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https://github.com/logos-messaging/nim-ffi.git
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3240ac0080
5a: record {.ffiHost.} procs in a compile-time registry (FFIHostMeta /
ffiHostRegistry), populated by the macro, so generators can see host fns.
5b: the Go generator emits an idiomatic wrapper over the host C ABI:
- a single //export cgo trampoline backs every host fn; a cgo.Handle in
userData selects the Go closure;
- the closure runs on a fresh GOROUTINE so the FFI thread is never blocked
(the non-blocking contract), then answers via <lib>_host_complete by token;
- a per-host `Set<Name>(func(string) (string, error))` method registers it.
Validated end to end with `go run` (examples/host_demo): Go UseToken -> Nim
{.ffi.} handler -> await fetchToken {.ffiHost.} -> Go trampoline -> goroutine
runs the closure -> host_complete -> future resolves on the loop thread ->
"token[TOK-session]" back in Go. Timer's Go output is unchanged (no host fns);
its regenerated .h just gains the always-exported host ABI decls.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
38 lines
906 B
Go
38 lines
906 B
Go
// Go example for a {.ffiHost.} host callback.
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//
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// `fetchToken` is implemented HERE (the Go app) and registered with
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// SetFetchToken. When we call UseToken, the Nim library calls back into this Go
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// closure for a token — the closure runs on a goroutine the generated wrapper
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// spawns (never blocking the FFI thread) and answers via host_complete.
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package main
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import (
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"fmt"
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"log"
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hd "host_demo"
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)
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func main() {
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node, err := hd.NewHost_demo()
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if err != nil {
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log.Fatalf("create: %v", err)
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}
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defer node.Destroy()
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// The host's implementation of the {.ffiHost.} fetchToken.
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node.SetFetchToken(func(key string) (string, error) {
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return "TOK-" + key, nil
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})
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res, err := node.UseToken("session")
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if err != nil {
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log.Fatalf("useToken: %v", err)
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}
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fmt.Printf("result: %s\n", res)
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if res != "token[TOK-session]" {
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log.Fatalf("unexpected result: %q", res)
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}
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fmt.Println("OK")
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}
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