JSON

A single, platform-agnostic JSON codec for Go that optimizes WebAssembly binary size by using zero reflection. It relies on fmt.Fielder for struct encoding/decoding, which is typically generated by ormc.

Index

• Architecture
• Usage
• API
• Benchmarks
• Contributing
• License

Architecture

• Zero Reflection: Uses type switches and fmt.Fielder instead of the reflect package.
• Platform-Agnostic: Identical behavior on all platforms (WASM, Linux, macOS, etc.).
• TinyGo Compatible: Optimized for minimal binary size and memory usage.
• Fielder-Only: Only types implementing fmt.Fielder can be directly encoded or decoded.

Usage

Structs

Structs MUST implement fmt.Fielder to be supported. This is normally handled by generating code with ormc.

package main

import (
    "github.com/tinywasm/fmt"
    "github.com/tinywasm/json"
)

// User implements fmt.Fielder (typically via ormc)
type User struct {
    Name string
}

func (u *User) Schema() []fmt.Field {
    return []fmt.Field{{Name: "Name", Type: fmt.FieldText, JSON: "name"}}
}
func (u *User) Pointers() []any { return []any{&u.Name} }

func main() {
    u := User{Name: "Alice"}

    var out string
    if err := json.Encode(&u, &out); err != nil {
        panic(err)
    }
    // out: {"name":"Alice"}

    var result User
    if err := json.Decode(out, &result); err != nil {
        panic(err)
    }
}

API

Encode(data fmt.Fielder, output any) error

Serializes a Fielder to JSON.

• data: Must implement fmt.Fielder.
• output: *[]byte, *string, or io.Writer.

Decode(input any, data fmt.Fielder) error

Parses JSON into a Fielder.

• input: []byte, string, or io.Reader.
• data: Must implement fmt.Fielder.

Benchmarks

tinywasm/json is 77% smaller than encoding/json in WASM (~27 KB vs ~119 KB) and zero-reflect, eliminating reflection overhead and heavy dependencies.

Benchmark	tinywasm/json	encoding/json
Encode	641 ns/op	573 ns/op
Decode	1709 ns/op	2184 ns/op

See full results and analysis in benchmarks/README.md.

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Contributing

License

See LICENSE for details.