public void TryToFillSearchBufferBasedOnLz77Token(Lz77Buffer lz77Buffer, Lz77Token lz77Token)
{
if (lz77Buffer == null)
{
throw new ArgumentNullException(nameof(lz77Buffer));
}
if (lz77Token == null)
{
throw new ArgumentNullException(nameof(lz77Token));
}
for (int index = 0; index < lz77Token.Length + 1; index++)
{
if (index > lz77Buffer.LookAheadBuffer.Count - 1)
{
break;
}
if (lz77Buffer.SearchBuffer.Count >= lz77Buffer.SearchBuffer.Capacity)
{
lz77Buffer.SearchBuffer.RemoveAt(0);
}
lz77Buffer.SearchBuffer.Add(lz77Buffer.LookAheadBuffer[index]);
}
}
public static Lz77Buffer GetLz77Buffer6()
{
var lz77Buffer = new Lz77Buffer(4, 4);
lz77Buffer.LookAheadBuffer.Add(21);
lz77Buffer.LookAheadBuffer.Add(22);
lz77Buffer.LookAheadBuffer.Add(23);
lz77Buffer.LookAheadBuffer.Add(24);
lz77Buffer.LookAheadBuffer.Add(25);
lz77Buffer.LookAheadBuffer.Add(26);
lz77Buffer.LookAheadBuffer.Add(27);
lz77Buffer.LookAheadBuffer.Add(28);
lz77Buffer.LookAheadBuffer.Add(31);
lz77Buffer.SearchBuffer.Add(20);
lz77Buffer.SearchBuffer.Add(21);
lz77Buffer.SearchBuffer.Add(22);
lz77Buffer.SearchBuffer.Add(23);
lz77Buffer.SearchBuffer.Add(24);
lz77Buffer.SearchBuffer.Add(25);
lz77Buffer.SearchBuffer.Add(26);
lz77Buffer.SearchBuffer.Add(27);
lz77Buffer.SearchBuffer.Add(28);
return(lz77Buffer);
}
public static Lz77Buffer GetLz77Buffer1()
{
var lz77Buffer = new Lz77Buffer(2, 2);
lz77Buffer.LookAheadBuffer.Add(20);
lz77Buffer.LookAheadBuffer.Add(21);
return(lz77Buffer);
}
public void Setup()
{
lz77BufferManager = new Lz77BufferManager();
lz77Buffer = Constants.GetLz77Buffer1();
lz77Token = Constants.ExpectedTokenForLz77Buffer1();
fileReaderMock = new Mock <IFileReader>();
SetupFileReaderMock();
}
public void ConstructorSetsLookAheadBufferAsExpected()
{
var lz77Buffer = new Lz77Buffer(offset, length);
var lookAheadBuffer = lz77Buffer.LookAheadBuffer;
Assert.IsNotNull(lookAheadBuffer);
Assert.AreEqual(0, lookAheadBuffer.Count);
Assert.AreEqual(Math.Pow(2, length) - 1, lookAheadBuffer.Capacity);
}
public void ConstructorSetsSearchBufferAsExpected()
{
var lz77Buffer = new Lz77Buffer(offset, length);
var searchBuffer = lz77Buffer.SearchBuffer;
Assert.IsNotNull(searchBuffer);
Assert.AreEqual(0, searchBuffer.Count);
Assert.AreEqual(Math.Pow(2, offset) - 1, searchBuffer.Capacity);
}
public Lz77Encoder(ILz77TokenExtractor lz77TokenExtractor, ILz77BufferManager lz77BufferManager, ILz77TokenWriter lz77TokenWriter)
{
this.lz77TokenExtractor = lz77TokenExtractor;
this.lz77BufferManager = lz77BufferManager;
this.lz77TokenWriter = lz77TokenWriter;
Lz77Buffer = new Lz77Buffer(4, 4);
TokensFromPreviousRun = new List <Lz77Token>();
}
public static Lz77Buffer GetLz77Buffer3()
{
var lz77Buffer = new Lz77Buffer(3, 3);
lz77Buffer.LookAheadBuffer.Add(20);
lz77Buffer.LookAheadBuffer.Add(21);
