pinecone-io/dtoa

Fast functions for printing floating-point primitives to an io::Write

Pinecone modifications

This branch has been modified so the output matches that of nholmann/json.

We use this for serializing f64 before sending in a JSON object tospanner.

Internally spanner appears to use zetasql (https://github.com/google/zetasql) which uses nholmann/json (https://github.com/nlohmann/json/).

ZetaSQL will not accept a float in a json structure if it does not roundtrip to the same value when serialized. By serializing the floats using a grisu2 implementation equivalent to nholmann/json, we are guaranteed that the float will be accepted.

You can test this out by pulling the zetasql repo and running:

bazel run //zetasql/tools/execute_query:execute_query \
    -- "select PARSE_JSON('2.250497700094831e+307');"

The tests require data generated by the nholmann/json library. To generate it:

$ git submodule init
$ git submodule update
$ c++ -I"nholmann_json/include" -std=c++17 -o gen_test_data gen_test_data.cc
$ ./gen_test_data
$ cargo test

dtoa

This crate provides fast conversion of floating point primitives to decimal strings. The implementation is a straightforward Rust port of Milo Yip's C++ implementation dtoa.h. The original C++ code of each function is included in comments.

See also itoa for printing integer primitives.

Version requirement: rustc 1.36+

[dependencies]
dtoa = "1.0"

Example

fn main() {
    let mut buffer = dtoa::Buffer::new();
    let printed = buffer.format(2.71828f64);
    assert_eq!(printed, "2.71828");
}

Performance (lower is better)

License

^{Licensed under either of Apache License, Version 2.0 or MIT license at your option.}
_{Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.}