1/*
2 * Copyright (C) 2014 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 com.android.internal.util;
18
19import libcore.io.Streams;
20
21import java.io.IOException;
22import java.io.InputStream;
23
24/**
25 * Reads exact number of bytes from wrapped stream, returning EOF once those
26 * bytes have been read.
27 */
28public class SizedInputStream extends InputStream {
29    private final InputStream mWrapped;
30    private long mLength;
31
32    public SizedInputStream(InputStream wrapped, long length) {
33        mWrapped = wrapped;
34        mLength = length;
35    }
36
37    @Override
38    public void close() throws IOException {
39        super.close();
40        mWrapped.close();
41    }
42
43    @Override
44    public int read() throws IOException {
45        return Streams.readSingleByte(this);
46    }
47
48    @Override
49    public int read(byte[] buffer, int byteOffset, int byteCount) throws IOException {
50        if (mLength <= 0) {
51            return -1;
52        } else if (byteCount > mLength) {
53            byteCount = (int) mLength;
54        }
55
56        final int n = mWrapped.read(buffer, byteOffset, byteCount);
57        if (n == -1) {
58            if (mLength > 0) {
59                throw new IOException("Unexpected EOF; expected " + mLength + " more bytes");
60            }
61        } else {
62            mLength -= n;
63        }
64        return n;
65    }
66}
67