Double the speed of DecimalFormat creation.

Our calls to unum_setSymbol were making us O(n^2); switching to the C++ API
and doing a bulk update is a huge win. (ICU is really a C++ library with a
C wrapper. It's always going to be slightly wasteful to go via C, but here
it's especially harmful.)

The new ScopedJavaUnicodeString provides a best-of-breed bridge between Java
strings on the Java heap and the UnicodeString type that ICU wants. I'll come
back and switch more of our ICU JNI over in a later patch.

1 files changed, 50 insertions, 0 deletions

diff --git a/icu/src/main/native/ScopedJavaUnicodeString.h b/icu/src/main/native/ScopedJavaUnicodeString.h
new file mode 100644
index 0000000..3486aac
--- /dev/null
+++ b/icu/src/main/native/ScopedJavaUnicodeString.h
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef SCOPED_JAVA_UNICODE_STRING_H_included
+#define SCOPED_JAVA_UNICODE_STRING_H_included
+
+#include "JNIHelp.h"
+
+// A smart pointer that provides access to an ICU UnicodeString given a JNI
+// jstring. We give ICU a direct pointer to the characters on the Java heap.
+// It's clever enough to copy-on-write if necessary, but we only provide
+// const UnicodeString access anyway because attempted write access seems
+// likely to be an error.
+class ScopedJavaUnicodeString {
+public:
+    ScopedJavaUnicodeString(JNIEnv* env, jstring s) : mEnv(env), mString(s) {
+        mChars = env->GetStringChars(mString, NULL);
+        const int32_t charCount = env->GetStringLength(mString);
+        mUnicodeString.setTo(false, mChars, charCount);
+    }
+
+    ~ScopedJavaUnicodeString() {
+        mEnv->ReleaseStringChars(mString, mChars);
+    }
+
+    const UnicodeString& unicodeString() {
+        return mUnicodeString;
+    }
+
+private:
+    JNIEnv* mEnv;
+    jstring mString;
+    const UChar* mChars;
+    UnicodeString mUnicodeString;
+};
+
+#endif  // SCOPED_JAVA_UNICODE_STRING_H_included