Implement case mapping using the Unicode default case mapping algorithm.

runtime/vm/unicode.h

Index: runtime/vm/unicode.h
diff --git a/runtime/vm/unicode.h b/runtime/vm/unicode.h
index 19119bbf579cf9a4e37a17099e25ca4404a3a59f..4301addebd42fb43f5bb58731ef22abd5f039348 100644
--- a/runtime/vm/unicode.h
+++ b/runtime/vm/unicode.h
@@ -33,6 +33,70 @@ class Utf8 : AllStatic {
   static bool Decode(const char* src, uint32_t* dst, intptr_t len);
 };
 
+
+class CaseMapping : AllStatic {
+ public:
+  // Maps a code point to uppercase.
+  static int32_t ToUpper(int32_t code_point) {
+    return Convert(code_point, kUppercase);
+  }
+
+  // Maps a code point to lowercase.
+  static int32_t ToLower(int32_t code_point) {
+    return Convert(code_point, kLowercase);
+  }
+
+ private:
+  // Property is a delta to the uppercase mapping.
+  static const int32_t kUppercase = 1;
+
+  // Property is a delta to the uppercase mapping.
+  static const int32_t kLowercase = 2;
+
+  // Property is an index into the exception table.
+  static const int32_t kException = 3;
+
+  // Type bit-field parameters
+  static const int32_t kTypeShift = 2;
+  static const int32_t kTypeMask = 3;
+
+  // The size of the stage 1 index.
+  // TODO(cshapiro): improve indexing so this value is unnecessary.
+  static const int kStage1Size = 261;
+
+  // The size of a stage 2 block in bytes.
+  static const int kBlockSizeLog2 = 8;
+  static const int kBlockSize = 1 << kBlockSizeLog2;
+
+  static int32_t Convert(int32_t ch, int32_t mapping) {
+    if (ch <= 0xFF) {
+      int32_t info = stage2_[ch];
+      if ((info & kTypeMask) == mapping) {
+        ch += info >> kTypeShift;
+      }
+    } else if (ch <= (kStage1Size << kBlockSizeLog2)) {
+      int16_t offset = stage1_[ch >> kBlockSizeLog2] << kBlockSizeLog2;
+      int32_t info = stage2_[offset + (ch & (kBlockSize - 1))];
+      int32_t type = info & kTypeMask;
+      if (type == mapping) {
+        ch += (info >> kTypeShift);
+      } else if (type == kException) {
+        ch += stage2_exception_[info >> kTypeShift][mapping - 1];
+      }
+    }
+    return ch;
+  }
+
+  // Index into the data array.
+  static const uint8_t stage1_[];
+
+  // Data for small code points with one mapping
+  static const int16_t stage2_[];
+
+  // Data for large code points or code points with both mappings.
+  static const int32_t stage2_exception_[][2];
+};
+
 }  // namespace dart
 
 #endif  // VM_UNICODE_H_