public void ConstructorSetsPublicPropertiesAsExpected()
{
const int limit = 300;
const OnFullDictionaryOption onFullDictionaryOption = OnFullDictionaryOption.Empty;
var lzWDictionary = new LzWDictionary(limit, onFullDictionaryOption);
Assert.AreEqual(limit, lzWDictionary.Limit);
Assert.AreEqual(onFullDictionaryOption, lzWDictionary.OnFullDictionaryOption);
}
private void InterpretHeader(IFileReader fileReader)
{
numberOfBitsForIndex = (byte)fileReader.ReadBits(4);
var onFullDictionaryOption = fileReader.ReadBit()
? OnFullDictionaryOption.Freeze
: OnFullDictionaryOption.Empty;
lzWDictionary = new LzWDictionary((int)Math.Pow(2, numberOfBitsForIndex) - 1, onFullDictionaryOption);
}
public void ContainsIndexReturnsTrueForValuesFrom0To255()
{
var allAreContained = true;
var lzWDictionary = new LzWDictionary(258, OnFullDictionaryOption.Empty);
for (uint i = 0; i < 256; i++)
{
if (!lzWDictionary.ContainsIndex(i))
{
allAreContained = false;
break;
}
}
Assert.IsTrue(allAreContained);
}
public void ContainsStringReturnsTrueForStringsComposedOfASingleCharacter()
{
var allAreContained = true;
var lzWDictionary = new LzWDictionary(258, OnFullDictionaryOption.Empty);
for (int i = 0; i < 256; i++)
{
var str = ((char)((byte)i)).ToString();
if (!lzWDictionary.ContainsString(str))
{
allAreContained = false;
break;
}
}
Assert.IsTrue(allAreContained);
}
public void ConstructorThrowsArgumentExceptionForLimitSmallerThan256()
{
var lzWDictionary = new LzWDictionary(200, OnFullDictionaryOption.Empty);
}
public void EncodeFile(IFileReader fileReader, IFileWriter fileWriter, OnFullDictionaryOption onFullDictionaryOption, int numberOfBitsIndex)
{
if (fileReader == null)
{
throw new ArgumentNullException(nameof(fileReader));
}
if (fileWriter == null)
{
throw new ArgumentNullException(nameof(fileWriter));
}
if (numberOfBitsIndex < 9 || numberOfBitsIndex > 15)
{
throw new ArgumentException($"{nameof(numberOfBitsIndex)} must be at least 9, and at most 15");
}
WriteHeader(fileWriter, onFullDictionaryOption, numberOfBitsIndex);
IndexesFromLastRun.Clear();
LzWDictionary = new LzWDictionary((int)Math.Pow(2, numberOfBitsIndex) - 1, onFullDictionaryOption);
var lastCharacter = (char)fileReader.ReadBits(8);
var shouldStop = false;
while (true)
{
var currentString = lastCharacter.ToString();
uint lastIndex = 0;
if (shouldStop)
{
break;
}
while (true)
{
if (LzWDictionary.ContainsString(currentString))
{
lastIndex = LzWDictionary.GetIndexByString(currentString);
if (shouldStop)
{
fileWriter.WriteValueOnBits(lastIndex, (byte)numberOfBitsIndex);
IndexesFromLastRun.Add(lastIndex);
break;
}
}
else
{
LzWDictionary.Add(currentString);
fileWriter.WriteValueOnBits(lastIndex, (byte)numberOfBitsIndex);
IndexesFromLastRun.Add(lastIndex);
break;
}
if (!fileReader.ReachedEndOfFile)
{
var readByte = (byte)fileReader.ReadBits(8);
currentString += (char)readByte;
lastCharacter = (char)readByte;
}
else
{
shouldStop = true;
}
}
}
fileWriter.Flush();
}
