static unsafe void HgtTest()
{
const string TestFile = "../../../N00E032.hgt";
if (!File.Exists(TestFile))
{
throw new FileNotFoundException(TestFile);
}
var raw = File.ReadAllBytes(TestFile);
var rawValues = Enumerable.Range(0, raw.Length / 2).Select(i => (short)(ushort)(raw[i * 2] << 8 | raw[i * 2 + 1])).ToArray();
Console.WriteLine();
// --- Raw-Data ---
Console.WriteLine(" Raw Size: {0:N0} Bytes", raw.Length);
Console.WriteLine();
// --- GZip (level 9) ---
Console.WriteLine(" Gnu-Zip: {0:N0} Bytes", GZipTest(raw));
Console.WriteLine();
// --- Delta-GZip ---
var deltaValues = new short[rawValues.Length];
deltaValues[0] = rawValues[0];
for (int i = 1; i < deltaValues.Length; i++)
{
deltaValues[i] = (short)(rawValues[i] - rawValues[i - 1]);
}
var deltaData = new byte[raw.Length];
fixed(byte *deltaDataP = deltaData)
fixed(short *deltaValuesP = deltaValues)
{
OutputWindow.CopyBytes((byte *)deltaValuesP, deltaDataP, deltaData.Length);
}
Console.WriteLine(" Delta-GZip: {0:N0} Bytes", GZipTest(deltaData));
Console.WriteLine();
// --- Protobuffer-Delta-GZip ---
int outputProtoBytes = 0;
var protoBuf = new byte[deltaData.Length * 2];
foreach (var val in deltaValues)
{
uint u = (uint)(val << 1 ^ val >> 31); // ZigZag
if (u >= 128)
{
protoBuf[outputProtoBytes++] = (byte)(128 | u & 127);
if ((u >> 7) >= 128)
{
protoBuf[outputProtoBytes++] = (byte)(128 | u >> 7 & 127);
if ((u >> 14) >= 128)
{
throw new IndexOutOfRangeException();
}
protoBuf[outputProtoBytes++] = (byte)(u >> 14);
}
else
{
protoBuf[outputProtoBytes++] = (byte)(u >> 7);
}
}
else
{
protoBuf[outputProtoBytes++] = (byte)u;
}
}
Array.Resize(ref protoBuf, outputProtoBytes);
Console.WriteLine(" Proto-GZip: {0:N0} Bytes", GZipTest(protoBuf));
Console.WriteLine();
// --- Stats ---
var stats = string.Join("\r\n", rawValues.GroupBy(x => x).OrderBy(x => - x.Count()).Select(x => x.Key + ": " + x.Count()));
var statsDelta = string.Join("\r\n", deltaValues.GroupBy(x => x).OrderBy(x => - x.Count()).Select(x => x.Key + ": " + x.Count()));
}