VAXG_to_uint64le.m

function uint32le = VAXG_to_uint64le(doubleVAXG)
%VAXG_TO_UINT64LE Converts from VAXG (double) to IEEE-LE (UINT32)
% This function converts floating point numbers initialized in MATLAB  
% into equivalent 64bit unsigned integers, and then splits the result
% into a vector columns of raw 32bit unsigned integers (little endian)
% using the specification for the VAXG floating point number format.
% VAXG is a 64bit or 'double precision' floating point format:
%  http://www.opengroup.org/onlinepubs/9629399/chap14.htm#tagfcjh_20
%
% The function is intended to be called from FWRITEVAX.
%
% See also VAXF_TO_UINT32LE, VAXD_TO_UINT64LE, FWRITEVAX
%
%  2009 The MathWorks, Inc. MATLAB and Simulink are registered trademarks
% of The MathWorks, Inc. See www.mathworks.com/trademarks for a list of 
% additional trademarks. Other product or brand names may be trademarks or 
% registered trademarks of their respective holders.

%% Define floating value properties for VAX architecture
% The generic equation for a floating point number is:
% V = (-1)^double(S) * M * A^(double(E)-B);
% Substituting M = C + F 
% V = (-1)^double(S) * (C+F) * A^(double(E)-B);
%
% Performing inverse operations to solve for E and F:
% 0 <= 1 + log(M)/log(2) < 1  (VAX specific)
% E = (floor) (logV / D) + 1 + B   
% F = V / ((A ^ (E-B)) - C)
%
% V = value, S = sign, M = mantissa, A = base, E = exponent, B = exponent 
% bias, C = mantissa constant, F = fraction

A = 2;      % VAX specific
B = 1024;    % VAX specific
C = 0.5;    % VAX specific
D = log(2); % VAX specific

%% Determine the sign bit. If -ve transform to positive.
S = zeros(size(doubleVAXG));
if any(doubleVAXG(:) < 0)
	indices = find(doubleVAXG < 0);
    doubleVAXG(indices) = (-1) .* doubleVAXG(indices);
    S = zeros(size(doubleVAXG));
    S(indices) = 1;
end

%% Decompose the floating point number to SEF (Sign, Exp, Fract)
E = floor((log(doubleVAXG)./ D) + 1 + B); 
F = ((doubleVAXG ./ A.^(double(E)-B))) - C; 
% Convert floating point fraction to unsigned integer
F = F * 9007199254740992;   %VAX Specific 9007199254740992=2^53

%% Shift the bits of S, E and F
% VAX FLOAT BYTES  &lt;-----WORD1----&gt;&lt;-----WORD2----&gt;&lt;-----WORD1----&gt;&lt;-----WORD2----&gt;
% VAX FLOAT BITS   0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF
% Sign Exp Fract   SEEEEEEEEEEEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF

S = bitshift(bitshift(uint64(S),0), 63);
E = bitshift(bitshift(uint64(E),0), 53);
F = bitshift(bitshift(uint64(F),0), 12);

%% Combine the S, E and F into the unsigned integer value
vaxInt = bitor(bitor(S,bitshift(E,-1)),bitshift(F,-12));

%% Convert to raw 32bit integers
% Flip the upper and lower bits (based on how Vax data storage format)
% VAX (64bit)      &lt;--WORD1--&gt;&lt;--WORD2--&gt;&lt;--WORD3--&gt;&lt;--WORD4--&gt;
% IEEE-LE (32bit)  &lt;--WORD2--&gt;&lt;--WORD1--&gt;
% IEEE-LE (32bit)  &lt;--WORD4--&gt;&lt;--WORD3--&gt;

% Split IEEE UINT64: &lt;--WORD1--&gt;&lt;--WORD2--&gt;|&lt;--WORD3--&gt;&lt;--WORD4--&gt;
%                    \____________________/ \____________________/
%                          vaxIntA               vaxIntB

vaxIntA = uint32(bitshift(bitshift(vaxInt,0), -32));
vaxIntB = uint32(bitshift(bitshift(vaxInt,32), -32));

% Swap WORD1 and WORD2

word2 = bitshift(bitshift(vaxIntA, 16), -16);
word1 = bitshift(vaxIntA, -16);
uint32leA = bitor(bitshift(word2,16), word1);

% Swap WORD3 and WORD4

word4 = bitshift(bitshift(vaxIntB, 16), -16);
word3 = bitshift(vaxIntB, -16);
uint32leB = bitor(bitshift(word4,16), word3);

uint32le(:,1) = reshape(uint32leA, numel(uint32leA), []);  %&lt;--WORD2--&gt;&lt;--WORD1--&gt;
uint32le(:,2) = reshape(uint32leB, numel(uint32leB), []);  %&lt;--WORD4--&gt;&lt;--WORD3--&gt;

uint32le = uint32le';