/// <summary>
/// Construct the log buffers for a given log file.
/// </summary>
/// <param name="logFileName"></param>
public LogBuffers(string logFileName)
{
try
{
var fileInfo = new FileInfo(logFileName);
var logLength = fileInfo.Length;
// if log length exceeds MAX_INT we need multiple mapped buffers, (see FileChannel.map doc).
if (logLength < int.MaxValue)
{
var mappedBuffer = IoUtil.MapExistingFile(logFileName, MapMode.ReadWrite); // TODO Java has sparse hint & Little Endian
_mappedByteBuffers = new[] { mappedBuffer };
_logMetaDataBuffer = new UnsafeBuffer(mappedBuffer.Pointer,
(int)(logLength - LogBufferDescriptor.LOG_META_DATA_LENGTH),
LogBufferDescriptor.LOG_META_DATA_LENGTH);
int termLength = LogBufferDescriptor.TermLength(_logMetaDataBuffer);
int pageSize = LogBufferDescriptor.PageSize(_logMetaDataBuffer);
LogBufferDescriptor.CheckTermLength(termLength);
LogBufferDescriptor.CheckPageSize(pageSize);
_termLength = termLength;
for (var i = 0; i < LogBufferDescriptor.PARTITION_COUNT; i++)
{
_termBuffers[i] = new UnsafeBuffer(mappedBuffer.Pointer, i * termLength, termLength);
}
}
else
{
_mappedByteBuffers = new MappedByteBuffer[LogBufferDescriptor.PARTITION_COUNT + 1];
int assumedTermLength = LogBufferDescriptor.TERM_MAX_LENGTH;
long metaDataSectionOffset = assumedTermLength * (long)LogBufferDescriptor.PARTITION_COUNT;
long metaDataMappingLength = logLength - metaDataSectionOffset;
var memoryMappedFile = IoUtil.OpenMemoryMappedFile(logFileName);
var metaDataMappedBuffer =
new MappedByteBuffer(memoryMappedFile, metaDataSectionOffset, metaDataMappingLength); // Little Endian
_mappedByteBuffers[LogBufferDescriptor.LOG_META_DATA_SECTION_INDEX] = metaDataMappedBuffer;
_logMetaDataBuffer = new UnsafeBuffer(
metaDataMappedBuffer.Pointer,
(int)metaDataMappingLength - LogBufferDescriptor.LOG_META_DATA_LENGTH,
LogBufferDescriptor.LOG_META_DATA_LENGTH);
int metaDataTermLength = LogBufferDescriptor.TermLength(_logMetaDataBuffer);
int pageSize = LogBufferDescriptor.PageSize(_logMetaDataBuffer);
LogBufferDescriptor.CheckPageSize(pageSize);
if (metaDataTermLength != assumedTermLength)
{
throw new InvalidOperationException(
$"assumed term length {assumedTermLength} does not match metadta: termLength = {metaDataTermLength}");
}
_termLength = assumedTermLength;
for (var i = 0; i < LogBufferDescriptor.PARTITION_COUNT; i++)
{
long position = assumedTermLength * (long)i;
_mappedByteBuffers[i] = new MappedByteBuffer(memoryMappedFile, position, assumedTermLength); // Little Endian
_termBuffers[i] = new UnsafeBuffer(_mappedByteBuffers[i].Pointer, 0, assumedTermLength);
}
}
}
catch (InvalidOperationException ex)
{
Dispose();
throw ex;
}
}