bat/tests/syntax-tests/highlighted/Go/main.go
2020-10-04 11:25:11 +02:00

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// The hugeparam command identifies by-value parameters that are larger than n bytes.
//
// Example:
// $ ./hugeparams encoding/xml
package main
import (
 "flag"
 "fmt"
 "go/ast"
 "go/token"
 "go/types"
 "log"
 "golang.org/x/tools/go/loader"
)
//!+
var bytesFlag = flag.Int("bytes", 48, "maximum parameter size in bytes")
var sizeof = (&types.StdSizes{8, 8}).Sizeof // the sizeof function
func PrintHugeParams(fset *token.FileSet, info *types.Info, files []*ast.File) {
 checkTuple := func(descr string, tuple *types.Tuple) {
 for i := 0; i < tuple.Len(); i++ {
 v := tuple.At(i)
 if sz := sizeof(v.Type()); sz > int64(*bytesFlag) {
 fmt.Printf("%s: %q %s: %s = %d bytes\n",
 fset.Position(v.Pos()),
 v.Name(), descr, v.Type(), sz)
 }
 }
 }
 checkSig := func(sig *types.Signature) {
 checkTuple("parameter", sig.Params())
 checkTuple("result", sig.Results())
 }
 for _, file := range files {
 ast.Inspect(file, func(n ast.Node) bool {
 switch n := n.(type) {
 case *ast.FuncDecl:
 checkSig(info.Defs[n.Name].Type().(*types.Signature))
 case *ast.FuncLit:
 checkSig(info.Types[n.Type].Type.(*types.Signature))
 }
 return true
 })
 }
}
//!-
func main() {
 flag.Parse()
 // The loader loads a complete Go program from source code.
 var conf loader.Config
 _, err := conf.FromArgs(flag.Args(), false)
 if err != nil {
 log.Fatal(err) // command syntax error
 }
 lprog, err := conf.Load()
 if err != nil {
 log.Fatal(err) // load error
 }
 for _, info := range lprog.InitialPackages() {
 PrintHugeParams(lprog.Fset, &info.Info, info.Files)
 }
}
/*
//!+output
% ./hugeparam encoding/xml
/go/src/encoding/xml/marshal.go:167:50: "start" parameter: encoding/xml.StartElement = 56 bytes
/go/src/encoding/xml/marshal.go:734:97: "" result: encoding/xml.StartElement = 56 bytes
/go/src/encoding/xml/marshal.go:761:51: "start" parameter: encoding/xml.StartElement = 56 bytes
/go/src/encoding/xml/marshal.go:781:68: "start" parameter: encoding/xml.StartElement = 56 bytes
/go/src/encoding/xml/xml.go:72:30: "" result: encoding/xml.StartElement = 56 bytes
//!-output
*/