lz77Buffer.LookAheadBuffer.Add(22);
lz77Buffer.SearchBuffer.Add(19);
lz77Buffer.SearchBuffer.Add(20);
lz77Buffer.SearchBuffer.Add(21);
return(lz77Buffer);
}
private bool Lz77BufferContainsGivenSequence(Lz77Buffer lz77Buffer, List <byte> sequence, int indexOfFirstByteFoundInSearchBuffer, out byte byteThatWasNotContained)
{
// TODO: Maybe implement properly at some other time
//var lookAheadBufferIndex = 0;
for (int index = 0; index < sequence.Count; index++)
{
var searchBufferIndex = indexOfFirstByteFoundInSearchBuffer + index;
var contains = true;
if (searchBufferIndex > lz77Buffer.SearchBuffer.Count - 1)
{
contains = false;
}
else
{
if (searchBufferIndex >= 0)
{
if (lz77Buffer.SearchBuffer[searchBufferIndex] != sequence[index])
{
contains = false;
}
}
else
{
contains = false;
}
// TODO: Maybe implement properly at some other time
//else
//{
// if (Lz77Buffer.LookAheadBuffer[lookAheadBufferIndex] != sequence[index])
// {
// contains = false;
// }
// lookAheadBufferIndex++;
//}
}
if (!contains)
{
byteThatWasNotContained = sequence[index];
return(false);
}
}
byteThatWasNotContained = 0;
return(true);
}
public void EncodeFile(IFileReader fileReader, IFileWriter fileWriter, int bitsForOffset, int bitsForLength)
{
if (fileReader == null)
{
throw new ArgumentNullException(nameof(fileReader));
}
if (fileWriter == null)
{
throw new ArgumentNullException(nameof(fileWriter));
}
if (bitsForOffset < 3 || bitsForOffset > 15)
{
throw new ArgumentException($"{nameof(bitsForOffset)} should be between 3 and 15");
}
if (bitsForLength < 2 || bitsForLength > 7)
{
throw new ArgumentException($"{nameof(bitsForLength)} should be between 3 and 15");
}
if (Lz77Buffer.Length != bitsForLength || Lz77Buffer.Offset != bitsForOffset)
{
Lz77Buffer.SetOffsetAndLimit(bitsForLength, bitsForLength);
}
WriteHeader(fileWriter, bitsForOffset, bitsForLength);
TokensFromPreviousRun.Clear();
lz77BufferManager.TryToFillLookAheadBuffer(Lz77Buffer, fileReader);
while (Lz77Buffer.LookAheadBuffer.Count > 0)
{
var lz77Token = lz77TokenExtractor.GetLz77TokenFromLz77Buffer(Lz77Buffer);
lz77BufferManager.TryToFillSearchBufferBasedOnLz77Token(Lz77Buffer, lz77Token);
lz77BufferManager.EmptyLookAheadBufferBasedOnLz77Token(Lz77Buffer, lz77Token);
lz77BufferManager.TryToFillLookAheadBuffer(Lz77Buffer, fileReader);
lz77TokenWriter.WriteToken(lz77Token, fileWriter, bitsForOffset, bitsForLength);
TokensFromPreviousRun.Add(lz77Token);
}
fileWriter.Flush();
}
public void TryToFillLookAheadBuffer(Lz77Buffer lz77Buffer, IFileReader fileReader)
{
if (lz77Buffer == null)
{
throw new ArgumentNullException(nameof(lz77Buffer));
}
if (fileReader == null)
{
throw new ArgumentNullException(nameof(fileReader));
}
while (lz77Buffer.LookAheadBuffer.Count < lz77Buffer.LookAheadBuffer.Capacity && !fileReader.ReachedEndOfFile)
{
