/// <exception cref="NGit.Errors.MissingObjectException"></exception>
/// <exception cref="NGit.Errors.IncorrectObjectTypeException"></exception>
/// <exception cref="System.IO.IOException"></exception>
/// <exception cref="NGit.Errors.LargeObjectException"></exception>
private DeltaIndex Index(DeltaWindowEntry ent)
{
DeltaIndex idx = ent.index;
if (idx == null)
{
try
{
idx = new DeltaIndex(Buffer(ent));
}
catch (OutOfMemoryException noMemory)
{
LargeObjectException.OutOfMemory e;
e = new LargeObjectException.OutOfMemory(noMemory);
e.SetObjectId(ent.@object);
throw e;
}
if (0 < maxMemory)
{
loaded += idx.GetIndexSize() - idx.GetSourceSize();
}
ent.index = idx;
}
return(idx);
}
internal DeltaWindow(PackConfig pc, DeltaCache dc, ObjectReader or)
{
// The object we are currently considering needs a lot of state:
config = pc;
deltaCache = dc;
reader = or;
// C Git increases the window size supplied by the user by 1.
// We don't know why it does this, but if the user asks for
// window=10, it actually processes with window=11. Because
// the window size has the largest direct impact on the final
// pack file size, we match this odd behavior here to give us
// a better chance of producing a similar sized pack as C Git.
//
// We would prefer to directly honor the user's request since
// PackWriter has a minimum of 2 for the window size, but then
// users might complain that JGit is creating a bigger pack file.
//
window = new DeltaWindowEntry[config.GetDeltaSearchWindowSize() + 1];
for (int i = 0; i < window.Length; i++)
{
window[i] = new DeltaWindowEntry();
}
maxMemory = config.GetDeltaSearchMemoryLimit();
maxDepth = config.GetMaxDeltaDepth();
}
/// <exception cref="NGit.Errors.MissingObjectException"></exception>
/// <exception cref="NGit.Errors.IncorrectObjectTypeException"></exception>
/// <exception cref="System.IO.IOException"></exception>
/// <exception cref="NGit.Errors.LargeObjectException"></exception>
private byte[] Buffer(DeltaWindowEntry ent)
{
byte[] buf = ent.buffer;
if (buf == null)
{
buf = PackWriter.Buffer(config, reader, ent.@object);
if (0 < maxMemory)
{
loaded += buf.Length;
}
ent.buffer = buf;
}
return(buf);
}
private void Clear(DeltaWindowEntry ent)
{
if (ent.index != null)
{
loaded -= ent.index.GetIndexSize();
}
else
{
if (res.buffer != null)
{
loaded -= ent.buffer.Length;
}
}
ent.Set(null);
}
// We should drop the current source entry from the window,
// it is somehow invalid for us to work with.
private bool IsBetterDelta(DeltaWindowEntry src, TemporaryBuffer.Heap resDelta)
{
if (bestDelta == null)
{
return(true);
}
// If both delta sequences are the same length, use the one
// that has a shorter delta chain since it would be faster
// to access during reads.
//
if (resDelta.Length() == bestDelta.Length())
{
return(src.Depth() < window[bestSlot].Depth());
}
return(resDelta.Length() < bestDelta.Length());
}
/// <exception cref="System.IO.IOException"></exception>
internal virtual void Search(ProgressMonitor monitor, ObjectToPack[] toSearch, int
off, int cnt)
{
try
{
for (int end = off + cnt; off < end; off++)
{
res = window[resSlot];
if (0 < maxMemory)
{
Clear(res);
int tail = Next(resSlot);
long need = EstimateSize(toSearch[off]);
while (maxMemory < loaded + need && tail != resSlot)
{
Clear(window[tail]);
tail = Next(tail);
}
}
res.Set(toSearch[off]);
if ([email protected]())
{
// We don't actually want to make a delta for
// them, just need to push them into the window
// so they can be read by other objects.
//
KeepInWindow();
}
else
{
// Search for a delta for the current window slot.
//
monitor.Update(1);
Search();
}
}
}
finally
{
if (deflater != null)
{
deflater.Finish();
}
}
}
private void ShuffleBaseUpInPriority()
{
// Shuffle the entire window so that the best match we just used
// is at our current index, and our current object is at the index
// before it. Slide any entries in between to make space.
