fpspreadsheet: Redo automatic file format detection: Add method CheckFileFormat to each reader for overriding (check file header or whatever).

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@6764 8e941d3f-bd1b-0410-a28a-d453659cc2b4

components/fpspreadsheet/source/common/fpsopendocument.pas

@@ -171,6 +171,9 @@ type
     constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
 
+    { File format detection }
+    class function CheckFileFormat(AStream: TStream): Boolean; override;
+
     { General reading methods }
     procedure ReadFromStream(AStream: TStream;
       APassword: String = ''; AParams: TsStreamParams = []); override;
@@ -1159,6 +1162,11 @@ begin
   end;
 end;
 
+class function TsSpreadOpenDocReader.CheckFileFormat(AStream: TStream): Boolean;
+begin
+  Result := HasZipHeader(AStream);
+end;
+
 function TsSpreadOpenDocReader.ExtractFormatIndexFromStyle(ACellStyleName: String;
   ACol: Integer): Integer;
 var

components/fpspreadsheet/source/common/fpspreadsheet.pas

@@ -8488,8 +8488,7 @@ end;
 {@@ ----------------------------------------------------------------------------
   Helper method for determining the spreadsheet type. Read the first few bytes
   of a file and determines the spreadsheet type from the characteristic
-  signature. Only implemented for xls files where several file types have the
-  same extension
+  signature.
 -------------------------------------------------------------------------------}
 class procedure TsWorkbook.GetFormatFromFileHeader(const AFileName: TFileName;
   out AFormatIDs: TsSpreadFormatIDArray);
@@ -8505,85 +8504,32 @@ begin
 end;
 
 {@@ ----------------------------------------------------------------------------
-  Helper method for determining the spreadsheet format. Read the first few bytes
-  of a stream and determines the spreadsheet type from the characteristic
-  signature.
+  Helper method for determining the spreadsheet format. Reads the first
+  few bytes of a stream and determines the spreadsheet type from the
+  characteristic signature.
 -------------------------------------------------------------------------------}
 class procedure TsWorkbook.GetFormatFromFileHeader(AStream: TStream;
   out AFormatIDs: TsSpreadFormatIDArray); overload;
-const
-  BIFF2_HEADER: array[0..3] of byte = (
-    $09,$00, $04,$00);  // they are common to all BIFF2 files that I've seen
-  BIFF58_HEADER: array[0..7] of byte = (
-    $D0,$CF, $11,$E0, $A1,$B1, $1A,$E1);
-  ZIP_HEADER: array[0..1] of byte = (
-    byte('P'), byte('K'));
-
-  function ValidOLEStream(AStream: TStream; AName: String): Boolean;
-  var
-    fsOLE: TVirtualLayer_OLE;
-  begin
-    AStream.Position := 0;
-    fsOLE := TVirtualLayer_OLE.Create(AStream);
-    try
-      fsOLE.Initialize;
-      Result := fsOLE.FileExists('/'+AName);
-    finally
-      fsOLE.Free;
-    end;
-  end;
-
 var
-  buf: packed array[0..7] of byte = (0,0,0,0,0,0,0,0);
-  i: Integer;
+  reader: TsSpreadReaderClass;
+  fmtIDs: TsSpreadformatIDArray;
+  i, j: Integer;
 begin
   SetLength(AFormatIDs, 0);
-
   if AStream = nil then
     exit;
 
-  // Read first 8 bytes
-  i := AStream.Read(buf, Length(buf));
-  if i < Length(buf) then
-    exit;
-
-  // Check for zip header of xlsx and ods
-  if (buf[0] = ZIP_HEADER[0]) and (buf[1] = ZIP_HEADER[1]) then begin
-    SetLength(AFormatIDs, 2);
-    AFormatIDs[0] := ord(sfOOXML);
-    AFormatIDs[1] := ord(sfOpenDocument);
-    exit;
-  end;
-
-  // Check for Excel 2
-  for i:=0 to High(BIFF2_HEADER) do
-    if buf[i] = BIFF2_HEADER[i] then
-    begin
-      SetLength(AFormatIDs, 1);
-      AFormatIDs[0] := ord(sfExcel2);
-      exit;
+  fmtIDs := GetSpreadFormats(faRead, [ord(sfExcel8)]);
+  SetLength(AFormatIDs, Length(fmtIDs));
+  j := 0;
+  for i:=0 to High(fmtIDs) do begin
+    reader := GetSpreadReaderClass(fmtIDs[i]);
+    if Assigned(reader) and reader.CheckFileFormat(AStream) then begin
+      AFormatIDs[j] := fmtIDs[i];
+      inc(j);
     end;
-
-  // Check for Excel 5 or 8
-  for i:=0 to High(BIFF58_HEADER) do
-    if buf[i] <> BIFF58_HEADER[i] then
-      exit;
-
-  // Now we know that the file is a Microsoft compound document.
-
-  // We check for Excel 5 in which the stream is named "Book"
-  if ValidOLEStream(AStream, 'Book') then begin
-    SetLength(AFormatIDs, 1);
-    AFormatIDs[0] := ord(sfExcel5);
-    exit;
-  end;
-
-  // Now we check for Excel 8 which names the stream "Workbook"
-  if ValidOLEStream(AStream, 'Workbook') then begin
-    SetLength(AFormatIDs, 1);
-    AFormatIDs[0] := ord(sfExcel8);
-    exit;
   end;
+  SetLength(AFormatIDs, j);
 end;
 
