SamFile.cpp

/*
 *  Copyright (C) 2010  Regents of the University of Michigan
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include <stdexcept>
#include "SamFile.h"
#include "SamFileHeader.h"
#include "SamRecord.h"
#include "BamInterface.h"
#include "SamInterface.h"

// Constructor, init variables.
SamFile::SamFile()
    : myFilePtr(NULL),
      myInterfacePtr(NULL),
      myStatistics(NULL),
      myStatus(),
      myBamIndex(NULL),
      myRefPtr(NULL),
      myReadTranslation(SamRecord::NONE),
      myWriteTranslation(SamRecord::NONE)
{
    resetFile();
}


// Constructor, init variables.
SamFile::SamFile(ErrorHandler::HandlingType errorHandlingType)
    : myFilePtr(NULL),
      myInterfacePtr(NULL),
      myStatistics(NULL),
      myStatus(errorHandlingType),
      myBamIndex(NULL),
      myRefPtr(NULL),
      myReadTranslation(SamRecord::NONE),
      myWriteTranslation(SamRecord::NONE)
{
    resetFile();
}


// Constructor, init variables and open the specified file based on the
// specified mode (READ/WRITE).
SamFile::SamFile(const char* filename, OpenType mode)
    : myFilePtr(NULL),
      myInterfacePtr(NULL),
      myStatistics(NULL),
      myStatus(),
      myBamIndex(NULL),
      myRefPtr(NULL),
      myReadTranslation(SamRecord::NONE),
      myWriteTranslation(SamRecord::NONE)
{
    resetFile();

    bool openStatus = true;
    if(mode == READ)
    {
        // open the file for read.
        openStatus = OpenForRead(filename);
    }
    else
    {
        // open the file for write.
        openStatus = OpenForWrite(filename);
    }
    if(!openStatus)
    {
        // Failed to open the file - print error and abort.
        fprintf(stderr, "%s\n", GetStatusMessage());
        std::cerr << "FAILURE - EXITING!!!" << std::endl;
        exit(-1);
    }
}


// Constructor, init variables and open the specified file based on the
// specified mode (READ/WRITE).  Default is READ..
SamFile::SamFile(const char* filename, OpenType mode,
                 ErrorHandler::HandlingType errorHandlingType)
    : myFilePtr(NULL),
      myInterfacePtr(NULL),
      myStatistics(NULL),
      myStatus(errorHandlingType),
      myBamIndex(NULL),
      myRefPtr(NULL),
      myReadTranslation(SamRecord::NONE),
      myWriteTranslation(SamRecord::NONE)
{
    resetFile();

    bool openStatus = true;
    if(mode == READ)
    {
        // open the file for read.
        openStatus = OpenForRead(filename);
    }
    else
    {
        // open the file for write.
        openStatus = OpenForWrite(filename);
    }
    if(!openStatus)
    {
        // Failed to open the file - print error and abort.
        fprintf(stderr, "%s\n", GetStatusMessage());
        std::cerr << "FAILURE - EXITING!!!" << std::endl;
        exit(-1);
    }
}


SamFile::~SamFile()
{
    resetFile();
    if(myStatistics != NULL)
    {
        delete myStatistics;
    }
}


// Open a sam/bam file for reading with the specified filename.
bool SamFile::OpenForRead(const char * filename)
{
    // Reset for any previously operated on files.
    resetFile();

    int lastchar = 0;

    while (filename[lastchar] != 0) lastchar++;

    // If at least one character, check for '-'.
    if((lastchar >= 1) && (filename[0] == '-'))
    {
        // Read from stdin - determine type of file to read.
        // Determine if compressed bam.
        if(strcmp(filename, "-.bam") == 0)
        {
            // Compressed bam - open as bgzf.
            // -.bam is the filename, read compressed bam from stdin
            filename = "-";
            myFilePtr = ifopen(filename, "rb", InputFile::BGZF);
            
            myInterfacePtr = new BamInterface;

            // Read the magic string.
            char magic[4];
            ifread(myFilePtr, magic, 4);
        }
        else if(strcmp(filename, "-.ubam") == 0)
        {
            // uncompressed BAM File.
            // -.ubam is the filename, read uncompressed bam from stdin
            filename = "-";
            myFilePtr = ifopen(filename, "rb", InputFile::UNCOMPRESSED);
        
            myInterfacePtr = new BamInterface;

