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/*
* Copyright (C) 2020 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.
*/
package android.util;
import android.annotation.NonNull;
import dalvik.annotation.optimization.FastNative;
/**
* Specializations of {@code libcore.util.CharsetUtils} which enable efficient
* in-place encoding without making any new allocations.
* <p>
* These methods purposefully accept only non-movable byte array addresses to
* avoid extra JNI overhead.
* <p>
* Callers are cautioned that there is a long-standing ART bug that emits
* non-standard 4-byte sequences, as described by {@code kUtfUse4ByteSequence}
* in {@code art/runtime/jni/jni_internal.cc}. If precise modified UTF-8
* encoding is required, use {@link com.android.internal.util.ModifiedUtf8}
* instead.
*
* @hide
*/
public class CharsetUtils {
/**
* Attempt to encode the given string as modified UTF-8 into the destination
* byte array without making any new allocations.
* <p>
* Callers are cautioned that there is a long-standing ART bug that emits
* non-standard 4-byte sequences, as described by
* {@code kUtfUse4ByteSequence} in {@code art/runtime/jni/jni_internal.cc}.
* If precise modified UTF-8 encoding is required, use
* {@link com.android.internal.util.ModifiedUtf8} instead.
*
* @param src string value to be encoded
* @param dest destination byte array to encode into
* @param destOff offset into destination where encoding should begin
* @param destLen length of destination
* @return positive value when encoding succeeded, or negative value when
* failed; the magnitude of the value is the number of bytes
* required to encode the string.
*/
public static int toModifiedUtf8Bytes(@NonNull String src,
long dest, int destOff, int destLen) {
return toModifiedUtf8Bytes(src, src.length(), dest, destOff, destLen);
}
/**
* Attempt to encode the given string as modified UTF-8 into the destination
* byte array without making any new allocations.
* <p>
* Callers are cautioned that there is a long-standing ART bug that emits
* non-standard 4-byte sequences, as described by
* {@code kUtfUse4ByteSequence} in {@code art/runtime/jni/jni_internal.cc}.
* If precise modified UTF-8 encoding is required, use
* {@link com.android.internal.util.ModifiedUtf8} instead.
*
* @param src string value to be encoded
* @param srcLen exact length of string to be encoded
* @param dest destination byte array to encode into
* @param destOff offset into destination where encoding should begin
* @param destLen length of destination
* @return positive value when encoding succeeded, or negative value when
* failed; the magnitude of the value is the number of bytes
* required to encode the string.
*/
@FastNative
private static native int toModifiedUtf8Bytes(@NonNull String src, int srcLen,
long dest, int destOff, int destLen);
/**
* Attempt to decode a modified UTF-8 string from the source byte array.
* <p>
* Callers are cautioned that there is a long-standing ART bug that emits
* non-standard 4-byte sequences, as described by
* {@code kUtfUse4ByteSequence} in {@code art/runtime/jni/jni_internal.cc}.
* If precise modified UTF-8 encoding is required, use
* {@link com.android.internal.util.ModifiedUtf8} instead.
*
* @param src source byte array to decode from
* @param srcOff offset into source where decoding should begin
* @param srcLen length of source that should be decoded
* @return the successfully decoded string
*/
@FastNative
public static native @NonNull String fromModifiedUtf8Bytes(
long src, int srcOff, int srcLen);
}
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