 {@@ ----------------------------------------------------------------------------
@@ -8694,22 +8640,11 @@ var
   fmtID: TsSpreadFormatID;
   fileFormats: TsSpreadFormatIDArray;
   i: Integer;
-  found: Boolean;
+  ext: String;
 begin
   if not FileExists(AFileName) then
     raise EFPSpreadsheetReader.CreateFmt(rsFileNotFound, [AFileName]);
 
-  // First try to determine file format from the extension
-  if GetFormatFromFileName(AFilename, fmtID) then begin
-    try
-      ReadFromFile(AFileName, fmtID, APassword, AParams);
-      exit;
-    except
-      // format does not match. We must continue with rest of procedure
-    end;
-  end else
-    fmtID := MaxInt;
-
   // Try to get file format from file header
   GetFormatFromFileHeader(AFileName, fileformats);
   if Length(fileformats) = 0 then
@@ -8719,21 +8654,14 @@ begin
   if Length(fileformats) = 0 then
     fileformats := GetSpreadFormats(faRead, [ord(sfExcel8)]);
 
-  // Remove already tested format
-  found := false;
-  i := 0;
-  while (i <= High(fileFormats)) do begin
-    if fileFormats[i] = fmtID then begin
-      found := true;
-      inc(i);
-      while (i <= High(fileFormats)) do begin
-        fileFormats[i-1] := fileFormats[i];
-        inc(i);
-      end;
-    end else
-     inc(i);
-  end;
-  if found then SetLength(fileFormats, Length(fileFormats)-1);
+  // Move file format corresponding to file extension to the top to load it first.
+  ext := Lowercase(ExtractFileExt(AFileName));
+  for i := 0 to High(fileformats) do
+    if ext = GetSpreadFormatExt(fileformats[i]) then begin
+      fmtID := fileformats[0];
+      fileFormats[0] := fileformats[i];
+      fileFormats[i] := fmtID;
+    end;
 
   // No file format found for this file --> error
   if Length(fileformats) = 0 then
@@ -8747,7 +8675,6 @@ begin
       success := true;
       break;  // Exit the loop if we reach this point successfully.
     except
-      //success := false;
     end;
   end;
 

components/fpspreadsheet/source/common/fpsreaderwriter.pas

@@ -46,6 +46,8 @@ type
   { TsBasicSpreadReader }
   TsBasicSpreadReader = class(TsBasicSpreadReaderWriter)
   public
+    { File format detection }
+    class function CheckFileFormat(AStream: TStream): boolean; virtual; abstract;
     { General writing methods }
     procedure ReadFromFile(AFileName: string; APassword: String = '';
       AParams: TsStreamParams = []); virtual; abstract;
@@ -92,6 +94,8 @@ type
 
     { Helper methods }
     procedure AddBuiltinNumFormats; virtual;
+    {@@ More detailed check for file format }
+    class function CheckFileFormatDetails(AStream: TStream): Boolean; virtual;
     {@@ Removes column records if all of them have the same column width }
     procedure FixCols(AWorksheet: TsBasicWorksheet);
     {@@ Removes row records if all of them have the same row height }
@@ -113,7 +117,9 @@ type
     constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
 
-    { General writing methods }
+    { File format detection }
+    class function CheckFileFormat(AStream: TStream): Boolean; override;
+    { General reading methods }
     procedure ReadFromFile(AFileName: string; APassword: String = '';
       AParams: TsStreamParams = []); override;
     procedure ReadFromStream(AStream: TStream; APassword: String = '';
@@ -350,6 +356,24 @@ begin
   // to be overridden by descendants
 end;
 
