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<< Click to Display Table of Contents >> Delphi Examples: DbiDoRestructure |
  
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<< Click to Display Table of Contents >> Delphi Examples: DbiDoRestructure |
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Example 1: Add a validity check to the specified field.
The field must be a longint, and the TTable must be open.
This example uses the following input:
fDbiDoRestructure(Table4, Table4.Fields[0], @Min, @Max, nil, True);
(This input works for the EMPLOYEE.DB table.)
procedure fDbiDoRestructure(Tbl: TTable; Field: TField; MinVal, MaxVal, DefVal: pLongint; Required: Boolean);
var
hDb: hDbiDb;
TblDesc: CRTblDesc;
VChk: pVChkDesc;
Dir: string;
NumVChks: Word;
OpType: CROpType;
begin
NumVChks := 0;
SetLength(Dir, dbiMaxNameLen + 1);
Check(DbiGetDirectory(Tbl.DBHandle, False, PChar(Dir)));
SetLength(Dir, StrLen(PChar(Dir)));
VChk := AllocMem(sizeof(VChkDesc));
try
FillChar(TblDesc, sizeof(CRTblDesc), #0);
VChk.iFldNum := Field.Index + 1;
Tbl.DisableControls;
Tbl.Close;
Check(DbiOpenDatabase(nil, nil, dbiReadWrite, dbiOpenExcl, nil, 0, nil, nil,
hDb));
Check(DbiSetDirectory(hDb, PChar(Dir)));
with VChk^ do begin
bRequired := Required;
if (MinVal <> nil) then begin
Inc(NumVChks);
bHasMinVal := True;
move(MinVal^, aMinVal, sizeof(MinVal^));
end
else
bHasMinVal := False;
if (MaxVal <> nil) then begin
Inc(NumVChks);
bHasMaxVal := True;
move(MaxVal^, aMaxVal, sizeof(MaxVal^));
end
else
bHasMaxVal := False;
if (DefVal <> nil) then begin
Inc(NumVChks);
bHasDefVal := True;
move(DefVal^, aDefVal, sizeof(DefVal^));
end
else
bHasDefVal := False;
end;
TblDesc.iValChkCount := NumVChks;
TblDesc.pVChkDesc := VChk;
OpType := crADD;
TblDesc.pecrValChkOp := @OpType;
StrPCopy(TblDesc.szTblName, Tbl.TableName);
StrCopy(TblDesc.szTblType, szParadox);
Check(DbiDoRestructure(hDb, 1, @TblDesc, nil, nil, nil, False));
finally
Check(DbiCloseDatabase(hDb));
FreeMem(VChk, sizeof(VChkDesc));
Tbl.EnableControls;
Tbl.Open;
end;
end;
Example 2: Pack a Paradox (with DbiDoRestructure) or dBASE table.
This example will pack a Paradox or dBASE table therefore removing already deleted rows in a table. This function will also regenerate all out-of-date indexes (maintained indexes). This example uses the following input:
PackTable(Table1)
The function is defined as follows:
// Pack a Paradox or dBASE table
// The table must be opened execlusively before calling this function...
procedure PackTable(Table: TTable);
var
Props: CURProps;
hDb: hDBIDb;
TableDesc: CRTblDesc;
begin
// Make sure the table is open exclusively so we can get the db handle...
if not Table.Active then
raise EDatabaseError.Create('Table must be opened to pack');
if not Table.Exclusive then
raise EDatabaseError.Create('Table must be opened exclusively to pack');
// Get the table properties to determine table type...
Check(DbiGetCursorProps(Table.Handle, Props));
// If the table is a Paradox table, you must call DbiDoRestructure...
if (Props.szTableType = szPARADOX) then begin
// Blank out the structure...
FillChar(TableDesc, sizeof(TableDesc), 0);
// Get the database handle from the table's cursor handle...
Check(DbiGetObjFromObj(hDBIObj(Table.Handle), objDATABASE, hDBIObj(hDb)));
// Put the table name in the table descriptor...
StrPCopy(TableDesc.szTblName, Table.TableName);
// Put the table type in the table descriptor...
StrPCopy(TableDesc.szTblType, Props.szTableType);
// Set the Pack option in the table descriptor to TRUE...
TableDesc.bPack := True;
// Close the table so the restructure can complete...
Table.Close;
// Call DbiDoRestructure...
Check(DbiDoRestructure(hDb, 1, @TableDesc, nil, nil, nil, False));
end
else
// If the table is a dBASE table, simply call DbiPackTable...
if (Props.szTableType = szDBASE) then
Check(DbiPackTable(Table.DBHandle, Table.Handle, nil, szDBASE, True))
else
// Pack only works on PAradox or dBASE; nothing else...
raise EDatabaseError.Create('Table must be either of Paradox or dBASE ' +
'type to pack');
Table.Open;
end;
Example 3: Alter a field in a Paradox or dBASE table.
