strlwr 和 strupr 模拟

.DATA
strlwr_table    BYTE    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20
        BYTE    21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40
        BYTE    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64
        BYTE    97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122    ; To lower case.
        BYTE    91, 92, 93, 94, 95, 96
        BYTE    97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122    ; Original lower case.
        BYTE    123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143
        BYTE    144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164
        BYTE    165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185
        BYTE    186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206
        BYTE    207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227
        BYTE    228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248
        BYTE    249, 250, 251, 252, 253, 254, 255

strupr_table    BYTE    0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20
        BYTE    21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40
        BYTE    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64
        BYTE    65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90    ; Original upper case.
        BYTE    91, 92, 93, 94, 95, 96
        BYTE    65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90    ; To upper case.
        BYTE    123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143
        BYTE    144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164
        BYTE    165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185
        BYTE    186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206
        BYTE    207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227
        BYTE    228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248
        BYTE    249, 250, 251, 252, 253, 254, 255

.CODE

; Prototype
;    eax strlwr(char *str) ;
; Param
;    str: The address of null terminated string.
; Return
;    eax: The address of the null terminated string.
; Function own stack and response for adjust ESP after called.
strlwr    PROC NEAR32
    push    ebp
    mov    ebp, esp
    pushf
    push    ebx
    push    esi
    push    edi
    
    ; Get address of traslation table.
    lea    ebx, strlwr_table
    ; Save address of the string to be translated.
    mov    eax, [ebp + 8]
    push    eax
    ; Initailization
    mov    esi, eax
    mov    edi, eax
    cld

while_strlwr:
    cmp    BYTE PTR [esi], 0
    je    exit_strlwr
    lodsb
    xlat
    stosb
    loop    while_strlwr

exit_strlwr:
    pop    eax
    pop    edi
    pop    esi
    pop    ebx
    popf
    pop    ebp
    ret    4
strlwr    ENDP

; Prototype
;    eax strupr(char *str) ;
; Param
;    str: The address of null terminated string.
; Return
;    eax: The address of the null terminated string.
; Function own stack and response for adjust ESP after called.
strupr    PROC NEAR32
    push    ebp
    mov    ebp, esp
    pushf
    push    ebx
    push    esi
    push    edi
    
    ; Get address of traslation table.
    lea    ebx, strupr_table
    ; Save address of the string to be translated.
    mov    eax, [ebp + 8]
    push    eax
    ; Initailization
    mov    esi, eax
    mov    edi, eax
    cld

while_strupr:
    cmp    BYTE PTR [esi], 0
    je    exit_strupr
    lodsb
    xlat
    stosb
    loop    while_strupr

exit_strupr:
    pop    eax
    pop    edi
    pop    esi
    pop    ebx
    popf
    pop    ebp
    ret    4
strupr    ENDP

　　

More practical version:

; Prototype
;    eax strlwr(char *str) ;
; Param
;    str: The address of null terminated string.
; Return
;    eax: The address of the null terminated string.
; Function own stack and response for adjust ESP after called.
strlwr    PROC NEAR32
    push    ebp
    mov    ebp, esp
    pushf
    push    esi
    push    edi

    ; Initialize
    mov    esi, [ebp + 8]
    mov    edi, esi
    mov    eax, 0
    cld

while_strlwr:
    lodsb            ; memory => al
    cmp    al, 0
    je    exit_strlwr
    or    al, 00100000b    ; Upper to lower
    stosb            ; al => memory
    jmp    while_strlwr
    
exit_strlwr:
    mov    eax, [ebp + 8]    ; Rtn: address of original string
    pop    edi
    pop    esi
    popf
    pop    ebp
    ret    4
strlwr    ENDP

; Prototype
;    eax strupr(char *str) ;
; Param
;    str: The address of null terminated string.
; Return
;    eax: The address of the null terminated string.
; Function own stack and response for adjust ESP after called.
strupr    PROC NEAR32
    push    ebp
    mov    ebp, esp
    pushf
    push    esi
    push    edi
    
    ; Initialize
    mov    esi, [ebp + 8]
    mov    edi, esi
    mov    eax, 0
    cld

while_strupr:
    lodsb            ; memory => al
    and    al, 11011111b    ; Lower to upper
    stosb            ; al => memory
    jnz    while_strupr

exit_strupr:
    mov    eax, [ebp + 8]    ; Rtn: address of original string
    pop    edi
    pop    esi
    popf
    pop    ebp
    ret    4
strupr    ENDP