kvisc/ka/crt/fmt/strtol.k

; The OS/K Team licenses this file to you under the MIT license.
; See the LICENSE file in the project root for more information.

;
; int strtol(const char *str, int base)
;
; eax = integer extracted from str
; edx = pointer to first invalid byte
;
strtol:
    mov ax2, 1
    jmp strtoq

;
; int strtoul(const char *str, int base)
;
; eax = integer extracted from str
; edx = pointer to first invalid byte
;
strtoul:
    nul ax2
    jmp strtoq

;
; int strtoq(const char *str, int base, bool signed)
;
; guesses base when 'base'=0
;
strtoq:
    nul eax, esi
    mov edx, ax0

    ; make sure base is in [2, 32]
    beq ax1, 1, .bad
    bltu 36, ax1, .bad

    ; empty string?
    bzr b[edx], .done

.skip_spc:
    bne b[edx], ' ', .no_spc
    inc edx
    jmp .skip_spc

.no_spc:
    ; skip +
    bne b[edx], '+', .no_plus
    inc edx

.no_plus:
    ; unsigned?
    bzr ax2, .unsigned

    ; parse '-'
    bne b[edx], '-', .unsigned
    inc edx
    mov esi, 1

.unsigned:
    ; base 0
    bzr ax1, .base_0

    ; base prefix?
    bne b[edx], '0', .main_loop

    inc edx
    movzx ecx, b[edx]

    ; "0x"/"0b" prefix
    jecxz .done ; "0"
    beq ecx, 'x', .parsed_0x
    beq ecx, 'b', .parsed_0b

    ; may be octal, but we don't care
    ; we accept "0110101010" (despite base=2) for instance
    jmp .main_loop

.parsed_0x:
    ; are we in base 16?
    ; if not, leave eax = 0 and *edx = 'x'
    bne ax1, 16, .done
    ; else
    inc edx
    jmp .main_loop

.parsed_0b:
    ; are we in base 2?
    ; if not, leave eax = 0 and *edx = 'b'
    bne ax1, 2, .done
    ; else
    inc edx
    jmp .main_loop

.base_0:
    ; guess base

    beq b[edx], '0', .b0_not10

    ; must be base 10
    mov ax1, 10
    jmp .main_loop

.b0_not10:
    inc edx

    bne b[edx], 'x', .b0_not16
    inc edx
    mov ax1, 16
    jmp .main_loop

.b0_not16:
    bne b[edx], 'b', .b0_not2
    inc edx
    mov ax1, 2
    jmp .main_loop

.b0_not2:
    ; take octal by default
    mov ax1, 8

.main_loop:
    movzx ecx, b[edx]
    inc edx

    ; between 0 and 9?
    bltu ecx, '0', .done
    bltu '9', ecx, .not_digit10

    ; yes
    sub ecx, '0'
    jmp .next

.not_digit10:
    bltu ecx, 'A', .done
    bltu 'Z', ecx, .not_digitAZ

    sub ecx, 55     ; 'A' - 10
    jmp .next

.not_digitAZ:
    bltu ecx, 'a', .done
    bltu 'z', ecx, .done

    sub ecx, 87     ; 'a' - 10
    jmp .next

.next:
    ; too large for base?
    blteu ax1, ecx, .done

    mul eax, ax1
    add eax, ecx
    jmp .main_loop

.done:
    ; negative?
    bzr esi, .r

    ; yes
    neg eax

.r:
    ret

.bad:
    ret