void ReadHeader()
{
// 1. Check the two magic bytes
Crc32Checksum headCRC = new Crc32Checksum();
int magic = baseInputStream.ReadByte();
if (magic < 0) {
throw new EndOfStreamException("EOS reading GZIP header");
}
headCRC.Update(magic);
if (magic != (GZipConstants.GzipMagic >> 8)) {
throw new GZipException("Error GZIP header, first magic byte doesn't match");
}
magic = baseInputStream.ReadByte();
if (magic < 0) {
throw new EndOfStreamException("EOS reading GZIP header");
}
if (magic != (GZipConstants.GzipMagic & 0xFF)) {
throw new GZipException("Error GZIP header, second magic byte doesn't match");
}
headCRC.Update(magic);
// 2. Check the compression type (must be 8)
int compressionType = baseInputStream.ReadByte();
if ( compressionType < 0 ) {
throw new EndOfStreamException("EOS reading GZIP header");
}
if ( compressionType != 8 ) {
throw new GZipException("Error GZIP header, data not in deflate format");
}
headCRC.Update(compressionType);
// 3. Check the flags
int flags = baseInputStream.ReadByte();
if (flags < 0) {
throw new EndOfStreamException("EOS reading 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 & 0xE0) != 0) {
throw new GZipException("Reserved flag bits in 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 EndOfStreamException("EOS reading 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 EndOfStreamException("EOS reading GZIP header");
}
headCRC.Update(readByte);
}
if (baseInputStream.ReadByte() < 0 || baseInputStream.ReadByte() < 0) {
throw new EndOfStreamException("EOS reading GZIP header");
}
int len1, len2;
len1 = baseInputStream.ReadByte();
len2 = baseInputStream.ReadByte();
if ((len1 < 0) || (len2 < 0)) {
throw new EndOfStreamException("EOS reading GZIP header");
}
headCRC.Update(len1);
headCRC.Update(len2);
int extraLen = (len1 << 8) | len2;
for (int i = 0; i < extraLen;i++) {
int readByte = baseInputStream.ReadByte();
if (readByte < 0)
{
throw new EndOfStreamException("EOS reading 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 EndOfStreamException("EOS reading GZIP header");
}
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 EndOfStreamException("EOS reading GZIP header");
}
headCRC.Update(readByte);
}
// 10. Read header CRC
if ((flags & GZipConstants.FHCRC) != 0) {
int tempByte;
int crcval = baseInputStream.ReadByte();
if (crcval < 0) {
throw new EndOfStreamException("EOS reading GZIP header");
}
tempByte = baseInputStream.ReadByte();
if (tempByte < 0) {
throw new EndOfStreamException("EOS reading GZIP header");
}
crcval = (crcval << 8) | tempByte;
if (crcval != ((int) headCRC.Value & 0xffff)) {
throw new GZipException("Header CRC value mismatch");
}
}
readGZIPHeader = true;
}
/// <summary>
/// Test an archive for integrity/validity
/// </summary>
/// <param name="testData">Perform low level data Crc check</param>
/// <param name="strategy">The <see cref="TestStrategy"></see> to apply.</param>
/// <param name="resultHandler">The <see cref="ZipTestResultHandler"></see> handler to call during testing.</param>
/// <returns>true if all tests pass, false otherwise</returns>
/// <exception cref="ObjectDisposedException">The object has already been closed.</exception>
public bool TestArchive(bool testData, TestStrategy strategy, ZipTestResultHandler resultHandler)
{
if (_isDisposed) {
throw new ObjectDisposedException("ZipFile");
}
TestStatus status = new TestStatus(this);
if ( resultHandler != null ) {
resultHandler(status, null);
}
HeaderTest test = testData ? (HeaderTest.Header | HeaderTest.Extract) : HeaderTest.Header;
bool testing = true;
try {
int entryIndex = 0;
while ( testing && (entryIndex < Count) ) {
if ( resultHandler != null ) {
status.SetEntry(this[entryIndex]);
status.SetOperation(TestOperation.EntryHeader);
resultHandler(status, null);
}
try {
TestLocalHeader(this[entryIndex], test);
}
catch(ZipException ex) {
status.AddError();
if ( resultHandler != null ) {
resultHandler(status,
string.Format("Exception during test - '{0}'", ex.Message));
}
if ( strategy == TestStrategy.FindFirstError ) {
testing = false;
}
}
if ( testing && testData && this[entryIndex].IsFile ) {
if ( resultHandler != null ) {