//
window[resSlot] = window[bestSlot];
DeltaWindowEntry next = res;
int slot = Prior(resSlot);
for (; slot != bestSlot; slot = Prior(slot))
{
DeltaWindowEntry e = window[slot];
window[slot] = next;
next = e;
}
window[slot] = next;
}
private static int DeltaSizeLimit(DeltaWindowEntry res, int maxDepth, DeltaWindowEntry
src)
{
// Ideally the delta is at least 50% of the original size,
// but we also want to account for delta header overhead in
// the pack file (to point to the delta base) so subtract off
// some of those header bytes from the limit.
//
int limit = res.Size() / 2 - 20;
// Distribute the delta limit over the entire chain length.
// This is weighted such that deeper items in the chain must
// be even smaller than if they were earlier in the chain, as
// they cost significantly more to unpack due to the increased
// number of recursive unpack calls.
//
int remainingDepth = maxDepth - src.Depth();
return((limit * remainingDepth) / maxDepth);
}
// We should drop the current source entry from the window,
// it is somehow invalid for us to work with.
private bool IsBetterDelta(DeltaWindowEntry src, TemporaryBuffer.Heap resDelta)
{
if (bestDelta == null)
{
return true;
}
// If both delta sequences are the same length, use the one
// that has a shorter delta chain since it would be faster
// to access during reads.
//
if (resDelta.Length() == bestDelta.Length())
{
return src.Depth() < window[bestSlot].Depth();
}
return resDelta.Length() < bestDelta.Length();
}
/// <exception cref="NGit.Errors.MissingObjectException"></exception>
/// <exception cref="NGit.Errors.IncorrectObjectTypeException"></exception>
/// <exception cref="System.IO.IOException"></exception>
/// <exception cref="NGit.Errors.LargeObjectException"></exception>
private DeltaIndex Index(DeltaWindowEntry ent)
{
DeltaIndex idx = ent.index;
if (idx == null)
{
try
{
idx = new DeltaIndex(Buffer(ent));
}
catch (OutOfMemoryException noMemory)
{
LargeObjectException.OutOfMemory e;
e = new LargeObjectException.OutOfMemory(noMemory);
e.SetObjectId(ent.@object);
throw e;
}
if (0 < maxMemory)
{
loaded += idx.GetIndexSize() - idx.GetSourceSize();
}
ent.index = idx;
}
return idx;
}
/// <exception cref="System.IO.IOException"></exception>
private int Delta(DeltaWindowEntry src, int srcSlot)
{
// Objects must use only the same type as their delta base.
// If we are looking at something where that isn't true we
// have exhausted everything of the correct type and should
// move on to the next thing to examine.
//
if (src.Type() != res.Type())
{
KeepInWindow();
return NEXT_RES;
}
// Only consider a source with a short enough delta chain.
if (src.Depth() > resMaxDepth)
{
return NEXT_SRC;
}
// Estimate a reasonable upper limit on delta size.
int msz = DeltaSizeLimit(res, resMaxDepth, src);
if (msz <= 8)
{
return NEXT_SRC;
}
// If we have to insert a lot to make this work, find another.
if (res.Size() - src.Size() > msz)
{
return NEXT_SRC;
}
// If the sizes are radically different, this is a bad pairing.
if (res.Size() < src.Size() / 16)
{
return NEXT_SRC;
}
DeltaIndex srcIndex;
try
{
srcIndex = Index(src);
}
catch (LargeObjectException)
{
// If the source is too big to work on, skip it.
DropFromWindow(srcSlot);
return NEXT_SRC;
}
catch (IOException notAvailable)
{
if ([email protected]())
{
// This is an edge that is suddenly not available.
