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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 #include "core_jni_helpers.h"
18 #include "nativehelper/scoped_primitive_array.h"
19 
20 namespace android {
21 
android_util_CharsetUtils_toModifiedUtf8Bytes(JNIEnv * env,jobject clazz,jstring src,jint srcLen,jlong dest,jint destOff,jint destLen)22 static jint android_util_CharsetUtils_toModifiedUtf8Bytes(JNIEnv *env, jobject clazz,
23         jstring src, jint srcLen, jlong dest, jint destOff, jint destLen) {
24     char *destPtr = reinterpret_cast<char*>(dest);
25 
26     // Quickly check if destination has plenty of room for worst-case
27     // 4-bytes-per-char encoded size
28     const size_t worstLen = (srcLen * 4);
29     if (destOff >= 0 && destOff + worstLen < destLen) {
30         env->GetStringUTFRegion(src, 0, srcLen, destPtr + destOff);
31         return strlen(destPtr + destOff + srcLen) + srcLen;
32     }
33 
34     // String still might fit in destination, but we need to measure
35     // its actual encoded size to be sure
36     const size_t encodedLen = env->GetStringUTFLength(src);
37     if (destOff >= 0 && destOff + encodedLen < destLen) {
38         env->GetStringUTFRegion(src, 0, srcLen, destPtr + destOff);
39         return encodedLen;
40     }
41 
42     return -encodedLen;
43 }
44 
android_util_CharsetUtils_fromModifiedUtf8Bytes(JNIEnv * env,jobject clazz,jlong src,jint srcOff,jint srcLen)45 static jstring android_util_CharsetUtils_fromModifiedUtf8Bytes(JNIEnv *env, jobject clazz,
46         jlong src, jint srcOff, jint srcLen) {
47     char *srcPtr = reinterpret_cast<char*>(src);
48 
49     // This is funky, but we need to temporarily swap a null byte so that
50     // JNI knows where the string ends; we'll put it back, we promise
51     char tmp = srcPtr[srcOff + srcLen];
52     srcPtr[srcOff + srcLen] = '\0';
53     jstring res = env->NewStringUTF(srcPtr + srcOff);
54     srcPtr[srcOff + srcLen] = tmp;
55     return res;
56 }
57 
58 static const JNINativeMethod methods[] = {
59     // @FastNative
60     {"toModifiedUtf8Bytes",      "(Ljava/lang/String;IJII)I",
61             (void*)android_util_CharsetUtils_toModifiedUtf8Bytes},
62     // @FastNative
63     {"fromModifiedUtf8Bytes",    "(JII)Ljava/lang/String;",
64             (void*)android_util_CharsetUtils_fromModifiedUtf8Bytes},
65 };
66 
register_android_util_CharsetUtils(JNIEnv * env)67 int register_android_util_CharsetUtils(JNIEnv *env) {
68     return RegisterMethodsOrDie(env, "android/util/CharsetUtils", methods, NELEM(methods));
69 }
70 
71 }
72