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@@ -101,16 +101,20 @@ uses
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//=== Memo and binary fields support
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//====================================================================
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type
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-
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+ // DBase III+ dbt memo file
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PDbtHdr = ^rDbtHdr;
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rDbtHdr = record
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- NextBlock : dword;
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- Dummy : array [4..7] of Byte;
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+ NextBlock : dword; // 0..3
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+ // Dummy in DBaseIII; size of blocks in memo file; default 512 bytes
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+ BlockSize : dword; // 4..7
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+ // DBF file name without extension
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DbfFile : array [0..7] of Byte; // 8..15
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+ // DBase III only: version number $03
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bVer : Byte; // 16
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- Dummy2 : array [17..19] of Byte;
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+ Dummy2 : array [17..19] of Byte; // 17..19
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+ // Block length in bytes; DBaseIII: always $01
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BlockLen : Word; // 20..21
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- Dummy3 : array [22..511] of Byte;
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+ Dummy3 : array [22..511] of Byte;// 22..511 First block; garbage contents
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end;
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PFptHdr = ^rFptHdr;
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@@ -121,10 +125,12 @@ type
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Dummy3 : array [8..511] of Byte;
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end;
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+ // Header of a memo data block:
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PBlockHdr = ^rBlockHdr;
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rBlockHdr = record
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- MemoType : Cardinal;
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- MemoSize : Cardinal;
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+ // DBase IV(+) identifier: $FF $FF $08 $00
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+ MemoType : Cardinal; // 0..4
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+ MemoSize : Cardinal; // 5..7
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end;
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@@ -184,7 +190,8 @@ begin
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RecordSize := GetBlockLen;
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// checking for right blocksize not needed for foxpro?
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// mod 128 <> 0 <-> and 0x7F <> 0
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- if (RecordSize = 0) and ((FDbfVersion in [xFoxPro,xVisualFoxPro]) or ((RecordSize and $7F) <> 0)) then
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+ if (RecordSize = 0) and
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+ ((FDbfVersion in [xFoxPro,xVisualFoxPro]) or ((RecordSize and $7F) <> 0)) then
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begin
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SetBlockLen(512);
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RecordSize := 512;
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@@ -271,15 +278,15 @@ begin
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// dbase III memo
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done := false;
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repeat
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- // scan for EOF
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+ // scan for EOF marker
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endMemo := MemScan(FBuffer, $1A, RecordSize);
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// EOF found?
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if endMemo <> nil then
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begin
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- // really EOF?
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- if (endMemo-FBuffer < RecordSize - 1) and ((endMemo[1] = #$1A) or (endMemo[1] = #0)) then
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+ // really EOF? expect another 1A or null character
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+ if (endMemo-FBuffer < RecordSize - 1) and
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+ ((endMemo[1] = #$1A) or (endMemo[1] = #0)) then
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begin
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- // yes, EOF found
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done := true;
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numBytes := endMemo - FBuffer;
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end else begin
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@@ -344,7 +351,7 @@ begin
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begin
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bytesBefore := SizeOf(rBlockHdr);
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bytesAfter := 0;
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- end else begin // dBase3 type
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+ end else begin // dBase3 type, Clipper?
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bytesBefore := 0;
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bytesAfter := 2;
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end;
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@@ -383,7 +390,7 @@ begin
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repeat
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// read bytes, don't overwrite header
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readBytes := Src.Read(FBuffer[bytesBefore], RecordSize{PDbtHdr(Header).BlockLen}-bytesBefore);
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- // end of input data reached ? check if need to write block terminators
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+ // end of input data reached? check if we need to write block terminators
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while (readBytes < RecordSize - bytesBefore) and (bytesAfter > 0) do
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begin
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FBuffer[readBytes] := #$1A;
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@@ -428,7 +435,7 @@ end;
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function TDbaseMemoFile.GetMemoSize: Integer;
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begin
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- // dBase4 memofiles contain small 'header'
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+ // dBase4 memofiles contain a small 'header'
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if PInteger(@FBuffer[0])^ = Integer(SwapIntLE($0008FFFF)) then
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Result := SwapIntLE(PBlockHdr(FBuffer)^.MemoSize)-8
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else
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reiniero