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Variable-length integers: bytes are a MSB base-128 encoding of the number. The high bit in each byte signifies whether another digit follows. To make the encoding is one-to-one, one is subtracted from all but the last digit. Thus, the byte sequence a[] with length len, where all but the last byte has bit 128 set, encodes the number: (a[len-1] & 0x7F) + sum(i=1..len-1, 128^i*((a[len-i-1] & 0x7F)+1)) Properties: * Very small (0-127: 1 byte, 128-16511: 2 bytes, 16512-2113663: 3 bytes) * Every integer has exactly one encoding * Encoding does not depend on size of original integer typepull/145/head
Pieter Wuille
12 years ago
2 changed files with 138 additions and 1 deletions
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#include <boost/test/unit_test.hpp> |
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#include <string> |
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#include <vector> |
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#include "serialize.h" |
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using namespace std; |
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BOOST_AUTO_TEST_SUITE(serialize_tests) |
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BOOST_AUTO_TEST_CASE(varints) |
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{ |
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// encode
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CDataStream ss(SER_DISK, 0); |
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CDataStream::size_type size = 0; |
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for (int i = 0; i < 100000; i++) { |
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ss << VARINT(i); |
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size += ::GetSerializeSize(VARINT(i), 0, 0); |
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BOOST_CHECK(size == ss.size()); |
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} |
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for (uint64 i = 0; i < 100000000000ULL; i += 999999937) { |
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ss << VARINT(i); |
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size += ::GetSerializeSize(VARINT(i), 0, 0); |
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BOOST_CHECK(size == ss.size()); |
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} |
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// decode
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for (int i = 0; i < 100000; i++) { |
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int j; |
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ss >> VARINT(j); |
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BOOST_CHECK_MESSAGE(i == j, "decoded:" << j << " expected:" << i); |
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} |
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for (uint64 i = 0; i < 100000000000ULL; i += 999999937) { |
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uint64 j; |
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ss >> VARINT(j); |
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BOOST_CHECK_MESSAGE(i == j, "decoded:" << j << " expected:" << i); |
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} |
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} |
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BOOST_AUTO_TEST_SUITE_END() |
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