */
+		g_free(buffer->buffer);
+
+		/* allocate a new buffer; align at 64kB boundaries */
+		buffer->buffer = g_malloc((size | 0xffff) + 1);
+	}
+
+	return buffer->buffer;
+}
+
+#endif