Libpointers and multilevel pointers

2011 10 12
2 个回答
8 次查看（30 天）

0 个投票

Hi there,
I am stuck with shared library and multilevel pointers and was hoping that some of you may help. I need to use a DLL which notably provides two functions:
char ** functionOne();
[stringPtrPtr] = functionOne(); (matlab equivalent)
void functionTwo(char * Text);
functionTwo(cstring); (matlab equivalent)
The first one is recognized as returning stringPtrPtr data. Which seems allright so far. Matlab is indeed able to read the array of string returned.
Then, I need to provide functionTwo with one of the elements of the array of strings returned by functionOne.
I'm doing: TextArray = calllib(DLL_Alias , 'functionOne');
get(TextArray) shows:
  • DataType = stringPtrPtr
  • Value = {'Text1', 'Text2', ...}, hence a cell array of strings
Which synthax, if it is possible, do I have to use to provide Text1 or Text2's addresses to functionTwo ?
  • Writing:
TAval = TextArray.Value();
calllib(DLL_Alias, TAval{1}) % for text1
calllib(DLL_Alias, TAval{2}) % for text2
fails as TAval{1} is a string and not a pointer
  • Writing:
calllib(DLL_Alias, TextArray) % for text 1
calllib(DLL_Alias, TextArray+1) % for text 2
fails as TextArray or TextArray+1 are interpreted as stringPtrPtr and not cstring (nor stringPtr).
I've also tried to force the datatype to stringPtr or cstring, which Matlab seems to refuse.
Any hint?
Thanks, Matthieu

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回答（2 个）

Philip Borghesani
Philip Borghesani 2011-10-14

0 个投票

calllib(DLL_Alias, 'functionTwo', TAval{1}) % for text1
Should work. Note that in your example you forgot 'functionTwo'. MATLAB strings are automatically converted into pointers (cstrings) in function calls.
Example code:
cd (fullfile(matlabroot,'extern','examples','shrlib'));
loadlibrary shrlibsample
strings={'str1','str2'};
[s1,s2]=calllib('shrlibsample','stringToUpper',strings{2})
If you still have problems please post your MATLAB version.

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Matthieu
Matthieu
2011-10-12

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