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diff --git a/1Tdata/xbase/xbase64-4.1.4/docs/html/xbc5.html b/1Tdata/xbase/xbase64-4.1.4/docs/html/xbc5.html deleted file mode 100755 index 66b0f62..0000000 --- a/1Tdata/xbase/xbase64-4.1.4/docs/html/xbc5.html +++ /dev/null @@ -1,437 +0,0 @@ -<!DOCTYPE HTML PUBLIC> -<html> -<title>Xbase DBMS Chapter 5</title> -<body BGCOLOR=#FFFFFF> -<H1><p align="center">Index Overview</p></H1> -<p align="center">Chapter Updated 04/29/23</p><hr> - -The objective of this chapter is to provide information regarding -the basic concepts of index processing for the Xbase library.<br><br> - - -<h3>Overview</h3> - -The Xbase64 library is designed to support multiple index types simultaneously. -Dbase, Clipper and Foxbase each had their own index formats and ultimately the -goal is to provide support for all the legacy index file formats. - -<br><br> -The 4.0.x rewrite includes the NDX and MDX formats. Earlier versions of the -library included an NTX format which will be brought forward into the -library rewrite at some point in the future. - - -<h3>Tags</h3> - -Each index file contains one or more tags depending on the file type. Each tag is a sort order -and has characteristics: Sort order (ASC or DESC), unique or not unique and some formats support filtering. -Each open table (dbf file) has an "active tag" for database operations. - -<h3>Index processing design</h3> - -The library is construcuted to handle index files with multiple tags per file. Single tag files like the NDX indices -are treated as a multi tag file, but there is only one tag. This allows for maximum flexibility for future -additional index types. - - - -<h3>Index updates</h3> - -The library automatically updates all tags in all open index files. - - -<br><br> -<h3>Index File Types</h3> - -<table border=1> -<tr><th>File<br>Type</th><th>Source</th><th>Max Tags<br>Per File</th><th>Auto Opened</th><th>Sort Order</th><th>Unique Keys</th> - <th>Reclaimed Nodes</th><th>Filter Support</th><th>Status</th></tr> -<tr> - <td>NDX</td><td>dBase</td> - <td><center>1</center></td> - <td><center>Optional</center></td> - <td>ASC only</td> - <td><center>Y</center></td> - <td><center>N</center></td> - <td><center>N</center></td> - <td><center>Available in 4.0.1</center></td> -</tr> -<tr> - <td>MDX</td><td>dBase</td> - <td><center>47</center></td> - <td><center>Yes</center></td> - <td><center>ASC or DESC</center></td> - <td><center>Y</center></td> - <td><center>Y</center></td> - <td><center>Y</center></td> - <td><center>Available in 4.0.1</center></td> -</tr> -<tr> - <td>NTX</td> - <td>Clipper</td> - <td><center>1</center></td> - <td><center>Optional</center></td> - <td><center></center></td> - <td><center></center></td> - <td><center></center></td> - <td><center></center></td> - <td><center>Pending retrofit</center></td> -</tr> -<tr> - <td>CDX</td> - <td>Fox Pro</td> - <td><center></center></td> - <td><center></center></td> - <td><center></center></td> - <td><center></center></td> - <td><center></center></td> - <td><center></center></td> - <td><center>Pending development</center></td> -<tr> -<tr> - <td>IDX</td><td>Fox Pro</td> - <td></td> - <td></td> - <td></td> - <td></td> - <td></td> - <td></td> - <td>Pending development</td> -<tr> - -</table> - -<br><br> -<h3>Index/Tag Methods</h3> - - -<table border=1> -<tr><th width=45%>Method</th><th>Description</th></tr> -<tr> - <td>xbInt16 xbDbf::CheckTagIntegrity( xbInt16 iTagOpt, xbInt16 iOutputOpt ) - </td><td>Checks a tag for missing or duplicate entries. Available if XB_DEBUG_SUPPORT is on.</td> -</tr> -<tr> - <td>xbInt16 xbDbf::CloseIndexFile( xbIx *pIx ) - </td><td>Close an index file. Indices are automatically closed when the table is closed. - <br>Not typically called in an application program.</td> -</tr> -<tr> - <td>xbInt16 xbDbf::CreateTag( const xbString &sIxType, const xbString &sName, const xbString &sKey, const xbString &sFilter, - xbInt16 iDescending, xbInt16 iUnique, xbInt16 iOverLay, xbIx **xbIxOut, void **vpTagOut ); - </td><td>Create a new tag.</td> -</tr> -<tr> - <td>xbInt16 xbDbf::DeleteTag( const xbString &sIxType, const xbString &sName ) - </td><td>Delete existing tag.</td> -</tr> -<tr> - <td>xbInt16 xbDbf::Find( xbString &sKey )<br>xbInt16 xbDbf::Find( xbDate &dtKey )<br>xbInt16 xbDbf::Find( xbDouble &dKey ) - </td><td>Find key value for the active tag.