PcmBuffer: move code to new class ReusableBuffer

ReusableBuffer is more generic.

Makefile.am

@@ -261,6 +261,7 @@ endif
 # Generic utility library
 
 libutil_a_SOURCES = \
+	src/util/ReusableArray.hxx \
 	src/util/AllocatedArray.hxx \
 	src/util/StringUtil.cxx src/util/StringUtil.hxx \
 	src/util/Tokenizer.cxx src/util/Tokenizer.hxx \

src/pcm/PcmBuffer.cxx

@@ -21,16 +21,6 @@
 #include "PcmBuffer.hxx"
 #include "poison.h"
 
-/**
- * Align the specified size to the next 8k boundary.
- */
-constexpr
-static size_t
-align_8k(size_t size)
-{
-	return ((size - 1) | 0x1fff) + 1;
-}
-
 void *
 PcmBuffer::Get(size_t new_size)
 {
@@ -39,18 +29,5 @@ PcmBuffer::Get(size_t new_size)
 		   be an error condition */
 		new_size = 1;
 
-	if (size < new_size) {
-		/* free the old buffer */
-		g_free(buffer);
-
-		size = align_8k(new_size);
-		buffer = g_malloc(size);
-	} else {
-		/* discard old buffer contents */
-		poison_undefined(buffer, size);
-	}
-
-	assert(size >= new_size);
-
-	return buffer;
+	return buffer.Get(new_size);
 }

src/pcm/PcmBuffer.hxx

@@ -20,33 +20,22 @@
 #ifndef PCM_BUFFER_HXX
 #define PCM_BUFFER_HXX
 
-#include "check.h"
+#include "util/ReusableArray.hxx"
 #include "gcc.h"
 
-#include <glib.h>
-
-#include <assert.h>
+#include <stdint.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 PcmBuffer {
-	void *buffer;
-
-	size_t size;
-
-	PcmBuffer():buffer(nullptr), size(0) {}
-
-	~PcmBuffer() {
-		g_free(buffer);
-	}
+class PcmBuffer {
+	ReusableArray<uint8_t, 8192> buffer;
 
+public:
 	void Clear() {
-		g_free(buffer);
-		buffer = nullptr;
-		size = 0;
+		buffer.Clear();
 	}
 
 	/**

src/pcm/PcmChannels.hxx

@@ -23,7 +23,7 @@
 #include <stdint.h>
 #include <stddef.h>
 
-struct PcmBuffer;
+class PcmBuffer;
 
 /**
  * Changes the number of channels in 16 bit PCM data.

src/pcm/PcmDsdUsb.hxx

@@ -25,7 +25,7 @@
 #include <stdint.h>
 #include <stddef.h>
 
-struct PcmBuffer;
+class PcmBuffer;
 
 /**
  * Pack DSD 1 bit samples into (padded) 24 bit PCM samples for

src/pcm/PcmFormat.hxx

@@ -25,7 +25,7 @@
 #include <stdint.h>
 #include <stddef.h>
 
-struct PcmBuffer;
+class PcmBuffer;
 class PcmDither;
 
 /**

src/util/ReusableArray.hxx

@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 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 REUSABLE_ARRAY_HXX
+#define REUSABLE_ARRAY_HXX
+
+#include <stddef.h>
+
+#include "gcc.h"
+
+/**
+ * Manager for a temporary array which grows as needed.  This attempts
+ * to reduce the number of consecutive heap allocations and
+ * deallocations.
+ *
+ * @param T the array element type
+ * @param M always allocate multiples of this number; must be a power of 2
+ */
+template<typename T, size_t M=1>
+class ReusableArray {
+	T *buffer;
+	size_t capacity;
+
+public:
+	ReusableArray():buffer(nullptr), capacity(0) {}
+
+	ReusableArray(const ReusableArray &other) = delete;
+	ReusableArray &operator=(const ReusableArray &other) = delete;
+
+	~ReusableArray() {
+		delete[] buffer;
+	}
+
+	/**
+	 * Free resources allocated by this object.  This invalidates
+	 * the buffer returned by Get().
+	 */
+	void Clear() {
+		delete[] buffer;
+		buffer = nullptr;
+		capacity = 0;
+	}
+
+	/**
+	 * Get the buffer, and guarantee a minimum size.  This buffer
+	 * becomes invalid with the next Get() call.
+	 */
+	gcc_malloc
+	T *Get(size_t size) {
+		if (gcc_unlikely(size > capacity)) {
+			/* too small: grow */
+			delete[] buffer;
+
+			capacity = ((size - 1) | (M - 1)) + 1;
+			buffer = new T[capacity];
+		}
+
+		return buffer;
+	}
+};
+
+#endif