Damm algorithm: Difference between revisions
Add ARM Assembly
(PHP implementation of Damm algorithm) |
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{{output}}
<lang applescript>{"5724 is valid", "57240 is valid", "572400 is valid", "87591 is invalid", "100 is invalid", "3922446 is valid"}</lang>
=={{header|ARM Assembly}}==
<lang>.text
.global _start
@@@ Check if the zero-terminated ASCII string in [r0],
@@@ which should contain a decimal number, has a
@@@ matching check digit. Zero flag set if true,
@@@ check digit returned in r0.
damm: mov r1,#0 @ R1 = interim digit
ldr r2,=3f @ R2 = table base address
1: ldrb r3,[r0],#1 @ Load byte
tst r3,r3 @ Zero yet?
beq 2f @ If so, stop
sub r3,r3,#'0 @ Subtract ASCII 0
lsl r1,r1,#1 @ Table lookup
add r1,r1,r1,lsl#2 @ R3 = R1*10 + R3
add r3,r1,r3
ldrb r1,[r2,r3] @ R1 = new interim digit
b 1b @ Next value
2: movs r0,r1 @ Set flag according to r0.
bx lr
3: .byte 0,3,1,7,5,9,8,6,4,2 @ Since the table is constant,
.byte 7,0,9,2,1,5,4,8,6,3 @ it can be stored as part of
.byte 4,2,0,6,8,7,1,3,5,9 @ the subroutine.
.byte 1,7,5,0,9,8,3,4,2,6 @ This way the OS will even mark
.byte 6,1,2,3,0,4,5,9,7,8 @ it as read-only, so we can
.byte 3,6,7,4,2,0,9,5,8,1 @ be sure nothing changes it.
.byte 5,8,6,9,7,2,0,1,3,4
.byte 8,9,4,5,3,6,2,0,1,7
.byte 9,4,3,8,6,1,7,2,0,5
.byte 2,5,8,1,4,3,6,7,9,0
.align 4 @ Instructions must be word-aligned
@@@ Grab the argument from the command line, and see
@@@ if it matches.
_start: pop {r0} @ Is there even an argument?
cmp r0,#2
movne r7,#1 @ If not, exit immediately
swine #0
add sp,sp,#4 @ Discard program name
pop {r0} @ Grab argument
bl damm @ Check if it matches
ldreq r1,=pass @ If yes, say 'pass'
ldrne r1,=fail @ If not, say 'fail'
mov r0,#1 @ Print string to stdout
mov r2,#5 @ Both are 5 characters
mov r7,#4 @ Write syscall = 4
swi #0
mov r0,#0 @ Exit
mov r7,#1
swi #0
pass: .ascii "Pass\n"
fail: .ascii "Fail\n"</lang>
{{out}}
<pre>$ for x in 5724 5725 112946 112949; do echo -n $x:; ./damm $x; done
5724:Pass
5725:Fail
112946:Pass
112949:Fail</pre>
=={{header|AutoHotkey}}==
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