HE/bit2int.m

function y = bit2int(x, N, varargin)
    %BIT2INT Convert bits to integers
    %
    %   Y = BIT2INT(X,N) converts N column-wise bit elements in X to
    %   nonnegative integer values, with the first or the top-most bit
    %   being the MSB (most significant bit). X can be a column vector,
    %   matrix or an array with 3 dimensions. Number of rows in X must be
    %   an integer multiple of N. Y has same dimensions as X, except that
    %   the number of rows in Y are N times less than the number of rows in
    %   X. The datatype of X can be any of the built-in numeric types or
    %   logical. When the datatype of X is -
    %   - double or logical, datatype of Y is double.
    %   - single, datatype of Y is single.
    %   - a built-in integer type, Y has the same datatype as X unless the
    %   values in Y cannot be represented in that datatype without loss of
    %   data. If values in Y are larger than the intmax of the datatype of
    %   X, then Y is of the smallest datatype that can fit the values
    %   without loss of data. The datatype of Y has same signedness as that
    %   of X.
    %   - double or logical, N must be no larger than 53.
    %   - single, N must be no larger than 24.
    %   - a built-in signed integer type, N must be no larger than 63.
    %   - a built-in unsigned integer type, N must be no larger than 64.
    %
    %   Y = BIT2INT(X,N,MSBFIRST) specifies MSB orientation in MSBFIRST.
    %   When MSBFIRST is true, the first bit in each set of N column-wise
    %   bits in X is the MSB; when MSBFIRST is false, the first bit in each
    %   set of N column-wise bits in X is the LSB (least significant bit).
    %
    %   Y = BIT2INT(___,IsSigned=TF) specifies TF as a logical which can be
    %   either true or false to indicate the signed-ness of the integer.
    %   Default is false. When TF is true, then the first bit in each block
    %   of N bits is considered to be a signed bit and the output may
    %   contain negative values. If the datatype of X is any of the
    %   unsigned integer types with TF set to true, then the datatype of Y
    %   is the smallest signed integer type that can support the number of
    %   input bits.
    %
    %   Examples:
    %
    %   A1 = [1 0 1 0 1 0 1 0]';
    %   N1 = 8;
    %   B1 = bit2int(A1, N1);
    %
    %   A2 = int8([1 1 0; 0 1 1]');
    %   N2 = 3;
    %   msbFirst = false;
    %   B2 = bit2int(A2, N2, msbFirst);
    %
    %   A3 = randi([0,1], 32, 2, 2, 'uint8');
    %   N3 = 16;
    %   B3 = bit2int(A3, N3);
    %
    %   A4 = [-110, 103, -103, 99];
    %   C4 = int2bit(A4,8);
    %   B4 = bit2int(C4,8,IsSigned=true);
    %
    %   See also INT2BIT.
    
    %   Copyright 2021-2022 The MathWorks, Inc.
    
    %#codegen
    narginchk(2,5);
    validateattributes(x, {'numeric','logical'}, {'3d','nonempty','binary'}, '', 'X');
    if nargin == 2
        MSBFirst = true;
        IsSigned = false;
    elseif nargin == 3
        % If 3 inputs, then third argument must be MSBFirst option
        IsSigned = false;
        MSBFirst = varargin{1};
        validateattributes(MSBFirst, {'logical','numeric'}, {'scalar','binary'}, '', 'MSBFirst');
    else
        % Then either 4 inputs with name-value is possible or 5 inputs with
        % MSBFirst option and name-value of IsSigned is possible
        if nargin == 4
            signedOption = {varargin{1:2}}; % Codegen does not support cellarray(...). So use curly braces
            MSBFirst = true;
        else % nargin == 5
            MSBFirst = varargin{1};
            signedOption = {varargin{2:3}};
            validateattributes(MSBFirst, {'logical','numeric'}, {'scalar','binary'}, '', 'MSBFirst');
        end

        defaults = struct("IsSigned",false);
        res = comm.internal.utilities.nvParser(defaults, signedOption{:});
        IsSigned = res.IsSigned;
        validateattributes(IsSigned, {'logical','numeric'}, {'scalar','binary'}, '', 'IsSigned');
    end
    
    isSim = comm.internal.utilities.isSim();
    if ~isSim
        coder.internal.prefer_const(N);
    end
    isInputLogical = islogical(x);