</td> -</tr> -<tr> - <td>xbIx * xbDbf::GetCurIx() const - </td><td>Returns a pointer to the current index object.</td> -</tr> - <td>xbString & xbDbf::GetCurIxType() const - </td><td>Returns the current index type.</td> -</tr> -</tr> - <td>void * xbDbf::GetCurTag() const - </td><td>Retrieve pointer to the current active tag.</td> -</tr> -<tr> - <td>const xbString & xbDbf::GetCurTagName() const - </td><td>Returns the current tag name.</td> -</tr> - <td>xbInt16 xbDbf::GetFirstKey() - </td><td>Retrieve the first key for the active tag.</td> -</tr> -<tr> - <td>xbIxList * xbDbf::GetIxList() const - </td><td>Returns a pointer to the list of active indices. -</tr> -<tr> - <td>xbInt16 xbDbf::GetLastKey() - </td><td>Retrieve the last key for the active tag.</td> -</tr> -<tr> - <td>xbInt16 xbDbf::GetNextKey() - </td><td>Retrieve the next key for the active tag.</td> -</tr> -<tr> - <td>xbInt32 xbDbf::GetPhysicalIxCnt() const - </td><td>Returns count of number of physical files opened for DBF table.</td> -</tr> -<tr> - <td>xbInt16 xbDbf::GetPrevKey() - </td><td>Retrieve the previous key for the active tag.</td> -<tr> - <td>xbLinkListNode<xbTag *> * xbDbf::GetTagList() const - </td><td>Returns pointer to linked list of open tags for the DBF file/table.</td> -</tr> -<tr> - <td>xbInt16 xbDbf::OpenIndex( const xbString &sIxType, const xbString &sIndexName ) - </td><td>Open an index file. Only used for index files that aren't automatically opened.</td> -</tr> -<tr> - <td>xbInt16 xbDbf::Reindex( xbInt16 iTagOpt ) - </td><td>Rebuild a tag. Available if XB_DEBUG_SUPPORT is on.</td> -</tr> -<tr> - <td>xbInt16 xbDbf::SetCurTag( const xbString &sTagName )<br> - void xbDbf::SetCurTag( const xbString &sIxType, xbIx *pIx, void *vpTag ) - </td><td>Set current tag.</td> -</tr> -</table> -<br><br> - - -<h3>Internal Data Storage</h3> - -<table border=1> -<tr><th>Type<th>Stored in DBF as</th><th>Stored in NDX as</th><th>Stored in MDX as</th></tr> -<tr><td>C</td><td>Character data</td><td>Character data</td><td>Character data</td></tr> -<tr><td>F</td><td>Text numbers</td><td>xbDouble</td><td>xbBcd</td></tr> -<tr><td>N</td><td>Text numbers</td><td>xbDouble</td><td>xbBcd</td></tr> -<tr><td>D</td><td>Text YYYYMMDD</td><td>xbDouble Julian</td><td>xbDouble Julian</td></tr> -</table> -<br><br> - -<hr> -<h2>NDX Indices</h2> -The objective of this section is to provide information regarding the -basic concepts of how .NDX index files work in the Xbase64 library. -Information in this section has been acquired by searching the internet -and by examining the structure of known good NDX indexes.<br><br> - -<h4>NDX Index File Characteristics</h4> - -<li>NDX indices maintain keys in ascending sort order only.<br><br> -<li>NDX indices support <em>unique</em> or <em>non unique</em> keys.<br><br> - -<em>Unique</em> keys must be unique if the UniqueKeyOption is not set to XB_EMULATE_DBASE. -If the UniqueKeyOption is set to XB_EMULATE_DBASE, then the database update routines will -add a record to the table, but not add a corresponding duplicate key to the index tag. -The UniqueKeyOption is off (don't allow duplicates) by default. -<br><br> - -<em>Non-unique</em> Keys are not required to be unique, duplicate -keys are allowed if the index is created with the XB_NOT_UNIQUE -setting. Duplicate keys are stored in record number order.<br><br> - -<li>NDX indexes are automatically updated by the Xbase library after the -indices are opened.<br> -<li>Character keys are left justified and padded on the right with spaces.<br> -<li>Numeric keys are stored as eight byte double values.<br> -<li>Date kets are stored as julian eigth byte double values.<br> - -<h4>NDX File Internals</h4> - -NDX files are comprised of two or more 512 byte blocks or nodes of -information. There are three types of nodes: Head Nodes, Interior -Nodes and Leaf Nodes.<br><br> - -<li>The <em>Head Node</em> is the first node in the file starting at -position zero (0) and contains information about the NDX file. There -is only one Head Node in each index and it always starts at the -beginning of the file.