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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package noder
import (
"bytes"
"fmt"
"io"
"cmd/compile/internal/base"
"cmd/compile/internal/typecheck"
"cmd/internal/bio"
)
// writeNewExportFunc is a hook that can be added to append extra
// export data after the normal export data section. It allows
// experimenting with new export data format designs without requiring
// immediate support in the go/internal or x/tools importers.
var writeNewExportFunc func(out io.Writer)
func WriteExports(out *bio.Writer) {
// When unified IR exports are enable, we simply append it to the
// end of the normal export data (with compiler extensions
// disabled), and write an extra header giving its size.
//
// If the compiler sees this header, it knows to read the new data
// instead; meanwhile the go/types importers will silently ignore it
// and continue processing the old export instead.
//
// This allows us to experiment with changes to the new export data
// format without needing to update the go/internal/gcimporter or
// (worse) x/tools/go/gcexportdata.
useNewExport := writeNewExportFunc != nil
var old, new bytes.Buffer
typecheck.WriteExports(&old, !useNewExport)
if useNewExport {
writeNewExportFunc(&new)
}
oldLen := old.Len()
newLen := new.Len()
if useNewExport {
fmt.Fprintf(out, "\nnewexportsize %v\n", newLen)
}
// The linker also looks for the $$ marker - use char after $$ to distinguish format.
out.WriteString("\n$$B\n") // indicate binary export format
io.Copy(out, &old)
out.WriteString("\n$$\n")
io.Copy(out, &new)
if base.Debug.Export != 0 {
fmt.Printf("BenchmarkExportSize:%s 1 %d bytes\n", base.Ctxt.Pkgpath, oldLen)
if useNewExport {
fmt.Printf("BenchmarkNewExportSize:%s 1 %d bytes\n", base.Ctxt.Pkgpath, newLen)
}
}
}
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