Write a program to reverse a character string with an odd number of characters pointed at by r0. Assume the string you are copying is non?null (it contains at least one character) and that it is terminated by 0x0D (the number of characters included the terminator). You must not use an additional memory buffer (i.e., you can use only registers and the string storage itself).
What will be an ideal response?
AREA ReverseString2, CODE, READWRITE
ADR r0,Source ;r0 points to source
MOV r3,r0 ;keep a copy of the start of the source
FindEnd LDRB r2,[r0],#1 ;read a byte and update pointer
CMP r2,#0x0D ;test for end
BNE FindEnd ;continue until terminator found
Reverse LDRB r2,[r3],#1 ;REVERSE Repeat (Pick up char from front)
LDRB r4,[r0,#-1]! ; Pick up char from end
STRB r2,[r0,#0] ; Do the swap ? note offsets
STRB r4,[r3,#-1] ;
CMP r3,r0 ;have we finished
BLE Reverse
MOV r0, #0x18 ;angel_SWIreason_ReportException
LDR r1, =0x20026 ;ADP_Stopped_ApplicationExit
SVC #0x123456 ;ARM semihosting (formerly SWI)
AREA ReverseString2, DATA, READWRITE
DCD 0xFFFFFFFF ;this is just a marker to help me read the code
Source DCB "12345",0x0D
END
Computer Science & Information Technology
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