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Diffstat (limited to 'src/core/xbblockread.cpp')
| -rwxr-xr-x | src/core/xbblockread.cpp | 279 |
1 files changed, 279 insertions, 0 deletions
diff --git a/src/core/xbblockread.cpp b/src/core/xbblockread.cpp new file mode 100755 index 0000000..7e2c5fc --- /dev/null +++ b/src/core/xbblockread.cpp @@ -0,0 +1,279 @@ +/* xbblockread.cpp + +XBase64 Software Library + +Copyright (c) 1997,2003,2014,2022,2023 Gary A Kunkel + +The xb64 software library is covered under the terms of the GPL Version 3, 2007 license. + +Email Contact: + + XDB-devel@lists.sourceforge.net + XDB-users@lists.sourceforge.net + +This module handles block read methods. Block reading is used for performance improvement +during sequential access processing. + +*/ + +#include "xbase.h" + +#ifdef XB_BLOCKREAD_SUPPORT + +namespace xb{ + +/************************************************************************/ +xbBlockRead::xbBlockRead( xbDbf * d ) { + pBlock = NULL; + ulBlkSize = 0; + ulFirstBlkRec = 0; + ulRecCnt = 0; + ulMaxRecs = 0; + bEof = xbFalse; + this->dbf = d; + tFmTime = 0; +} +/************************************************************************/ +xbBlockRead::~xbBlockRead(){ + if( pBlock ){ + free( pBlock ); + pBlock = NULL; + } +} + +/************************************************************************/ +//! @brief Dump read block internals to stdout. +/*! + Dump the current read block internals to stdout. +*/ + + +#ifdef XB_DEBUG_SUPPORT +void xbBlockRead::DumpReadBlockInternals(){ + + xbUInt32 ulRecCnt; + dbf->GetRecordCnt( ulRecCnt ); + + std::cout << "------- DumpBlockInternals ---------" << std::endl; + std::cout << "Dflt Blk Size = [" << dbf->GetXbasePtr()->GetDefaultBlockReadSize() + << "]" << std::endl; + std::cout << "Dbf Record Count = [" << ulRecCnt << "]" << std::endl; + std::cout << "Dbf Record Len = [" << dbf->GetRecordLen() << "]" << std::endl; + std::cout << "ulBlkSize = [" << ulBlkSize << "]" << std::endl; + std::cout << "ulMaxRecs = [" << ulMaxRecs << "]" << std::endl; + std::cout << "ulFirstBlkRec = [" << ulFirstBlkRec << "]" << std::endl; + std::cout << "ulRecCnt = [" << ulRecCnt << "]" << std::endl; + std::cout << "bEof = [" << bEof << "]" << std::endl; +} +#endif // XB_DEBUG_SUPPORT +/************************************************************************/ +//! @brief Get the first record number in the current block. +/*! + Retrieve the first record numer in the current block.<br> + + \returns First record number in the current block. +*/ + +xbUInt32 xbBlockRead::GetBlockFirstRecNo() const{ + return ulFirstBlkRec; +} +/************************************************************************/ +//! @brief Get record for specified record number. +/*! + Retrieve a record from read block buffer and copy it into the record buffer. + If the current record is not in the current block, the routine calls + GetBlockForRecNo to load the currect block from disk.<br><br> + For performance reasons, this method assumes a valid record number has been + passed.<br><br> + + \param ulRecNo - Record number to retrieve. + \returns <a href="xbretcod_8h.html">Return Codes</a> +*/ + +xbInt16 xbBlockRead::GetRecord( xbUInt32 ulRecNo ){ + xbInt16 iRc = 0; + xbInt16 iErrorStop = 0; + + // std::cout << "xbBlockRead::GetRecord( " << ulRecNo << ")\n"; + + try{ + if( !( ulRecNo >= ulFirstBlkRec && ulRecNo < (ulFirstBlkRec + ulRecCnt))){ + if(( iRc = GetBlockForRecNo( ulRecNo )) != XB_NO_ERROR ){ + iErrorStop = 100; + throw iRc; + } + } + char *s = pBlock; + s += (ulRecNo - ulFirstBlkRec) * dbf->GetRecordLen(); + char *t = dbf->RecBuf; + xbUInt32 ulRecLen = dbf->GetRecordLen(); + for( xbUInt32 l = 0; l < ulRecLen; l++ ){ + *t = *s; + t++; + s++; + } + dbf->ulCurRec = ulRecNo; + } + catch (xbInt16 iRc ){ + xbString sMsg; + sMsg.Sprintf( "xbBlockRead::GetBlockForRecNo() Exception Caught. Error Stop = [%d] iRc = [%d]", iErrorStop, iRc ); + dbf->GetXbasePtr()->WriteLogMessage( sMsg.Str() ); + dbf->GetXbasePtr()->WriteLogMessage( dbf->GetXbasePtr()->GetErrorMessage( iRc )); + } + return iRc; +} + +/************************************************************************/ +//! @brief Get record for specified record number. +/*! + Retrieve a block containing specified record. This routine calculates the + correct block in the DBF file, updates the internal block fields and retrieves + the block of records from disk and loads into the block buffer.