/// <summary>
/// Closes the zip input stream
/// </summary>
public override void Close()
{
base.Close();
crc = null;
entry = null;
}
void ReadHeader()
{
/* 1. Check the two magic bytes */
Crc32 headCRC = new Crc32();
int magic = baseInputStream.ReadByte();
if (magic < 0) {
eos = true;
return;
}
headCRC.Update(magic);
if (magic != (GZipConstants.GZIP_MAGIC >> 8)) {
throw new GZipException("Error baseInputStream GZIP header, first byte doesn't match");
}
magic = baseInputStream.ReadByte();
if (magic != (GZipConstants.GZIP_MAGIC & 0xFF)) {
throw new GZipException("Error baseInputStream GZIP header, second byte doesn't match");
}
headCRC.Update(magic);
/* 2. Check the compression type (must be 8) */
int CM = baseInputStream.ReadByte();
if (CM != 8) {
throw new GZipException("Error baseInputStream GZIP header, data not baseInputStream deflate format");
}
headCRC.Update(CM);
/* 3. Check the flags */
int flags = baseInputStream.ReadByte();
if (flags < 0) {
throw new GZipException("Early EOF baseInputStream GZIP header");
}
headCRC.Update(flags);
/* This flag byte is divided into individual bits as follows:
bit 0 FTEXT
bit 1 FHCRC
bit 2 FEXTRA
bit 3 FNAME
bit 4 FCOMMENT
bit 5 reserved
bit 6 reserved
bit 7 reserved
*/
/* 3.1 Check the reserved bits are zero */
if ((flags & 0xd0) != 0) {
throw new GZipException("Reserved flag bits baseInputStream GZIP header != 0");
}
/* 4.-6. Skip the modification time, extra flags, and OS type */
for (int i=0; i< 6; i++) {
int readByte = baseInputStream.ReadByte();
if (readByte < 0) {
throw new GZipException("Early EOF baseInputStream GZIP header");
}
headCRC.Update(readByte);
}
/* 7. Read extra field */
if ((flags & GZipConstants.FEXTRA) != 0) {
/* Skip subfield id */
for (int i=0; i< 2; i++) {
int readByte = baseInputStream.ReadByte();
if (readByte < 0) {
throw new GZipException("Early EOF baseInputStream GZIP header");
}
headCRC.Update(readByte);
}
if (baseInputStream.ReadByte() < 0 || baseInputStream.ReadByte() < 0) {
throw new GZipException("Early EOF baseInputStream GZIP header");
}
int len1, len2, extraLen;
len1 = baseInputStream.ReadByte();
len2 = baseInputStream.ReadByte();
if ((len1 < 0) || (len2 < 0)) {
throw new GZipException("Early EOF baseInputStream GZIP header");
}
headCRC.Update(len1);
headCRC.Update(len2);
extraLen = (len1 << 8) | len2;
for (int i = 0; i < extraLen;i++) {
int readByte = baseInputStream.ReadByte();
if (readByte < 0)
{
throw new GZipException("Early EOF baseInputStream GZIP header");
}
headCRC.Update(readByte);
}
}
/* 8. Read file name */
if ((flags & GZipConstants.FNAME) != 0) {
int readByte;
while ( (readByte = baseInputStream.ReadByte()) > 0) {
headCRC.Update(readByte);
}
if (readByte < 0) {
throw new GZipException("Early EOF baseInputStream GZIP file name");
}
headCRC.Update(readByte);
}
/* 9. Read comment */
if ((flags & GZipConstants.FCOMMENT) != 0) {
int readByte;
while ( (readByte = baseInputStream.ReadByte()) > 0) {
headCRC.Update(readByte);
}
if (readByte < 0) {
throw new GZipException("Early EOF baseInputStream GZIP comment");
}
headCRC.Update(readByte);
}
/* 10. Read header CRC */
if ((flags & GZipConstants.FHCRC) != 0) {
int tempByte;
int crcval = baseInputStream.ReadByte();
if (crcval < 0) {
throw new GZipException("Early EOF baseInputStream GZIP header");
}
tempByte = baseInputStream.ReadByte();
if (tempByte < 0) {
throw new GZipException("Early EOF baseInputStream GZIP header");
}
crcval = (crcval << 8) | tempByte;
if (crcval != ((int) headCRC.Value & 0xffff)) {
throw new GZipException("Header CRC value mismatch");
}
}
readGZIPHeader = true;
}