mirror of
https://github.com/gopl-zh/gopl-zh.github.com.git
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98 lines
2.0 KiB
Go
98 lines
2.0 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 339.
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package sexpr
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import (
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"bytes"
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"fmt"
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"reflect"
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)
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//!+Marshal
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// Marshal encodes a Go value in S-expression form.
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func Marshal(v interface{}) ([]byte, error) {
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var buf bytes.Buffer
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if err := encode(&buf, reflect.ValueOf(v)); err != nil {
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return nil, err
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}
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return buf.Bytes(), nil
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}
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//!-Marshal
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// encode writes to buf an S-expression representation of v.
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//!+encode
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func encode(buf *bytes.Buffer, v reflect.Value) error {
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switch v.Kind() {
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case reflect.Invalid:
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buf.WriteString("nil")
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case reflect.Int, reflect.Int8, reflect.Int16,
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reflect.Int32, reflect.Int64:
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fmt.Fprintf(buf, "%d", v.Int())
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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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fmt.Fprintf(buf, "%d", v.Uint())
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case reflect.String:
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fmt.Fprintf(buf, "%q", v.String())
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case reflect.Ptr:
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return encode(buf, v.Elem())
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case reflect.Array, reflect.Slice: // (value ...)
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buf.WriteByte('(')
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for i := 0; i < v.Len(); i++ {
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if i > 0 {
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buf.WriteByte(' ')
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}
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if err := encode(buf, v.Index(i)); err != nil {
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return err
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}
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}
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buf.WriteByte(')')
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case reflect.Struct: // ((name value) ...)
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buf.WriteByte('(')
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for i := 0; i < v.NumField(); i++ {
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if i > 0 {
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buf.WriteByte(' ')
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}
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fmt.Fprintf(buf, "(%s ", v.Type().Field(i).Name)
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if err := encode(buf, v.Field(i)); err != nil {
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return err
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}
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buf.WriteByte(')')
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}
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buf.WriteByte(')')
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case reflect.Map: // ((key value) ...)
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buf.WriteByte('(')
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for i, key := range v.MapKeys() {
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if i > 0 {
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buf.WriteByte(' ')
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}
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buf.WriteByte('(')
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if err := encode(buf, key); err != nil {
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return err
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}
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buf.WriteByte(' ')
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if err := encode(buf, v.MapIndex(key)); err != nil {
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return err
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}
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buf.WriteByte(')')
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}
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buf.WriteByte(')')
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default: // float, complex, bool, chan, func, interface
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return fmt.Errorf("unsupported type: %s", v.Type())
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}
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return nil
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}
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//!-encode
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