android_os_MemoryFile.cpp revision 963cd006c45716b034f656bf7e7179e6476f7e4d 
1/*
2 * Copyright (C) 2008 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#define LOG_TAG "MemoryFile"
18#include <utils/Log.h>
19
20#include <cutils/ashmem.h>
21#include <android_runtime/AndroidRuntime.h>
22#include "JNIHelp.h"
23#include <unistd.h>
24#include <sys/mman.h>
25
26
27namespace android {
28
29static jobject android_os_MemoryFile_open(JNIEnv* env, jobject clazz, jstring name, jint length)
30{
31    const char* namestr = (name ? env->GetStringUTFChars(name, NULL) : NULL);
32
33    // round up length to page boundary
34    length = (((length - 1) / getpagesize()) + 1) * getpagesize();
35    int result = ashmem_create_region(namestr, length);
36
37    if (name)
38        env->ReleaseStringUTFChars(name, namestr);
39
40    if (result < 0) {
41        jniThrowException(env, "java/io/IOException", "ashmem_create_region failed");
42        return NULL;
43    }
44
45    return jniCreateFileDescriptor(env, result);
46}
47
48static jint android_os_MemoryFile_mmap(JNIEnv* env, jobject clazz, jobject fileDescriptor,
49        jint length, jint prot)
50{
51    int fd = jniGetFDFromFileDescriptor(env, fileDescriptor);
52    jint result = (jint)mmap(NULL, length, prot, MAP_SHARED, fd, 0);
53    if (!result)
54        jniThrowException(env, "java/io/IOException", "mmap failed");
55    return result;
56}
57
58static void android_os_MemoryFile_munmap(JNIEnv* env, jobject clazz, jint addr, jint length)
59{
60    int result = munmap((void *)addr, length);
61    if (result < 0)
62        jniThrowException(env, "java/io/IOException", "munmap failed");
63}
64
65static void android_os_MemoryFile_close(JNIEnv* env, jobject clazz, jobject fileDescriptor)
66{
67    int fd = jniGetFDFromFileDescriptor(env, fileDescriptor);
68    if (fd >= 0) {
69        jniSetFileDescriptorOfFD(env, fileDescriptor, -1);
70        close(fd);
71    }
72}
73
74static jint android_os_MemoryFile_read(JNIEnv* env, jobject clazz,
75        jobject fileDescriptor, jint address, jbyteArray buffer, jint srcOffset, jint destOffset,
76        jint count, jboolean unpinned)
77{
78    int fd = jniGetFDFromFileDescriptor(env, fileDescriptor);
79    if (unpinned && ashmem_pin_region(fd, 0, 0) == ASHMEM_WAS_PURGED) {
80        ashmem_unpin_region(fd, 0, 0);
81        jniThrowException(env, "java/io/IOException", "ashmem region was purged");
82        return -1;
83    }
84
85    env->SetByteArrayRegion(buffer, destOffset, count, (const jbyte *)address + srcOffset);
86
87    if (unpinned) {
88        ashmem_unpin_region(fd, 0, 0);
89    }
90    return count;
91}
92
93static jint android_os_MemoryFile_write(JNIEnv* env, jobject clazz,
94        jobject fileDescriptor, jint address, jbyteArray buffer, jint srcOffset, jint destOffset,
95        jint count, jboolean unpinned)
96{
97    int fd = jniGetFDFromFileDescriptor(env, fileDescriptor);
98    if (unpinned && ashmem_pin_region(fd, 0, 0) == ASHMEM_WAS_PURGED) {
99        ashmem_unpin_region(fd, 0, 0);
100        jniThrowException(env, "java/io/IOException", "ashmem region was purged");
101        return -1;
102    }
103
104    env->GetByteArrayRegion(buffer, srcOffset, count, (jbyte *)address + destOffset);
105
106    if (unpinned) {
107        ashmem_unpin_region(fd, 0, 0);
108    }
109    return count;
110}
111
112static void android_os_MemoryFile_pin(JNIEnv* env, jobject clazz, jobject fileDescriptor, jboolean pin)
113{
114    int fd = jniGetFDFromFileDescriptor(env, fileDescriptor);
115    int result = (pin ? ashmem_pin_region(fd, 0, 0) : ashmem_unpin_region(fd, 0, 0));
116    if (result < 0) {
117        jniThrowException(env, "java/io/IOException", NULL);
118    }
119}
120
121static jboolean android_os_MemoryFile_is_ashmem_region(JNIEnv* env, jobject clazz,
122        jobject fileDescriptor) {
123    int fd = jniGetFDFromFileDescriptor(env, fileDescriptor);
124    // Use ASHMEM_GET_SIZE to find out if the fd refers to an ashmem region.
125    // ASHMEM_GET_SIZE should succeed for all ashmem regions, and the kernel
126    // should return ENOTTY for all other valid file descriptors
127    int result = ashmem_get_size_region(fd);
128    if (result < 0) {
129        if (errno == ENOTTY) {
130            // ENOTTY means that the ioctl does not apply to this object,
131            // i.e., it is not an ashmem region.
132            return JNI_FALSE;
133        }
134        // Some other error, throw exception
135        jniThrowIOException(env, errno);
136        return JNI_FALSE;
137    }
138    return JNI_TRUE;
139}
140
141static const JNINativeMethod methods[] = {
142    {"native_open",  "(Ljava/lang/String;I)Ljava/io/FileDescriptor;", (void*)android_os_MemoryFile_open},
143    {"native_mmap",  "(Ljava/io/FileDescriptor;II)I", (void*)android_os_MemoryFile_mmap},
144    {"native_munmap", "(II)V", (void*)android_os_MemoryFile_munmap},
145    {"native_close", "(Ljava/io/FileDescriptor;)V", (void*)android_os_MemoryFile_close},
146    {"native_read",  "(Ljava/io/FileDescriptor;I[BIIIZ)I", (void*)android_os_MemoryFile_read},
147    {"native_write", "(Ljava/io/FileDescriptor;I[BIIIZ)V", (void*)android_os_MemoryFile_write},
148    {"native_pin",   "(Ljava/io/FileDescriptor;Z)V", (void*)android_os_MemoryFile_pin},
149    {"native_is_ashmem_region", "(Ljava/io/FileDescriptor;)Z",
150            (void*)android_os_MemoryFile_is_ashmem_region}
151};
152
153static const char* const kClassPathName = "android/os/MemoryFile";
154
155int register_android_os_MemoryFile(JNIEnv* env)
156{
157    jclass clazz;
158
159    clazz = env->FindClass(kClassPathName);
160    LOG_FATAL_IF(clazz == NULL, "Unable to find class android.os.FileUtils");
161
162    return AndroidRuntime::registerNativeMethods(
163        env, kClassPathName,
164        methods, NELEM(methods));
165}
166
167}
168