public async Task <byte[]> ExtractAsync(HttpZipEntry entry)
{
try
{
// MAKE A HTTP CALL USING THE RANGE HEADER
var fileHeaderLength = 30 + entry.FileNameLength + entry.ExtraFieldLength;
var rangeStart = entry.FileOffset;
var rangeFinish = entry.FileOffset + fileHeaderLength + entry.CompressedSize;
this.httpClient.DefaultRequestHeaders.Range = new RangeHeaderValue(rangeStart, rangeFinish);
var byteArray = await httpClient.GetByteArrayAsync(this.httpUrl);
// LOCATE DATA BOUNDS
// https://en.wikipedia.org/wiki/Zip_(file_format)#Local_file_header
var fileSignature = BitConverter.ToInt32(byteArray, 0);
var bitFlag = BitConverter.ToInt16(byteArray, 6);
var compressionMethod = BitConverter.ToInt16(byteArray, 8);
var crc = BitConverter.ToInt32(byteArray, 14);
var compressedSize = BitConverter.ToInt32(byteArray, 18);
var uncompressedSize = BitConverter.ToInt32(byteArray, 22);
var fileNameLength = BitConverter.ToInt16(byteArray, 26); // (n)
var extraFieldLength = BitConverter.ToInt16(byteArray, 28); // (m)
var fileDataOffset = 30 + fileNameLength + extraFieldLength;
var fileDataSize = entry.CompressedSize;
// EXTRACT DATA BUFFER
var fileDataBuffer = new byte[fileDataSize];
Array.Copy(byteArray, fileDataOffset, fileDataBuffer, 0, fileDataSize);
Array.Clear(byteArray, 0, byteArray.Length);
byteArray = null;
/* STORED */
if (entry.CompressionMethod == 0)
{
return(fileDataBuffer);
}
/* DEFLATED */
if (entry.CompressionMethod == 8)
{
var deflatedArray = new byte[entry.UncompressedSize];
using (var compressedStream = new MemoryStream(fileDataBuffer))
{
using (var deflateStream = new System.IO.Compression.DeflateStream(compressedStream, CompressionMode.Decompress))
{
await deflateStream.ReadAsync(deflatedArray, 0, deflatedArray.Length);
}
/*
* using (var deflatedStream = new MemoryStream())
* {
* var deflater = new System.IO.Compression.DeflateStream(compressedStream, CompressionMode.Decompress, true);
*
* byte[] buffer = new byte[1024];
* var bytesPending = entry.UncompressedSize;
* while (bytesPending > 0)
* {
* var bytesRead = deflater.Read(buffer, 0, (int)Math.Min(bytesPending, buffer.Length));
* deflatedStream.Write(buffer, 0, bytesRead);
* bytesPending -= (uint)bytesRead;
* if (bytesRead == 0) { break; }
* }
*
* deflatedArray = deflatedStream.ToArray();
* }
*/
}
return(deflatedArray);
}
// NOT SUPPORTED COMPRESSION METHOD
throw new NotSupportedException($"The compression method [{entry.CompressionMethod}] is not supported");
}
catch (Exception) { throw; }
}