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Performance ​

json-as includes several performance-oriented implementations for strings and arrays:

  • naive
  • SWAR
  • SIMD

Enabling SIMD ​

Compile with:

bash
asc assembly/index.ts --transform json-as --enable simd

Fast generated struct deserialization ​

Generated fast struct deserialization is opt-in:

bash
JSON_USE_FAST_PATH=1

Without that environment variable, the default path stays conservative.

Benchmark commands ​

bash
bun run bench:as medium --mode swar
bun run bench:as medium --mode simd
bun run bench:as str-deserialize --mode swar
bun run bench:as str-deserialize --mode simd

Notes ​

  • plain strings and escaped strings behave very differently
  • SIMD wins more clearly on larger, regular payloads
  • whole-object benchmarks and isolated string benchmarks can tell different stories