public void Dispose()
{
if (!this.LeaveHttpClientOpen)
{
this.httpClient.Dispose(); this.httpClient = null;
}
this.directoryData = null;
this.ContentLength = -1;
}
private async Task <bool> LocateDirectoryAsync()
{
try
{
// INITIALIZE
this.directoryData = new HttpZipDirectory {
Offset = -1
};
var secureMargin = 22;
var chunkSize = 256;
var rangeStart = this.ContentLength - secureMargin;
var rangeFinish = this.ContentLength;
// TRY TO FOUND THE CENTRAL DIRECTORY FOUR TIMES SLOWLY INCREASING THE CHUNK SIZE
short tries = 1;
while (this.directoryData.Offset == -1 && tries <= 4)
{
// MAKE A HTTP CALL USING THE RANGE HEADER
rangeStart -= (chunkSize * tries);
this.httpClient.DefaultRequestHeaders.Range = new RangeHeaderValue(rangeStart, rangeFinish);
var byteArray = await httpClient.GetByteArrayAsync(this.httpUrl);
// TRY TO LOCATE THE END OF CENTRAL DIRECTORY DEFINED BY
// 50 4B 05 06
// https://en.wikipedia.org/wiki/Zip_(file_format)#End_of_central_directory_record_(EOCD)
int pos = (byteArray.Length - secureMargin);
while (pos >= 0)
{
// FOUND CENTRAL DIRECTORY
if (byteArray[pos + 0] == 0x50 &&
byteArray[pos + 1] == 0x4b &&
byteArray[pos + 2] == 0x05 &&
byteArray[pos + 3] == 0x06)
{
this.directoryData.Size = BitConverter.ToInt32(byteArray, pos + 12);
this.directoryData.Offset = BitConverter.ToInt32(byteArray, pos + 16);
this.directoryData.Entries = BitConverter.ToInt16(byteArray, pos + 10);
return(true);
}
else
{
pos--;
}
}
tries++;
}
return(false);
}
catch (Exception) { throw; }
}