<br><br> - - -<TABLE BORDER> -<CAPTION ALIGN="TOP"><h3>NDX Header Node</H3></CAPTION> -<TR VALIGN="BASELINE"> -<TR><TH ALIGN="LEFT">Type<TD>Size<TD>Field Name<TD>Description -<TR><TH ALIGN="LEFT">xbLong<TD>4<TD>StartNode<TD>This identifies the root node of - the index. The Header node is node 0. -<TR><TH ALIGN="LEFT">xbLong<TD>4<TD>Total Nodes<TD>This is the count of the total - nodes in the index. The count includes the header node. -<TR><TH ALIGN="LEFT">xbLong<TD>4<TD>NoOfKeys<TD>Total number of keys in the index +1 -<TR><TH ALIGN="LEFT">xbUShort<TD>2<TD>KeyLen<TD>The index key length -<TR><TH ALIGN="LEFT">xbUShort<TD>2<TD>KeysPerNode<TD>The maximum number of keys per node -<TR><TH ALIGN="LEFT">xbUShort<TD>2<TD>KeyType<TD>Type of key<br> -00 - Character<br>01 - Numeric -<TR><TH ALIGN="LEFT">xbLong<TD>4<TD>Keysize<TD>Key record size + 8 -<TR><TH ALIGN="LEFT">char<TD>1<TD>Unknown<TD>Reserved -<TR><TH ALIGN="LEFT">char<TD>1<TD>Unique<TD>Unique indicator<br> -00 - Not Unique - XB_NON_UNIQUE<br>01 - Unique - XB_UNIQUE -<TR><TH ALIGN="LEFT">char<TD>488<TD>KeyExpression<TD>Key expression string -<TR><TH ALIGN="LEFT"><TD>512<TD><TD>Total bytes in node -</TABLE> -<br><br> -The following structure is used by the Xbase64 NDX routines: -<xmp> - struct NdxHeadNode{ - xbLong StartNode; /* header node is node 0 */ - xbLong TotalNodes; /* includes header node */ - xbLong NoOfKeys; /* actual count + 1 */ - xbUShort KeyLen; /* length of key data */ - xbUShort KeysPerNode; /* max number of keys per node */ - xbUShort KeyType; /* 00 = Char, 01 = Numeric */ - xbLong KeySize; /* KeyLen + 8 */ - char Reserved1; /* Not sure about this one */ - char Unique; /* 00 = not unique, 01 = unique*/ - char KeyExpression[488]; /* key definition */ - } -</xmp> -<br><br> - -<h4>Interior and Leaf Nodes</h4> - -Interior Nodes and Leaf Nodes share the same structure in an NDX file. -The difference between the two types is that interior nodes point to -other interior nodes or leaf nodes and leaf nodes point to records in -a DBF file. Interior nodes are optional nodes in an NDX file, -however if there are more than a few keys in the index there will -certainly be one or more interior nodes in the file. There will -always be at least one leaf node in the file. Leaf nodes contain DBF -record numbers which point to the location of the record in the -DBF file.<br><br> - -Interior nodes have field LeftNodeNo valued which points to the node -which points to the keys which are less than the key value in the KeyVal -field. There is one more LeftNodeNo value in the node than there are keys. -The Last LeftNodeNo points to the node which is greater than the highest -key value in the node. Interior nodes have 0 in the value for the -DbfRecNo field.<br><br> - -Leaf nodes have 0 in the LeftNodeNo field but do have a value in the -DbfRecNo field which points to a DFB record.<br><br> - - -<TABLE BORDER> -<CAPTION ALIGN="TOP"><h3>NDX Interior Node and Leaf Node Structure</H3></CAPTION> -<TR VALIGN="BASELINE"> -<TR><TH ALIGN="LEFT">Type<TD>Size<TD>Field Name<TD>Description -<TR><TH ALIGN="LEFT">xbLong<TD>4<TD>NoOfKeysThisNode<TD>The number of key values in this node. -<TR><TH ALIGN="LEFT">char<TD>508<TD>KeyRec<TD>A repeating structure of - pointers and keys. See the next table for the KeyRec structure. -</TABLE> -<br><br> -<TABLE BORDER> -<CAPTION ALIGN="TOP"><h3>KeyRec Structure</H3></CAPTION> -<TR VALIGN="BASELINE"> -<TR><TH ALIGN="LEFT">Type<TD>Size<TD>Field Name<TD>Description -<TR><TH ALIGN="LEFT">xbLong<TD>4<TD>LeftNodeNo<TD>The node number of the lower node - for this key. 0 in Leaf Nodes. -<TR><TH ALIGN="LEFT">xbLong<TD>4<TD>DbfRecNo<TD>The DBF record number for this key. - 0 in Interior Nodes. -<TR><TH ALIGN="LEFT">char<TD>KeyLen<TD>KeyValue<TD>The key value. -</TABLE> - -<br><br> -For those interested in knowing how the Xbase64 DBMS manipulates and -navigates index files, the following discussion may be helpfull.<br><br> - -Xbase64 DBMS navigates through NDX files by using an in-memory chain -of nodes of the current location / key in use. It starts by reading the -Head Node of the index, which points to the first node of the file. The -first node of the file will be a leaf node if the index is small or will -be an interior node if the index has more than one leaf node. The first -interior node is loaded into memory, added to the node chain and points -to the next node to read. The node is made up of one or more keys. If -it is a leaf node, the logic looks for a matching key on the node. -Otherwise, if it is an interior node, the logic looks at the keys until the -search key is greater than or equal to the key in the node and then -traverses down the tree to the next node. It continues down the tree, -adding the nodes to the in-memory node chain until it reaches the correct -leaf node. If it finds a matching key in the leaf node, it returns a -XB_FOUND condition. If it doesn't find an exact match in the leaf node, it -returns a XB_NOT_FOUND condition and stops on the key which is greater than -the search key given. -<br><br> -<hr> - -<h2>MDX Indices</h2> -The objective of this section is to provide information regarding the -basic concepts of how .MDX index files work in the Xbase64 library.