91 lines
2.3 KiB
Go
91 lines
2.3 KiB
Go
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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// See page 333.
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// Package display provides a means to display structured data.
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package display
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import (
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"fmt"
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"reflect"
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"strconv"
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)
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//!+Display
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func Display(name string, x interface{}) {
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fmt.Printf("Display %s (%T):\n", name, x)
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display(name, reflect.ValueOf(x))
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}
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//!-Display
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// formatAtom formats a value without inspecting its internal structure.
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// It is a copy of the the function in gopl.io/ch11/format.
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func formatAtom(v reflect.Value) string {
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switch v.Kind() {
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case reflect.Invalid:
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return "invalid"
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case reflect.Int, reflect.Int8, reflect.Int16,
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reflect.Int32, reflect.Int64:
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return strconv.FormatInt(v.Int(), 10)
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case reflect.Uint, reflect.Uint8, reflect.Uint16,
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reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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return strconv.FormatUint(v.Uint(), 10)
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// ...floating-point and complex cases omitted for brevity...
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case reflect.Bool:
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if v.Bool() {
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return "true"
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}
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return "false"
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case reflect.String:
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return strconv.Quote(v.String())
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case reflect.Chan, reflect.Func, reflect.Ptr,
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reflect.Slice, reflect.Map:
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return v.Type().String() + " 0x" +
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strconv.FormatUint(uint64(v.Pointer()), 16)
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default: // reflect.Array, reflect.Struct, reflect.Interface
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return v.Type().String() + " value"
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}
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}
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//!+display
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func display(path string, v reflect.Value) {
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switch v.Kind() {
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case reflect.Invalid:
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fmt.Printf("%s = invalid\n", path)
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case reflect.Slice, reflect.Array:
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for i := 0; i < v.Len(); i++ {
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display(fmt.Sprintf("%s[%d]", path, i), v.Index(i))
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}
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case reflect.Struct:
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for i := 0; i < v.NumField(); i++ {
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fieldPath := fmt.Sprintf("%s.%s", path, v.Type().Field(i).Name)
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display(fieldPath, v.Field(i))
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}
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case reflect.Map:
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for _, key := range v.MapKeys() {
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display(fmt.Sprintf("%s[%s]", path,
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formatAtom(key)), v.MapIndex(key))
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}
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case reflect.Ptr:
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if v.IsNil() {
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fmt.Printf("%s = nil\n", path)
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} else {
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display(fmt.Sprintf("(*%s)", path), v.Elem())
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}
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case reflect.Interface:
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if v.IsNil() {
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fmt.Printf("%s = nil\n", path)
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} else {
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fmt.Printf("%s.type = %s\n", path, v.Elem().Type())
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display(path+".value", v.Elem())
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}
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default: // basic types, channels, funcs
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fmt.Printf("%s = %s\n", path, formatAtom(v))
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}
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}
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//!-display
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