DropFromWindow(srcSlot);
return NEXT_SRC;
}
else
{
throw;
}
}
byte[] resBuf;
try
{
resBuf = Buffer(res);
}
catch (LargeObjectException)
{
// If its too big, move on to another item.
return NEXT_RES;
}
// If we already have a delta for the current object, abort
// encoding early if this new pairing produces a larger delta.
if (bestDelta != null && bestDelta.Length() < msz)
{
msz = (int)bestDelta.Length();
}
TemporaryBuffer.Heap delta = new TemporaryBuffer.Heap(msz);
try
{
if (!srcIndex.Encode(delta, resBuf, msz))
{
return NEXT_SRC;
}
}
catch (IOException)
{
// This only happens when the heap overflows our limit.
return NEXT_SRC;
}
if (IsBetterDelta(src, delta))
{
bestDelta = delta;
bestSlot = srcSlot;
}
return NEXT_SRC;
}
private void Clear(DeltaWindowEntry ent)
{
if (ent.index != null)
{
loaded -= ent.index.GetIndexSize();
}
else
{
if (res.buffer != null)
{
loaded -= ent.buffer.Length;
}
}
ent.Set(null);
}
/// <exception cref="NGit.Errors.MissingObjectException"></exception>
/// <exception cref="NGit.Errors.IncorrectObjectTypeException"></exception>
/// <exception cref="System.IO.IOException"></exception>
/// <exception cref="NGit.Errors.LargeObjectException"></exception>
private byte[] Buffer(DeltaWindowEntry ent)
{
byte[] buf = ent.buffer;
if (buf == null)
{
buf = PackWriter.Buffer(config, reader, ent.@object);
if (0 < maxMemory)
{
loaded += buf.Length;
}
ent.buffer = buf;
}
return buf;
}
private static int DeltaSizeLimit(DeltaWindowEntry res, int maxDepth, DeltaWindowEntry
src)
{
// Ideally the delta is at least 50% of the original size,
// but we also want to account for delta header overhead in
// the pack file (to point to the delta base) so subtract off
// some of those header bytes from the limit.
//
int limit = res.Size() / 2 - 20;
// Distribute the delta limit over the entire chain length.
// This is weighted such that deeper items in the chain must
// be even smaller than if they were earlier in the chain, as
// they cost significantly more to unpack due to the increased
// number of recursive unpack calls.
//
int remainingDepth = maxDepth - src.Depth();
return (limit * remainingDepth) / maxDepth;
}
/// <exception cref="System.IO.IOException"></exception>
internal virtual void Search(ProgressMonitor monitor, ObjectToPack[] toSearch, int
off, int cnt)
{
try
{
for (int end = off + cnt; off < end; off++)
{
res = window[resSlot];
if (0 < maxMemory)
{
Clear(res);
int tail = Next(resSlot);
long need = EstimateSize(toSearch[off]);
while (maxMemory < loaded + need && tail != resSlot)
{
Clear(window[tail]);
tail = Next(tail);
}
}
res.Set(toSearch[off]);
if ([email protected]())
{
// We don't actually want to make a delta for
// them, just need to push them into the window
// so they can be read by other objects.
//
KeepInWindow();
}
else
{
// Search for a delta for the current window slot.
//
monitor.Update(1);
Search();
}
}
}
finally
{
if (deflater != null)
{
deflater.Finish();
}
}
}
internal DeltaWindow(PackConfig pc, DeltaCache dc, ObjectReader or)
{
// The object we are currently considering needs a lot of state:
config = pc;
deltaCache = dc;
reader = or;
// C Git increases the window size supplied by the user by 1.
// We don't know why it does this, but if the user asks for
// window=10, it actually processes with window=11. Because
// the window size has the largest direct impact on the final
// pack file size, we match this odd behavior here to give us
// a better chance of producing a similar sized pack as C Git.
//
// We would prefer to directly honor the user's request since
// PackWriter has a minimum of 2 for the window size, but then
// users might complain that JGit is creating a bigger pack file.
//
window = new DeltaWindowEntry[config.GetDeltaSearchWindowSize() + 1];
for (int i = 0; i < window.Length; i++)
{
window[i] = new DeltaWindowEntry();
}
maxMemory = config.GetDeltaSearchMemoryLimit();
maxDepth = config.GetMaxDeltaDepth();
}
/// <exception cref="System.IO.IOException"></exception>
private int Delta(DeltaWindowEntry src, int srcSlot)
{
// Objects must use only the same type as their delta base.
