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bertos/io/reblock.c

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+/**
+ * \file
+ * <!--
+ * This file is part of BeRTOS.
+ *
+ * Bertos 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 St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As a special exception, you may use this file as part of a free software
+ * library without restriction.  Specifically, if other files instantiate
+ * templates or use macros or inline functions from this file, or you compile
+ * this file and link it with other files to produce an executable, this
+ * file does not by itself cause the resulting executable to be covered by
+ * the GNU General Public License.  This exception does not however
+ * invalidate any other reasons why the executable file might be covered by
+ * the GNU General Public License.
+ *
+ * Copyright 2011 Develer S.r.l. (http://www.develer.com/)
+ *
+ * -->
+ *
+ * \brief KBlock block size reducer
+ *
+ * This module allows access to a KBlock device using a smaller block
+ * size than the native one exported by the device.
+ * Note that the device being remapped needs either to be opened in buffered
+ * mode or to support partial writes.
+ *
+ * \author Stefano Fedrigo <aleph@develer.com>
+ *
+ * $WIZ$ module_depends = "kblock"
+ */
+
+#include "reblock.h"
+#include <string.h> /* memset */
+
+
+static size_t reblock_readDirect(struct KBlock *b, block_idx_t idx, void *buf, size_t offset, size_t size)
+{
+	Reblock *r = REBLOCK_CAST(b);
+
+	offset += idx % (r->native_fd->blk_size / r->fd.blk_size) * r->fd.blk_size;
+	idx    =  idx / (r->native_fd->blk_size / r->fd.blk_size);
+
+	return kblock_read(r->native_fd, idx, buf, offset, size);
+}
+
+
+static size_t reblock_writeDirect(struct KBlock *b, block_idx_t idx, const void *buf, size_t offset, size_t size)
+{
+	Reblock *r = REBLOCK_CAST(b);
+
+	offset += idx % (r->native_fd->blk_size / r->fd.blk_size) * r->fd.blk_size;
+	idx    =  idx / (r->native_fd->blk_size / r->fd.blk_size);
+
+	return kblock_write(r->native_fd, idx, buf, offset, size);
+}
+
+
+static int reblock_error(struct KBlock *b)
+{
+	return kblock_error(REBLOCK_CAST(b)->native_fd);
+}
+
+static void reblock_clearerr(struct KBlock *b)
+{
+	kblock_clearerr(REBLOCK_CAST(b)->native_fd);
+}
+
+static int reblock_close(struct KBlock *b)
+{
+	return kblock_close(REBLOCK_CAST(b)->native_fd);
+}
+
+
+static const KBlockVTable reblock_vt =
+{
+	.readDirect = reblock_readDirect,
+	.writeDirect = reblock_writeDirect,
+
+	.error = reblock_error,
+	.clearerr = reblock_clearerr,
+	.close = reblock_close,
+};
+
+
+/*
+ * Initialize reblock device.
+ *
+ * \param rbl           kblock reblock device
+ * \param native_fd     kblock descriptor of the reblocked device
+ * \param new_blk_size  new block size to export
+ *
+ * \note new block size is required to be a submultiple of the
+ *       native device block size.
+ */
+void reblock_init(Reblock *rbl, KBlock *native_fd, size_t new_blk_size)
+{
+	ASSERT(new_blk_size);
+	ASSERT(new_blk_size < native_fd->blk_size);
+	ASSERT(native_fd->blk_size % new_blk_size == 0);
+	ASSERT(kblock_buffered(native_fd) || kblock_partialWrite(native_fd));
+
+	memset(rbl, 0, sizeof(Reblock));
+
+	DB(rbl->fd.priv.type = KBT_REBLOCK);
+
+	rbl->fd.blk_size = new_blk_size;
+	rbl->fd.blk_cnt = native_fd->blk_cnt * (native_fd->blk_size / new_blk_size);
+
+	rbl->fd.priv.flags |= KB_PARTIAL_WRITE;
+	rbl->fd.priv.vt = &reblock_vt;
+
+	rbl->native_fd = native_fd;
+}