+{@@ ----------------------------------------------------------------------------
+  Must be overridden to check the file header for the signature of the file.
+  Returns true by default which means that the file is qualified for trying to
+  be loaded.
+-------------------------------------------------------------------------------}
+class function TsCustomSpreadReader.CheckFileFormat(AStream: TStream): boolean;
+begin
+  Result := true;
+end;
+
+{@@ ----------------------------------------------------------------------------
+  More details check for file format
+-------------------------------------------------------------------------------}
+class function TsCustomSpreadReader.CheckFileFormatDetails(AStream: TStream): Boolean;
+begin
+  Result := true;
+end;
+
 {@@ ----------------------------------------------------------------------------
   Deletes unnecessary column records as they are written by some
   Office applications when they convert a file to another format.

components/fpspreadsheet/source/common/fpsxmlcommon.pas

@@ -57,6 +57,8 @@ function CreateTempStream(AWorkbook: TsBasicWorkbook;
   AFileNameBase: String): TStream;
 procedure DestroyTempStream(AStream: TStream);
 
+function HasZipHeader(AStream: TStream): Boolean;
+
 
 implementation
 
@@ -410,5 +412,26 @@ begin
 end;
 
 
+{ Returns true if the file begins with a ZIP header *PK'. Needed for
+  file format detection. }
+function HasZipHeader(AStream: TStream): Boolean;
+const
+  ZIP_HEADER: packed array[0..1] of char = ('P', 'K');
+var
+  P: Int64;
+  buf: packed array[0..1] of char;
+begin
+  Result := false;
+  P := AStream.Position;
+  try
+    AStream.Position := 0;
+    if AStream.Read(buf, 2) < 2 then
+      exit;
+    Result := (buf[0] = ZIP_HEADER[0]) and (buf[1] = ZIP_HEADER[1]);
+  finally
+    AStream.Position := P;
+  end;
+end;
+
 end.
 

components/fpspreadsheet/source/common/xlsbiff2.pas

@@ -79,6 +79,8 @@ type
     { General reading methods }
     procedure ReadFromStream(AStream: TStream; APassword: String = '';
       AParams: TsStreamParams = []); override;
+    { File format detection }
+    class function CheckfileFormat(AStream: TStream): Boolean; override;
   end;
 
 
@@ -331,6 +333,35 @@ begin
   FFirstNumFormatIndexInFile := 0;
 end;
 
+{@@ ----------------------------------------------------------------------------
+  Checks the header of the stream for the signature of BIFF2 files
+-------------------------------------------------------------------------------}
+class function TsSpreadBIFF2Reader.CheckFileFormat(AStream: TStream): Boolean;
+const
+  BIFF2_HEADER: packed array[0..3] of byte = (
+    $09,$00, $04,$00);  // they are common to all BIFF2 files that I've seen
+var
+  P: Int64;
+  buf: packed array[0..3] of byte;
+  n: Integer;
+begin
+  Result := false;
+  P := AStream.Position;
+  try
+    AStream.Position := 0;
+    n := AStream.Read(buf, SizeOf(buf));
+    if n < Length(BIFF2_HEADER) then
+      exit;
+    for n:=0 to High(buf) do
+      if buf[n] <> BIFF2_HEADER[n] then
+        exit;
+    Result := true;
+  finally
+    AStream.Position := P;
+  end;
+end;
+
+
 procedure TsSpreadBIFF2Reader.ReadBlank(AStream: TStream);
 var
   ARow, ACol: Cardinal;

components/fpspreadsheet/source/common/xlsbiff5.pas

@@ -72,6 +72,7 @@ type
 
   TsSpreadBIFF5Reader = class(TsSpreadBIFFReader)
   protected
+    class function CheckFileFormatDetails(AStream: TStream): Boolean; override;
     procedure PopulatePalette; override;
     { Record writing methods }
     procedure ReadBOUNDSHEET(AStream: TStream);
@@ -229,7 +230,7 @@ uses
   LazLogger,
  {$ENDIF}
   Math,
-  fpsStrings, fpspreadsheet, fpsReaderWriter, fpsStreams,
+  uvirtuallayer_ole, fpsStrings, fpspreadsheet, fpsReaderWriter, fpsStreams,
   fpsPalette, fpsNumFormat, xlsconst;
 
 const
@@ -363,6 +364,24 @@ type
 {                           TsSpreadBIFF5Reader                                }
 {------------------------------------------------------------------------------}
 
