# Double reading (Scilab gateway)

How to read matrices of double in a gateway.

## Calling Sequence

Input argument profile:

    SciErr getMatrixOfDouble(void* _pvCtx, int* _piAddress, int* _piRows, int* _piCols, double** _pdblReal)

    SciErr getComplexMatrixOfDouble(void* _pvCtx, int* _piAddress, int* _piRows, int* _piCols, double** _pdblReal, double** _pdblImg)

Named variable profile:

    SciErr readNamedMatrixOfDouble(void* _pvCtx, const char* _pstName, int* _piRows, int* _piCols, double* _pdblReal)

    SciErr readNamedComplexMatrixOfDouble(void* _pvCtx, const char* _pstName, int* _piRows, int* _piCols, double* _pdblReal, double* _pdblImg)

## Arguments

_pvCtx

  Scilab environment pointer, pass in "pvApiCtx" provided by api_scilab.h

_piAddress

  Address of the Scilab variable.

_pstName

  Name of the variable for "named" functions.

_piRows

  Return number of rows.

_piCols

  Return number of columns.

_pdblReal

  Return address of real data array (size: _iCols * _iRows). For "Named" function, _pdblReal must be allocated before calling function.

_pdblImg
  Return address of imaginary data array (size: _iCols * _iRows). For "Named" function, _pdblImg must be allocated before calling function.
SciErr

  Error structure where is stored errors messages history and first error number.

## Description

This help describes how matrix of doubles can be handled through the Scilab API.

## Gateway Source

    #include "api_scilab.h"
    int read_double(char *fname,unsigned long fname_len)
    {
    	SciErr sciErr;
    	int i;
    	//first variable info : real matrix of double
    	int iType			= 0;
    	int iRows			= 0;
    	int iCols			= 0;
    	int iComplex		= 0;
    	int *piAddr			= NULL;
    	double* pdblReal	= NULL;
    	double* pdblImg		= NULL;

    	//check input and output arguments
        CheckInputArgument(pvApiCtx, 1, 1);
        CheckOutputArgument(pvApiCtx, 1, 1);

        /************************
    	*    First variable    *
    	************************/

    	//get variable address of the first input argument
    	sciErr = getVarAddressFromPosition(pvApiCtx, 1, &piAddr);
    	if(sciErr.iErr)
    	{
    		printError(&sciErr, 0);
    		return 0;
    	}

    	//check type
    	sciErr = getVarType(pvApiCtx, piAddr, &iType);
    	if(sciErr.iErr || iType != sci_matrix)
    	{
    		printError(&sciErr, 0);
    		return 0;
    	}

    	//get complexity
    	iComplex	= isVarComplex(pvApiCtx, piAddr);

    	//check complexity
    	if(iComplex)
    	{
    		//get size and data from Scilab memory
    		sciErr = getComplexMatrixOfDouble(pvApiCtx, piAddr, &iRows, &iCols, &pdblReal, &pdblImg);
    	}
    	else
    	{
    		//get size and data from Scilab memory
    		sciErr = getMatrixOfDouble(pvApiCtx, piAddr, &iRows, &iCols, &pdblReal);
    	}

    	if(sciErr.iErr)
    	{
    		printError(&sciErr, 0);
    		return 0;
    	}

    	//Do something with data
    	//if variable is complex, switch real part and imaginary part otherwise multiply by -1
    	if(iComplex)
    	{
    		sciErr = createComplexMatrixOfDouble(pvApiCtx, nbInputArgument(pvApiCtx) + 1, iRows, iCols, pdblImg, pdblReal);
    	}
    	else
    	{
    		for(i = 0 ; i < iRows * iCols ; i++)
    		{
    			pdblReal[i] = pdblReal[i] * -1;
    		}
    		sciErr = createMatrixOfDouble(pvApiCtx, nbInputArgument(pvApiCtx) + 1, iRows, iCols, pdblReal);
    	}

    	if(sciErr.iErr)
    	{
    		printError(&sciErr, 0);
    		return 0;
    	}

        AssignOutputVariable(pvApiCtx, 1) = nbInputArgument(pvApiCtx) + 1;
    	return 0;
    }

## Scilab test script

    a = [   0 1 2 3; ..
            4 5 6 7; ..
            8 9 10 11];
    b = [   23*%i,      1+22*%i,    2+21*%i,    3+20*%i,    4+19*%i,    5+18*%i; ..
            6+17*%i,    7+16*%i,    8+15*%i,    9+14*%i,     10+13*%i,  11+12*%i; ..
            12+11*%i,   13+10*%i,   14+9*%i,    15+8*%i,    16+7*%i,    17+6*%i; ..
            18+5*%i,    19+4*%i,    20+3*%i,    21+2*%i,    22+1*%i,    23];

    a2 = read_double(a);
    b2 = read_double(b);

    if or(a2 <> a * -1) then error("failed"), end
    if or(b2 <> (imag(b) + real(b) * %i)) then error("failed"), end