如何检查字符是否是汇编中的字母? [英] How can I check if a character is a letter in assembly?

问题描述

因此，我有一段代码设置边界，以检查字符是否是字母(不是数字，不是符号)，但是我认为它不适用于大写和小写之间的字符.你能帮我吗?谢谢！

So, I have a block of code which sets the bounders to check if a character is a letter (not numbers, not symbols), but I don't think it works for the characters in between upper and lower case. Can you help? Thanks!

mov al, byte ptr[esi + ecx]; move the first character to al
cmp al, 0                  ; compare al with null which is the end of string
je done                    ; if yes, jump to done
cmp al, 0x41               ; compare al with "A" (upper bounder)
jl next_char               ; jump to next character if less
cmp al, 0x7A               ; compare al with "z" (lower bounder)
jg next_char               ; jump to next character if greater
//do something if it's a letter
next_char:
//do something different

推荐答案

您需要具有将多个条件组合在一起的逻辑，类似于"C"语句: if((c> ='A'&& c< ='Z')||(c> ='a'&&c; lt =='z'))

You need to have a logic that combines multiple conditions similar to what would be a "C" statement: if((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'))

您可以这样做:

...
je done                    ; if yes, jump to done
cmp al, 0x41               ; compare al with "A"
jl next_char               ; jump to next character if less
cmp al, 0x5A               ; compare al with "Z"
jle found_letter           ; if al is >= "A" && <= "Z" -> found a letter
cmp al, 0x61               ; compare al with "a"
jl next_char               ; jump to next character if less (since it's between "Z" & "a")
cmp al, 0x7A               ; compare al with "z"
jg next_char               ; above "Z" -> not a character
found_letter:
// ...
next_char:
// ...

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