decoder_buffer: convert to C++

src/DecoderBuffer.cxx

@@ -0,0 +1,167 @@
+/*
+ * 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.
+ */
+
+#include "config.h"
+#include "DecoderBuffer.hxx"
+#include "decoder_api.h"
+
+#include <glib.h>
+
+#include <assert.h>
+
+struct DecoderBuffer {
+	struct decoder *decoder;
+	struct input_stream *is;
+
+	/** the allocated size of the buffer */
+	size_t size;
+
+	/** the current length of the buffer */
+	size_t length;
+
+	/** number of bytes already consumed at the beginning of the
+	    buffer */
+	size_t consumed;
+
+	/** the actual buffer (dynamic size) */
+	unsigned char data[sizeof(size_t)];
+};
+
+DecoderBuffer *
+decoder_buffer_new(struct decoder *decoder, struct input_stream *is,
+		   size_t size)
+{
+	DecoderBuffer *buffer = (DecoderBuffer *)
+		g_malloc(sizeof(*buffer) - sizeof(buffer->data) + size);
+
+	assert(is != nullptr);
+	assert(size > 0);
+
+	buffer->decoder = decoder;
+	buffer->is = is;
+	buffer->size = size;
+	buffer->length = 0;
+	buffer->consumed = 0;
+
+	return buffer;
+}
+
+void
+decoder_buffer_free(DecoderBuffer *buffer)
+{
+	assert(buffer != nullptr);
+
+	g_free(buffer);
+}
+
+bool
+decoder_buffer_is_empty(const DecoderBuffer *buffer)
+{
+	return buffer->consumed == buffer->length;
+}
+
+bool
+decoder_buffer_is_full(const DecoderBuffer *buffer)
+{
+	return buffer->consumed == 0 && buffer->length == buffer->size;
+}
+
+static void
+decoder_buffer_shift(DecoderBuffer *buffer)
+{
+	assert(buffer->consumed > 0);
+
+	buffer->length -= buffer->consumed;
+	memmove(buffer->data, buffer->data + buffer->consumed, buffer->length);
+	buffer->consumed = 0;
+}
+
+bool
+decoder_buffer_fill(DecoderBuffer *buffer)
+{
+	size_t nbytes;
+
+	if (buffer->consumed > 0)
+		decoder_buffer_shift(buffer);
+
+	if (buffer->length >= buffer->size)
+		/* buffer is full */
+		return false;
+
+	nbytes = decoder_read(buffer->decoder, buffer->is,
+			      buffer->data + buffer->length,
+			      buffer->size - buffer->length);
+	if (nbytes == 0)
+		/* end of file, I/O error or decoder command
+		   received */
+		return false;
+
+	buffer->length += nbytes;
+	assert(buffer->length <= buffer->size);
+
+	return true;
+}
+
+const void *
+decoder_buffer_read(const DecoderBuffer *buffer, size_t *length_r)
+{
+	if (buffer->consumed >= buffer->length)
+		/* buffer is empty */
+		return nullptr;
+
+	*length_r = buffer->length - buffer->consumed;
+	return buffer->data + buffer->consumed;
+}
+
+void
+decoder_buffer_consume(DecoderBuffer *buffer, size_t nbytes)
+{
+	/* just move the "consumed" pointer - decoder_buffer_shift()
+	   will do the real work later (called by
+	   decoder_buffer_fill()) */
+	buffer->consumed += nbytes;
+
+	assert(buffer->consumed <= buffer->length);
+}
+
+bool
+decoder_buffer_skip(DecoderBuffer *buffer, size_t nbytes)
+{
+	size_t length;
+	const void *data;
+	bool success;
+
+	/* this could probably be optimized by seeking */
+
+	while (true) {
+		data = decoder_buffer_read(buffer, &length);
+		if (data != nullptr) {
+			if (length > nbytes)
+				length = nbytes;
+			decoder_buffer_consume(buffer, length);
+			nbytes -= length;
+			if (nbytes == 0)
+				return true;
+		}
+
+		success = decoder_buffer_fill(buffer);
+		if (!success)
+			return false;
+	}
+}