lz77Buffer.LookAheadBuffer.Add((byte)fileReader.ReadBits(8));
}
}
private List <int> GetIndexesOfGivenByte(Lz77Buffer lz77Buffer, byte b)
{
if (!lz77Buffer.SearchBuffer.Contains(b))
{
return(new List <int>());
}
var indexes = new List <int>();
for (int index = 0; index < lz77Buffer.SearchBuffer.Count; index++)
{
if (lz77Buffer.SearchBuffer[index] == b)
{
indexes.Add(index);
}
}
return(indexes);
}
public void EmptyLookAheadBufferBasedOnLz77Token(Lz77Buffer lz77Buffer, Lz77Token lz77Token)
{
if (lz77Buffer == null)
{
throw new ArgumentNullException(nameof(lz77Buffer));
}
if (lz77Token == null)
{
throw new ArgumentNullException(nameof(lz77Token));
}
var bytesToRemove = lz77Token.Length + 1;
while (bytesToRemove > 0 && lz77Buffer.LookAheadBuffer.Count > 0)
{
lz77Buffer.LookAheadBuffer.RemoveAt(0);
bytesToRemove--;
}
}
public void ConstructorThrowsArgumentExceptionForOffsetSmallerThanOne()
{
var lz77Buffer = new Lz77Buffer(0, length);
}
public void ConstructorThrowsArgumentExceptionForLengthSmallerThanOne()
{
var lz77Buffer = new Lz77Buffer(offset, -2);
}
public void ConstructorSetsLengthPropertyAsExpected()
{
var lz77Buffer = new Lz77Buffer(offset, length);
Assert.AreEqual(length, lz77Buffer.Length);
}
public Lz77Token GetLz77TokenFromLz77Buffer(Lz77Buffer lz77Buffer)
{
if (lz77Buffer == null)
{
throw new ArgumentNullException(nameof(lz77Buffer));
}
if (lz77Buffer.LookAheadBuffer.Count == 0)
{
throw new ArgumentException("Look ahead buffer shouldn't be empty");
}
var firstByteToLookFor = lz77Buffer.LookAheadBuffer[0];
if (!lz77Buffer.SearchBuffer.Contains(firstByteToLookFor))
{
return(new Lz77Token
{
Byte = firstByteToLookFor,
Length = 0,
Position = 0
});
}
var bytesFoundFinal = 0;
var indexFinal = lz77Buffer.SearchBuffer.Count - 1 - lz77Buffer.SearchBuffer.IndexOf(firstByteToLookFor);
byte byteThatWasNotContainedFinal = 0;
var indexes = GetIndexesOfGivenByte(lz77Buffer, firstByteToLookFor);
foreach (var index in indexes)
{
var bytesFoundInCurrentIteration = 0;
var bytesToLookFor = new List <byte> {
firstByteToLookFor
};
byte byteThatWasNotContained = 0;
while (Lz77BufferContainsGivenSequence(lz77Buffer, bytesToLookFor, index, out byteThatWasNotContained))
{
if (bytesFoundInCurrentIteration >= lz77Buffer.LookAheadBuffer.Count)
{
break;
}
bytesFoundInCurrentIteration++;
if (bytesFoundInCurrentIteration < lz77Buffer.LookAheadBuffer.Count)
{
bytesToLookFor.Add(lz77Buffer.LookAheadBuffer[bytesFoundInCurrentIteration]);
}
else
{
break;
}
}
if (bytesFoundInCurrentIteration >= bytesFoundFinal)
{
bytesFoundFinal = bytesFoundInCurrentIteration;
indexFinal = lz77Buffer.SearchBuffer.Count - 1 - index;
byteThatWasNotContainedFinal = byteThatWasNotContained;
}
}
return(new Lz77Token
{
Byte = byteThatWasNotContainedFinal,
Length = bytesFoundFinal,
Position = indexFinal
});
}
