| 1 | // Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. |
| 2 | |
| 3 | namespace WixToolset.Dtf.Compression |
| 4 | { |
| 5 | using System; |
| 6 | using System.IO; |
| 7 | |
| 8 | /// <summary> |
| 9 | /// Wraps a source stream and offsets all read/write/seek calls by a given value. |
| 10 | /// </summary> |
| 11 | /// <remarks> |
| 12 | /// This class is used to trick archive an packing or unpacking process |
| 13 | /// into reading or writing at an offset into a file, primarily for |
| 14 | /// self-extracting packages. |
| 15 | /// </remarks> |
| 16 | public class OffsetStream : Stream |
| 17 | { |
| 18 | private Stream source; |
| 19 | private long sourceOffset; |
| 20 | |
| 21 | /// <summary> |
| 22 | /// Creates a new OffsetStream instance from a source stream |
| 23 | /// and using a specified offset. |
| 24 | /// </summary> |
| 25 | /// <param name="source">Underlying stream for which all calls will be offset.</param> |
| 26 | /// <param name="offset">Positive or negative number of bytes to offset.</param> |
| 27 | public OffsetStream(Stream source, long offset) |
| 28 | { |
| 29 | if (source == null) |
| 30 | { |
| 31 | throw new ArgumentNullException("source"); |
| 32 | } |
| 33 | |
| 34 | this.source = source; |
| 35 | this.sourceOffset = offset; |
| 36 | |
| 37 | this.source.Seek(this.sourceOffset, SeekOrigin.Current); |
| 38 | } |
| 39 | |
| 40 | /// <summary> |
| 41 | /// Gets the underlying stream that this OffsetStream calls into. |
| 42 | /// </summary> |
| 43 | public Stream Source |
| 44 | { |
| 45 | get { return this.source; } |
| 46 | } |
| 47 | |
| 48 | /// <summary> |
| 49 | /// Gets the number of bytes to offset all calls before |
| 50 | /// redirecting to the underlying stream. |
| 51 | /// </summary> |
| 52 | public long Offset |
| 53 | { |
| 54 | get { return this.sourceOffset; } |
| 55 | } |
| 56 | |
| 57 | /// <summary> |
| 58 | /// Gets a value indicating whether the source stream supports reading. |
| 59 | /// </summary> |
| 60 | /// <value>true if the stream supports reading; otherwise, false.</value> |
| 61 | public override bool CanRead |
| 62 | { |
| 63 | get |
| 64 | { |
| 65 | return this.source.CanRead; |
| 66 | } |
| 67 | } |
| 68 | |
| 69 | /// <summary> |
| 70 | /// Gets a value indicating whether the source stream supports writing. |
| 71 | /// </summary> |
| 72 | /// <value>true if the stream supports writing; otherwise, false.</value> |
| 73 | public override bool CanWrite |
| 74 | { |
| 75 | get |
| 76 | { |
| 77 | return this.source.CanWrite; |
| 78 | } |
| 79 | } |
| 80 | |
| 81 | /// <summary> |
| 82 | /// Gets a value indicating whether the source stream supports seeking. |
| 83 | /// </summary> |
| 84 | /// <value>true if the stream supports seeking; otherwise, false.</value> |
| 85 | public override bool CanSeek |
| 86 | { |
| 87 | get |
| 88 | { |
| 89 | return this.source.CanSeek; |
| 90 | } |
| 91 | } |
| 92 | |
| 93 | /// <summary> |
| 94 | /// Gets the effective length of the stream, which is equal to |
| 95 | /// the length of the source stream minus the offset. |
| 96 | /// </summary> |
| 97 | public override long Length |
| 98 | { |
| 99 | get { return this.source.Length - this.sourceOffset; } |
| 100 | } |
| 101 | |
| 102 | /// <summary> |
| 103 | /// Gets or sets the effective position of the stream, which |
| 104 | /// is equal to the position of the source stream minus the offset. |
| 105 | /// </summary> |
| 106 | public override long Position |
| 107 | { |
| 108 | get { return this.source.Position - this.sourceOffset; } |
| 109 | set { this.source.Position = value + this.sourceOffset; } |
| 110 | } |
| 111 | |
| 112 | /// <summary> |
| 113 | /// Reads a sequence of bytes from the source stream and advances |
| 114 | /// the position within the stream by the number of bytes read. |
| 115 | /// </summary> |
| 116 | /// <param name="buffer">An array of bytes. When this method returns, the buffer |
| 117 | /// contains the specified byte array with the values between offset and |
