Add some APIs to StringUtils (flutter/engine#25043)

* Add the following APIs to StringUtils:

- NumberToString16
- JoinString
- ReplaceChars
- WideToUTF16
- UTF16ToWide

Implement the following APIs for Windows:

- UTF8ToUTF16
- UTF16ToUTF8

* Review comments

Add a couple TODOs for decimal formatting and use std::u16string::npos
rather than std::string::npos.

* Update licences_flutter

Co-authored-by: Chris Bracken <chris@bracken.jp>

engine/src/flutter/ci/licenses_golden/licenses_flutter

@@ -1596,6 +1596,8 @@ FILE: ../../../flutter/third_party/accessibility/base/simple_token.h
 FILE: ../../../flutter/third_party/accessibility/base/string_utils.cc
 FILE: ../../../flutter/third_party/accessibility/base/string_utils.h
 FILE: ../../../flutter/third_party/accessibility/base/string_utils_unittest.cc
+FILE: ../../../flutter/third_party/accessibility/base/win/string_conversion.cc
+FILE: ../../../flutter/third_party/accessibility/base/win/string_conversion.h
 FILE: ../../../flutter/third_party/accessibility/gfx/transform.cc
 FILE: ../../../flutter/third_party/accessibility/gfx/transform.h
 FILE: ../../../flutter/third_party/tonic/common/build_config.h

engine/src/flutter/third_party/accessibility/base/BUILD.gn

@@ -23,8 +23,10 @@ source_set("base") {
     "string_utils.h",
   ]
   if (is_win) {
-    # TODO: codecvt_utf8_utf16 is deprecated in C++17
-    defines = [ "_SILENCE_ALL_CXX17_DEPRECATION_WARNINGS" ]
+    sources += [
+      "win/string_conversion.cc",
+      "win/string_conversion.h",
+    ]
   }
   if (is_mac) {
     sources += [

engine/src/flutter/third_party/accessibility/base/string_utils.cc

@@ -10,6 +10,10 @@
 #include <regex>
 #include <sstream>
 
+#if defined(_WIN32)
+#include "base/win/string_conversion.h"
+#endif
+
 #include "no_destructor.h"
 
 namespace base {
@@ -19,19 +23,47 @@ std::u16string ASCIIToUTF16(std::string src) {
 }
 
 std::u16string UTF8ToUTF16(std::string src) {
+#if defined(_WIN32)
+  return WideToUTF16(win::Utf16FromUtf8(src));
+#else
   std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t> convert;
   return convert.from_bytes(src);
+#endif
 }
 
 std::string UTF16ToUTF8(std::u16string src) {
+#if defined(_WIN32)
+  return win::Utf8FromUtf16(UTF16ToWide(src));
+#else
   std::wstring_convert<std::codecvt_utf8_utf16<char16_t>, char16_t> convert;
   return convert.to_bytes(src);
+#endif
+}
+
+std::u16string WideToUTF16(const std::wstring& src) {
+  return std::u16string(src.begin(), src.end());
+}
+
+std::wstring UTF16ToWide(const std::u16string& src) {
+  return std::wstring(src.begin(), src.end());
 }
 
 std::u16string NumberToString16(float number) {
   return ASCIIToUTF16(NumberToString(number));
 }
 
+std::u16string NumberToString16(int32_t number) {
+  return ASCIIToUTF16(NumberToString(number));
+}
+
+std::u16string NumberToString16(unsigned int number) {
+  return ASCIIToUTF16(NumberToString(number));
+}
+
+std::u16string NumberToString16(double number) {
+  return ASCIIToUTF16(NumberToString(number));
+}
+
 std::string NumberToString(int32_t number) {
   return std::to_string(number);
 }
@@ -41,6 +73,14 @@ std::string NumberToString(unsigned int number) {
 }
 
 std::string NumberToString(float number) {
+  // TODO(gw280): Format decimals to the shortest reasonable representation.
+  // See: https://github.com/flutter/flutter/issues/78460
+  return std::to_string(number);
+}
+
+std::string NumberToString(double number) {
+  // TODO(gw280): Format decimals to the shortest reasonable representation.
+  // See: https://github.com/flutter/flutter/issues/78460
   return std::to_string(number);
 }
 
@@ -56,6 +96,20 @@ std::string JoinString(std::vector<std::string> tokens, std::string delimiter) {
   return imploded.str();
 }
 
+std::u16string JoinString(std::vector<std::u16string> tokens,
+                          std::u16string delimiter) {
+  std::u16string result;
+  for (size_t i = 0; i < tokens.size(); i++) {
+    if (i == tokens.size() - 1) {
+      result.append(tokens[i]);
+    } else {
+      result.append(tokens[i]);
+      result.append(delimiter);
+    }
+  }
+  return result;
+}
+
 void ReplaceChars(std::string in,
                   std::string from,
                   std::string to,
@@ -68,6 +122,18 @@ void ReplaceChars(std::string in,
   *out = in;
 }
 