status.SetOperation(TestOperation.EntryData);
resultHandler(status, null);
}
Crc32Checksum crc = new Crc32Checksum();
using (Stream entryStream = this.GetInputStream(this[entryIndex]))
{
byte[] buffer = new byte[4096];
long totalBytes = 0;
int bytesRead;
while ((bytesRead = entryStream.Read(buffer, 0, buffer.Length)) > 0)
{
crc.Update(buffer, 0, bytesRead);
if (resultHandler != null)
{
totalBytes += bytesRead;
status.SetBytesTested(totalBytes);
resultHandler(status, null);
}
}
}
if (this[entryIndex].Crc != crc.Value) {
status.AddError();
if ( resultHandler != null ) {
resultHandler(status, "CRC mismatch");
}
if ( strategy == TestStrategy.FindFirstError ) {
testing = false;
}
}
if (( this[entryIndex].Flags & (int)GeneralBitFlags.Descriptor) != 0 ) {
ZipHelperStream helper = new ZipHelperStream(_baseStream);
DescriptorData data = new DescriptorData();
helper.ReadDataDescriptor(this[entryIndex].LocalHeaderRequiresZip64, data);
if (this[entryIndex].Crc != data.Crc) {
status.AddError();
}
if (this[entryIndex].CompressedSize != data.CompressedSize) {
status.AddError();
}
if (this[entryIndex].Size != data.Size) {
status.AddError();
}
}
}
if ( resultHandler != null ) {
status.SetOperation(TestOperation.EntryComplete);
resultHandler(status, null);
}
entryIndex += 1;
}
if ( resultHandler != null ) {
status.SetOperation(TestOperation.MiscellaneousTests);
resultHandler(status, null);
}
// TODO: the 'Corrina Johns' test where local headers are missing from
// the central directory. They are therefore invisible to many archivers.
}
catch (Exception ex) {
status.AddError();
if ( resultHandler != null ) {
resultHandler(status, string.Format("Exception during test - '{0}'", ex.Message));
}
}
if ( resultHandler != null ) {
status.SetOperation(TestOperation.Complete);
status.SetEntry(null);
resultHandler(status, null);
}
return (status.ErrorCount == 0);
}
void CopyBytes(ZipUpdate update, Stream destination, Stream source,
long bytesToCopy, bool updateCrc)
{
if ( destination == source ) {
throw new InvalidOperationException("Destination and source are the same");
}
// NOTE: Compressed size is updated elsewhere.
Crc32Checksum crc = new Crc32Checksum();
byte[] buffer = GetBuffer();
long targetBytes = bytesToCopy;
long totalBytesRead = 0;
int bytesRead;
do {
int readSize = buffer.Length;
if ( bytesToCopy < readSize ) {
readSize = (int)bytesToCopy;
}
bytesRead = source.Read(buffer, 0, readSize);
if ( bytesRead > 0 ) {
if ( updateCrc ) {
crc.Update(buffer, 0, bytesRead);
}
destination.Write(buffer, 0, bytesRead);
bytesToCopy -= bytesRead;
totalBytesRead += bytesRead;
}
}
while ( (bytesRead > 0) && (bytesToCopy > 0) );
if ( totalBytesRead != targetBytes ) {
throw new ZipException(string.Format("Failed to copy bytes expected {0} read {1}", targetBytes, totalBytesRead));
}
if ( updateCrc ) {
update.OutEntry.Crc = crc.Value;
}
}
void CopyEntryDataDirect(ZipUpdate update, Stream stream, bool updateCrc, ref long destinationPosition, ref long sourcePosition)
{
long bytesToCopy = update.Entry.CompressedSize;
// NOTE: Compressed size is updated elsewhere.
Crc32Checksum crc = new Crc32Checksum();
byte[] buffer = GetBuffer();
long targetBytes = bytesToCopy;
long totalBytesRead = 0;
int bytesRead;
do
{
int readSize = buffer.Length;
if ( bytesToCopy < readSize ) {
readSize = (int)bytesToCopy;
}
stream.Position = sourcePosition;
bytesRead = stream.Read(buffer, 0, readSize);
if ( bytesRead > 0 ) {
if ( updateCrc ) {
crc.Update(buffer, 0, bytesRead);
}
stream.Position = destinationPosition;
stream.Write(buffer, 0, bytesRead);
destinationPosition += bytesRead;
sourcePosition += bytesRead;
bytesToCopy -= bytesRead;
totalBytesRead += bytesRead;
}
}
while ( (bytesRead > 0) && (bytesToCopy > 0) );
if ( totalBytesRead != targetBytes ) {
throw new ZipException(string.Format("Failed to copy bytes expected {0} read {1}", targetBytes, totalBytesRead));
}
if ( updateCrc ) {
update.OutEntry.Crc = crc.Value;
}
}
/// <summary>
/// Closes the zip input stream
/// </summary>
public override void Close()
{
internalReader = ReadingNotAvailable;
crc = null;
entry = null;
base.Close();
}
