internal const int OPTIMAL_ML = 0x0F + 4 - 1; // match length that doesn't require an additional byte
/// <summary>
/// Compress <c>bytes[off:off+len]</c> into <paramref name="out"/> using
/// at most 16KB of memory. <paramref name="ht"/> shouldn't be shared across threads
/// but can safely be reused.
/// </summary>
public static void Compress(byte[] bytes, int off, int len, DataOutput @out, HashTable ht)
{
int @base = off;
int end = off + len;
int anchor = off++;
if (len > LAST_LITERALS + MIN_MATCH)
{
int limit = end - LAST_LITERALS;
int matchLimit = limit - MIN_MATCH;
ht.Reset(len);
int hashLog = ht.hashLog;
PackedInt32s.Mutable hashTable = ht.hashTable;
while (off <= limit)
{
// find a match
int @ref;
while (true)
{
if (off >= matchLimit)
{
goto mainBreak;
}
int v = ReadInt32(bytes, off);
int h = Hash(v, hashLog);
@ref = @base + (int)hashTable.Get(h);
if (Debugging.AssertsEnabled) Debugging.Assert(PackedInt32s.BitsRequired(off - @base) <= hashTable.BitsPerValue);
hashTable.Set(h, off - @base);
if (off - @ref < MAX_DISTANCE && ReadInt32(bytes, @ref) == v)
{
break;
}
++off;
}
// compute match length
int matchLen = MIN_MATCH + CommonBytes(bytes, @ref + MIN_MATCH, off + MIN_MATCH, limit);
EncodeSequence(bytes, anchor, @ref, off, matchLen, @out);
off += matchLen;
anchor = off;
//mainContinue: ; // LUCENENET NOTE: Not Referenced
}
mainBreak: ;
}
// last literals
int literalLen = end - anchor;
if (Debugging.AssertsEnabled) Debugging.Assert(literalLen >= LAST_LITERALS || literalLen == len);
EncodeLastLiterals(bytes, anchor, end - anchor, @out);
}
internal void Reset(int len)
{
int bitsPerOffset = PackedInt32s.BitsRequired(len - LAST_LITERALS);
int bitsPerOffsetLog = 32 - (bitsPerOffset - 1).LeadingZeroCount();
hashLog = MEMORY_USAGE + 3 - bitsPerOffsetLog;
if (hashTable == null || hashTable.Count < 1 << hashLog || hashTable.BitsPerValue < bitsPerOffset)
{
hashTable = PackedInt32s.GetMutable(1 << hashLog, bitsPerOffset, PackedInt32s.DEFAULT);
}
else
{
hashTable.Clear();
}
}