+{@@ ----------------------------------------------------------------------------
+  Checks, for automatic file format detection, whether tie OLE stream is named
+  'Book' - this is typical of BIFF5 files.
+-------------------------------------------------------------------------------}
+class function TsSpreadBIFF5Reader.CheckFileFormatDetails(AStream: TStream): Boolean;
+var
+  fsOLE: TVirtualLayer_OLE;
+begin
+  AStream.Position := 0;
+  fsOLE := TVirtualLayer_OLE.Create(AStream);
+  try
+    fsOLE.Initialize;
+    Result := fsOLE.FileExists('/Book');
+  finally
+    fsOLE.Free;
+  end;
+end;
+
 {@@ ----------------------------------------------------------------------------
   Populates the reader's default palette using the BIFF5 default colors.
 -------------------------------------------------------------------------------}

components/fpspreadsheet/source/common/xlsbiff8.pas

@@ -133,6 +133,7 @@ type
     function ReadWideString(const AStream: TStream;
       const AUse8BitLength: Boolean): WideString; overload;
   protected
+    class function CheckFileFormatDetails(AStream: TStream): Boolean; override;
     procedure PopulatePalette; override;
     procedure ReadBOUNDSHEET(AStream: TStream);
     procedure ReadCONTINUE(const AStream: TStream);
@@ -366,8 +367,8 @@ uses
   LazLogger,
  {$ENDIF}
   Math, lconvencoding, LazFileUtils, URIParser,
-  fpsStrings, {%H-}fpsPatches, fpsStreams, fpsReaderWriter, fpsPalette,
-  fpspreadsheet, fpsNumFormat, fpsExprParser, xlsEscher;
+  uvirtuallayer_ole, fpsStrings, {%H-}fpsPatches, fpsStreams, fpsReaderWriter,
+  fpsPalette, fpspreadsheet, fpsNumFormat, fpsExprParser, xlsEscher;
 
 const
    { Excel record IDs }
@@ -794,6 +795,24 @@ begin
   inherited;
 end;
 
+{@@ ----------------------------------------------------------------------------
+  Checks, for automatic file format detection, whether tie OLE stream is named
+  'Workbook' - this is typical of BIFF8 files.
+-------------------------------------------------------------------------------}
+class function TsSpreadBIFF8Reader.CheckFileFormatDetails(AStream: TStream): Boolean;
+var
+  fsOLE: TVirtualLayer_OLE;
+begin
+  AStream.Position := 0;
+  fsOLE := TVirtualLayer_OLE.Create(AStream);
+  try
+    fsOLE.Initialize;
+    Result := fsOLE.FileExists('/Workbook');
+  finally
+    fsOLE.Free;
+  end;
+end;
+
 {@@ ----------------------------------------------------------------------------
   Populates the reader's default palette using the BIFF8 default colors.
 -------------------------------------------------------------------------------}

components/fpspreadsheet/source/common/xlscommon.pas

@@ -562,6 +562,8 @@ type
   public
     constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
+    { File format detection }
+    class function CheckFileFormat(AStream: TStream): Boolean; override;
   end;
 
 
@@ -1180,6 +1182,35 @@ begin
   );
 end;
 
+{@@ ----------------------------------------------------------------------------
+  Checks the stream header to verify that the file is a BIFF5 or BIFF8 file.
+-------------------------------------------------------------------------------}
+class function TsSpreadBIFFReader.CheckFileFormat(AStream: TStream): Boolean;
+const
+  BIFF58_HEADER: packed array[0..7] of byte = (
+    $D0,$CF, $11,$E0, $A1,$B1, $1A,$E1);
+var
+  P: Int64;
+  buf: packed array[0..7] of byte;
+  n: Integer;
+begin
+  Result := false;
+  P := AStream.Position;
+  try
+    AStream.Position := 0;
+    n := AStream.Read(buf, Length(buf));
+    if n <> Length(BIFF58_HEADER) then
+      exit;
+    for n:=0 to High(BIFF58_HEADER) do
+      if buf[n] <> BIFF58_HEADER[n] then
+        exit;
+    Result := CheckFileFormatDetails(AStream);
+  finally
+    AStream.Position := P;
+  end;
+end;
+
+
 {@@ ----------------------------------------------------------------------------
   Applies the XF formatting referred to by XFIndex to the specified cell
 -------------------------------------------------------------------------------}

components/fpspreadsheet/source/common/xlsxooxml.pas

@@ -103,6 +103,7 @@ type
   public
     constructor Create(AWorkbook: TsBasicWorkbook); override;
     destructor Destroy; override;
+    class function CheckFileFormat(AStream: TStream): Boolean; override;
     procedure ReadFromStream(AStream: TStream; APassword: String = '';
       AParams: TsStreamParams = []); override;
   end;
@@ -490,6 +491,11 @@ begin
   end;
 end;
 
+class function TsSpreadOOXMLReader.CheckFileFormat(AStream: TStream): Boolean;
+begin
+  Result := HasZipHeader(AStream);
+end;
+
 function TsSpreadOOXMLReader.FindCommentsFileName(ANode: TDOMNode): String;
 var
   s: String;