strlen and strcmp implementation in x86 FASM assembly
0
I wrote my own implementation of strlen and strcmp from C in x86 FASM and I would like to know is there anything that should be changed or improved.
strlen needs string in eax and its returning length of that string into ebx.
strlen:
mov ebx,0
strlen_loop:
cmp byte [eax+ebx],0
je strlen_end
inc ebx
jmp strlen_loop
strlen_end:
inc ebx
ret
strcmp needs two strings (one in eax, second in ebx) and returns 0 if strings are equal or 1/-1 if they are not into ecx.
strcmp:
mov ecx,0
strcmp_loop:
mov byte dl,[eax+ecx]
mov byte dh,[ebx+ecx]
inc ecx
cmp dl,0
je strcmp_end_0
cmp byte dl,dh
je strcmp_loop
jl strcmp_end_1
jg strcmp_end_2
strcmp_end_0:
cmp dh,0
jne strcmp_end_1
xor ecx,ecx
ret
strcmp_end_1:
mov ecx,1
ret
strcmp_end_2:
mov ecx,-1
ret
strings reinventing-the-wheel x86
asked 5 hours ago
DeBos
64
|
show 1 more comment
0
I wrote my own implementation of strlen and strcmp from C in x86 FASM and I would like to know is there anything that should be changed or improved.
strlen needs string in eax and its returning length of that string into ebx.
strlen:
mov ebx,0
strlen_loop:
cmp byte [eax+ebx],0
je strlen_end
inc ebx
jmp strlen_loop
strlen_end:
inc ebx
ret
strcmp needs two strings (one in eax, second in ebx) and returns 0 if strings are equal or 1/-1 if they are not into ecx.
strcmp:
mov ecx,0
strcmp_loop:
mov byte dl,[eax+ecx]
mov byte dh,[ebx+ecx]
inc ecx
cmp dl,0
je strcmp_end_0
cmp byte dl,dh
je strcmp_loop
jl strcmp_end_1
jg strcmp_end_2
strcmp_end_0:
cmp dh,0
jne strcmp_end_1
xor ecx,ecx
ret
strcmp_end_1:
mov ecx,1
ret
strcmp_end_2:
mov ecx,-1
ret
strings reinventing-the-wheel x86
asked 5 hours ago
DeBos
64
Welcome to Code Review! Does the current code work as expected?
– Mast
4 hours ago
Its not full code that u can compile and run, but only code of my implementations of that functions. I checked both codes and I'm getting expected results, so I think it works.
– DeBos
4 hours ago
Unless I am mistaken, strcmp does not return ecx=0 for identical strings. – strlen seems to include the trailing zero in the count, which is unconventional.
– Martin R
14 mins ago
I think that strcmp should return 0 for identical strings (quora.com/What-does-strcmp-mean-in-C++). In my implementation strlen includes trailing zero, so you don't need to add 1 to length everytime when you want to print this string
– DeBos
11 mins ago
@DeBos: What I meant is that your implementation does not return zero for identical strings, but the current value of ecx. Perhaps I am overlooking something?
– Martin R
10 mins ago
|
show 1 more comment
0
0
0
I wrote my own implementation of strlen and strcmp from C in x86 FASM and I would like to know is there anything that should be changed or improved.
strlen needs string in eax and its returning length of that string into ebx.
strlen:
mov ebx,0
strlen_loop:
cmp byte [eax+ebx],0
je strlen_end
inc ebx
jmp strlen_loop
strlen_end:
inc ebx
ret
strcmp needs two strings (one in eax, second in ebx) and returns 0 if strings are equal or 1/-1 if they are not into ecx.
strcmp:
mov ecx,0
strcmp_loop:
mov byte dl,[eax+ecx]
mov byte dh,[ebx+ecx]
inc ecx
cmp dl,0
je strcmp_end_0
cmp byte dl,dh
je strcmp_loop
jl strcmp_end_1
jg strcmp_end_2
strcmp_end_0:
cmp dh,0
jne strcmp_end_1
xor ecx,ecx
ret
strcmp_end_1:
mov ecx,1
ret
strcmp_end_2:
mov ecx,-1
ret
strings reinventing-the-wheel x86
asked 5 hours ago
DeBos
64
I wrote my own implementation of strlen and strcmp from C in x86 FASM and I would like to know is there anything that should be changed or improved.
strlen needs string in eax and its returning length of that string into ebx.
strlen:
mov ebx,0
strlen_loop:
cmp byte [eax+ebx],0
je strlen_end
inc ebx
jmp strlen_loop
strlen_end:
inc ebx
ret
strcmp needs two strings (one in eax, second in ebx) and returns 0 if strings are equal or 1/-1 if they are not into ecx.
strcmp:
mov ecx,0
strcmp_loop:
mov byte dl,[eax+ecx]
mov byte dh,[ebx+ecx]
inc ecx
cmp dl,0
je strcmp_end_0
cmp byte dl,dh
je strcmp_loop
jl strcmp_end_1
jg strcmp_end_2
strcmp_end_0:
cmp dh,0
jne strcmp_end_1
xor ecx,ecx
ret
strcmp_end_1:
mov ecx,1
ret
strcmp_end_2:
mov ecx,-1
ret
strings reinventing-the-wheel x86
strings reinventing-the-wheel x86
asked 5 hours ago
DeBos
64
asked 5 hours ago
DeBos
64
edited 7 mins ago
asked 5 hours ago
DeBos
64
asked 5 hours ago
DeBos
64
asked 5 hours ago
DeBos
64
64
Welcome to Code Review! Does the current code work as expected?
