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author | Martin Ankerl <martin.ankerl@gmail.com> | 2021-02-14 12:10:15 +0100 |
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committer | Martin Ankerl <martin.ankerl@gmail.com> | 2021-02-16 07:33:55 +0100 |
commit | 74bf850ac47735f2ef4306059d3e664d40cac85e (patch) | |
tree | 50bd032ac0db483949f6731ddb040bce4065af1f /src/util/strencodings.cpp | |
parent | 489030f2a8f89e7ae5031351fc3d0db83e3911ea (diff) | |
download | bitcoin-74bf850ac47735f2ef4306059d3e664d40cac85e.tar.xz |
faster HexStr => 13% faster blockToJSON
`std::string`'s push_back is rather slow because it needs to check & update the string size. For
`HexStr` the output string size is already easily know, so we can initially create the string with
the correct size and then just assign the data.
`HexStr` is heavily usd in `blockToJSON`, so this change is a noticeable benefit. Benchmark on an i7-8700 @3.2GHz:
* 71,315,461.00 ns/op master
* 62,842,490.00 ns/op this commit
So this little change makes `blockToJSON` about ~13% faster.
Diffstat (limited to 'src/util/strencodings.cpp')
-rw-r--r-- | src/util/strencodings.cpp | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/src/util/strencodings.cpp b/src/util/strencodings.cpp index f3d54a2ac9..deabc05de4 100644 --- a/src/util/strencodings.cpp +++ b/src/util/strencodings.cpp @@ -579,13 +579,14 @@ std::string Capitalize(std::string str) std::string HexStr(const Span<const uint8_t> s) { - std::string rv; + std::string rv(s.size() * 2, '\0'); static constexpr char hexmap[16] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' }; - rv.reserve(s.size() * 2); - for (uint8_t v: s) { - rv.push_back(hexmap[v >> 4]); - rv.push_back(hexmap[v & 15]); + auto it = rv.begin(); + for (uint8_t v : s) { + *it++ = hexmap[v >> 4]; + *it++ = hexmap[v & 15]; } + assert(it == rv.end()); return rv; } |