<br><br> + + \param ulRecNo - Record number to retrieve. + \returns <a href="xbretcod_8h.html">Return Codes</a> +*/ + +xbInt16 xbBlockRead::GetBlockForRecNo( xbUInt32 ulRecNo ){ + + xbInt16 iRc = 0; + xbInt16 iErrorStop = 0; + + try{ + xbUInt32 ulDbfRecCnt; + + if(( iRc = dbf->GetRecordCnt( ulDbfRecCnt )) != XB_NO_ERROR ){ + iErrorStop = 100; + throw iRc; + } + + // calc to determine block number for the requested record, 0 based offset + xbUInt32 ulBlockNo = (xbUInt32)(ulRecNo / ulMaxRecs); + if( ulRecNo % ulMaxRecs == 0 ) ulBlockNo--; + + // calc the first record + ulFirstBlkRec = (ulBlockNo * ulMaxRecs); + + // calc the record count + if(( ulFirstBlkRec + ulMaxRecs) > ulDbfRecCnt ){ + ulRecCnt = ulDbfRecCnt - ulFirstBlkRec; + bEof = xbTrue; + } else { + ulRecCnt = ulMaxRecs; + bEof = xbFalse; + } + + // position accordingly + xbInt64 ulStartPos = dbf->GetHeaderLen() + ((xbInt64) ulFirstBlkRec * dbf->GetRecordLen()); + if(( dbf->xbFseek( ulStartPos, SEEK_SET )) != XB_NO_ERROR ){ + iErrorStop = 110; + iRc = XB_SEEK_ERROR; + throw iRc; + } + + if(( dbf->GetFileMtime( tFmTime )) != XB_NO_ERROR ){ + iErrorStop = 120; + throw iRc; + } + // read it + if(( dbf->xbFread( (void *) pBlock, ulRecCnt * dbf->GetRecordLen(), 1 )) != XB_NO_ERROR ){ + iErrorStop = 130; + throw iRc; + } + + ulFirstBlkRec++; // zero offset in the routine, regular record number from ths point forward + } + catch (xbInt16 iRc ){ + xbString sMsg; + sMsg.Sprintf( "xbBlockRead::GetBlockForRecNo() Exception Caught. Error Stop = [%d] iRc = [%d]", iErrorStop, iRc ); + dbf->GetXbasePtr()->WriteLogMessage( sMsg.Str() ); + dbf->GetXbasePtr()->WriteLogMessage( dbf->GetXbasePtr()->GetErrorMessage( iRc )); + } + return iRc; +} + +/************************************************************************/ +//! @brief Get the current block size. +/*! + Retrieve the current block size.<br><br> + + \returns Current Block Size. +*/ + +xbUInt32 xbBlockRead::GetBlockSize() const{ + return ulBlkSize; +} + +/************************************************************************/ +//! @brief Get the current block record count. +/*! + Retrieve the current number of records loaded in the block.<br><br> + + \returns Current Block Size. +*/ + +xbUInt32 xbBlockRead::GetBlockRecCnt() const { + return ulRecCnt; +} + +/************************************************************************/ +//! @brief Init the block processing for a iven DBF file. +/*! + Initialize the settings for a given DBF file.<br> + This routine may adjust the block size as needed to eliminate unused + memory or adjust it bigger if too small. + + \param ulRecNo - ulBlockSize - Block size to allocate. If 0 or missing, it uses default block size of 32K. + \returns <a href="xbretcod_8h.html">Return Codes</a> +*/ + +xbInt16 xbBlockRead::Init(xbUInt32 ulBlockSize ){ + + xbInt16 iRc = 0; + xbInt16 iErrorStop = 0; + + try{ + + // calculate the block size + if( ulBlockSize == 0 ) + ulBlkSize = dbf->GetXbasePtr()->GetDefaultBlockReadSize(); + + // if not big enough to handle more than one record, bump it up to something meaningful + if( ulBlkSize < (xbUInt32)(dbf->GetRecordLen() * 2 )) + ulBlkSize = (xbUInt32) dbf->GetRecordLen() * 10; + + ulMaxRecs = (xbUInt32) ulBlkSize / dbf->GetRecordLen(); + ulBlkSize = ulMaxRecs * dbf->GetRecordLen(); + + // allocate memory for the block + if(( pBlock = (char *) calloc( 1, ulBlkSize )) == NULL ){ + iErrorStop = 100; + throw iRc; + } + } + catch (xbInt16 iRc ){ + xbString sMsg; + sMsg.Sprintf( "xbBlockRead::Init() Exception Caught. Error Stop = [%d] iRc = [%d]", iErrorStop, iRc ); + dbf->GetXbasePtr()->WriteLogMessage( sMsg.Str() ); + dbf->GetXbasePtr()->WriteLogMessage( dbf->GetXbasePtr()->GetErrorMessage( iRc )); + } + return iRc; +} + +/************************************************************************/ +//! @brief Set the block size. +/*! + St block size for this DBF file.<br>. + + \param ulBlkSize - Block Size. + \returns XB_NO_ERROR +*/ + +xbInt16 xbBlockRead::SetBlockSize( xbUInt32 ulBlkSize ){ + this->ulBlkSize = ulBlkSize; + return XB_NO_ERROR; +} + +/************************************************************************/ +} /* namespace */ +#endif /* XB_BLOCKREAD_SUPPORT */
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