This optimization is based on a few assumptions: - Most strings are ASCII only. - Most strings had their coderange scanned already. If the above is true, then by checking the string coderange, we can use a much more streamlined function to encode ASCII strings. Before: ``` == Encoding twitter.json (466906 bytes) ruby 3.4.0preview2 (2024-10-07 master 32c733f57b) +YJIT +PRISM [arm64-darwin23] Warming up -------------------------------------- json 140.000 i/100ms oj 230.000 i/100ms rapidjson 108.000 i/100ms Calculating ------------------------------------- json 1.464k (± 1.4%) i/s (682.83 μs/i) - 7.420k in 5.067573s oj 2.338k (± 1.5%) i/s (427.64 μs/i) - 11.730k in 5.017336s rapidjson 1.075k (± 1.6%) i/s (930.40 μs/i) - 5.400k in 5.025469s Comparison: json: 1464.5 i/s oj: 2338.4 i/s - 1.60x faster rapidjson: 1074.8 i/s - 1.36x slower ``` After: ``` == Encoding twitter.json (466906 bytes) ruby 3.4.0preview2 (2024-10-07 master 32c733f57b) +YJIT +PRISM [arm64-darwin23] Warming up -------------------------------------- json 189.000 i/100ms oj 228.000 i/100ms rapidjson 108.000 i/100ms Calculating ------------------------------------- json 1.903k (± 1.2%) i/s (525.55 μs/i) - 9.639k in 5.066521s oj 2.306k (± 1.3%) i/s (433.71 μs/i) - 11.628k in 5.044096s rapidjson 1.069k (± 2.4%) i/s (935.38 μs/i) - 5.400k in 5.053794s Comparison: json: 1902.8 i/s oj: 2305.7 i/s - 1.21x faster rapidjson: 1069.1 i/s - 1.78x slower ```