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> Main > smallest case insenstive compare? |
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bitshifter 26 Jun 2011, 20:27
20 bytes, possibly dangerous, somewhat incomplete, and totally untested...
Code: stricmp: ; in: ds:si -> string 1 ; ds:di -> string 2 lodsb and al,0xDF ;force uppercase xchg al,ah xchg si,di lodsb xchg si,di and al,0xDF ;force uppercase cmp al,ah jnz notsame test ah,ah jnz stricmp same: ; ... notsame: ; ... Now wheres Loco when you need him? |
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26 Jun 2011, 20:27 |
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LocoDelAssembly 26 Jun 2011, 22:04
bitshifter, not sure what do you expect from me?
 Maybe it is MHajduk who you are actually waiting for? 
Anyway, your code will handle some cases incorrectly, for instance "[" will be the up-cased version of "{", so the comparison wht36 makes to make sure the byte is in the ['a'..'z'] range is necessary. If this will become some sort of contest for inlined pseudo-stricmp code, both yours and wht36's submission would be incorrect, it should be part of the solution to stop at the first occurrence of char zero, otherwise it will always result in fail/notsame situation or access violation (or even infinite loop in 16-bit environment if the proper conditions are given like comparing buffers full of zeroes). |
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26 Jun 2011, 22:04 |
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Picnic 26 Jun 2011, 22:23
Twenty messy bytes that just came out of my head.
I'm too sleepy to try nineteen. In: si, di Out: zero flag set = equal Code: equal: lodsb or al, al jz @F mov ah, [di] inc di or ax, 2020h ;force lowercase cmp al, ah jz equal ret @@: cmp byte [di], 0 ret Zzz... |
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26 Jun 2011, 22:23 |
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bitshifter 26 Jun 2011, 23:06
31 bytes (and hopefully bulletproof)
Code: uprswp: lodsb xchg si,di cmp al,'a' jb .done cmp al,'z' ja .done sub al,32 .done: ret stricmp: ; in: ds:si -> string 1, ds:di -> string 2 ; out: zf = 1 if same, zf = 0 if not same call uprswp xchg ah,al call uprswp cmp ah,al jnz .done cmp al,0 jnz stricmp .done: ret Although the real stricmp returns < = > and follows an ABI calling convention... In the real world: I would give up the couple of bytes to change uprswp into toupper just so it could be reused later in life (if part of a library or something) |
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26 Jun 2011, 23:06 |
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bitshifter 27 Jun 2011, 04:33
30 bytes (some rearranging and call/ret bashing)
Code: ; in: ds:si -> string 1, ds:di -> string 2 ; out: zf = 1 if same, zf = 0 if not same stricmp: push .here .muck: lodsb xchg si,di cmp al,'a' jb .done cmp al,'z' ja .done sub al,32 .done: ret .here: xchg ah,al call .muck cmp ah,al jnz .done cmp al,0 jnz stricmp ret I still have not tested any of this crap  |
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27 Jun 2011, 04:33 |
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wht36 27 Jun 2011, 08:28
LocoDelAssembly wrote: ...If this will become some sort of contest for inlined pseudo-stricmp code, both yours and wht36's submission would be incorrect, it should be part of the solution to stop at the first occurrence of char zero, otherwise it will always result in fail/notsame situation or access violation (or even infinite loop in 16-bit environment if the proper conditions are given like comparing buffers full of zeroes). Ok, for a full strcmpi, it would be 28 bytes Code: equal: ;some code here for match cmp al,0 ;test for end of both strings je done strcmpi: ;compares ESI to EDI; returns ZF set if complete match, ESI & EDI after last char matched mov ah,[edi] lodsb inc edi xor ah,al je equal cmp ah,20h ;test for possible upper vs lower case jne fail or ah,al ;coerce to lower case sub ah,'a' cmp ah,'z'-'a' jbe equal fail: ;some code here for fail ;e.g. cmp al,13 ;ignore cr/lf done: ret With a bit more mangling, bitshifter's code would also be 28 bytes as well (haven't tested it though) Code: stricmp: push .here .muck: lodsb xchg si,di sub al,'a' cmp al,'z'-'a' ja .done sub al,32 .done: ret .here: xchg ah,al call .muck cmp ah,al jnz .done cmp al,0-'a' jnz stricmp ret |
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27 Jun 2011, 08:28 |
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Madis731 27 Jun 2011, 10:38
So a SSE4.2 approach would fail here because right out of the box it will take 41 bytes. Adding por xmm,[MASK_20h] and some code to make it work in a case insensitive way, it will go up to 66 bytes.
strlen would be a better candidate for this kind of comp. http://www.strchr.com/strcmp_and_strlen_using_sse_4.2 |
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27 Jun 2011, 10:38 |
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