Change Details

`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. This is a backport of core#21173

`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. This is a backport of [[https://github.com/bitcoin/bitcoin/pull/21173 | core#21173]]

`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. This is a backport of [[https://github.com/bitcoin/bitcoin/pull/21173 | core#21173]]