mirror of https://github.com/status-im/nim-eth.git
28 lines
1.4 KiB
Markdown
28 lines
1.4 KiB
Markdown
# bloom: an Ethereum Bloom Filter
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# Introduction
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A Nim implementation of the bloom filter used by Ethereum.
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# Description
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[Bloom filters](https://en.wikipedia.org/wiki/Bloom_filter) are data structures that use hash functions to test whether an element is a member of a set. They work like other data structures but are probabilistic in nature: that is, they allow false positive matches but not false negative. Bloom filters use less storage space than other data structures.
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Ethereum bloom filters are implemented with the Keccak-256 cryptographic hash function.
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To see the bloom filter used in the context of Ethereum, please refer to the [Ethereum Yellow Paper](https://ethereum.github.io/yellowpaper/paper.pdf).
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# Usage
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```nim
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import eth/bloom, stint
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var f: BloomFilter
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f.incl("test1")
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assert("test1" in f)
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assert("test2" notin f)
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f.incl("test2")
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assert("test2" in f)
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assert(f.value.toHex == "80000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000200000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000000000")
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```
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