+void ReplaceChars(std::u16string in,
+                  std::u16string from,
+                  std::u16string to,
+                  std::u16string* out) {
+  size_t pos = in.find(from);
+  while (pos != std::u16string::npos) {
+    in.replace(pos, from.size(), to);
+    pos = in.find(from, pos + to.size());
+  }
+  *out = in;
+}
+
 const std::string& EmptyString() {
   static const base::NoDestructor<std::string> s;
   return *s;

engine/src/flutter/third_party/accessibility/base/string_utils.h

@@ -25,21 +25,34 @@ std::string StringPrintf(const std::string& format, Args... args) {
 std::u16string ASCIIToUTF16(std::string src);
 std::u16string UTF8ToUTF16(std::string src);
 std::string UTF16ToUTF8(std::u16string src);
+std::u16string WideToUTF16(const std::wstring& src);
+std::wstring UTF16ToWide(const std::u16string& src);
 
 std::u16string NumberToString16(float number);
+std::u16string NumberToString16(unsigned int number);
+std::u16string NumberToString16(int32_t number);
+std::u16string NumberToString16(double number);
+
 std::string NumberToString(unsigned int number);
 std::string NumberToString(int32_t number);
 std::string NumberToString(float number);
+std::string NumberToString(double number);
 
 std::string ToUpperASCII(std::string str);
 std::string ToLowerASCII(std::string str);
 
 std::string JoinString(std::vector<std::string> tokens, std::string delimiter);
+std::u16string JoinString(std::vector<std::u16string> tokens,
+                          std::u16string delimiter);
+
 void ReplaceChars(std::string in,
                   std::string from,
                   std::string to,
                   std::string* out);
-
+void ReplaceChars(std::u16string in,
+                  std::u16string from,
+                  std::u16string to,
+                  std::u16string* out);
 bool LowerCaseEqualsASCII(std::string a, std::string b);
 bool ContainsOnlyChars(std::u16string str, char16_t ch);
 

engine/src/flutter/third_party/accessibility/base/win/string_conversion.cc

@@ -0,0 +1,60 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// TODO(gw280): This is copied from shell/platform/win. When
+// https://github.com/flutter/flutter/issues/75653 is fixed, we should
+// deduplicate these and put them in fml.
+#include "string_conversion.h"
+
+#include <Windows.h>
+
+namespace base {
+namespace win {
+
+std::string Utf8FromUtf16(const std::wstring& utf16_string) {
+  if (utf16_string.empty()) {
+    return std::string();
+  }
+  int target_length = ::WideCharToMultiByte(
+      CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string.data(),
+      static_cast<int>(utf16_string.length()), nullptr, 0, nullptr, nullptr);
+  if (target_length == 0) {
+    return std::string();
+  }
+  std::string utf8_string;
+  utf8_string.resize(target_length);
+  int converted_length = ::WideCharToMultiByte(
+      CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string.data(),
+      static_cast<int>(utf16_string.length()), utf8_string.data(),
+      target_length, nullptr, nullptr);
+  if (converted_length == 0) {
+    return std::string();
+  }
+  return utf8_string;
+}
+
+std::wstring Utf16FromUtf8(const std::string& utf8_string) {
+  if (utf8_string.empty()) {
+    return std::wstring();
+  }
+  int target_length =
+      ::MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, utf8_string.data(),
+                            static_cast<int>(utf8_string.length()), nullptr, 0);
+  if (target_length == 0) {
+    return std::wstring();
+  }
+  std::wstring utf16_string;
+  utf16_string.resize(target_length);
+  int converted_length =
+      ::MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, utf8_string.data(),
+                            static_cast<int>(utf8_string.length()),
+                            utf16_string.data(), target_length);
+  if (converted_length == 0) {
+    return std::wstring();
+  }
+  return utf16_string;
+}
+
+}  // namespace win
+}  // namespace base

engine/src/flutter/third_party/accessibility/base/win/string_conversion.h

@@ -0,0 +1,24 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_SHELL_PLATFORM_WINDOWS_STRING_CONVERSION_H_
+#define FLUTTER_SHELL_PLATFORM_WINDOWS_STRING_CONVERSION_H_
+
+#include <string>
+
+namespace base {
+namespace win {
+
+// Converts a string from UTF-16 to UTF-8. Returns an empty string if the
+// input is not valid UTF-16.
+std::string Utf8FromUtf16(const std::wstring& utf16_string);
+
+// Converts a string from UTF-8 to UTF-16. Returns an empty string if the
+// input is not valid UTF-8.
+std::wstring Utf16FromUtf8(const std::string& utf8_string);
+
+}  // namespace win
+}  // namespace base
+
+#endif  // FLUTTER_SHELL_PLATFORM_WINDOWS_STRING_CONVERSION_H_