1 /*
2  * Copyright (C) 2011 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 java.nio;
18 
19 import android.system.ErrnoException;
20 import java.io.FileDescriptor;
21 import java.io.IOException;
22 import libcore.io.Libcore;
23 
24 /**
25  * Used to implement java.nio read(ByteBuffer[])/write(ByteBuffer[]) operations as POSIX readv(2)
26  * and writev(2) calls.
27  */
28 final class IoVec {
29     enum Direction { READV, WRITEV };
30 
31     private final ByteBuffer[] byteBuffers;
32     private final int offset;
33     private final int bufferCount;
34 
35     private final Object[] ioBuffers;
36     private final int[] offsets;
37     private final int[] byteCounts;
38 
39     private final Direction direction;
40 
IoVec(ByteBuffer[] byteBuffers, int offset, int bufferCount, Direction direction)41     IoVec(ByteBuffer[] byteBuffers, int offset, int bufferCount, Direction direction) {
42         this.byteBuffers = byteBuffers;
43         this.offset = offset;
44         this.bufferCount = bufferCount;
45         this.direction = direction;
46         this.ioBuffers = new Object[bufferCount];
47         this.offsets = new int[bufferCount];
48         this.byteCounts = new int[bufferCount];
49     }
50 
init()51     int init() {
52         int totalRemaining = 0;
53         for (int i = 0; i < bufferCount; ++i) {
54             ByteBuffer b = byteBuffers[i + offset];
55             if (direction == Direction.READV) {
56                 b.checkWritable();
57             }
58             int remaining = b.remaining();
59             if (b.isDirect()) {
60                 ioBuffers[i] = b;
61                 offsets[i] = b.position();
62             } else {
63                 ioBuffers[i] = NioUtils.unsafeArray(b);
64                 offsets[i] = NioUtils.unsafeArrayOffset(b) + b.position();
65             }
66             byteCounts[i] = remaining;
67             totalRemaining += remaining;
68         }
69         return totalRemaining;
70     }
71 
doTransfer(FileDescriptor fd)72     int doTransfer(FileDescriptor fd) throws IOException {
73         try {
74             if (direction == Direction.READV) {
75                 int result = Libcore.os.readv(fd, ioBuffers, offsets, byteCounts);
76                 if (result == 0) {
77                     result = -1;
78                 }
79                 return result;
80             } else {
81                 return Libcore.os.writev(fd, ioBuffers, offsets, byteCounts);
82             }
83         } catch (ErrnoException errnoException) {
84             throw errnoException.rethrowAsIOException();
85         }
86     }
87 
didTransfer(int byteCount)88     void didTransfer(int byteCount) {
89         for (int i = 0; byteCount > 0 && i < bufferCount; ++i) {
90             ByteBuffer b = byteBuffers[i + offset];
91             if (byteCounts[i] < byteCount) {
92                 b.position(b.limit());
93                 byteCount -= byteCounts[i];
94             } else {
95                 b.position((direction == Direction.WRITEV ? b.position() : 0) + byteCount);
96                 byteCount = 0;
97             }
98         }
99     }
100 }
101