87 lines
1.9 KiB
Markdown
87 lines
1.9 KiB
Markdown
---
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# Documentation: https://sourcethemes.com/academic/docs/managing-content/
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title: "Bit magic in C (and C++)"
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subtitle: ""
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summary: ""
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authors: []
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tags: []
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categories: []
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date: 2020-06-13T19:01:19+02:00
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lastmod: 2020-06-13T19:01:19+02:00
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featured: false
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draft: false
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# Featured image
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# To use, add an image named `featured.jpg/png` to your page's folder.
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# Focal points: Smart, Center, TopLeft, Top, TopRight, Left, Right, BottomLeft, Bottom, BottomRight.
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image:
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caption: ""
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focal_point: ""
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preview_only: false
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# Projects (optional).
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# Associate this post with one or more of your projects.
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# Simply enter your project's folder or file name without extension.
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# E.g. `projects = ["internal-project"]` references `content/project/deep-learning/index.md`.
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# Otherwise, set `projects = []`.
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projects: []
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---
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# Set a bit
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```c
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// Set one bit high at position "bit" in input and store to output
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output = input | (1 << bit);
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// Shorthand
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variable |= (1 << bit);
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// Multiple bits
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variable |= (0b101 << bit);
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```
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# Clear a bit
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```c
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// Clear one bit high at position "bit" in input and store to output
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output = input & ~(1 << bit);
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// Shorthand
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variable &= ~(1 << bit);
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// Multiple bits
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variable &= ~(0b101 << bit);
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```
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# Toggle a bit
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```c
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// Clear one bit high at position "bit" in input and store to output
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output = x ^ (1 << bit);
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// Shorthand
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variable ^= (1 << bit);
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// Multiple bits
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variable ^= (0b101 << bit);
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```
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# Math
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```c
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// Division using bitshift
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output = input >> 1; // Divide by 2
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output = input >> 2; // Divide by 4
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output = input >> 3; // Divide by 8
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// Multiply using bitshifting
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output = input << 1; // Multiply by 2
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output = input << 2; // Multiply by 4
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output = input << 3; // Multiply by 8
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```
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# Set X number of bits high.
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```c
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output = (0b1 << X) -1;
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```
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# Miccelean
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```c
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// Check if number is ODD
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if( (num & 1) == 1) {};
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// Flip signed integer
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num = ~num + 1;
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// Power of two
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num > 0 && (num & (num - 1)) == 0;
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``` |