/* ARM assembly Raspberry PI  */
/*  program vignere.s   */
/* REMARK 1 : this program use routines in a include file
   see task Include a file language arm assembly
   for the routine affichageMess conversion10
   see at end of this program the instruction include */

/*******************************************/
/* Constantes                              */
/*******************************************/
.include "../constantes.inc"

.equ BUFFERSIZE, 2000
/*******************************************/
/*   Macros                              */
/*******************************************/
//.include "../../ficmacros32.inc"            @ for developer debugging


/*******************************************/
/* Initialized data */
/*******************************************/
.data
szMessDebutPgm:   .asciz "Program 32 bits start. \n"
szCarriageReturn: .asciz "\n"
szMessFinOK:      .asciz "Program normal end. \n"
szMessError:      .asciz "\nError  Buffer too small!!!\n"
szMessString:     .asciz "String :\n"
szMessEncrip:     .asciz "\nEncrypted :\n"
szMessDecrip:     .asciz "\nDecrypted :\n"
szString1:        .asciz "ABCDEFGHIJKLMNOPQRSTUVWXYZ!.?abcdefghijklmnopqrstuvwxyz"
//szString1:         .asciz "attackatdawn"
//szString1:         .asciz "ATTACKATDAWN"
szKey1:           .asciz "LEMON"
/*******************************************/
/* UnInitialized data */
/*******************************************/
.bss
sBuffer1:                .skip  BUFFERSIZE
sBuffer2:                .skip  BUFFERSIZE
/*******************************************/
/*  code section */
/*******************************************/
.text
.global main
main:
    ldr r0,iAdrszMessDebutPgm
    bl affichageMess
    ldr r0,iAdrszMessString       @ display message
    bl affichageMess
    ldr r0,iAdrszString1          @ display string
    bl affichageMess
    ldr r0,iAdrszString1          @ string address
    ldr r1,iAdrszKey1             @ key
    ldr r2,iAdrsBuffer1           @ encrypted buffer
    bl encrypt
    cmp r0,#0
    ble 99f
    ldr r0,iAdrszMessEncrip
    bl affichageMess
    ldr r0,iAdrsBuffer1           @ display encrypted buffer
    bl affichageMess

    ldr r0,iAdrsBuffer1           @ encrypted buffer
    ldr r1,iAdrszKey1             @ key
    ldr r2,iAdrsBuffer2           @ decrypted buffer
    bl decrypt
    ldr r0,iAdrszMessDecrip
    bl affichageMess
    ldr r0,iAdrsBuffer2           @ display decrypted buffer
    bl affichageMess
    ldr r0,iAdrszCarriageReturn
    bl affichageMess

    ldr r0,iAdrszMessFinOK
    bl affichageMess
    b 100f
99:
    ldr r0,iAdrszMessError        @ error
    bl affichageMess
    mov r0, #1
100:                              @ standard end of the program
    mov r0, #0                    @ return code
    mov r7, #EXIT                 @ request to exit program
    svc 0                         @ perform system call
iAdrszMessString:         .int szMessString
iAdrszMessDecrip:         .int szMessDecrip
iAdrszMessEncrip:         .int szMessEncrip
iAdrszString1:            .int szString1
iAdrsBuffer1:             .int sBuffer1
iAdrsBuffer2:             .int sBuffer2
iAdrszKey1:               .int szKey1
iAdrszMessDebutPgm:       .int szMessDebutPgm
iAdrszMessFinOK:          .int szMessFinOK
iAdrszCarriageReturn:     .int szCarriageReturn
iAdrszMessError:          .int szMessError
/******************************************************************/
/*     encrypt strings                         */
/******************************************************************/
/* r0 contains the address of the string1 */
/* r1 contains key address
/* r2 contains the address of the encrypted string */
/* r0 return buffer lenght  */
encrypt:
    push {r3-r7,lr}           @ save  registers
    mov r3,#0                 @ counter byte string 1
    mov r5,#0                 @ counter byte buffer
1:
    mov r4,#0                 @ counter byte key
2:
    cmp r5,#BUFFERSIZE        @ max length buffer ?
    movge r0,#-1              @ error
    bge 100f
    ldrb r6,[r1,r4]           @ load a byte
    cmp r6,#0                 @ end key ?
    beq 1b
    sub r6,r6,#'A'            @ character rang in alfabet
    add r4,r4,#1
3:
    ldrb r7,[r0,r3]           @ load byte string 1
    cmp r7,#0                 @ zero final ?
    streqb r7,[r2,r5]
    moveq r0,r5
    beq 100f
    cmp r7,#65                @ < A ?
    addlt r3,#1
    blt 3b
    cmp r7,#90                @ > Z
    bgt 4f
    add r7,r6                 @ add key
    cmp r7,#90                @ > Z
    subgt r7,#26              @  - alphaget size
    strb r7,[r2,r5]           @ store result
    add r5,r5,#1
    add r3,r3,#1              @ other byte of string
    b 2b                      @ other byte of key
4:
    cmp r7,#97                @ < a ?
    addlt r3,#1
    blt 3b
    cmp r7,#122               @> z
    addgt r3,#1
    bgt 3b
    sub r7,#32                @ convert minuscul to majuscule
    add r7,r6                 @ add key
    cmp r7,#90                @ if > Z
    subgt r7,#26              @ - alphaget size
    strb r7,[r2,r5]           @ store result
    add r5,r5,#1
    add r3,#1
    b 2b

100:
    pop {r3-r7,lr}            @ restaur registers
    bx lr                     @ return
/******************************************************************/
/*     decrypt strings                                           */
/******************************************************************/
/* r0 contains the address of the encrypted string1 */
/* r1 contains the  key   */
/* r2 contains the address of the decrypted buffer */
decrypt:
    push {r3-r7,lr}           @ save  registers
    mov r3,#0                 @ counter byte string 1
    mov r5,#0                 @ counter byte buffer

1:
    mov r4,#0                 @ counter byte key
2:
    ldrb r6,[r1,r4]           @ load byte key
    cmp r6,#0                 @ end key
    beq 1b
    sub r6,r6,#'A'
    add r4,r4,#1
3:
    ldrb r7,[r0,r3]           @ load byte string 1
    cmp r7,#0                 @ zero final ?
    streqb r7,[r2,r5]
    moveq r0,r5
    beq 100f
    cmp r7,#65                @ < A ?
    addlt r3,#1
    blt 3b
    cmp r7,#90                @ > Z
    addgt r3,#1               @ no minuscul
    bgt 3b
    sub r7,r6                 @ add key
    cmp r7,#65                @ < A
    addlt r7,#26              @
    strb r7,[r2,r5]
    add r5,r5,#1
    add r3,r3,#1              @ other byte of string
    b 2b                      @ other byte of key


100:
    pop {r3-r7,lr}           @ restaur registers
    bx lr                    @ return

/***************************************************/
/*      ROUTINES INCLUDE                 */
/***************************************************/
.include "../affichage.inc"