/* ARM assembly Raspberry PI */ /* program incstring.s */ /* Constantes */ .equ BUFFERSIZE, 100 .equ STDIN, 0 @ Linux input console .equ STDOUT, 1 @ Linux output console .equ EXIT, 1 @ Linux syscall .equ READ, 3 @ Linux syscall .equ WRITE, 4 @ Linux syscall /* Initialized data */ .data szMessNum: .asciz "Enter number : \n" szCarriageReturn: .asciz "\n" szMessResult: .ascii "Increment number is = " @ message result sMessValeur: .fill 12, 1, ' ' .asciz "\n" /* UnInitialized data */ .bss sBuffer: .skip BUFFERSIZE /* code section */ .text .global main main: /* entry of program */ push {fp,lr} /* saves 2 registers */ ldr r0,iAdrszMessNum bl affichageMess mov r0,#STDIN @ Linux input console ldr r1,iAdrsBuffer @ buffer address mov r2,#BUFFERSIZE @ buffer size mov r7, #READ @ request to read datas swi 0 @ call system ldr r1,iAdrsBuffer @ buffer address mov r2,#0 @ end of string strb r2,[r1,r0] @ store byte at the end of input string (r0 @ ldr r0,iAdrsBuffer @ buffer address bl conversionAtoD @ conversion string in number in r0 @ increment r0 add r0,#1 @ conversion register to string ldr r1,iAdrsMessValeur bl conversion10S @ call conversion ldr r0,iAdrszMessResult bl affichageMess @ display message 100: /* standard end of the program */ mov r0, #0 @ return code pop {fp,lr} @restaur 2 registers mov r7, #EXIT @ request to exit program swi 0 @ perform the system call iAdrsMessValeur: .int sMessValeur iAdrszMessNum: .int szMessNum iAdrsBuffer: .int sBuffer iAdrszMessResult: .int szMessResult iAdrszCarriageReturn: .int szCarriageReturn /******************************************************************/ /* display text with size calculation */ /******************************************************************/ /* r0 contains the address of the message */ affichageMess: push {fp,lr} /* save registres */ push {r0,r1,r2,r7} /* save others registers */ mov r2,#0 /* counter length */ 1: /* loop length calculation */ ldrb r1,[r0,r2] /* read octet start position + index */ cmp r1,#0 /* if 0 its over */ addne r2,r2,#1 /* else add 1 in the length */ bne 1b /* and loop */ /* so here r2 contains the length of the message */ mov r1,r0 /* address message in r1 */ mov r0,#STDOUT /* code to write to the standard output Linux */ mov r7, #WRITE /* code call system "write" */ swi #0 /* call systeme */ pop {r0,r1,r2,r7} /* restaur others registers */ pop {fp,lr} /* restaur des 2 registres */ bx lr /* return */ /******************************************************************/ /* Convert a string to a number stored in a registry */ /******************************************************************/ /* r0 contains the address of the area terminated by 0 or 0A */ /* r0 returns a number */ conversionAtoD: push {fp,lr} @ save 2 registers push {r1-r7} @ save others registers mov r1,#0 mov r2,#10 @ factor mov r3,#0 @ counter mov r4,r0 @ save address string -> r4 mov r6,#0 @ positive sign by default mov r0,#0 @ initialization to 0 1: /* early space elimination loop */ ldrb r5,[r4,r3] @ loading in r5 of the byte located at the beginning + the position cmp r5,#0 @ end of string -> end routine beq 100f cmp r5,#0x0A @ end of string -> end routine beq 100f cmp r5,#' ' @ space ? addeq r3,r3,#1 @ yes we loop by moving one byte beq 1b cmp r5,#'-' @ first character is - moveq r6,#1 @ 1 -> r6 beq 3f @ then move on to the next position 2: /* beginning of digit processing loop */ cmp r5,#'0' @ character is not a number blt 3f cmp r5,#'9' @ character is not a number bgt 3f /* character is a number */ sub r5,#48 umull r0,r1,r2,r0 @ multiply par factor 10 cmp r1,#0 @ overflow ? bgt 99f @ overflow error add r0,r5 @ add to r0 3: add r3,r3,#1 @ advance to the next position ldrb r5,[r4,r3] @ load byte cmp r5,#0 @ end of string -> end routine beq 4f cmp r5,#0x0A @ end of string -> end routine beq 4f b 2b @ loop 4: cmp r6,#1 @ test r6 for sign moveq r1,#-1 muleq r0,r1,r0 @ if negatif, multiply par -1 b 100f 99: /* overflow error */ ldr r0,=szMessErrDep bl affichageMess mov r0,#0 @ return zero if error 100: pop {r1-r7} @ restaur other registers pop {fp,lr} @ restaur 2 registers bx lr @return procedure /* constante program */ szMessErrDep: .asciz "Too large: overflow 32 bits.\n" .align 4 /***************************************************/ /* Converting a register to a signed decimal */ /***************************************************/ /* r0 contains value and r1 area address */ conversion10S: push {r0-r4,lr} @ save registers mov r2,r1 /* debut zone stockage */ mov r3,#'+' /* par defaut le signe est + */ cmp r0,#0 @ negative number ? movlt r3,#'-' @ yes mvnlt r0,r0 @ number inversion addlt r0,#1 mov r4,#10 @ length area 1: @ start loop bl divisionpar10 add r1,#48 @ digit strb r1,[r2,r4] @ store digit on area sub r4,r4,#1 @ previous position cmp r0,#0 @ stop if quotient = 0 bne 1b strb r3,[r2,r4] @ store signe subs r4,r4,#1 @ previous position blt 100f @ if r4 < 0 -> end mov r1,#' ' @ space 2: strb r1,[r2,r4] @store byte space subs r4,r4,#1 @ previous position bge 2b @ loop if r4 > 0 100: pop {r0-r4,lr} @ restaur registers bx lr /***************************************************/ /* division par 10 signé */ /* Thanks to http://thinkingeek.com/arm-assembler-raspberry-pi/* /* and http://www.hackersdelight.org/ */ /***************************************************/ /* r0 dividende */ /* r0 quotient */ /* r1 remainder */ divisionpar10: /* r0 contains the argument to be divided by 10 */ push {r2-r4} /* save registers */ mov r4,r0 ldr r3, .Ls_magic_number_10 /* r1 <- magic_number */ smull r1, r2, r3, r0 /* r1 <- Lower32Bits(r1*r0). r2 <- Upper32Bits(r1*r0) */ mov r2, r2, ASR #2 /* r2 <- r2 >> 2 */ mov r1, r0, LSR #31 /* r1 <- r0 >> 31 */ add r0, r2, r1 /* r0 <- r2 + r1 */ add r2,r0,r0, lsl #2 /* r2 <- r0 * 5 */ sub r1,r4,r2, lsl #1 /* r1 <- r4 - (r2 * 2) = r4 - (r0 * 10) */ pop {r2-r4} bx lr /* leave function */ .align 4 .Ls_magic_number_10: .word 0x66666667