private static File MergePass(List <File> filesToMerge, MergeBuffer mergeBuffer)
{
File outFile = new File(
nBlocks: (uint)filesToMerge.Sum(file => file.nBlocks),
blockSize: filesToMerge[0].blockSize,
initializer: 0);
for (int bufferIndex = 0; bufferIndex < (int)mergeBuffer.BufferBlocks.Length; bufferIndex++)
{
mergeBuffer.BufferBlocks[bufferIndex]
.assignInputFile(filesToMerge[bufferIndex]);
}
mergeBuffer.OutputBuffer.assignOutputFile(outFile);
while (mergeBuffer.BufferBlocks.Any(block => block.HasNext))
{
var validBlocks = mergeBuffer.BufferBlocks.Where(block => block.HasNext);
var nextBlock = validBlocks.First(
block => block.peekNext == validBlocks.Min(blk => blk.peekNext));
mergeBuffer.OutputBuffer.writeNext(nextBlock.readNext());
}
return(outFile);
}
private static File MergePhase(File sourceFile, uint bufferSize, List <File> runFiles)
{
File sortedFile;
MergeBuffer mergeBuffer = new MergeBuffer(
nBlocks: bufferSize,
blockSize: sourceFile.blockSize);
int nMergingSources = (int)bufferSize - 1;
int nMergeRuns = (int)Math.Ceiling((decimal)(runFiles.Count / nMergingSources));
while (nMergeRuns > 1)
{
List <File> nextPassFiles = new List <File>();
for (int passIndex = 0; passIndex < nMergeRuns; passIndex++)
{
var filesToMerge = runFiles.GetRange(
index: passIndex * nMergingSources,
count: nMergingSources
);
var outFile = MergePass(filesToMerge, mergeBuffer);
nextPassFiles.Add(outFile);
}
runFiles = nextPassFiles;
nMergeRuns = (int)Math.Ceiling((decimal)runFiles.Count / nMergingSources);
}
sortedFile = MergePass(runFiles, mergeBuffer);
return(sortedFile);
}
