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
17package java.nio;
18
19import java.io.FileDescriptor;
20import java.io.IOException;
21import libcore.io.Libcore;
22import libcore.io.ErrnoException;
23
24/**
25 * Used to implement java.nio read(ByteBuffer[])/write(ByteBuffer[]) operations as POSIX readv(2)
26 * and writev(2) calls.
27 */
28final 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
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
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
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
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