mirror of
https://github.com/sigmasternchen/libsfuid
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51 lines
1.8 KiB
Markdown
51 lines
1.8 KiB
Markdown
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# libsfuid
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Semantic-Free Unique ID En-/Decoder Lib
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## What is this?
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This is a lib that encodes enumerated IDs into a seemingly random string of characters.
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Possible usecases include the obscuration of internal IDs in a system for user generated content so that no information about
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the existence of other postings is leaked to attackers.
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## So this is a library for hashing?
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Not quite. Although there are certain similarities.
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The biggest difference is that a hash is in general not reverseable. The encoded IDs of this library are. This might be useful
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because no redundant data has to be stored.
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By extension this means that there are no collisions in the generated IDs. Thus the input range of the encoder is limited.
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## How is this useful if the input range is limited?
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Well, by default the lib provides about 576 quadrillion unique IDs (2^59). If more are needed the settings can be tuned to get
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about 18 quintillion (2^64) unique IDs - at the expense of not using the output space efficiently.
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If you really need more then message me and I'll try to upgrade to 128 bit.
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## What about timing?
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I think I got it working pretty fast. On my laptop (i7-4600U) encoding takes about 500 ns. Decoding is a bit slower and takes
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about 2 µs. I provided the benchmark script I used in case you want to check on your own machine.
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## Does this work everywhere?
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Probably not. The lib needs a 128 bit integer type. So I don't think this is working on any 32 bit machines. Also the type
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definition I used is specific for GCC. If you get it to work on another compiler, please tell me.
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## How can I use it.
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Oh, that's pretty simple.
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```
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sfuid_settings_t settings = sfuid_default_settings;
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sfuid_init(settings);
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// Now we can use it.
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char* string = malloc(settings.length + 1);
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sfuid_encode(42, string);
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uint64_t result;
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sfuid_decode(string, &result);
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```
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