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fpspreadsheet: Avoid logging workbook error when reading Excel8 files containing comboboxes. Fix is not 100% safe, should not crash, though. Let's see...

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git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@4277 8e941d3f-bd1b-0410-a28a-d453659cc2b4
This commit is contained in:
wp_xxyyzz
2015-08-20 16:03:13 +00:00
parent 7fd6590a6b
commit bae47dcb21
1 changed files with 25 additions and 4 deletions
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29
components/fpspreadsheet/xlsbiff8.pas
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@ -523,18 +523,18 @@ var
subrecID, subrecSize: Word;
streamPos, p: Int64;
streamSize: Int64;
lastSubRec: Boolean;
objType: Word;
objID: Word;
begin
streamSize := AStream.Size;
lastSubRec := false;
while not lastSubRec do begin
while true do
begin
subrecID := WordLEToN(AStream.ReadWord);
subrecSize := WordLEToN(AStream.ReadWord);
streamPos := AStream.Position;
case subrecID of
INT_EXCEL_OBJID_FTCMO: // common object data
// This is the first sub-record of the OBJ record.
begin
objType := WordLEToN(AStream.ReadWord);
objID := WordLEToN(AStream.ReadWord);
@ -545,9 +545,30 @@ begin
end else
FCommentPending := false;
end;
INT_EXCEL_OBJID_FTLBSDATA:
if subrecSize = $1FEE then // this cannot be the true sub-record size !!!
// https://mail-archives.apache.org/mod_mbox/poi-dev/200409.mbox/%3CC1ECA5ECAA06A64D88D955E9E152680D32A5C5@SNOWBALL2.asc.com.au%3E
// "Every sheet I have looked at seems to have a 16 byte ftLbsData sub-record."
subrecSize := 16
// NOTE:
// This is a risky assumption. A more robust implementation must look at
// the individual elements of this subrecord, see https://searchcode.com/codesearch/view/47124816/
else
if subrecSize = 0 then
// From MS doc: "If cbFContinued is 0x0000, all of the fields in this
// structure except ft and cbFContinued MUST NOT exist."
exit; // We exit because the stream position cannot advance any more!
INT_EXCEL_OBJID_FTEND:
lastSubRec := true;
// This is the last sub-record.
exit;
end;
// The structure of the OBJ records is very chaotic. Therefore, it can easily
// occur that we are lost and read beyond stream end: Check for stream end
// and store an error. Normal reading will we resumed at the correct position
// by the main reading loop.
p := streamPos + subrecSize;
if p < streamSize then
AStream.Position := p