update length of corss-correlation

Author: gaoyongyu

main.m

@@ -1,19 +1,19 @@
 clear all;clc;close all;
 
 %%%% you can set arry a and arry b in different value, try some trails
-a = [1 2  8 8];  
+a = [1 2 8 8];  
 b = [2 2 33 0 12 2];
 
 %compute convolution
-res = my_conv(a,b);
+res = my_conv(a,b); %or my_conv(a,b, 'conv')
 c = conv(a, b);
-e = my_conv_usingfft(a, b);
-
-%compute corss correlation
+e = my_conv_usingfft(a, b);%or my_conv(a,b, 'conv')
+% 
+% %compute corss correlation
 d = xcorr(a, b);
 b = flip(b);
-f = my_conv_usingfft(a,b);
-g = my_conv(a, b);
+f = my_conv_usingfft(a,b, 'corr');
+g = my_conv(a, b, 'corr');
 
 %%%
 %%% Check the results of my function with official function

my_conv.m

@@ -1,6 +1,21 @@
-function [ convRes ] = my_conv(aSignal, bSignal)
-aLen= length(aSignal);
+function [ convRes ] = my_conv(aSignal, bSignal, mode)
+aLen= length(aSignal); 
 bLen = length(bSignal);
+if (nargin < 3)
+    mode = 'conv';
+end
+if (mode == 'corr')
+    if (aLen > bLen)
+        bSignal = [bSignal zeros(1, aLen - bLen)];
+        bLen = length(bSignal);
+    else
+        aSignal = [aSignal zeros(1, bLen - aLen)];
+        aLen = length(aSignal);
+    end
+end
+
+
+
 N = aLen + bLen - 1;           %lenth of convolution results must be aLen + bLen -1
 
 bSignal = [bSignal  zeros(1, aLen - 1)]; 

my_conv_usingfft.m

@@ -1,9 +1,22 @@
-function [ c ] = my_conv_usingfft( a ,b )
-alen = length(a);
-blen = length(b);
+function [ c ] = my_conv_usingfft( a ,b, mode)
+aLen = length(a);
+bLen = length(b);
 
-a = [a zeros(1, blen-1)];
-b = [b zeros(1, alen-1)];
+if (nargin < 3)
+    mode = 'conv';
+end
+if (mode == 'corr')
+    if (aLen > bLen)
+        b = [b zeros(1, aLen - bLen)];
+        bLen = length(b);
+    else
+        a = [a zeros(1, bLen - aLen)];
+        aLen = length(a);
+    end
+end
+
+a = [a zeros(1, bLen-1)];
+b = [b zeros(1, aLen-1)];
 
 A = fft(a);
 B = fft(b);