/// <summary>Read the index from disk, if it has changed on disk.</summary>
/// <remarks>
/// Read the index from disk, if it has changed on disk.
/// <p>
/// This method tries to avoid loading the index if it has not changed since
/// the last time we consulted it. A missing index file will be treated as
/// though it were present but had no file entries in it.
/// </remarks>
/// <exception cref="System.IO.IOException">
/// the index file is present but could not be read. This
/// DirCache instance may not be populated correctly.
/// </exception>
/// <exception cref="NGit.Errors.CorruptObjectException">
/// the index file is using a format or extension that this
/// library does not support.
/// </exception>
public virtual void Read()
{
if (liveFile == null)
{
throw new IOException(JGitText.Get().dirCacheDoesNotHaveABackingFile);
}
if (!liveFile.Exists())
{
Clear();
}
else
{
if (snapshot == null || snapshot.IsModified(liveFile))
{
try
{
FileInputStream inStream = new FileInputStream(liveFile);
try
{
Clear();
ReadFrom(inStream);
}
finally
{
try
{
inStream.Close();
}
catch (IOException)
{
}
}
}
catch (FileNotFoundException)
{
// Ignore any close failures.
// Someone must have deleted it between our exists test
// and actually opening the path. That's fine, its empty.
//
Clear();
}
snapshot = FileSnapshot.Save(liveFile);
}
}
}
/// <exception cref="System.IO.IOException"></exception>
/// <exception cref="NGit.Errors.CorruptObjectException"></exception>
private void ReadFrom(InputStream inStream)
{
BufferedInputStream @in = new BufferedInputStream(inStream);
MessageDigest md = Constants.NewMessageDigest();
// Read the index header and verify we understand it.
//
byte[] hdr = new byte[20];
IOUtil.ReadFully(@in, hdr, 0, 12);
md.Update(hdr, 0, 12);
if (!Is_DIRC(hdr))
{
throw new CorruptObjectException(JGitText.Get().notADIRCFile);
}
int ver = NB.DecodeInt32(hdr, 4);
bool extended = false;
if (ver == 3)
{
extended = true;
}
else
{
if (ver != 2)
{
throw new CorruptObjectException(MessageFormat.Format(JGitText.Get().unknownDIRCVersion
, ver));
}
}
entryCnt = NB.DecodeInt32(hdr, 8);
if (entryCnt < 0)
{
throw new CorruptObjectException(JGitText.Get().DIRCHasTooManyEntries);
}
// Load the individual file entries.
//
int infoLength = DirCacheEntry.GetMaximumInfoLength(extended);
byte[] infos = new byte[infoLength * entryCnt];
sortedEntries = new DirCacheEntry[entryCnt];
MutableInteger infoAt = new MutableInteger();
for (int i = 0; i < entryCnt; i++)
{
sortedEntries[i] = new DirCacheEntry(infos, infoAt, @in, md);
}
snapshot = FileSnapshot.Save(liveFile);
// After the file entries are index extensions, and then a footer.
//
for (; ;)
{
@in.Mark(21);
IOUtil.ReadFully(@in, hdr, 0, 20);
if (@in.Read() < 0)
{
// No extensions present; the file ended where we expected.
//
break;
}
@in.Reset();
md.Update(hdr, 0, 8);
IOUtil.SkipFully(@in, 8);
long sz = NB.DecodeUInt32(hdr, 4);
switch (NB.DecodeInt32(hdr, 0))
{
case EXT_TREE:
{
if (int.MaxValue < sz)
{
throw new CorruptObjectException(MessageFormat.Format(JGitText.Get().DIRCExtensionIsTooLargeAt
, FormatExtensionName(hdr), sz));
}
byte[] raw = new byte[(int)sz];
IOUtil.ReadFully(@in, raw, 0, raw.Length);
md.Update(raw, 0, raw.Length);
tree = new DirCacheTree(raw, new MutableInteger(), null);
break;
}
default:
{
if (hdr[0] >= 'A' && ((sbyte)hdr[0]) <= 'Z')
{
// The extension is optional and is here only as
// a performance optimization. Since we do not
// understand it, we can safely skip past it, after
// we include its data in our checksum.
//
SkipOptionalExtension(@in, md, hdr, sz);
}
else
{
// The extension is not an optimization and is
// _required_ to understand this index format.
// Since we did not trap it above we must abort.
//
throw new CorruptObjectException(MessageFormat.Format(JGitText.Get().DIRCExtensionNotSupportedByThisVersion
, FormatExtensionName(hdr)));
}
break;
}
}
}
byte[] exp = md.Digest();
if (!Arrays.Equals(exp, hdr))
{
throw new CorruptObjectException(JGitText.Get().DIRCChecksumMismatch);
}
}