public void TestBasic1()
{
var freqs = new uint[] { 10, 30, 10 }; // Symbol 0 occurs 10x, symbol 1 occurs 30x, symbol 2 occurs 10x
var ms = new MemoryStream();
var context = new ArithmeticSymbolArrayContext(freqs);
var encoder = new ArithmeticCodingWriter(ms, context);
for (int i = 0; i < 10; i++)
{
encoder.WriteSymbol(1);
encoder.WriteSymbol(0);
encoder.WriteSymbol(1);
encoder.WriteSymbol(2);
encoder.WriteSymbol(1);
}
encoder.Finalize();
ms.WriteByte(47);
ms = new MemoryStream(ms.ToArray());
var decoder = new ArithmeticCodingReader(ms, context);
for (int i = 0; i < 10; i++)
{
Assert.AreEqual(1, decoder.ReadSymbol());
Assert.AreEqual(0, decoder.ReadSymbol());
Assert.AreEqual(1, decoder.ReadSymbol());
Assert.AreEqual(2, decoder.ReadSymbol());
Assert.AreEqual(1, decoder.ReadSymbol());
}
decoder.Finalize();
Assert.AreEqual(47, ms.ReadByte());
}
public void TestArrayContext()
{
int count = 1000;
var ctx = new ArithmeticSymbolArrayContext(count);
Assert.AreEqual(0UL, ctx.GetSymbolFrequency(-1000));
Assert.AreEqual(0UL, ctx.GetSymbolFrequency(-1));
Assert.AreEqual(1UL, ctx.GetSymbolFrequency(0));
Assert.AreEqual(1UL, ctx.GetSymbolFrequency(1));
Assert.AreEqual(0UL, ctx.GetSymbolPosition(0));
Assert.AreEqual(1UL, ctx.GetSymbolPosition(1));
Assert.AreEqual(1UL, ctx.GetSymbolFrequency(count - 1));
Assert.AreEqual(0UL, ctx.GetSymbolFrequency(count));
Assert.AreEqual(0UL, ctx.GetSymbolFrequency(count + 1000));
ctx = new ArithmeticSymbolArrayContext(new uint[] { 1, 1, 1, 1 });
ctx.SetSymbolFrequency(1, 5);
ctx.SetSymbolFrequency(3, 5);
Assert.AreEqual(6UL, ctx.GetSymbolPosition(2));
}
public void TestAdvanced()
{
_rnd = new Random(12345);
int max = 1000;
var symbols = Enumerable.Range(1, 100_000).Select(_ => _rnd.Next(0, max)).ToArray();
var mainContext = new ArithmeticSymbolArrayContext(max, _ => 1);
var secondaryContext = new ArithmeticSymbolArrayContext(new uint[] { 3, 2, 1 });
var ms = new MemoryStream();
var encoder = new ArithmeticCodingWriter(ms, mainContext);
writeInt(ms, 12345);
for (int i = 0; i < symbols.Length; i++)
{
encoder.WriteSymbol(symbols[i]);
mainContext.IncrementSymbolFrequency(symbols[i]);
encoder.SetContext(mainContext);
if (i % 1000 == 999)
{
encoder.SetContext(secondaryContext);
encoder.WriteSymbol(0);
encoder.WriteSymbol(1);
encoder.WriteSymbol(0);
encoder.WriteSymbol(1);
encoder.WriteSymbol(0);
encoder.WriteSymbol(2);
encoder.SetContext(mainContext);
}
}
encoder.Finalize(false);
writeInt(ms, -54321); // to verify that the stream ends where we think it ends
var encoded = ms.ToArray();
ms = new MemoryStream(encoded);
mainContext = new ArithmeticSymbolArrayContext(max, _ => 1); // reset frequencies
Assert.AreEqual(12345, readInt(ms));
var decoder = new ArithmeticCodingReader(ms, mainContext);
for (int i = 0; i < symbols.Length; i++)
{
var sym = decoder.ReadSymbol();
Assert.AreEqual(symbols[i], sym);
mainContext.IncrementSymbolFrequency(sym);
decoder.SetContext(mainContext);
if (i % 1000 == 999)
{
decoder.SetContext(secondaryContext);
Assert.AreEqual(0, decoder.ReadSymbol());
Assert.AreEqual(1, decoder.ReadSymbol());
Assert.AreEqual(0, decoder.ReadSymbol());
Assert.AreEqual(1, decoder.ReadSymbol());
Assert.AreEqual(0, decoder.ReadSymbol());
Assert.AreEqual(2, decoder.ReadSymbol());
decoder.SetContext(mainContext);
}
}
decoder.Finalize(false);
Assert.AreEqual(-54321, readInt(ms));
}
