The C-Code is stored in a DLL. I can load the DLL in MATLAB with the loadlibrary function. I am having trouble passing the wchar_t*[] parameter to the function. I do not know how to create this data type in MATLAB. Does anyone know how to create this type to pass to the calllib function?
MATLAB Code:
loadlibrary('test.dll', 'test.h');
str = '0';
ptr = libpoiner('voidPtrPtr', [int8(str) 0])
calllib('test.dll', 'testFunction', ptr) %this parameter does not match the wchar*[] type
outVal = ptr.Value
C-Code:
void testFunction(wchar_t* str[])
{
str[0] = L"test";
}
Output:
MATLAB allows the function to complete. The outVal variable is filled with garbage values.
If you are able to modify the C header files, you may try the following:
Adjust the header file to convert all wchar_t * to unsigned short *.
On the MATLAB side, the corresponding type would then be a uint16 array.
You could then typecast the uint16 array to char.
I figured it out. I changed the MATLAB code to the following:
loadlibrary('test.dll', 'test.h');
str = '0';
ptr = libpoiner('voidPtrPtr', [uint16(str) 0])
calllib('test.dll', 'testFunction', ptr) %this parameter does not match the wchar*[] type
outVal = ptr.Value
expectedOutput = char(outVal); %convert to ASCII
It outputs the values in decimal which confused me. When I converted them to ASCII, everything made sense.
Related
I have a vector of cells (say, size of 50x1, called tokens) , each of which is a struct with properties x,f1,f2 which are strings representing numbers. for example, tokens{15} gives:
x: "-1.4343429"
f1: "15.7947111"
f2: "-5.8196158"
and I am trying to put those numbers into 3 vectors (each is also 50x1) whose type is float. So I create 3 vectors:
x = zeros(50,1,'single');
f1 = zeros(50,1,'single');
f2 = zeros(50,1,'single');
and that works fine (why wouldn't it?). But then when I try to populate those vectors: (L is a for loop index)
x(L)=tokens{L}.x;
.. also for the other 2
I get :
The following error occurred converting from string to single:
Conversion to single from string is not possible.
Which I can understand; implicit conversion doesn't work for single. It does work if x, f1 and f2 are of type 50x1 double.
The reason I am doing it with floats is because the data I get is from a C program which writes the some floats into a file to be read by matlab. If I try to convert the values into doubles in the C program I get rounding errors...
So, (after what I hope is a good question,) how might I be able to get the numbers in those strings, at the right precision? (all the strings have the same number of decimal places: 7).
The MCVE:
filedata = fopen('fname1.txt','rt');
%fname1.txt is created by a C program. I am quite sure that the problem isn't there.
scanned = textscan(filedata,'%s','Delimiter','\n');
raw = scanned{1};
stringValues = strings(50,1);
for K=1:length(raw)
stringValues(K)=raw{K};
end
clear K %purely for convenience
regex = 'x=(?<x>[\-\.0-9]*),f1=(?<f1>[\-\.0-9]*),f2=(?<f2>[\-\.0-9]*)';
tokens = regexp(stringValues,regex,'names');
x = zeros(50,1,'single');
f1 = zeros(50,1,'single');
f2 = zeros(50,1,'single');
for L=1:length(tokens)
x(L)=tokens{L}.x;
f1(L)=tokens{L}.f1;
f2(L)=tokens{L}.f2;
end
Use function str2double before assigning into yours arrays (and then cast it to single if you want). Strings (char arrays) must be explicitely converted to numbers before using them as numbers.
Can I specify the output type when using calllib? My problem is MATLAB is automatically converting my output to a double even though I need an int64 and am losing needed precision.
Example
I have the following function defined in my_header.h
__int64 my_function(int arg1);
I can call the function like this:
loadlibrary('my_library', 'my_header.h')
output = calllib('my_library', 'my_function', arg1)
But then output is a double and I am losing needed precision.
What I tried
output = int64(calllib('my_library', 'my_function', arg1))
as well as
output = zeros(1, 'int64')
output(1) = calllib('my_library', 'my_function', arg1)
but these just convert my double to int64 after it has already lost the needed precision.
In Matlab, I need to format a latex string containing a numeric variable.
The string is like: foo1 , where 1 is contained in variable X and must be subscript.
This line works if I write directly the value of variable
str = texlabel('foo_{1}')
I'm wondering how to insert the X instead of the value.
In fact this line
str = texlabel('foo_{X}')'
produce, of course, fooX
Thanks
The quickest method would be to include a call to sprintf:
X = 1;
str = texlabel(sprintf('foo_{%u}', X));
Which returns:
str =
{foo}_{{2}}
Which we can plot real quick with text(0.1, 0.1, str):
hi have a major problem in matlab. I have a function and it sometimes returns control ascii characters. How do i check for the presence of these control ascii ?.
my code looks like this
d = out.autoc
d sometimes receives control ascii characters instead of a actual double value. Does someone know how to catch such incompatible assignments ?
I think this should work but you may want to double check the ASCII codes to exclude.
%here I load Ctrl-C
s = sprintf('%s', 3);
code = bin2dec(dec2bin(s,8));
if code < 32
fprintf('ignore');
else
fprintf('do somsething');
end
If you want to check that the value of d is double, and not a string. You can check it this way:
if ~isnumeric(d) || ~isdouble(d)
fprintf('d is not of class double\n');
end
But if you want to assign the value of out.autoc to d only if out.autoc is double, you can do this:
if isnumeric(out.autoc) && isequal(class(out.autoc), 'double')
d = out.autoc;
else
fprintf('out.autoc is not of class double, no assignment made.\n');
end
I need to declare a function that has 32 arguments, so it would be handy to put an unique argument: an array of 32 elements.
I don't find the syntax to do that, I've tried everythinh like:
function x=myfunction(str(32)) (etc...)
But without success.
Unlike other languages, MATLAB can accept matrices as a single argument; so you could just check that the input argument is a vector of length 32:
function x = myfunction(arg)
if length(arg) ~= 32
error('Must supply 32 arguments!');
end
%# your code here
end
If it's a variable number of arguments, check out varargin:
function x = myfunction(varargin)
But for 32 arguments, consider using an input structure:
function x = myfunction(argStruct)
if length(fieldnames(argStruct)) ~= 32
error('not enough arguments!');
end
Supply arguments in the structure, then pass the structure:
>> myArgs = struct();
>> myArgs.arg1 = 5;
>> myArgs.arg2 = 7;
>> %#(etc)
>> x = myfunction(myArgs);
Then in the function, you could either call argStruct.arg1, etc, directly; or unpack it into 32 different variables inside the function. I would give the fields descriptive names so you don't refer to them as arg1, etc inside your function. For that many input arguments, people using the function probably won't remember the order in which your function requires them to pass inputs to. Doing it with a struct lets users pass in arguments without needing to think about what order those inputs are defined.
To add to #strictlyrude27's awesome answer, it looks like you may misunderstand how function declarations work in Matlab. You wrote:
function x=myfunction(str(32))
However, you don't need to declare the type of input in matlab. Just give it a name, and then use it. So, the proper syntax for a declaration would be:
function x = myfunction(myInput)