efi: Move efi_string utilities to the common directory

This file contains some useful utility functions which are not specific
to the EFI loader. Move them to lib/efi so they can be used by the app.

Signed-off-by: Simon Glass <sjg@chromium.org>

lib/efi/Makefile

@@ -9,3 +9,4 @@ obj-y += helper.o
 obj-y += load_options.o
 obj-y += memory.o
 obj-y += run.o
+obj-y += string.o

lib/efi/string.c

@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * String functions
+ *
+ * Copyright (c) 2020 AKASHI Takahiro, Linaro Limited
+ */
+
+#define LOG_CATEGORY LOGC_EFI
+
+#include <charset.h>
+#include <efi_loader.h>
+#include <malloc.h>
+
+/**
+ * efi_create_indexed_name - create a string name with an index
+ * @buffer:	Buffer
+ * @name:	Name string
+ * @index:	Index
+ *
+ * Create a utf-16 string with @name, appending @index.
+ * For example, u"Capsule0001"
+ *
+ * The caller must ensure that the buffer has enough space for the resulting
+ * string including the trailing L'\0'.
+ *
+ * Return: A pointer to the next position after the created string
+ *	   in @buffer, or NULL otherwise
+ */
+u16 *efi_create_indexed_name(u16 *buffer, size_t buffer_size, const char *name,
+			     unsigned int index)
+{
+	u16 *p = buffer;
+	char index_buf[5];
+	size_t size;
+
+	size = (utf8_utf16_strlen(name) * sizeof(u16) +
+		sizeof(index_buf) * sizeof(u16));
+	if (buffer_size < size)
+		return NULL;
+	utf8_utf16_strcpy(&p, name);
+	snprintf(index_buf, sizeof(index_buf), "%04X", index);
+	utf8_utf16_strcpy(&p, index_buf);
+
+	return p;
+}
+
+/**
+ * efi_convert_string - Convert an ASCII or UTF-8 string to UTF-16
+ * @str:	String to be converted
+ *
+ * Return: Converted string in UTF-16 format. The caller is responsible for
+ *         freeing this string when it is no longer needed.
+ */
+efi_string_t efi_convert_string(const char *str)
+{
+	efi_string_t str_16, tmp;
+	size_t sz_16;
+
+	sz_16 = utf8_utf16_strlen(str);
+	str_16 = calloc(sz_16 + 1, sizeof(u16));
+	if (!str_16)
+		return NULL;
+
+	tmp = str_16;
+	utf8_utf16_strcpy(&tmp, str);
+
+	return str_16;
+}