            // Read the magic string.
            char magic[4];
            ifread(myFilePtr, magic, 4);
        }
        else
        {
            // SAM File.
            // read sam from stdin
            filename = "-";
            myFilePtr = ifopen(filename, "rb", InputFile::UNCOMPRESSED);
            myInterfacePtr = new SamInterface;
        }
    }
    else
    {
        // Not from stdin.  Read the file to determine the type.
        myFilePtr = ifopen(filename, "rb");
        
        if (myFilePtr == NULL)
        {
            std::string errorMessage = "Failed to Open ";
            errorMessage += filename;
            errorMessage += " for reading";
            myStatus.setStatus(SamStatus::FAIL_IO, errorMessage.c_str());
            return(false);
        }
        
        char magic[4];
        ifread(myFilePtr, magic, 4);
        
        if (magic[0] == 'B' && magic[1] == 'A' && magic[2] == 'M' &&
            magic[3] == 1)
        {
            myInterfacePtr = new BamInterface;
            // Set that it is a bam file open for reading.  This is needed to
            // determine if an index file can be used.
            myIsBamOpenForRead = true;
        }
        else
        {
            // Not a bam, so rewind to the beginning of the file so it
            // can be read.
            ifrewind(myFilePtr);
            myInterfacePtr = new SamInterface;
        }
    }

    // File is open for reading.
    myIsOpenForRead = true;
    // Successfully opened the file.
    myStatus = SamStatus::SUCCESS;
    return(true);
}


// Open a sam/bam file for writing with the specified filename.
bool SamFile::OpenForWrite(const char * filename)
{
    // Reset for any previously operated on files.
    resetFile();
    
    int lastchar = 0;
    while (filename[lastchar] != 0) lastchar++;   
    if (lastchar >= 4 && 
        filename[lastchar - 4] == 'u' &&
        filename[lastchar - 3] == 'b' &&
        filename[lastchar - 2] == 'a' &&
        filename[lastchar - 1] == 'm')
    {
        // BAM File.
        // if -.ubam is the filename, write uncompressed bam to stdout
        if((lastchar == 6) && (filename[0] == '-') && (filename[1] == '.'))
        {
            filename = "-";
        }
        myFilePtr = ifopen(filename, "wb", InputFile::UNCOMPRESSED);

        myInterfacePtr = new BamInterface;
    }
    else if (lastchar >= 3 && 
             filename[lastchar - 3] == 'b' &&
             filename[lastchar - 2] == 'a' &&
             filename[lastchar - 1] == 'm')
    {
        // BAM File.
        // if -.bam is the filename, write compressed bam to stdout
        if((lastchar == 5) && (filename[0] == '-') && (filename[1] == '.'))
        {
            filename = "-";
        }
        myFilePtr = ifopen(filename, "wb", InputFile::BGZF);
        
        myInterfacePtr = new BamInterface;
    }
    else
    {
        // SAM File
        // if - (followed by anything is the filename,
        // write uncompressed sam to stdout
        if((lastchar >= 1) && (filename[0] == '-'))
        {
            filename = "-";
        }
        myFilePtr = ifopen(filename, "wb", InputFile::UNCOMPRESSED);
   
        myInterfacePtr = new SamInterface;
    }

    if (myFilePtr == NULL)
    {
        std::string errorMessage = "Failed to Open ";
        errorMessage += filename;
        errorMessage += " for writing";
        myStatus.setStatus(SamStatus::FAIL_IO, errorMessage.c_str());
        return(false);
    }
   
    myIsOpenForWrite = true;

    // Successfully opened the file.
    myStatus = SamStatus::SUCCESS;
    return(true);
}


// Read BAM Index file.
bool SamFile::ReadBamIndex(const char* bamIndexFilename)
{
    // Cleanup a previously setup index.
    if(myBamIndex != NULL)
    {
        delete myBamIndex;
        myBamIndex = NULL;
    }

