Revert 36459 - Breaks 7 WebKit tests...

base/string_util.cc

Index: base/string_util.cc
===================================================================
--- base/string_util.cc	(revision 36459)
+++ base/string_util.cc	(working copy)
@@ -24,8 +24,6 @@
 #include "base/logging.h"
 #include "base/singleton.h"
 #include "base/third_party/dmg_fp/dmg_fp.h"
-#include "base/utf_string_conversion_utils.h"
-#include "base/third_party/icu/icu_utf.h"
 
 namespace {
 
@@ -613,21 +611,142 @@
   return DoIsStringASCII(str);
 }
 
-bool IsStringUTF8(const std::string& str) {
-  const char *src = str.data();
-  int32 src_len = static_cast<int32>(str.length());
-  int32 char_index = 0;
+// Helper functions that determine whether the given character begins a
+// UTF-8 sequence of bytes with the given length. A character satisfies
+// "IsInUTF8Sequence" if it is anything but the first byte in a multi-byte
+// character.
+static inline bool IsBegin2ByteUTF8(int c) {
+  return (c & 0xE0) == 0xC0;
+}
+static inline bool IsBegin3ByteUTF8(int c) {
+  return (c & 0xF0) == 0xE0;
+}
+static inline bool IsBegin4ByteUTF8(int c) {
+  return (c & 0xF8) == 0xF0;
+}
+static inline bool IsInUTF8Sequence(int c) {
+  return (c & 0xC0) == 0x80;
+}
 
-  while (char_index < src_len) {
-    int32 code_point;
-    CBU8_NEXT(src, char_index, src_len, code_point);
-    if (!base::IsValidCodepoint(code_point))
+// This function was copied from Mozilla, with modifications. The original code
+// was 'IsUTF8' in xpcom/string/src/nsReadableUtils.cpp. The license block for
+// this function is:
+//   This function subject to the Mozilla Public License Version
+//   1.1 (the "License"); you may not use this code except in compliance with
+//   the License. You may obtain a copy of the License at
+//   http://www.mozilla.org/MPL/
+//
+//   Software distributed under the License is distributed on an "AS IS" basis,
+//   WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+//   for the specific language governing rights and limitations under the
+//   License.
+//
+//   The Original Code is mozilla.org code.
+//
+//   The Initial Developer of the Original Code is
+//   Netscape Communications Corporation.
+//   Portions created by the Initial Developer are Copyright (C) 2000
+//   the Initial Developer. All Rights Reserved.
+//
+//   Contributor(s):
+//     Scott Collins <scc@mozilla.org> (original author)
+//
+// This is a template so that it can be run on wide and 8-bit strings. We want
+// to run it on wide strings when we have input that we think may have
+// originally been UTF-8, but has been converted to wide characters because
+// that's what we (and Windows) use internally.
+template<typename CHAR>
+static bool IsStringUTF8T(const CHAR* str, size_t length) {
+  bool overlong = false;
+  bool surrogate = false;
+  bool nonchar = false;
+
+  // overlong byte upper bound
+  typename ToUnsigned<CHAR>::Unsigned olupper = 0;
+
+  // surrogate byte lower bound
+  typename ToUnsigned<CHAR>::Unsigned slower = 0;
+
+  // incremented when inside a multi-byte char to indicate how many bytes
+  // are left in the sequence
+  int positions_left = 0;
+
+  for (uintptr_t i = 0; i < length; i++) {
+    // This whole function assume an unsigned value so force its conversion to
+    // an unsigned value.
+    typename ToUnsigned<CHAR>::Unsigned c = str[i];
+    if (c < 0x80)
+      continue;  // ASCII
+
+    if (c <= 0xC1) {
+      // [80-BF] where not expected, [C0-C1] for overlong
       return false;
+    } else if (IsBegin2ByteUTF8(c)) {
+      positions_left = 1;
+    } else if (IsBegin3ByteUTF8(c)) {
+      positions_left = 2;
+      if (c == 0xE0) {
+        // to exclude E0[80-9F][80-BF]
+        overlong = true;
+        olupper = 0x9F;
+      } else if (c == 0xED) {
+        // ED[A0-BF][80-BF]: surrogate codepoint
+        surrogate = true;
+        slower = 0xA0;
+      } else if (c == 0xEF) {
+        // EF BF [BE-BF] : non-character
+        // TODO(jungshik): EF B7 [90-AF] should be checked as well.
+        nonchar = true;
+      }
+    } else if (c <= 0xF4) {
+      positions_left = 3;
+      nonchar = true;
+      if (c == 0xF0) {
+        // to exclude F0[80-8F][80-BF]{2}
+        overlong = true;
+        olupper = 0x8F;
+      } else if (c == 0xF4) {
+        // to exclude F4[90-BF][80-BF]
+        // actually not surrogates but codepoints beyond 0x10FFFF
+        surrogate = true;
+        slower = 0x90;
+      }
+    } else {
+      return false;
+    }
+
+    // eat the rest of this multi-byte character
+    while (positions_left) {
+      positions_left--;
+      i++;
+      c = str[i];
+      if (!c)
+        return false;  // end of string but not end of character sequence
+
+      // non-character : EF BF [BE-BF] or F[0-7] [89AB]F BF [BE-BF]
+      if (nonchar && ((!positions_left && c < 0xBE) ||
+                      (positions_left == 1 && c != 0xBF) ||
+                      (positions_left == 2 && 0x0F != (0x0F & c) ))) {
+        nonchar = false;
+      }
+      if (!IsInUTF8Sequence(c) || (overlong && c <= olupper) ||
+          (surrogate && slower <= c) || (nonchar && !positions_left) ) {
+        return false;
+      }
+      overlong = surrogate = false;
+    }
   }
-
   return true;
 }
 
+bool IsStringUTF8(const std::string& str) {
+  return IsStringUTF8T(str.data(), str.length());
+}
+
+bool IsStringWideUTF8(const std::wstring& str) {
+  return IsStringUTF8T(str.data(), str.length());
+}
+
 template<typename Iter>
 static inline bool DoLowerCaseEqualsASCII(Iter a_begin,
                                           Iter a_end,