// If we are looking at something where that isn't true we
// have exhausted everything of the correct type and should
// move on to the next thing to examine.
//
if (src.Type() != res.Type())
{
KeepInWindow();
return(NEXT_RES);
}
// Only consider a source with a short enough delta chain.
if (src.Depth() > resMaxDepth)
{
return(NEXT_SRC);
}
// Estimate a reasonable upper limit on delta size.
int msz = DeltaSizeLimit(res, resMaxDepth, src);
if (msz <= 8)
{
return(NEXT_SRC);
}
// If we have to insert a lot to make this work, find another.
if (res.Size() - src.Size() > msz)
{
return(NEXT_SRC);
}
// If the sizes are radically different, this is a bad pairing.
if (res.Size() < src.Size() / 16)
{
return(NEXT_SRC);
}
DeltaIndex srcIndex;
try
{
srcIndex = Index(src);
}
catch (LargeObjectException)
{
// If the source is too big to work on, skip it.
DropFromWindow(srcSlot);
return(NEXT_SRC);
}
catch (IOException notAvailable)
{
if ([email protected]())
{
// This is an edge that is suddenly not available.
DropFromWindow(srcSlot);
return(NEXT_SRC);
}
else
{
throw;
}
}
byte[] resBuf;
try
{
resBuf = Buffer(res);
}
catch (LargeObjectException)
{
// If its too big, move on to another item.
return(NEXT_RES);
}
// If we already have a delta for the current object, abort
// encoding early if this new pairing produces a larger delta.
if (bestDelta != null && bestDelta.Length() < msz)
{
msz = (int)bestDelta.Length();
}
TemporaryBuffer.Heap delta = new TemporaryBuffer.Heap(msz);
try
{
if (!srcIndex.Encode(delta, resBuf, msz))
{
return(NEXT_SRC);
}
}
catch (IOException)
{
// This only happens when the heap overflows our limit.
return(NEXT_SRC);
}
if (IsBetterDelta(src, delta))
{
bestDelta = delta;
bestSlot = srcSlot;
}
return(NEXT_SRC);
}
/// <exception cref="System.IO.IOException"></exception>
private void Search()
{
// TODO(spearce) If the object is used as a base for other
// objects in this pack we should limit the depth we create
// for ourselves to be the remainder of our longest dependent
// chain and the configured maximum depth. This can happen
// when the dependents are being reused out a pack, but we
// cannot be because we are near the edge of a thin pack.
//
resMaxDepth = maxDepth;
// Loop through the window backwards, considering every entry.
// This lets us look at the bigger objects that came before.
//
for (int srcSlot = Prior(resSlot); srcSlot != resSlot; srcSlot = Prior(srcSlot))
{
DeltaWindowEntry src = window[srcSlot];
if (src.Empty())
{
break;
}
if (Delta(src, srcSlot) == NEXT_RES)
{
bestDelta = null;
return;
}
}
// We couldn't find a suitable delta for this object, but it may
// still be able to act as a base for another one.
//
if (bestDelta == null)
{
KeepInWindow();
return;
}
// Select this best matching delta as the base for the object.
//
ObjectToPack srcObj = window[bestSlot].@object;
ObjectToPack resObj = res.@object;
if (srcObj.IsEdge())
{
// The source (the delta base) is an edge object outside of the
// pack. Its part of the common base set that the peer already
// has on hand, so we don't want to send it. We have to store
// an ObjectId and *NOT* an ObjectToPack for the base to ensure
// the base isn't included in the outgoing pack file.
//
resObj.SetDeltaBase(srcObj.Copy());
}
else
{
// The base is part of the pack we are sending, so it should be
// a direct pointer to the base.
//
resObj.SetDeltaBase(srcObj);
}
resObj.SetDeltaDepth(srcObj.GetDeltaDepth() + 1);
resObj.ClearReuseAsIs();
CacheDelta(srcObj, resObj);
// Discard the cached best result, otherwise it leaks.
//
bestDelta = null;
// If this should be the end of a chain, don't keep
// it in the window. Just move on to the next object.
//
if (resObj.GetDeltaDepth() == maxDepth)
{
return;
}
ShuffleBaseUpInPriority();
KeepInWindow();
}
