101 lines
2.7 KiB
Go
101 lines
2.7 KiB
Go
// Generate boilerplate code for setting similar structs from each other
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//go:build ignore
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package main
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import (
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"flag"
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"fmt"
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"io"
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"log"
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"os"
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"reflect"
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"strings"
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"github.com/aws/aws-sdk-go/service/s3"
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)
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// flags
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var (
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outputFile = flag.String("o", "", "Output file name, stdout if unset")
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)
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// globals
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var (
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out io.Writer = os.Stdout
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)
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// genSetFrom generates code to set the public members of a from b
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//
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// a and b should be pointers to structs
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//
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// a can be a different type from b
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//
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// Only the Fields which have the same name and assignable type on a
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// and b will be set.
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//
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// This is useful for copying between almost identical structures that
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// are frequently present in auto-generated code for cloud storage
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// interfaces.
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func genSetFrom(a, b interface{}) {
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name := fmt.Sprintf("setFrom_%T_%T", a, b)
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name = strings.Replace(name, ".", "", -1)
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name = strings.Replace(name, "*", "", -1)
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fmt.Fprintf(out, "\n// %s copies matching elements from a to b\n", name)
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fmt.Fprintf(out, "func %s(a %T, b %T) {\n", name, a, b)
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ta := reflect.TypeOf(a).Elem()
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tb := reflect.TypeOf(b).Elem()
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va := reflect.ValueOf(a).Elem()
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vb := reflect.ValueOf(b).Elem()
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for i := 0; i < tb.NumField(); i++ {
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bField := vb.Field(i)
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tbField := tb.Field(i)
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name := tbField.Name
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aField := va.FieldByName(name)
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taField, found := ta.FieldByName(name)
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if found && aField.IsValid() && bField.IsValid() && aField.CanSet() && tbField.Type.AssignableTo(taField.Type) {
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fmt.Fprintf(out, "\ta.%s = b.%s\n", name, name)
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}
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}
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fmt.Fprintf(out, "}\n")
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}
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func main() {
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flag.Parse()
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if *outputFile != "" {
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fd, err := os.Create(*outputFile)
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if err != nil {
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log.Fatal(err)
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}
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defer func() {
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err := fd.Close()
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if err != nil {
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log.Fatal(err)
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}
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}()
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out = fd
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}
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fmt.Fprintf(out, `// Code generated by "go run gen_setfrom.go"; DO NOT EDIT.
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package s3
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import "github.com/aws/aws-sdk-go/service/s3"
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`)
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genSetFrom(new(s3.ListObjectsInput), new(s3.ListObjectsV2Input))
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genSetFrom(new(s3.ListObjectsV2Output), new(s3.ListObjectsOutput))
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genSetFrom(new(s3.ListObjectVersionsInput), new(s3.ListObjectsV2Input))
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genSetFrom(new(s3.ObjectVersion), new(s3.DeleteMarkerEntry))
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genSetFrom(new(s3.ListObjectsV2Output), new(s3.ListObjectVersionsOutput))
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genSetFrom(new(s3.Object), new(s3.ObjectVersion))
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genSetFrom(new(s3.CreateMultipartUploadInput), new(s3.HeadObjectOutput))
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genSetFrom(new(s3.CreateMultipartUploadInput), new(s3.CopyObjectInput))
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genSetFrom(new(s3.UploadPartCopyInput), new(s3.CopyObjectInput))
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genSetFrom(new(s3.HeadObjectOutput), new(s3.GetObjectOutput))
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genSetFrom(new(s3.CreateMultipartUploadInput), new(s3.PutObjectInput))
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genSetFrom(new(s3.HeadObjectOutput), new(s3.PutObjectInput))
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genSetFrom(new(s3.CopyObjectInput), new(s3.PutObjectInput))
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}
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