Build automatically expanding buffers from struct buffer and erealloc().

src/core/ebuffer.c

+/*
+ * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * 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 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/**
+ * @file
+ *
+ * Automatically expanding buffers
+ *
+ */
+
+#include <errno.h>
+#include <gpxe/buffer.h>
+#include <gpxe/emalloc.h>
+#include <gpxe/ebuffer.h>
+
+/**
+ * Expand expandable buffer
+ *
+ * @v buffer		Buffer descriptor
+ * @v new_len		Required new size
+ * @ret rc		Return status code
+ */
+static int ebuffer_expand ( struct buffer *buffer, size_t new_len ) {
+	size_t actual_len = 1;
+	userptr_t new_addr;
+
+	/* Round new_len up to the nearest power of two, to reduce
+	 * total number of reallocations required.
+	 */
+	while ( actual_len < new_len )
+		actual_len <<= 1;
+
+	/* Reallocate buffer */
+	new_addr = erealloc ( buffer->addr, actual_len );
+	if ( ! new_addr )
+		return -ENOMEM;
+
+	buffer->addr = new_addr;
+	buffer->len = actual_len;
+	return 0;
+}
+
+/**
+ * Allocate expandable buffer
+ *
+ * @v buffer		Buffer descriptor
+ * @v len		Initial length (may be zero)
+ * @ret rc		Return status code
+ *
+ * Allocates space for the buffer and stores it in @c buffer->addr.
+ * The space must eventually be freed by calling efree(buffer->addr).
+ */
+int ebuffer_alloc ( struct buffer *buffer, size_t len ) {
+	memset ( buffer, 0, sizeof ( *buffer ) );
+	buffer->expand = ebuffer_expand;
+	return ebuffer_expand ( buffer, len );
+}

src/include/gpxe/ebuffer.h

+#ifndef _GPXE_EBUFFER_H
+#define _GPXE_EBUFFER_H
+
+/**
+ * @file
+ *
+ * Automatically expanding buffers
+ *
+ */
+
+extern int ebuffer_alloc ( struct buffer *buffer, size_t len );
+
+#endif /* _GPXE_EBUFFER_H */