<br> -Information for MDX files has been gathered by searching the internet -and by examining the structure of known good MDX index files.<br><br> - -<h4>MDX Index File Characteristics</h4> - -<li>MDX files are the same name as the corresponding DBF file with an MDX extension. -<li>MDX files are automatically opened by the library when the DBF file is opened. -<li>MDX index files (aka prod indices) contain from one to 47 tags, where each tag has it's own key characteristics. -<li>MDX indices maintain keys in either ascending or descending sort order. -<li>MDX indices support filtered keys. For example, a filter of <b>.NOT. DELETED()</b> will keep deleted records out -of the index tag. -<li>MDX indices are automatically updated by the Xbase library after the -indices are opened. -<li>MDX indices support <em>unique</em> or <em>non unique</em> keys.<br><br> - -<em>Unique</em> keys must be unique if the UniqueKeyOption is not set to XB_EMULATE_DBASE. -If the UniqueKeyOption is set to XB_EMULATE_DBASE, then the database update routines will -add a record to the table, but not add a corresponding duplicate key to the index tag. -The UniqueKeyOption is off (don't allow duplicates) by default. -<br><br> - -<em>Non-unique</em> Keys are not required to be unique, duplicate -keys are allowed if the index is created with the XB_NOT_UNIQUE -setting. Duplicate keys are stored in record number order.<br><br> - - -<li>Character keys are left justified and padded on the right with spaces. -<li>Numeric keys are stored as twelve byte BCD values. -<li>Date keys are stored as eight byte double julian values. - -<h4>MDX File Internals</h4> - -The following information is not needed to use the library, it is just included -for general information.<br><br> - -MDX files are comprised of 512 pages where multiple pages make a block. The default -setting is 1024 blocks, each block containing two pages.<br><br> - -The first four pages contain: -<li>Bytes 0 - 543 contain general file information. -<li>Bytes 544 - 2047 is a 47 item table containing specific tag information. -<br><br> - -Pages five and beyound: -<li>Bytes 2048 and beyond contain tag header blocks, interior nodes and leaf nodes. - -<br><br> - -<h4>Interior and Leaf Nodes</h4> - -Interior Nodes and Leaf Nodes share the same structure in an NDX file with -the exception that interior nodes have a non zero number immediately -after the rightmost key on the node. - -Interior nodes point to other interior nodes or leaf nodes and leaf nodes point -to records in a DBF file. Interior nodes are optional nodes in an MDX file, -however if there are more than a few keys in the index there will -certainly be one or more interior nodes in the file. There will -always be at least one leaf node per tag in the file. Leaf nodes -contain DBF record numbers which point to the location of the record -in the DBF file.<br><br> - -<hr> -<br><br> -<h2>TDX Indices</h2> -TDX index files are an Xbase64 library specific implementation of indexing which -can be used for creating temporary indices. They can be created as needed and are -automatically deleted when the table/DBF file is closed.<br><br> - -TDX files are built on the MDX index logic and supports the following functionality: -<li>Complex Key Expressions -<li>Filters -<li>Unique / Non-unique keys -<li>Ascending / Descending keys -<li>Max of 47 unique temporary index tags -<br><br> - -To create a temporary index, set the Type field to "TDX" when using the xbDbf::CreateTag() method. -All other functionality is the same when using temp indices. The only requirement is to set the -type when creating it.<br><br> - -Additionally, the create tag only defines the index. If the table is populated with data and -you need the index populated accordingly, use the xbDbf::Reindex() method to bring it up to data after -creating it. -<br><br> - -<hr> -<p><img src="xbase.jpg"><br><hr> -</BODY> -</HTML> |