How to compare strings - Another solution

[magicsign]

You can become crazy with this problem.
Lets see this other quick solution to compare strings.

Remember that strings are a sequence of bytes.
home : h(first byte),o(second byte),...,e(last byte),0 a tag to identify the end of the string.

Suppose you have a string inside a register : %esi and you want to compare only the first character with another one :

zero: .ascii "0"

leal zero,%edi

cmpsb #this command compares the first byte(the first character) of the strings inside the registers ESI,EDI.

#Some examples of what you can do now :

je label1 #jump to label 1 if the first characters of the strings inside ESI,EDI are equal

jne label2 #jump to label 2 if the first characters of the strings inside ESI,EDI are not equal

jl label3 #jump to label 3 if the first character of the string inside ESI is lower (ASCII) than the first character of the string inside EDI.

#Now if you want to compare the second character of each string you can simply add 1 to the registers and they will point to the their second character, example:

addl $1,%esi
addl $1,%edi

#Its nice if you want to make a loop...

http://faydoc.tripod.com/cpu/cmpsb.htm

http://www.asciitable.com/

[Goalatio]

Or you could do

mov cx,5 ;Compare first 5 bytes 
mov di,string1 
mov si,string2 
cld
repe cmpsb 
je location1 ;If strings are 100% equal, go to this location

Much easier, much more efficient..
repe = repeat while equal, so you don't have to worry about it slowing down because of how many strings you are comparing.