This example will alter an existing field in a Paradox or dBASE table. NOTE: You must fill in all options in the ChangeRec with 0 or '' if the option is not used in the restructure. FillChar can be used to do this:
Fillchar(MyChangeRec, sizeof(MyChangeRec), 0);
This example uses the following input:
ChangeField(Table1, Table1.FieldByName('FOO'), MyChangeRec)
ChangeRec is defined as follows:
type
ChangeRec = packed record
szName: DBINAME;
iType: Word;
iSubType: Word;
iLength: Word;
iPrecision: Byte;
end;
The function is defined as follows:
procedure ChangeField(Table: TTable; Field: TField; Rec: ChangeRec);
var
Props: CURProps;
hDb: hDBIDb;
TableDesc: CRTblDesc;
pFields: pFLDDesc;
pOp: pCROpType;
B: Byte;
begin
// Initialize the pointers...
pFields := nil;
pOp := nil;
// Make sure the table is open exclusively so we can get the db handle...
if not Table.Active then
raise EDatabaseError.Create('Table must be opened to restructure');
if not Table.Exclusive then
raise EDatabaseError.Create('Table must be opened exclusively' +
'to restructure');
Check(DbiSetProp(hDBIObj(Table.Handle), curxltMODE, Integer(xltNONE)));
// Get the table properties to determine table type...
Check(DbiGetCursorProps(Table.Handle, Props));
// Make sure the table is either Paradox or dBASE...
if (Props.szTableType <> szPARADOX) and (Props.szTableType <> szDBASE) then
raise EDatabaseError.Create('Field altering can only occur on Paradox' +
' or dBASE tables');
// Allocate memory for the field descriptor...
pFields := AllocMem(Table.FieldCount * sizeof(FLDDesc));
// Allocate memory for the operation descriptor...
pOp := AllocMem(Table.FieldCount * sizeof(CROpType));
try
// Set the pointer to the index in the operation descriptor to put
// crMODIFY (This means a modification to the record is going to happen)...
Inc(pOp, Field.Index);
pOp^ := crMODIFY;
Dec(pOp, Field.Index);
// Fill the field descriptor with the existing field information...
Check(DbiGetFieldDescs(Table.Handle, pFields));
// Set the pointer to the index in the field descriptor to make the
// midifications to the field
Inc(pFields, Field.Index);
// If the szName portion of the ChangeRec has something in it, change it...
if (Length(Rec.szName) > 0) then
pFields^.szName := Rec.szName;
// If the iType portion of the ChangeRec has something in it, change it...
if (Rec.iType > 0) then
pFields^.iFldType := Rec.iType;
// If the iSubType portion of the ChangeRec has something in it, change it...
if (Rec.iSubType > 0) then
pFields^.iSubType := Rec.iSubType;
// If the iLength portion of the ChangeRec has something in it, change it...
if (Rec.iLength > 0) then
pFields^.iUnits1 := Rec.iLength;
// If the iPrecision portion of the ChangeRec has something
// in it, change it...
if (Rec.iPrecision > 0) then
pFields^.iUnits2 := Rec.iPrecision;
Dec(pFields, Field.Index);
for B := 1 to Table.FieldCount do begin
pFields^.iFldNum := B;
Inc(pFields, 1);
end;
Dec(pFields, Table.FieldCount);
// Blank out the structure...
FillChar(TableDesc, sizeof(TableDesc), #0);
// Get the database handle from the table's cursor handle...
Check(DbiGetObjFromObj(hDBIObj(Table.Handle), objDATABASE, hDBIObj(hDb)));
// Put the table name in the table descriptor...
StrPCopy(TableDesc.szTblName, Table.TableName);
// Put the table type in the table descriptor...
StrPCopy(TableDesc.szTblType, Props.szTableType);
// The following three lines are necessary when doing any field restructure
// operations on a table...
// Set the field count for the table
TableDesc.iFldCount := Table.FieldCount;
// Link the operation descriptor to the table descriptor...
TableDesc.pecrFldOp := pOp;
// Link the field descriptor to the table descriptor...
TableDesc.pFldDesc := pFields;
// Close the table so the restructure can complete...
Table.Close;
// Call DbiDoRestructure...
Check(DbiDoRestructure(hDb, 1, @TableDesc, nil, nil, nil, False));
finally
if (pFields <> nil) then
FreeMem(pFields);
if (pOp <> nil) then
FreeMem(pOp);
end;
end;
Example 4: Add a master password to a Paradox table.
This example uses the following input:
AddMasterPassword(Table1, 'MyNewPassword')
The procedure is:
procedure AddMasterPassword(Table: TTable; pswd: string);
const
RESTRUCTURE_TRUE = WordBool(1);
var
TblDesc: CRTblDesc;
hDb: hDBIDb;
begin
{ Make sure that the table is opened and is exclusive }
if not Table.Active or not Table.Exclusive then
raise EDatabaseError.Create('Table must be opened in exclusive ' +
'mode to add passwords');
{ Initialize the table descriptor }
FillChar(TblDesc, SizeOf(CRTblDesc), #0);
with TblDesc do begin
{ Place the table name in descriptor }
StrPCopy(szTblName, Table.TableName);
{ Place the table type in descriptor }
StrCopy(szTblType, szPARADOX);
{ Master Password, Password }
StrPCopy(szPassword, pswd);
{ Set bProtected to True }
bProtected := RESTRUCTURE_TRUE;
end;
{ Get the database handle from the cursor handle }
Check(DbiGetObjFromObj(hDBIObj(Table.Handle), objDATABASE, hDBIObj(hDb)));
{ Close the table }
Table.Close;
{ Add the master password to the Paradox table }
Check(DbiDoRestructure(hDb, 1, @TblDesc, nil, nil, nil, False));
{ Add the new password to the session }
Session.AddPassword(pswd);
{ Re-Open the table }
Table.Open;
end;