    // Create a new bam index.
    myBamIndex = new BamIndex();
    SamStatus::Status indexStat = myBamIndex->readIndex(bamIndexFilename);

    if(indexStat != SamStatus::SUCCESS)
    {
        std::string errorMessage = "Failed to read the bam Index file: ";
        errorMessage += bamIndexFilename;
        myStatus.setStatus(indexStat, errorMessage.c_str());
        delete myBamIndex;
        myBamIndex = NULL;
        return(false);
    }
    myStatus = SamStatus::SUCCESS;
    return(true);
}


// Sets the reference to the specified genome sequence object.
void SamFile::SetReference(GenomeSequence* reference)
{
    myRefPtr = reference;
}


// Set the type of sequence translation to use when reading the sequence.
void SamFile::SetReadSequenceTranslation(SamRecord::SequenceTranslation translation)
{
    myReadTranslation = translation;
}


// Set the type of sequence translation to use when writing the sequence.
void SamFile::SetWriteSequenceTranslation(SamRecord::SequenceTranslation translation)
{
    myWriteTranslation = translation;
}

// Close the file if there is one open.
void SamFile::Close()
{
    // Resetting the file will close it if it is open, and
    // will reset all other variables.
    resetFile();
}


// Returns whether or not the end of the file has been reached.
// return: int - true = EOF; false = not eof.
bool SamFile::IsEOF()
{
    if (myFilePtr != NULL)
    {
        // File Pointer is set, so return if eof.
        return(ifeof(myFilePtr));
    }
    // File pointer is not set, so return true, eof.
    return true;
}


// Read the header from the currently opened file.
bool SamFile::ReadHeader(SamFileHeader& header)
{
    if(myIsOpenForRead == false)
    {
        // File is not open for read
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Cannot read header since the file is not open for reading");
        return(false);
    }

    if(myHasHeader == true)
    {
        // The header has already been read.
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Cannot read header since it has already been read.");
        return(false);
    }

    myStatus = myInterfacePtr->readHeader(myFilePtr, header);
    if(myStatus == SamStatus::SUCCESS)
    {
        // The header has now been successfully read.
        myHasHeader = true;
        return(true);
    }
    return(false);
}


// Write the header to the currently opened file.
bool SamFile::WriteHeader(SamFileHeader& header)
{
    if(myIsOpenForWrite == false)
    {
        // File is not open for write
        // -OR-
        // The header has already been written.
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Cannot write header since the file is not open for writing");
        return(false);
    }

    if(myHasHeader == true)
    {
        // The header has already been written.
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Cannot write header since it has already been written");
        return(false);
    }

    myStatus = myInterfacePtr->writeHeader(myFilePtr, header);
    if(myStatus == SamStatus::SUCCESS)
    {
        // The header has now been successfully written.
        myHasHeader = true;
        return(true);
    }

    // return the status.
    return(false);
}


// Read a record from the currently opened file.
bool SamFile::ReadRecord(SamFileHeader& header, 
                         SamRecord& record)
{
    myStatus = SamStatus::SUCCESS;

    if(myIsOpenForRead == false)
    {
        // File is not open for read
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Cannot read record since the file is not open for reading");
        throw(std::runtime_error("SOFTWARE BUG: trying to read a SAM/BAM record prior to opening the file."));
        return(false);
    }

    if(myHasHeader == false)
    {
        // The header has not yet been read.
        // TODO - maybe just read the header.
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Cannot read record since the header has not been read.");
        throw(std::runtime_error("SOFTWARE BUG: trying to read a SAM/BAM record prior to reading the header."));
        return(false);
    }

    // Check to see if a new region has been set.  If so, determine the
    // chunks for that region.
    if(myNewSection)
    {
        if(!processNewSection(header))
        {
            // Failed processing a new section.  Could be an 
            // order issue like the file not being open or the
            // indexed file not having been read.
            // processNewSection sets myStatus with the failure reason.
            return(false);
        }
    }

    // Check to see if the file should be read by index.
    if(myRefID != BamIndex::REF_ID_ALL)
    {
        // Reference ID is set, so read by index.
        return(readIndexedRecord(header, record));
    }

    record.setReference(myRefPtr);
    record.setSequenceTranslation(myReadTranslation);

