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..2dd99339a8667d9122c8b3ef7160bd8624370edb 100644
--- a/runtime/vm/unicode.h
+++ b/runtime/vm/unicode.h
@@ -33,6 +33,58 @@ 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 a stage 2 block in bytes.
+  static const size_t kBlockSize = 1<<8;

[Ivan Posva, 2011/10/18 22:01:13]

Please name the constant 8, then you can use it below as well.

[cshapiro, 2011/10/20 02:35:05]

Done.

+
+  static int32_t Convert(int32_t ch, int32_t mapping) {
+    int16_t offset = stage1_[ch / kBlockSize] * kBlockSize;

[Ivan Posva, 2011/10/18 22:01:13]

Replace the division with a shift with a constant value? How about replacing the
multiplication with a shift as well?

[cshapiro, 2011/10/20 02:35:05]

Done.

+    int32_t info = stage2_[offset + (ch % kBlockSize)];

[Ivan Posva, 2011/10/18 22:01:13]

Modulo -> and?

[cshapiro, 2011/10/20 02:35:05]

Done.

+    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_