1 /*
2  * Copyright (C) 2020 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package android.util;
18 
19 import android.annotation.NonNull;
20 
21 import dalvik.annotation.optimization.FastNative;
22 
23 /**
24  * Specializations of {@code libcore.util.CharsetUtils} which enable efficient
25  * in-place encoding without making any new allocations.
26  * <p>
27  * These methods purposefully accept only non-movable byte array addresses to
28  * avoid extra JNI overhead.
29  *
30  * @hide
31  */
32 public class CharsetUtils {
33     /**
34      * Attempt to encode the given string as modified UTF-8 into the destination
35      * byte array without making any new allocations.
36      *
37      * @param src string value to be encoded
38      * @param dest destination byte array to encode into
39      * @param destOff offset into destination where encoding should begin
40      * @param destLen length of destination
41      * @return positive value when encoding succeeded, or negative value when
42      *         failed; the magnitude of the value is the number of bytes
43      *         required to encode the string.
44      */
toModifiedUtf8Bytes(@onNull String src, long dest, int destOff, int destLen)45     public static int toModifiedUtf8Bytes(@NonNull String src,
46             long dest, int destOff, int destLen) {
47         return toModifiedUtf8Bytes(src, src.length(), dest, destOff, destLen);
48     }
49 
50     /**
51      * Attempt to encode the given string as modified UTF-8 into the destination
52      * byte array without making any new allocations.
53      *
54      * @param src string value to be encoded
55      * @param srcLen exact length of string to be encoded
56      * @param dest destination byte array to encode into
57      * @param destOff offset into destination where encoding should begin
58      * @param destLen length of destination
59      * @return positive value when encoding succeeded, or negative value when
60      *         failed; the magnitude of the value is the number of bytes
61      *         required to encode the string.
62      */
63     @FastNative
toModifiedUtf8Bytes(@onNull String src, int srcLen, long dest, int destOff, int destLen)64     private static native int toModifiedUtf8Bytes(@NonNull String src, int srcLen,
65             long dest, int destOff, int destLen);
66 
67     /**
68      * Attempt to decode a modified UTF-8 string from the source byte array.
69      *
70      * @param src source byte array to decode from
71      * @param srcOff offset into source where decoding should begin
72      * @param srcLen length of source that should be decoded
73      * @return the successfully decoded string
74      */
75     @FastNative
fromModifiedUtf8Bytes( long src, int srcOff, int srcLen)76     public static native @NonNull String fromModifiedUtf8Bytes(
77             long src, int srcOff, int srcLen);
78 }
79