    // File is open for reading and the header has been read, so read the next
    // record.
    myInterfacePtr->readRecord(myFilePtr, header, record, myStatus);
    if(myStatus == SamStatus::SUCCESS)
    {
        // A record was successfully read, so increment the record count.
        myRecordCount++;

        if(myStatistics != NULL)
        {
            // Statistics should be updated.
            myStatistics->updateStatistics(record);
        }

        // Successfully read the record, so check the sort order.
        if(!validateSortOrder(record, header))
        {
            // ValidateSortOrder sets the status on a failure.
            return(false);
        }
        return(true);
    }
    // Failed to read the record.
    return(false);
}



// Write a record to the currently opened file.
bool SamFile::WriteRecord(SamFileHeader& header, 
                          SamRecord& record)
{
    if(myIsOpenForWrite == false)
    {
        // File is not open for writing
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Cannot write record since the file is not open for writing");
        return(false);
    }

    if(myHasHeader == false)
    {
        // The header has not yet been written.
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Cannot write record since the header has not been written");
        return(false);
    }

    // Before trying to write the record, validate the sort order.
    if(!validateSortOrder(record, header))
    {
        // Not sorted like it is supposed to be, do not write the record
        myStatus.setStatus(SamStatus::INVALID_SORT, 
                           "Cannot write the record since the file is not properly sorted.");
        return(false);
    }

    if(myRefPtr != NULL)
    {
        record.setReference(myRefPtr);
    }

    // File is open for writing and the header has been written, so write the
    // record.
    myStatus = myInterfacePtr->writeRecord(myFilePtr, header, record,
                                           myWriteTranslation);

    if(myStatus == SamStatus::SUCCESS)
    {
        // A record was successfully written, so increment the record count.
        myRecordCount++;
        return(true);
    }
    return(false);
}


// Set the flag to validate that the file is sorted as it is read/written.
// Must be called after the file has been opened.
void SamFile::setSortedValidation(SortedType sortType)
{
    mySortedType = sortType;
}


// Return the number of records that have been read/written so far.
uint32_t SamFile::GetCurrentRecordCount()
{
    return(myRecordCount);
}


// Sets what part of the SamFile should be read.
bool SamFile::SetReadSection(int32_t refID)
{
    // No start/end specified, so set back to default -1.
    return(SetReadSection(refID, -1, -1));
}



// Sets what part of the SamFile should be read.
bool SamFile::SetReadSection(const char* refName)
{
    // No start/end specified, so set back to default -1.
    return(SetReadSection(refName, -1, -1));
}


// Sets what part of the BAM file should be read.
bool SamFile::SetReadSection(int32_t refID, int32_t start, int32_t end)
{
    // If there is not a BAM file open for reading, return failure.
    // Opening a new file clears the read section, so it must be
    // set after the file is opened.
    if(!myIsBamOpenForRead)
    {
        // There is not a BAM file open for reading.
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Canot set section since there is no bam file open");
        return(false);
    }

    myNewSection = true;
    myStartPos = start;
    myEndPos = end;
    myRefID = refID;
    myRefName.clear();
    myChunksToRead.clear();
    // Reset the end of the current chunk.  We are resetting our read, so
    // we no longer have a "current chunk" that we are reading.
    myCurrentChunkEnd = 0;
    myStatus = SamStatus::SUCCESS;
    
    return(true);
}


// Sets what part of the BAM file should be read.
bool SamFile::SetReadSection(const char* refName, int32_t start, int32_t end)
{
    // If there is not a BAM file open for reading, return failure.
    // Opening a new file clears the read section, so it must be
    // set after the file is opened.
    if(!myIsBamOpenForRead)
    {
        // There is not a BAM file open for reading.
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Canot set section since there is no bam file open");
        return(false);
    }

    myNewSection = true;
    myStartPos = start;
    myEndPos = end;
    if((strcmp(refName, "") == 0) || (strcmp(refName, "*") == 0))
    {
        // No Reference name specified, so read just the "-1" entries.
        myRefID = BamIndex::REF_ID_UNMAPPED;
    }
    else
    {
        // save the reference name and revert the reference ID to unknown
        // so it will be calculated later.
        myRefName = refName;
        myRefID = BamIndex::REF_ID_ALL;
    }
    myChunksToRead.clear();
    // Reset the end of the current chunk.  We are resetting our read, so
    // we no longer have a "current chunk" that we are reading.
    myCurrentChunkEnd = 0;
    myStatus = SamStatus::SUCCESS;
    
    return(true);
}


// Returns the number of bases in the passed in read that overlap the
// region that is currently set.
uint32_t SamFile::GetNumOverlaps(SamRecord& samRecord)
{
    if(myRefPtr != NULL)
    {
        samRecord.setReference(myRefPtr);
    }
    samRecord.setSequenceTranslation(myReadTranslation);

