mirror of
https://github.com/ClassiCube/ClassiCube.git
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124 lines
2.9 KiB
C#
124 lines
2.9 KiB
C#
// Copyright 2014-2017 ClassicalSharp | Licensed under BSD-3
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using System;
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using System.IO;
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namespace ClassicalSharp.Network {
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internal class GZipHeaderReader {
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enum State {
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Header1, Header2, CompressionMethod, Flags,
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LastModifiedTime, CompressionFlags, OperatingSystem,
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HeaderChecksum, Filename, Comment, Done,
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}
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State state = State.Header1;
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public bool done;
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int flags;
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int partsRead;
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public bool ReadHeader(Stream s) {
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switch (state) {
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case State.Header1:
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if (!ReadAndCheckHeaderByte(s, 0x1F))
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return false;
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goto case State.Header2;
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case State.Header2:
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if (!ReadAndCheckHeaderByte(s, 0x8B))
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return false;
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goto case State.CompressionMethod;
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case State.CompressionMethod:
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if (!ReadAndCheckHeaderByte(s, 0x08))
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return false;
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goto case State.Flags;
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case State.Flags:
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if (!ReadHeaderByte(s, out flags))
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return false;
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if ((flags & 0x04) != 0)
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throw new NotSupportedException("Unsupported gzip flags: " + flags);
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goto case State.LastModifiedTime;
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case State.LastModifiedTime:
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for (; partsRead < 4; partsRead++) {
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int part = s.ReadByte();
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if (part == -1)
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return false;
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}
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partsRead = 0;
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state = State.CompressionFlags;
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goto case State.CompressionFlags;
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case State.CompressionFlags:
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int comFlags;
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if (!ReadHeaderByte(s, out comFlags))
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return false;
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goto case State.OperatingSystem;
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case State.OperatingSystem:
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int os;
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if (!ReadHeaderByte(s, out os))
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return false;
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goto case State.Filename;
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case State.Filename:
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if ((flags & 0x08) != 0) {
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for (; ;) {
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int part = s.ReadByte();
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if (part == -1) return false;
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if (part == 0) break;
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}
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}
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state = State.Comment;
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goto case State.Comment;
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case State.Comment:
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if ((flags & 0x10) != 0) {
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for (; ;) {
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int part = s.ReadByte();
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if (part == -1) return false;
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if (part == 0) break;
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}
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}
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state = State.HeaderChecksum;
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goto case State.HeaderChecksum;
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case State.HeaderChecksum:
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if ((flags & 0x02) != 0) {
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for (; partsRead < 2; partsRead++) {
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int part = s.ReadByte();
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if (part == -1)
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return false;
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}
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}
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partsRead = 0;
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state = State.Done;
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done = true;
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return true;
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}
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return true;
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}
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bool ReadAndCheckHeaderByte(Stream s, byte expected) {
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int value;
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if (!ReadHeaderByte(s, out value))
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return false;
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if (value != expected)
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throw new InvalidDataException("Unepxected constant in GZip header. (" + expected + "-" + value + ")");
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return true;
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}
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bool ReadHeaderByte(Stream s, out int value) {
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value = s.ReadByte();
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if (value == -1)
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return false;
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state++;
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return true;
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}
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}
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} |