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117 lines
2.2 KiB
HTML
117 lines
2.2 KiB
HTML
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="utf-8"/>
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<meta content="IE=edge" http-equiv="X-UA-Compatible"/>
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<meta content="width=device-width, initial-scale=1.0" name="viewport"/>
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<title>
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Ari::web -> Blog
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</title>
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<meta content="website webdev linux programming ari terminal dark blog javascript opensource free" name="keywords"/>
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<meta content="Blog on 2022-01-20 16:58:31 EET - Fast atoi in C(++)" name="description"/>
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<meta content="follow" name="robots"/>
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</head>
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<body>
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<div>
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<h1>
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Fast atoi in C(++)
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</h1>
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<p>
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2022-01-20 16:58:31 EET |
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<a href="..">
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back
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</a>
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<a href="/">
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home
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</a>
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<a href="/git">
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git
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</a>
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</p>
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<hr/>
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<p>
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<code>
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std::atoi
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</code>
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(in C++) is fast on its own but can be slow
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so for stuff you need speed you can use this:
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</p>
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<ul>
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<li>
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Option one
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</li>
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</ul>
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<p>
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```
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int fast_atoi(const char *int_string) {
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int value = 0;
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</p>
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<pre><code>while (*int_string && *int_string >= '0' && *int_string <= '9')
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value = value * 10 + (*int_string++ - '0');
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return value;
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</code></pre>
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<p>
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}
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```
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</p>
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<p>
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This requires no headers, just pure C (also valid in C++),
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you can put this into your code and it will just work!
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</p>
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<ul>
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<li>
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Option two
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</li>
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</ul>
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<p>
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```
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</p>
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<h1>
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include
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<assert.h>
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</assert.h>
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</h1>
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<p>
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int fast_atoi(char *int_string) {
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int value = 0;
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</p>
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<pre><code>while (*int_string) {
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if (!(*int_string >= '0' && *int_string <= '9'))
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assert(0 && "atoi(): invalid int_string");
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value = value * 10 + (*int_string++ - '0');
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}
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return value;
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</code></pre>
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<p>
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}
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```
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</p>
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<p>
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This option is throws an assertion error if it encounters an
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invalid string but this requires
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<code>
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assert.h
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</code>
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as a dependency.
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</p>
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<p>
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In C++
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<code>
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assert.h
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</code>
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should be replaced with
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<code>
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cassert
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</code>
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.
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</p>
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</div>
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</body>
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</html>
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