    % When N is equal to the max int supported (for example, N==8 for
    % int8), -2^N calculation gives us -2^N + 1 because first 2^N gets
    % calculated which cannot be fit into its native integer type (for
    % example, int8 for N=8). To handle this corner case, subtract one
    % after calculating negative value.
    subone = false;

    if isfloat(x) || isInputLogical
        if isa(x, 'single')
            maxN = 24;
        else
            maxN = 53;
        end

        validateattributes(N, {'numeric'}, {'scalar','positive','integer','<=',maxN}, '', 'N');
        if isInputLogical
            xNew = double(x);
            isInputFloat = false;
        else
            xNew = x;
            isInputFloat = true;
        end
        prototype = xNew(1);        
    else
        % built-in integers
        bitClass = class(x);
        if bitClass(1) == 'u'
            maxN = 64;
        else
            maxN = 63;
        end
        validateattributes(N, {'numeric'}, {'scalar','positive','integer','<=',maxN}, '', 'N');
        coder.internal.errorIf(~isSim && ~coder.internal.isConst(N), ...
            'comm:bit2int:NNotConst');
        if bitClass(1) == 'u' && IsSigned
            bitClassMax = intmax(bitClass(2:end));
        else
            bitClassMax = intmax(bitClass);
        end

        if IsSigned
            c = '';
        else
            c = 'u';
        end

        if bitClass(1) == 'u' || IsSigned
            if N <= 8
                typeMax = intmax([c 'int8']);
                subone = N==8;
            elseif N <= 16
                typeMax = intmax([c 'int16']);
                subone = N==16;
            elseif N <= 32
                typeMax = intmax([c 'int32']);
                subone = N==32;
            else
                typeMax = intmax([c 'int64']);
                subone = N==64;
            end
        else
            if N <= 7
                typeMax = intmax('int8');
            elseif N <= 15
                typeMax = intmax('int16');
            elseif N <= 31
                typeMax = intmax('int32');
            else
                typeMax = intmax('int64');
            end
        end

        if bitClassMax > typeMax
            prototype = bitClassMax;
            subone = false;
        else
            prototype = typeMax;
        end
        xNew = x;
        isInputFloat = false;
    end
    useN = cast(N,'like',prototype);
    
    if isInputFloat || (isSim && isInputLogical)

        inSize = size(xNew);
        nIntsPerCol = inSize(1)/double(N);
        coder.internal.errorIf(nIntsPerCol ~= floor(nIntsPerCol), 'comm:bit2int:InvalidInputDims');
        outSize = inSize;
        outSize(1) = nIntsPerCol;
        xMat = reshape(xNew, useN, []);
        if MSBFirst
            powOf2 = pow2(useN-1:-1:0);
            powOf2(1) = (1-2*IsSigned)*powOf2(1);
        else
            powOf2 = pow2(0:useN-1);
            powOf2(end) = (1-2*IsSigned)*powOf2(end);
        end
        
        y = reshape(powOf2 * xMat, outSize);
        
    else

        Nidx = coder.internal.indexInt(useN);
        [nRows,nCols,nPages] = size(xNew);
        nIntsPerCol = idivide(nRows, Nidx);
        coder.internal.errorIf(Nidx*nIntsPerCol ~= nRows, ...
            'comm:bit2int:InvalidInputDims');

        y = coder.nullcopy(zeros(nIntsPerCol, nCols, nPages, 'like', prototype));

        powOf2 = cast(2, 'like', y) .^ (useN-1:-1:0)';
        powOf2(1) = (1-2*IsSigned)*powOf2(1)-1*subone*IsSigned;
        xTmp = cast(xNew, 'like', y);
        nInts = nIntsPerCol * coder.internal.indexInt(nCols) * coder.internal.indexInt(nPages);
        if MSBFirst
            idx = 1:Nidx;
        else
            idx = Nidx:-1:1;
        end
        for k=1:nInts
            bits = xTmp(Nidx*(k-1) + idx);
            y(k) = sum(bits(:) .* powOf2, 'native');
        end
    end
        
end