95 lines
2 KiB
Go
95 lines
2 KiB
Go
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// 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 349.
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// Package params provides a reflection-based parser for URL parameters.
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package params
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import (
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"fmt"
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"net/http"
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"reflect"
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"strconv"
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"strings"
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)
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//!+Unpack
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// Unpack populates the fields of the struct pointed to by ptr
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// from the HTTP request parameters in req.
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func Unpack(req *http.Request, ptr interface{}) error {
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if err := req.ParseForm(); err != nil {
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return err
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}
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// OMIT
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// Build map of fields keyed by effective name.
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fields := make(map[string]reflect.Value)
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v := reflect.ValueOf(ptr).Elem() // the struct variable
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for i := 0; i < v.NumField(); i++ {
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fieldInfo := v.Type().Field(i) // a reflect.StructField
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tag := fieldInfo.Tag // a reflect.StructTag
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name := tag.Get("http")
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if name == "" {
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name = strings.ToLower(fieldInfo.Name)
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}
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fields[name] = v.Field(i)
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}
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// OMIT
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// Update struct field for each parameter in the request.
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for name, values := range req.Form {
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f := fields[name]
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if !f.IsValid() {
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continue // ignore unrecognized HTTP parameters
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}
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for _, value := range values {
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if f.Kind() == reflect.Slice {
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elem := reflect.New(f.Type().Elem()).Elem()
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if err := populate(elem, value); err != nil {
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return fmt.Errorf("%s: %v", name, err)
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}
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f.Set(reflect.Append(f, elem))
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} else {
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if err := populate(f, value); err != nil {
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return fmt.Errorf("%s: %v", name, err)
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}
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}
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}
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}
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return nil
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}
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//!-Unpack
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//!+populate
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func populate(v reflect.Value, value string) error {
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switch v.Kind() {
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case reflect.String:
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v.SetString(value)
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case reflect.Int:
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i, err := strconv.ParseInt(value, 10, 64)
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if err != nil {
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return err
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}
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v.SetInt(i)
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case reflect.Bool:
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b, err := strconv.ParseBool(value)
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if err != nil {
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return err
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}
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v.SetBool(b)
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default:
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return fmt.Errorf("unsupported kind %s", v.Type())
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}
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return nil
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}
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//!-populate
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