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tailscale/internal/deepprint/deepprint.go

104 lines
2.7 KiB
Go

// Copyright (c) 2020 Tailscale Inc & 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 deepprint walks a Go value recursively, in a predictable
// order, without looping, and prints each value out to a given
// Writer, which is assumed to be a hash.Hash, as this package doesn't
// format things nicely.
//
// This is intended as a lighter version of go-spew, etc. We don't need its
// features when our writer is just a hash.
package deepprint
import (
"crypto/sha256"
"fmt"
"io"
"reflect"
)
func Hash(v ...interface{}) string {
h := sha256.New()
Print(h, v)
return fmt.Sprintf("%x", h.Sum(nil))
}
// UpdateHash sets last to the hash of v and reports whether its value changed.
func UpdateHash(last *string, v ...interface{}) (changed bool) {
sig := Hash(v)
if *last != sig {
*last = sig
return true
}
return false
}
func Print(w io.Writer, v ...interface{}) {
print(w, reflect.ValueOf(v), make(map[uintptr]bool))
}
func print(w io.Writer, v reflect.Value, visited map[uintptr]bool) {
if !v.IsValid() {
return
}
switch v.Kind() {
default:
panic(fmt.Sprintf("unhandled kind %v for type %v", v.Kind(), v.Type()))
case reflect.Ptr:
ptr := v.Pointer()
if visited[ptr] {
return
}
visited[ptr] = true
print(w, v.Elem(), visited)
return
case reflect.Struct:
fmt.Fprintf(w, "struct{\n")
t := v.Type()
for i, n := 0, v.NumField(); i < n; i++ {
sf := t.Field(i)
fmt.Fprintf(w, "%s: ", sf.Name)
print(w, v.Field(i), visited)
fmt.Fprintf(w, "\n")
}
case reflect.Slice, reflect.Array:
if v.Type().Elem().Kind() == reflect.Uint8 && v.CanInterface() {
fmt.Fprintf(w, "%q", v.Interface())
return
}
fmt.Fprintf(w, "[%d]{\n", v.Len())
for i, ln := 0, v.Len(); i < ln; i++ {
fmt.Fprintf(w, " [%d]: ", i)
print(w, v.Index(i), visited)
fmt.Fprintf(w, "\n")
}
fmt.Fprintf(w, "}\n")
case reflect.Interface:
print(w, v.Elem(), visited)
case reflect.Map:
sm := newSortedMap(v)
fmt.Fprintf(w, "map[%d]{\n", len(sm.Key))
for i, k := range sm.Key {
print(w, k, visited)
fmt.Fprintf(w, ": ")
print(w, sm.Value[i], visited)
fmt.Fprintf(w, "\n")
}
fmt.Fprintf(w, "}\n")
case reflect.String:
fmt.Fprintf(w, "%s", v.String())
case reflect.Bool:
fmt.Fprintf(w, "%v", v.Bool())
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
fmt.Fprintf(w, "%v", v.Int())
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
fmt.Fprintf(w, "%v", v.Uint())
case reflect.Float32, reflect.Float64:
fmt.Fprintf(w, "%v", v.Float())
case reflect.Complex64, reflect.Complex128:
fmt.Fprintf(w, "%v", v.Complex())
}
}