    // Get the overlaps in the sam record for the region currently set
    // for this file.
    return(samRecord.getNumOverlaps(myStartPos, myEndPos));
}


void SamFile::GenerateStatistics(bool genStats)
{
    if(genStats)
    {
        if(myStatistics == NULL)
        {
            // Want to generate statistics, but do not yet have the
            // structure for them, so create one.
            myStatistics = new SamStatistics();
        }
    }
    else
    {
        // Do not generate statistics, so if myStatistics is not NULL, 
        // delete it.
        if(myStatistics != NULL)
        {
            delete myStatistics;
            myStatistics = NULL;
        }
    }

}


// Reset variables for each file.
void SamFile::resetFile()
{
    // Close the file.
    if (myFilePtr != NULL)
    {
        // If we already have an open file, close it.
        ifclose(myFilePtr);
        myFilePtr = NULL;
    }
    if(myInterfacePtr != NULL)
    {
        delete myInterfacePtr;
        myInterfacePtr = NULL;
    }

    myIsOpenForRead = false;
    myIsOpenForWrite = false;
    myHasHeader = false;
    mySortedType = UNSORTED;
    myPrevReadName = "";
    myPrevCoord = -1;
    myPrevRefID = 0;
    myRecordCount = 0;
    myStatus = SamStatus::SUCCESS;

    // Reset indexed bam values.
    myIsBamOpenForRead = false;
    myRefID = BamIndex::REF_ID_ALL;
    myStartPos = -1;
    myEndPos = -1;
    myNewSection = false;
    myCurrentChunkEnd = 0;
    myChunksToRead.clear();
    if(myBamIndex != NULL)
    {
        delete myBamIndex;
        myBamIndex = NULL;
    }

    // If statistics are being generated, reset them.
    if(myStatistics != NULL)
    {
        myStatistics->reset();
    }

    myRefName.clear();
}


// Validate that the record is sorted compared to the previously read record
// if there is one, according to the specified sort order.
// If the sort order is UNSORTED, true is returned.
bool SamFile::validateSortOrder(SamRecord& record, SamFileHeader& header)
{
    if(myRefPtr != NULL)
    {
        record.setReference(myRefPtr);
    }
    record.setSequenceTranslation(myReadTranslation);

    bool status = false;
    if(mySortedType == UNSORTED)
    {
        // Unsorted, so nothing to validate, just return true.
        status = true;
    }
    else 
    {
        // Check to see if mySortedType is based on the header.
        if(mySortedType == FLAG)
        {
            // Determine the sorted type from what was read out of the header.
            mySortedType = getSortOrderFromHeader(header);
        }

