static async Task <bool> ReadEntry(HttpClient httpClient, Uri url, CDHeader cdh, BinaryReader br, string destinationDirectory)
{
string compressedFilePath = Path.Combine(destinationDirectory, $"{Path.GetFileName (cdh.FileName)}.deflated");
Console.WriteLine($" {cdh.FileName} (offset: {cdh.RelativeOffsetOfLocalHeader})");
(bool success, Stream contentStream) = await ReadFileData(httpClient, url, cdh);
if (!success)
{
Console.Error.WriteLine("Failed to read file data");
return(false);
}
using (var destFile = new BinaryWriter(File.OpenWrite(compressedFilePath))) {
using (var fbr = new BinaryReader(contentStream)) {
if (!await DownloadAndExtract(fbr, contentStream, destFile, compressedFilePath))
{
return(CleanupAndReturn(false));
}
}
}
return(CleanupAndReturn(true));
bool CleanupAndReturn(bool retval)
{
if (File.Exists(compressedFilePath))
{
File.Delete(compressedFilePath);
}
return(retval);
}
}
static (bool success, CDHeader cdh) ReadCDHeader(BinaryReader cdr, long dataLength, ref long nread)
{
var cdh = new CDHeader();
bool worked;
string whatFailed = null;
cdh.Signature = ReadUInt(cdr, dataLength, ref nread, out worked);
if (!worked || cdh.Signature != CDHeaderSignature)
{
whatFailed = "Signature ({cdh.Signature:x} != {CDHeaderSignature:x})";
goto failed;
}
cdh.VersionMadeBy = ReadUShort(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "VersionMadeBy";
goto failed;
}
cdh.VersionNeededToExtract = ReadUShort(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "VersionNeededToExtract";
goto failed;
}
cdh.GeneralPurposeBitFlag = ReadUShort(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "GeneralPurposeBitFlag";
goto failed;
}
cdh.CompressionMethod = ReadUShort(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "CompressionMethod";
goto failed;
}
cdh.LastModFileTime = ReadUShort(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "LastModFileTime";
goto failed;
}
cdh.LastModFileDate = ReadUShort(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "LastModFileDate";
goto failed;
}
cdh.CRC32 = ReadUInt(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "CRC32";
goto failed;
}
cdh.CompressedSize = ReadUInt(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "CompressedSize";
goto failed;
}
cdh.UncompressedSize = ReadUInt(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "UncompressedSize";
goto failed;
}
cdh.FileNameLength = ReadUShort(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "FileNameLength";
goto failed;
}
cdh.ExtraFieldLength = ReadUShort(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "ExtraFieldLength";
goto failed;
}
cdh.FileCommentLength = ReadUShort(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "FileCommentLength";
goto failed;
}
cdh.DiskNumberStart = ReadUShort(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "DiskNumberStart";
goto failed;
}
cdh.InternalFileAttributes = ReadUShort(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "InternalFileAttributes";
goto failed;
}
cdh.ExternalFileAttributes = ReadUInt(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "ExternalFileAttributes";
goto failed;
}
cdh.RelativeOffsetOfLocalHeader = ReadUInt(cdr, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "RelativeOffsetOfLocalHeader";
goto failed;
}
byte[] bytes = ReadBytes(cdr, cdh.FileNameLength, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "FileName (bytes)";
goto failed;
}
cdh.FileName = Encoding.ASCII.GetString(bytes);
if (!worked)
{
whatFailed = "FileName (ASCII decode)";
goto failed;
}
if (cdh.ExtraFieldLength > 0)
{
cdh.ExtraField = ReadBytes(cdr, cdh.ExtraFieldLength, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "ExtraField";
goto failed;
}
}
if (cdh.FileCommentLength > 0)
{
bytes = ReadBytes(cdr, cdh.FileCommentLength, dataLength, ref nread, out worked);
if (!worked)
{
whatFailed = "FileComment (bytes)";
goto failed;
}
cdh.FileComment = Encoding.ASCII.GetString(bytes);
}
return(true, cdh);
failed:
if (!String.IsNullOrEmpty(whatFailed))
{
Console.Error.WriteLine($"Failed to read a central directory header field: {whatFailed}");
}
return(false, null);
}
static async Task <(bool success, Stream data)> ReadFileData(HttpClient httpClient, Uri url, CDHeader cdh)
{
long fileOffset = cdh.RelativeOffsetOfLocalHeader;
long dataSize =
cdh.CompressedSize +
30 + // local file header size, the static portion
cdh.FileName.Length + // They're the same in both haders
cdh.ExtraFieldLength + // This may differ between headers...
16384; // ...so we add some extra padding
var req = new HttpRequestMessage(HttpMethod.Get, url);
req.Headers.ConnectionClose = true;
req.Headers.Range = new RangeHeaderValue(fileOffset, fileOffset + dataSize);
HttpResponseMessage resp = await httpClient.SendAsync(req).ConfigureAwait(false);
if (!resp.IsSuccessStatusCode)
{
Console.Error.WriteLine($"Failed to read file data: HTTP error {resp.StatusCode}");
return(false, null);
}
Stream s = await resp.Content.ReadAsStreamAsync().ConfigureAwait(false);
if (s.Length < dataSize)
{
Console.Error.WriteLine($"Failed to read file data: invalid data length ({s.Length} < {dataSize})");
s.Dispose();
return(false, null);
}
return(true, s);
}
