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38 lines
1.4 KiB
Markdown
38 lines
1.4 KiB
Markdown
# consteval-huffman
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Allows for long strings of text or data to be compressed at compile-time, with an efficient decoder routine for decompression at run-time. The decoder conforms to `std::forward_iterator`, allowing for use in ranged-for or standard algorithms.
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Compression is achieved using [Huffman coding](https://en.wikipedia.org/wiki/Huffman_coding), which works by creating short codes (measured in bits) for frequently-occuring characters. This works best on larger pieces of data, or more so data that is limited in its range of values (e.g. written text).
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## Use cases
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**1. Text configurations (e.g. JSON)**
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A ~3.5kB string of JSON can be compressed down ~2.5kB ([see it on Godbolt](https://godbolt.org/z/1MzG1v)).
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**2. Scripts (e.g. Lisp)**
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A ~40 line comment-including sample of Lisp can be reduced from 1,662 bytes to 1,244 (418 bytes saved) ([Godbolt](https://godbolt.org/z/jcnKza)).
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## How to Use
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```cpp
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#include "consteval_huffman.hpp"
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constexpr static const char some_data_raw[] = /* insert text here */;
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// Creates an object with the compressed data
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// If data is not smaller after compression, huffman_compress will keep the data uncompressed
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constinit static const auto some_data = huffman_compress<some_data_raw>();
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// Or, with a set data length:
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// ... some_data = huffman_compress<some_data_raw, 1500>();
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int main()
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{
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// Decompress and print out the data
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for (auto c : some_data)
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putchar(c);
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}
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```
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