        if(mySortedType == QUERY_NAME)
        {
            // Validate that it is sorted by query name.
            // Get the query name from the record.
            const char* readName = record.getReadName();
            if(myPrevReadName.compare(readName) > 0)
            {
                // The previous name is greater than the new record's name, so
                // return false.
                String errorMessage = "ERROR: File is not sorted at record ";
                errorMessage += myRecordCount;
                myStatus.setStatus(SamStatus::INVALID_SORT, 
                                   errorMessage.c_str());
                status = false;
            }
            else
            {
                myPrevReadName = readName;
                status = true;
            }
        }
        else 
        {
            // Validate that it is sorted by COORDINATES.
            // Get the leftmost coordinate and the reference index.
            int32_t refID = record.getReferenceID();
            int32_t coord = record.get0BasedPosition();
            // The unmapped reference id is at the end of a sorted file.
            if(refID == BamIndex::REF_ID_UNMAPPED)
            {
                // A new reference ID that is for the unmapped reads
                // is always valid.
                status = true;
                myPrevRefID = refID;
                myPrevCoord = coord;
            }
            else if(myPrevRefID == BamIndex::REF_ID_UNMAPPED)
            {
                // Previous reference ID was for unmapped reads, but the
                // current one is not, so this is not sorted.
                String errorMessage = "ERROR: File is not sorted at record ";
                errorMessage += myRecordCount;
                myStatus.setStatus(SamStatus::INVALID_SORT, 
                                   errorMessage.c_str());
                status = false;
            }
            else if(refID < myPrevRefID)
            {
                // Current reference id is less than the previous one, 
                //meaning that it is not sorted.
                String errorMessage = "ERROR: File is not sorted at record ";
                errorMessage += myRecordCount;
                myStatus.setStatus(SamStatus::INVALID_SORT, 
                                   errorMessage.c_str());
                status = false;
            }
            else
            {
                // The reference IDs are in the correct order.
                if(refID > myPrevRefID)
                {
                    // New reference id, so set the previous coordinate to -1
                    myPrevCoord = -1;
                }
            
                // Check the coordinates.
                if(coord < myPrevCoord)
                {
                    // New Coord is less than the previous position.
                    String errorMessage = "ERROR: File is not sorted at record ";
                    errorMessage += myRecordCount;
                    myStatus.setStatus(SamStatus::INVALID_SORT, 
                                       errorMessage.c_str());
                    status = false;
                }
                else
                {
                    myPrevRefID = refID;
                    myPrevCoord = coord;
                    status = true;
                }
            }
        }
    }

    return(status);
}


SamFile::SortedType SamFile::getSortOrderFromHeader(SamFileHeader& header)
{
    const char* tag = header.getSortOrder();
   
    // Default to unsorted since if it is not specified in the header
    // that is the value that should be used.
    SortedType headerSortOrder = UNSORTED;
    if(strcmp(tag, "queryname") == 0)
    {
        headerSortOrder = QUERY_NAME;
    }
    else if(strcmp(tag, "coordinate") == 0)
    {
        headerSortOrder = COORDINATE;
    }
    return(headerSortOrder);
}


// Read a record from the currently opened file based on the indexing info.
bool SamFile::readIndexedRecord(SamFileHeader& header, 
                                SamRecord& record)
{
    record.setReference(myRefPtr);
    record.setSequenceTranslation(myReadTranslation);

    // A section to read is set and the file is open for reading, as verified
    // prior to calling into this protected method.
    bool recordFound = false;
    while(!recordFound)
    {
        // Check to see if we have more to read out of the current chunk.
        // By checking the current position in relation to the current
        // end chunk.  If the current position is >= the end of the
        // current chunk, then we must see to the next chunk.
        uint64_t currentPos = iftell(myFilePtr);
        if(currentPos >= myCurrentChunkEnd)
        {
            // If there are no more chunks to process, return failure.
            if(myChunksToRead.empty())
            {
                myStatus = SamStatus::NO_MORE_RECS;
                return(false);
            }
      
            // There are more chunks left, so get the next chunk.
            Chunk newChunk = myChunksToRead.pop();

            // Move to the location of the new chunk if it is not adjacent
            // to the current chunk.
            if(newChunk.chunk_beg != currentPos)
            {
                // New chunk is not adjacent, so move to it.
                if(ifseek(myFilePtr, newChunk.chunk_beg, SEEK_SET) != true)
                {
                    // seek failed, cannot retrieve next record, return failure.
                    myStatus.setStatus(SamStatus::FAIL_IO, 
                                       "Failed to seek to the next record");
                    return(false);
                }
            }
            // Seek succeeded, set the end of the new chunk.
            myCurrentChunkEnd = newChunk.chunk_end;
        }

        // At the position of the next record.  Read the record.
        myInterfacePtr->readRecord(myFilePtr, header, record, myStatus);
        if(myStatus != SamStatus::SUCCESS)
        {
            // Reading the record failed, return failure.
            return(false);
        }

        // Successfully read the record.  Check to see if it is in the correct 
        // reference/position.
        if(record.getReferenceID() != myRefID)
        {
            // Incorrect reference ID, return failure.
            myStatus = SamStatus::NO_MORE_RECS;
            return(false);
        }
   
        // Found a record.
        recordFound = true;

        // If start/end position are set, verify that the alignment falls
        // completely within those.
        if((myStartPos != -1) && (myEndPos != -1))
        {
            // Start & end are specified, so check if the alignment 
            // overlaps this section.

