[lib][uefi] Use utf16 charset functions

Author: zhangxp1998

.clang-format

@@ -11,4 +11,4 @@ ColumnLimit: 0
 IndentCaseLabels: true
 IndentGotoLabels: false
 AlignConsecutiveMacros:
-  Enabled: true
+  Enabled: true

lib/uefi/.clang-format

@@ -0,0 +1,4 @@
+---
+Language: Cpp
+IndentWidth: 2
+

lib/uefi/charset.cpp

@@ -46,14 +46,14 @@ int utf16_strcmp(const char16_t *s1, const char16_t *s2) {
  * This function converts utf-8 string to utf-16 string. However
  * it only supports us-ascii input right now.
  */
-int utf8_to_utf16(char16_t *dest, const char *src, size_t size) {
+size_t utf8_to_utf16(char16_t *dest, const char *src, size_t size) {
   size_t i = 0;
   for (; i < size - 1 && *src; i++, src++) {
     dest[i] = *src;
   }
 
   dest[i] = 0;
-  return 0;
+  return i;
 }
 
 /**
@@ -62,12 +62,12 @@ int utf8_to_utf16(char16_t *dest, const char *src, size_t size) {
  * This function converts utf-16 string to utf-8 string. However
  * it only supports us-ascii output right now.
  */
-int utf16_to_utf8(char *dest, const char16_t *src, size_t size) {
+size_t utf16_to_utf8(char *dest, const char16_t *src, size_t size) {
   size_t i = 0;
   for (; i < size - 1 && *src; i++, src++) {
     dest[i] = *src;
   }
 
   dest[i] = 0;
-  return 0;
+  return i;
 }

lib/uefi/charset.h

@@ -22,7 +22,8 @@
 
 size_t utf16_strlen(const char16_t *str);
 int utf16_strcmp(const char16_t *s1, const char16_t *s2);
-int utf8_to_utf16(char16_t *dest, const char *src, size_t size);
-int utf16_to_utf8(char *dest, const char16_t *src, size_t size);
+// Return number of characters converted, including the null terminator
+size_t utf8_to_utf16(char16_t *dest, const char *src, size_t size);
+size_t utf16_to_utf8(char *dest, const char16_t *src, size_t size);
 
 #endif

lib/uefi/runtime_service_provider.cpp

@@ -22,12 +22,11 @@
 #include <string.h>
 #include <uefi/types.h>
 
+#include "charset.h"
 #include "variable_mem.h"
 
 namespace {
 
-constexpr auto &&kSecureBoot = "SecureBoot";
-
 EFI_STATUS GetVariable(char16_t *VariableName, EfiGuid *VendorGuid,
                        uint32_t *Attributes, size_t *DataSize, void *Data) {
 
@@ -36,16 +35,8 @@ EFI_STATUS GetVariable(char16_t *VariableName, EfiGuid *VendorGuid,
   }
 
   char buffer[512];
-  size_t i = 0;
-  while (VariableName[i] && i < sizeof(buffer)) {
-    size_t j = 0;
-    for (j = 0; j < sizeof(buffer) - 1 && VariableName[i + j]; j++) {
-      buffer[j] = VariableName[i + j];
-    }
-    i += j;
-  }
-  buffer[i] = 0;
-  if (strncmp(buffer, kSecureBoot, sizeof(kSecureBoot)) == 0 || strcmp(buffer, "SetupMode") == 0) {
+  utf16_to_utf8(buffer, VariableName, sizeof(buffer));
+  if (utf16_strcmp(VariableName, u"SecureBoot") == 0 && utf16_strcmp(VariableName, u"SetupMode") == 0) {
     if (DataSize) {
       *DataSize = 1;
     }