private void WriteFiller(uint word, int count)
{
Contract.Requires(count > 0);
uint previous = m_current;
if (previous == word)
{ // continuation of current run
m_counter += count;
return;
}
if (previous == NO_VALUE)
{ // start of new run
m_counter += count;
m_current = word;
return;
}
// switch from one type to the other
m_words += m_counter;
if (previous == CompressedWord.ALL_ZEROES)
{
m_writer.WriteFixed32(CompressedWord.MakeZeroes(m_counter));
}
else
{
m_writer.WriteFixed32(CompressedWord.MakeOnes(m_counter));
}
m_counter = count;
}
/// <summary>Flush the curernt state of the writer</summary>
/// <remarks>Writing after calling flush may break filler sequences into chunks, and reduce the efficiency of the compression.
/// It should only be called if you need to split a bitmap streaming into physical chunks (sending on a socket, writing to disk, ...)
/// </remarks>
public void Flush()
{
if (m_packed)
{
ThrowAlreadyPacked();
}
// either previous was a literal, or a run of zeroes or ones.
Contract.Requires(m_counter == 0 ? (m_current == NO_VALUE) : (m_current == CompressedWord.ALL_ZEROES || m_current == CompressedWord.ALL_ONES));
int counter = m_counter;
if (counter > 0 && m_current == CompressedWord.ALL_ONES)
{ // complete the last run only if it was all 1's
m_writer.WriteFixed32(CompressedWord.MakeOnes(counter));
m_words += counter;
}
m_counter = 0;
m_current = NO_VALUE;
}
private void WriteLiteral(uint word, int count)
{
Contract.Requires(count > 0);
uint previous = m_current;
int counter = m_counter;
// finish whatever was left open previously
if (previous != NO_VALUE)
{ // need to close previous filler
Contract.Assert(counter > 0);
if (previous == CompressedWord.ALL_ZEROES)
{
m_writer.WriteFixed32(CompressedWord.MakeZeroes(counter));
}
else if (previous == CompressedWord.ALL_ONES)
{
m_writer.WriteFixed32(CompressedWord.MakeOnes(counter));
}
else
{
Contract.Assert(counter == 1);
m_writer.WriteFixed32(CompressedWord.MakeLiteral(previous));
}
m_words += counter;
}
// output the current literal
int n = count;
uint w = CompressedWord.MakeLiteral(word);
while (n-- > 0)
{
m_writer.WriteFixed32(w);
}
m_words += count;
m_current = NO_VALUE;
m_counter = 0;
}
/// <summary>Set a bit in the bitmap.</summary>
/// <param name="index">Absolute index (0-based) of the bit to set</param>
/// <returns>True if the bit was changed from 0 to 1; or false if it was already set.</returns>
public bool Set(int index)
{
if (index < 0)
{
throw new ArgumentException("Bit index cannot be less than zero.", "index");
}
//Console.WriteLine("Set({0}) on {1}-words bitmap", index, m_size);
if (index > m_highest)
{
m_highest = index;
}
if (index < m_lowest)
{
m_lowest = index;
}
uint mask;
int wordIndex = GetWordIndex(index, out mask);
//Console.WriteLine("> bitOffset {0} is in data word #{1} with mask {2}", index, wordIndex, mask);
int offset, position, count;
if (!GetCompressedWordIndex(wordIndex, out offset, out position))
{ // falls outside the bitmap, need to add new words
count = wordIndex - position;
if (count > 0)
{
//Console.WriteLine("> outside by {0}, need filler", count);
EnsureCapacity(m_size + 2);
m_words[m_size++] = CompressedWord.MakeZeroes(count);
}
else
{
//Console.WriteLine("> outside, right next to it");
EnsureCapacity(m_size + 1);
}
m_words[m_size++] = CompressedWord.MakeLiteral(mask);
return(true);
}
//Console.WriteLine("> would be in slot #{0} which starts at data-word #{1}", offset, position);
// read the existing word
var word = m_words[offset];
// we can patch literals in place
if (word.IsLiteral)
{
//Console.WriteLine("> PATCH [...] [{0}:0x{0:X8}] [...]", offset, mask);
var before = word.RawValue;
var after = before | mask;
if (before == after)
{
return(false);
}
if (after == CompressedWord.ALL_ONES)
{ // convert to an all 1 literal!
if (offset > 0)
{
// check if we can merge with a previous 1-filler
var prev = m_words[offset - 1];
if (!prev.IsLiteral && prev.FillBit == 1)
{
m_words[offset - 1] = CompressedWord.MakeOnes(prev.FillCount + 1);
int r = m_size - offset - 1;
if (r > 0)
{
Array.Copy(m_words, offset + 1, m_words, offset, r);
}
--m_size;
return(true);
}
}
//TODO: also need to check if the next one is also a filler!
// convert this one to a filler
after = CompressedWord.MakeOnes(1);
}
m_words[offset] = new CompressedWord(after);
return(true);
}
// if it an all-1 filler, our job is already done
if (word.FillBit == 1)
{
//Console.WriteLine("> was already a 1-filler");
return(false);
}
// for all-1 fillers, we must break them so that we can insert a new literal
SplitFiller(word, offset, mask, wordIndex - position);
return(true);
}
