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Merge #7656: Improve EncodeBase58 performance

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3252208 Improve EncodeBase58 performance (João Barbosa)
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Wladimir J. van der Laan 2016-03-21 12:03:50 +01:00
commit 7b832d286b
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1 changed files with 8 additions and 3 deletions
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11
src/base58.cpp
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@ -68,26 +68,31 @@ std::string EncodeBase58(const unsigned char* pbegin, const unsigned char* pend)
{ {
// Skip & count leading zeroes. // Skip & count leading zeroes.
int zeroes = 0; int zeroes = 0;
int length = 0;
while (pbegin != pend && *pbegin == 0) { while (pbegin != pend && *pbegin == 0) {
pbegin++; pbegin++;
zeroes++; zeroes++;
} }
// Allocate enough space in big-endian base58 representation. // Allocate enough space in big-endian base58 representation.
std::vector<unsigned char> b58((pend - pbegin) * 138 / 100 + 1); // log(256) / log(58), rounded up. int size = (pend - pbegin) * 138 / 100 + 1; // log(256) / log(58), rounded up.
std::vector<unsigned char> b58(size);
// Process the bytes. // Process the bytes.
while (pbegin != pend) { while (pbegin != pend) {
int carry = *pbegin; int carry = *pbegin;
int i = 0;
// Apply "b58 = b58 * 256 + ch". // Apply "b58 = b58 * 256 + ch".
for (std::vector<unsigned char>::reverse_iterator it = b58.rbegin(); it != b58.rend(); it++) { for (std::vector<unsigned char>::reverse_iterator it = b58.rbegin(); (carry != 0 || i < length) && (it != b58.rend()); it++, i++) {
carry += 256 * (*it); carry += 256 * (*it);
*it = carry % 58; *it = carry % 58;
carry /= 58; carry /= 58;
} }
assert(carry == 0); assert(carry == 0);
length = i;
pbegin++; pbegin++;
} }
// Skip leading zeroes in base58 result. // Skip leading zeroes in base58 result.
std::vector<unsigned char>::iterator it = b58.begin(); std::vector<unsigned char>::iterator it = b58.begin() + (size - length);
while (it != b58.end() && *it == 0) while (it != b58.end() && *it == 0)
it++; it++;
// Translate the result into a string. // Translate the result into a string.