partition: check GPT partition table

Now only support GPT partition table. MBR partition table isn't
supported yet.

Signed-off-by: Haojian Zhuang <haojian.zhuang@linaro.org>
diff --git a/drivers/partition/gpt.c b/drivers/partition/gpt.c
new file mode 100644
index 0000000..9240d5a
--- /dev/null
+++ b/drivers/partition/gpt.c
@@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2016, ARM Limited and Contributors. All rights reserved.
+ *
+ * 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.
+ *
+ * Neither the name of ARM nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without specific
+ * prior written permission.
+ *
+ * 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 COPYRIGHT HOLDER 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.
+ */
+
+#include <assert.h>
+#include <debug.h>
+#include <errno.h>
+#include <gpt.h>
+#include <string.h>
+
+static int unicode_to_ascii(unsigned short *str_in, unsigned char *str_out)
+{
+	uint8_t *name = (uint8_t *)str_in;
+	int i;
+
+	assert((str_in != NULL) && (str_out != NULL) && (name[0] != '\0'));
+
+	/* check whether the unicode string is valid */
+	for (i = 1; i < (EFI_NAMELEN << 1); i += 2) {
+		if (name[i] != '\0')
+			return -EINVAL;
+	}
+	/* convert the unicode string to ascii string */
+	for (i = 0; i < (EFI_NAMELEN << 1); i += 2) {
+		str_out[i >> 1] = name[i];
+		if (name[i] == '\0')
+			break;
+	}
+	return 0;
+}
+
+int parse_gpt_entry(gpt_entry_t *gpt_entry, partition_entry_t *entry)
+{
+	int result;
+
+	assert((gpt_entry != 0) && (entry != 0));
+
+	if ((gpt_entry->first_lba == 0) && (gpt_entry->last_lba == 0)) {
+		return -EINVAL;
+	}
+
+	memset(entry, 0, sizeof(partition_entry_t));
+	result = unicode_to_ascii(gpt_entry->name, (uint8_t *)entry->name);
+	if (result != 0) {
+		return result;
+	}
+	entry->start = (uint64_t)gpt_entry->first_lba * PARTITION_BLOCK_SIZE;
+	entry->length = (uint64_t)(gpt_entry->last_lba -
+				   gpt_entry->first_lba + 1) *
+			PARTITION_BLOCK_SIZE;
+	return 0;
+}