private void CopyEntries(DeltaIndexScanner scan)
{
// Rebuild the entries list from the scanner, positioning all
// blocks in the same hash chain next to each other. We can
// then later discard the next list, along with the scanner.
//
int next = 1;
for (int i = 0; i < table.Length; i++)
{
int h = table[i];
if (h == 0)
{
continue;
}
table[i] = next;
do
{
entries[next++] = scan.entries[h];
h = scan.next[h];
}
while (h != 0);
}
}
private int CountEntries(DeltaIndexScanner scan)
{
// Figure out exactly how many entries we need. As we do the
// enumeration truncate any delta chains longer than what we
// are willing to scan during encode. This keeps the encode
// logic linear in the size of the input rather than quadratic.
//
int cnt = 0;
for (int i = 0; i < table.Length; i++)
{
int h = table[i];
if (h == 0)
{
continue;
}
int len = 0;
do
{
if (++len == MAX_CHAIN_LENGTH)
{
scan.next[h] = 0;
break;
}
h = scan.next[h];
}
while (h != 0);
cnt += len;
}
return cnt;
}
/// <summary>Construct an index from the source file.</summary>
/// <remarks>Construct an index from the source file.</remarks>
/// <param name="sourceBuffer">
/// the source file's raw contents. The buffer will be held by the
/// index instance to facilitate matching, and therefore must not
/// be modified by the caller.
/// </param>
public DeltaIndex(byte[] sourceBuffer)
{
src = sourceBuffer;
DeltaIndexScanner scan = new DeltaIndexScanner(src, src.Length);
// Reuse the same table the scanner made. We will replace the
// values at each position, but we want the same-length array.
//
table = scan.table;
tableMask = scan.tableMask;
// Because entry index 0 means there are no entries for the
// slot in the table, we have to allocate one extra position.
//
entries = new long[1 + CountEntries(scan)];
CopyEntries(scan);
}