– Mast
4 hours ago
Its not full code that u can compile and run, but only code of my implementations of that functions. I checked both codes and I'm getting expected results, so I think it works.
– DeBos
4 hours ago
Unless I am mistaken, strcmp does not return ecx=0 for identical strings. – strlen seems to include the trailing zero in the count, which is unconventional.
– Martin R
14 mins ago
I think that strcmp should return 0 for identical strings (quora.com/What-does-strcmp-mean-in-C++). In my implementation strlen includes trailing zero, so you don't need to add 1 to length everytime when you want to print this string
– DeBos
11 mins ago
@DeBos: What I meant is that your implementation does not return zero for identical strings, but the current value of ecx. Perhaps I am overlooking something?
– Martin R
10 mins ago
|
show 1 more comment
Welcome to Code Review! Does the current code work as expected?
– Mast
4 hours ago
Its not full code that u can compile and run, but only code of my implementations of that functions. I checked both codes and I'm getting expected results, so I think it works.
– DeBos
4 hours ago
Unless I am mistaken, strcmp does not return ecx=0 for identical strings. – strlen seems to include the trailing zero in the count, which is unconventional.
– Martin R
14 mins ago
I think that strcmp should return 0 for identical strings (quora.com/What-does-strcmp-mean-in-C++). In my implementation strlen includes trailing zero, so you don't need to add 1 to length everytime when you want to print this string
– DeBos
11 mins ago
@DeBos: What I meant is that your implementation does not return zero for identical strings, but the current value of ecx. Perhaps I am overlooking something?
– Martin R
10 mins ago
Welcome to Code Review! Does the current code work as expected?
– Mast
4 hours ago
Welcome to Code Review! Does the current code work as expected?
– Mast
4 hours ago
Its not full code that u can compile and run, but only code of my implementations of that functions. I checked both codes and I'm getting expected results, so I think it works.
– DeBos
4 hours ago
Its not full code that u can compile and run, but only code of my implementations of that functions. I checked both codes and I'm getting expected results, so I think it works.
– DeBos
4 hours ago
Unless I am mistaken, strcmp does not return ecx=0 for identical strings. – strlen seems to include the trailing zero in the count, which is unconventional.
– Martin R
14 mins ago
Unless I am mistaken, strcmp does not return ecx=0 for identical strings. – strlen seems to include the trailing zero in the count, which is unconventional.
– Martin R
14 mins ago
I think that strcmp should return 0 for identical strings (quora.com/What-does-strcmp-mean-in-C++). In my implementation strlen includes trailing zero, so you don't need to add 1 to length everytime when you want to print this string
– DeBos
11 mins ago
I think that strcmp should return 0 for identical strings (quora.com/What-does-strcmp-mean-in-C++). In my implementation strlen includes trailing zero, so you don't need to add 1 to length everytime when you want to print this string
– DeBos
11 mins ago
@DeBos: What I meant is that your implementation does not return zero for identical strings, but the current value of ecx. Perhaps I am overlooking something?
– Martin R
10 mins ago
@DeBos: What I meant is that your implementation does not return zero for identical strings, but the current value of ecx. Perhaps I am overlooking something?
– Martin R
10 mins ago
|
show 1 more comment
active
oldest
votes
Your Answer
StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["\$", "\$"]]);
});
});
}, "mathjax-editing");
StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "196"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
draft saved
draft discarded
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fcodereview.stackexchange.com%2fquestions%2f210689%2fstrlen-and-strcmp-implementation-in-x86-fasm-assembly%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
active
oldest
votes
active
oldest
votes
active
oldest
votes
active
oldest
votes
draft saved
draft discarded
Thanks for contributing an answer to Code Review Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
draft saved
draft discarded
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fcodereview.stackexchange.com%2fquestions%2f210689%2fstrlen-and-strcmp-implementation-in-x86-fasm-assembly%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Welcome to Code Review! Does the current code work as expected?
– Mast
4 hours ago
Its not full code that u can compile and run, but only code of my implementations of that functions. I checked both codes and I'm getting expected results, so I think it works.
– DeBos
4 hours ago
Unless I am mistaken, strcmp does not return ecx=0 for identical strings. – strlen seems to include the trailing zero in the count, which is unconventional.
– Martin R
14 mins ago
I think that strcmp should return 0 for identical strings (quora.com/What-does-strcmp-mean-in-C++). In my implementation strlen includes trailing zero, so you don't need to add 1 to length everytime when you want to print this string
– DeBos
11 mins ago
@DeBos: What I meant is that your implementation does not return zero for identical strings, but the current value of ecx. Perhaps I am overlooking something?
– Martin R
10 mins ago