Make UTF16ToASCII and UTF16TOUTF8 take a StringPiece

base/strings/utf_string_conversions.cc

Index: base/strings/utf_string_conversions.cc
diff --git a/base/strings/utf_string_conversions.cc b/base/strings/utf_string_conversions.cc
index 1480d48086fed618ffbcc95cf918d8a0c1ebcb7e..b6cf6ff9b101446d026484df7e1c569fcec434bf 100644
--- a/base/strings/utf_string_conversions.cc
+++ b/base/strings/utf_string_conversions.cc
@@ -73,7 +73,7 @@ bool UTF8ToWide(const char* src, size_t src_len, std::wstring* output) {
   }
 }
 
-std::wstring UTF8ToWide(const StringPiece& utf8) {
+std::wstring UTF8ToWide(StringPiece utf8) {
   if (IsStringASCII(utf8)) {
     return std::wstring(utf8.begin(), utf8.end());
   }
@@ -153,7 +153,7 @@ bool UTF8ToUTF16(const char* src, size_t src_len, string16* output) {
   }
 }
 
-string16 UTF8ToUTF16(const StringPiece& utf8) {
+string16 UTF8ToUTF16(StringPiece utf8) {
   if (IsStringASCII(utf8)) {
     return string16(utf8.begin(), utf8.end());
   }
@@ -176,7 +176,7 @@ bool UTF16ToUTF8(const char16* src, size_t src_len, std::string* output) {
   }
 }
 
-std::string UTF16ToUTF8(const string16& utf16) {
+std::string UTF16ToUTF8(StringPiece16 utf16) {
   if (IsStringASCII(utf16)) {
     return std::string(utf16.begin(), utf16.end());
   }
@@ -195,7 +195,7 @@ bool UTF8ToUTF16(const char* src, size_t src_len, string16* output) {
   return UTF8ToWide(src, src_len, output);
 }
 
-string16 UTF8ToUTF16(const StringPiece& utf8) {
+string16 UTF8ToUTF16(StringPiece utf8) {
   return UTF8ToWide(utf8);
 }
 
@@ -203,18 +203,24 @@ bool UTF16ToUTF8(const char16* src, size_t src_len, std::string* output) {
   return WideToUTF8(src, src_len, output);
 }
 
-std::string UTF16ToUTF8(const string16& utf16) {
-  return WideToUTF8(utf16);
+std::string UTF16ToUTF8(StringPiece16 utf16) {
+  if (IsStringASCII(utf16))
+    return std::string(utf16.data(), utf16.data() + utf16.length());
+
+  std::string ret;
+  PrepareForUTF8Output(utf16.data(), utf16.length(), &ret);
+  ConvertUnicode(utf16.data(), utf16.length(), &ret);
+  return ret;
 }
 
 #endif
 
-string16 ASCIIToUTF16(const StringPiece& ascii) {
+string16 ASCIIToUTF16(StringPiece ascii) {
   DCHECK(IsStringASCII(ascii)) << ascii;
   return string16(ascii.begin(), ascii.end());
 }
 
-std::string UTF16ToASCII(const string16& utf16) {
+std::string UTF16ToASCII(StringPiece16 utf16) {
   DCHECK(IsStringASCII(utf16)) << UTF16ToUTF8(utf16);
   return std::string(utf16.begin(), utf16.end());
 }