/* ARM assembly AARCH64 Raspberry PI 3B */
/*  program caresarcode64.s   */
/************************************/
/* Constantes                       */
/************************************/
/* for this file see task include a file in language AArch64 assembly*/
.include "../includeConstantesARM64.inc"
.equ KEY,                 23
.equ STRINGSIZE,          500
/************************************/
/* Initialized data                 */
/************************************/
.data
szMessString:            .asciz "String :\n"
szMessEncrip:            .asciz "\nEncrypted :\n"
szMessDecrip:            .asciz "\nDecrypted :\n"
szString1:               .asciz "The quick brown fox jumps over the lazy dog."

szCarriageReturn:        .asciz "\n"
/************************************/
/* UnInitialized data               */
/************************************/
.bss
szString2:                .skip  STRINGSIZE
szString3:                .skip  STRINGSIZE
/************************************/
/*  code section                    */
/************************************/
.text
.global main
main:
    ldr x0,qAdrszMessString                     // display message
    bl affichageMess
    ldr x0,qAdrszString1                        // display string
    bl affichageMess
    ldr x0,qAdrszString1
    ldr x1,qAdrszString2
    mov x2,#KEY                                 // key
    bl encrypt
    ldr x0,qAdrszMessEncrip
    bl affichageMess
    ldr x0,qAdrszString2                        // display string
    bl affichageMess
    ldr x0,qAdrszString2
    ldr x1,qAdrszString3
    mov x2,#KEY                                 // key
    bl decrypt
    ldr x0,qAdrszMessDecrip
    bl affichageMess
    ldr x0,qAdrszString3                        // display string
    bl affichageMess
    ldr x0,qAdrszCarriageReturn
    bl affichageMess
100:                                            // standard end of the program
    mov x0, #0                                  // return code
    mov x8,EXIT
    svc 0                                       // perform system call
qAdrszMessString:         .quad szMessString
qAdrszMessDecrip:         .quad szMessDecrip
qAdrszMessEncrip:         .quad szMessEncrip
qAdrszString1:            .quad szString1
qAdrszString2:            .quad szString2
qAdrszString3:            .quad szString3
qAdrszCarriageReturn:     .quad szCarriageReturn
/******************************************************************/
/*     encrypt strings                         */
/******************************************************************/
/* x0 contains the address of the string1 */
/* x1 contains the address of the encrypted string */
/* x2 contains the key (1-25)                     */
encrypt:
    stp x3,lr,[sp,-16]!       // save  registers
    stp x4,x5,[sp,-16]!       // save  registers
    mov x3,#0                 // counter byte string 1
1:
    ldrb w4,[x0,x3]           // load byte string 1
    cmp w4,#0                 // zero final ?
    bne 2f
    strb w4,[x1,x3]
    mov x0,x3
    b 100f
2:
    cmp w4,#65                // < A ?
    bge 3f
    strb w4,[x1,x3]
    add x3,x3,#1
    b 1b                      // and loop
3:
    cmp x4,#90                // > Z
    bgt 4f
    add x4,x4,x2              // add key
    cmp x4,#90                // > Z
    sub x5,x4,26
    csel x4,x5,x4,gt
    //subgt x4,#26
    strb w4,[x1,x3]
    add x3,x3,#1
    b 1b
4:
    cmp x4,#97                // < a ?
    bge 5f
    strb w4,[x1,x3]
    add x3,x3,#1
    b 1b
5:
    cmp x4,#122               //> z
    ble 6f
    strb w4,[x1,x3]
    add x3,x3,#1
    b 1b
6:
    add x4,x4,x2
    cmp x4,#122
    sub x5,x4,26
    csel x4,x5,x4,gt
    //subgt x4,#26
    strb w4,[x1,x3]
    add x3,x3,#1
    b 1b

100:
    ldp x4,x5,[sp],16        // restaur  registers
    ldp x3,lr,[sp],16            // restaur  registers
    ret
/******************************************************************/
/*     decrypt strings                                           */
/******************************************************************/
/* x0 contains the address of the encrypted string1 */
/* x1 contains the address of the decrypted string */
/* x2 contains the key (1-25)                     */
decrypt:
    stp x3,lr,[sp,-16]!      // save  registers
    stp x4,x5,[sp,-16]!      // save  registers
    mov x3,#0                // counter byte string 1
1:
    ldrb w4,[x0,x3]          // load byte string 1
    cmp x4,#0                // zero final ?
    bne 2f
    strb w4,[x1,x3]
    mov x0,x3
    b 100f
2:
    cmp x4,#65               // < A ?
    bge 3f
    strb w4,[x1,x3]
    add x3,x3,#1
    b 1b                     // and loop
3:
    cmp x4,#90               // > Z
    bgt 4f
    sub x4,x4,x2             // substract key
    cmp x4,#65               // < A
    add x5,x4,26
    csel x4,x5,x4,lt
    //addlt x4,#26
    strb w4,[x1,x3]
    add x3,x3,#1
    b 1b
4:
    cmp x4,#97               // < a ?
    bge 5f
    strb w4,[x1,x3]
    add x3,x3,#1
    b 1b
5:
    cmp x4,#122              // > z
    ble 6f
    strb w4,[x1,x3]
    add x3,x3,#1
    b 1b
6:
    sub x4,x4,x2                // substract key
    cmp x4,#97               // < a
    add x5,x4,26
    csel x4,x5,x4,lt
    //addlt x4,#26
    strb w4,[x1,x3]
    add x3,x3,#1
    b 1b

100:
    ldp x4,x5,[sp],16        // restaur  registers
    ldp x3,lr,[sp],16        // restaur  registers
    ret
/***************************************************/
/*      ROUTINES INCLUDE                           */
/***************************************************/
.include "../includeARM64.inc"