            // If the alignment start is greater than the end of the region,
            // return NO_MORE_RECS.
            if(record.get0BasedPosition() >= myEndPos)
            {
                myStatus = SamStatus::NO_MORE_RECS;
                return(false);
            }

            // We know the start is less than the end position, so the alignment
            // overlaps the region if the alignment end position is greater than the
            // start of the region.
            if(record.get0BasedAlignmentEnd() < myStartPos)
            {
                // If it does not overlap the region, so go to the next
                // record...set recordFound back to false.
                recordFound = false;
            }
        }
    }

    // Successfully read the record, so check the sort order.
    if(!validateSortOrder(record, header))
    {
        myStatus.setStatus(SamStatus::INVALID_SORT, 
                           "The file is not properly sorted.");
        return(false);
    }
   
    // If it made it here, then the record was successfully read
    // and met the criteria, so return success.
    myRecordCount++;

    if(myStatistics != NULL)
    {
        // Successfully read, statistics should be updated.
        myStatistics->updateStatistics(record);
    }
    
    return(true);
}


bool SamFile::processNewSection(SamFileHeader &header)
{
    myNewSection = false;

    // If there is no index file, return failure.
    if(myBamIndex == NULL)
    {
        // No bam index has been read.
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Canot read section since there is no index file open");
        throw(std::runtime_error("SOFTWARE BUG: trying to read a BAM record by section prior to opening the BAM Index file."));
        return(false);
    }

    // If there is not a BAM file open for reading, return failure.
    if(!myIsBamOpenForRead)
    {
        // There is not a BAM file open for reading.
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Canot read section since there is no bam file open");
        throw(std::runtime_error("SOFTWARE BUG: trying to read a BAM record by section without opening a BAM file."));
        return(false);
    }

    if(myHasHeader == false)
    {
        // The header has not yet been read.
        myStatus.setStatus(SamStatus::FAIL_ORDER, 
                           "Cannot read record since the header has not been read.");
        throw(std::runtime_error("SOFTWARE BUG: trying to read a BAM record by section prior to opening the header."));
        return(false);
    }

    myChunksToRead.clear();
    // Reset the end of the current chunk.  We are resetting our read, so
    // we no longer have a "current chunk" that we are reading.
    myCurrentChunkEnd = 0;

    // Check to see if the read section was set based on the reference name
    // but not yet converted to reference id.
    if(!myRefName.empty())
    {
        myRefID = header.getReferenceID(myRefName.c_str());
        // Clear the myRefName length so this code is only executed once.
        myRefName.clear();
    }

    // Get the chunks associated with this reference region.
    if(myBamIndex->getChunksForRegion(myRefID, myStartPos, myEndPos, 
                                      myChunksToRead) == true)
    {
        myStatus = SamStatus::SUCCESS;
    }
    else
    {
        myStatus.setStatus(SamStatus::FAIL_PARSE, 
                           "Failed to get the specified region.");
    }
    return(true);
}


// Default Constructor.
SamFileReader::SamFileReader()
{
}


// Constructor that opens the specified file for read.
SamFileReader::SamFileReader(const char* filename)
{
    if(!OpenForRead(filename))
    {
        // Failed to open for reading - print error and abort.
        fprintf(stderr, "%s\n", GetStatusMessage());
        std::cerr << "FAILURE - EXITING!!!" << std::endl;
        exit(-1);
    }
}


SamFileReader::~SamFileReader()
{
}


// Default Constructor.
SamFileWriter::SamFileWriter()
{
}


// Constructor that opens the specified file for write.
SamFileWriter::SamFileWriter(const char* filename)
{
    if(!OpenForWrite(filename))
    {
        // Failed to open for reading - print error and abort.
        fprintf(stderr, "%s\n", GetStatusMessage());
        std::cerr << "FAILURE - EXITING!!!" << std::endl;
        exit(-1);
    }
}


SamFileWriter::~SamFileWriter()
{
}