public void DecodeFile(IFileReader fileReader, IFileWriter fileWriter)
{
if (fileReader == null)
{
throw new ArgumentNullException(nameof(fileReader));
}
if (fileWriter == null)
{
throw new ArgumentNullException(nameof(fileWriter));
}
InterpretHeader(fileReader);
var firstIndex = fileReader.ReadBits(numberOfBitsForIndex);
var firstString = lzWDictionary.GetStringByIndex(firstIndex);
firstString.WriteToFile(fileWriter);
var lastString = firstString;
while (!fileReader.ReachedEndOfFile && fileReader.BitsLeft >= numberOfBitsForIndex)
{
var currentIndex = fileReader.ReadBits(numberOfBitsForIndex);
string currentString;
if (lzWDictionary.ContainsIndex(currentIndex))
{
currentString = lzWDictionary.GetStringByIndex(currentIndex);
var dictionaryNewString = lastString + currentString[0];
lzWDictionary.Add(dictionaryNewString);
}
else
{
var dictionaryNewString = lastString + lastString[0];
lzWDictionary.Add(dictionaryNewString);
currentString = lzWDictionary.GetStringByIndex(currentIndex);
}
currentString.WriteToFile(fileWriter);
lastString = currentString;
}
}
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();
}