| 118 | /// (offset + count - 1) replaced by the bytes read from the current source.</param> |
| 119 | /// <param name="offset">The zero-based byte offset in buffer at which to begin |
| 120 | /// storing the data read from the current stream.</param> |
| 121 | /// <param name="count">The maximum number of bytes to be read from the current stream.</param> |
| 122 | /// <returns>The total number of bytes read into the buffer. This can be less |
| 123 | /// than the number of bytes requested if that many bytes are not currently available, |
| 124 | /// or zero (0) if the end of the stream has been reached.</returns> |
| 125 | public override int Read(byte[] buffer, int offset, int count) |
| 126 | { |
| 127 | return this.source.Read(buffer, offset, count); |
| 128 | } |
| 129 | |
| 130 | /// <summary> |
| 131 | /// Writes a sequence of bytes to the source stream and advances the |
| 132 | /// current position within this stream by the number of bytes written. |
| 133 | /// </summary> |
| 134 | /// <param name="buffer">An array of bytes. This method copies count |
| 135 | /// bytes from buffer to the current stream.</param> |
| 136 | /// <param name="offset">The zero-based byte offset in buffer at which |
| 137 | /// to begin copying bytes to the current stream.</param> |
| 138 | /// <param name="count">The number of bytes to be written to the |
| 139 | /// current stream.</param> |
| 140 | public override void Write(byte[] buffer, int offset, int count) |
| 141 | { |
| 142 | this.source.Write(buffer, offset, count); |
| 143 | } |
| 144 | |
| 145 | /// <summary> |
| 146 | /// Reads a byte from the stream and advances the position within the |
| 147 | /// source stream by one byte, or returns -1 if at the end of the stream. |
| 148 | /// </summary> |
| 149 | /// <returns>The unsigned byte cast to an Int32, or -1 if at the |
| 150 | /// end of the stream.</returns> |
| 151 | public override int ReadByte() |
| 152 | { |
| 153 | return this.source.ReadByte(); |
| 154 | } |
| 155 | |
| 156 | /// <summary> |
| 157 | /// Writes a byte to the current position in the source stream and |
| 158 | /// advances the position within the stream by one byte. |
| 159 | /// </summary> |
| 160 | /// <param name="value">The byte to write to the stream.</param> |
| 161 | public override void WriteByte(byte value) |
| 162 | { |
| 163 | this.source.WriteByte(value); |
| 164 | } |
| 165 | |
| 166 | /// <summary> |
| 167 | /// Flushes the source stream. |
| 168 | /// </summary> |
| 169 | public override void Flush() |
| 170 | { |
| 171 | this.source.Flush(); |
| 172 | } |
| 173 | |
| 174 | /// <summary> |
| 175 | /// Sets the position within the current stream, which is |
| 176 | /// equal to the position within the source stream minus the offset. |
| 177 | /// </summary> |
| 178 | /// <param name="offset">A byte offset relative to the origin parameter.</param> |
| 179 | /// <param name="origin">A value of type SeekOrigin indicating |
| 180 | /// the reference point used to obtain the new position.</param> |
| 181 | /// <returns>The new position within the current stream.</returns> |
| 182 | public override long Seek(long offset, SeekOrigin origin) |
| 183 | { |
| 184 | return this.source.Seek(offset + (origin == SeekOrigin.Begin ? this.sourceOffset : 0), origin) - this.sourceOffset; |
| 185 | } |
| 186 | |
| 187 | /// <summary> |
| 188 | /// Sets the effective length of the stream, which is equal to |
| 189 | /// the length of the source stream minus the offset. |
| 190 | /// </summary> |
| 191 | /// <param name="value">The desired length of the |
| 192 | /// current stream in bytes.</param> |
| 193 | public override void SetLength(long value) |
| 194 | { |
| 195 | this.source.SetLength(value + this.sourceOffset); |
| 196 | } |
| 197 | |
| 198 | /// <summary> |
| 199 | /// Closes the underlying stream. |
| 200 | /// </summary> |
| 201 | public override void Close() |
| 202 | { |
| 203 | this.source.Close(); |
| 204 | } |
| 205 | } |
| 206 | } |