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214 lines
6.3 KiB
214 lines
6.3 KiB
package param
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import (
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"encoding"
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"fmt"
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"reflect"
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"strconv"
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"strings"
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)
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var textUnmarshalerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
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// Generic parse dispatcher. This function's signature is the interface of all
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// parse functions. `key` is the entire key that is currently being parsed, such
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// as "foo[bar][]". `keytail` is the portion of the string that the current
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// parser is responsible for, for instance "[bar][]". `values` is the list of
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// values assigned to this key, and `target` is where the resulting typed value
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// should be Set() to.
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func parse(key, keytail string, values []string, target reflect.Value) {
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t := target.Type()
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if reflect.PtrTo(t).Implements(textUnmarshalerType) {
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parseTextUnmarshaler(key, keytail, values, target)
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return
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}
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switch k := target.Kind(); k {
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case reflect.Bool:
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parseBool(key, keytail, values, target)
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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parseInt(key, keytail, values, target)
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
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parseUint(key, keytail, values, target)
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case reflect.Float32, reflect.Float64:
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parseFloat(key, keytail, values, target)
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case reflect.Map:
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parseMap(key, keytail, values, target)
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case reflect.Ptr:
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parsePtr(key, keytail, values, target)
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case reflect.Slice:
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parseSlice(key, keytail, values, target)
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case reflect.String:
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parseString(key, keytail, values, target)
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case reflect.Struct:
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parseStruct(key, keytail, values, target)
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default:
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pebkac("unsupported object of type %v and kind %v.",
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target.Type(), k)
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}
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}
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// We pass down both the full key ("foo[bar][]") and the part the current layer
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// is responsible for making sense of ("[bar][]"). This computes the other thing
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// you probably want to know, which is the path you took to get here ("foo").
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func kpath(key, keytail string) string {
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l, t := len(key), len(keytail)
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return key[:l-t]
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}
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// Helper for validating that a value has been passed exactly once, and that the
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// user is not attempting to nest on the key.
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func primitive(tipe, key, keytail string, values []string) {
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if keytail != "" {
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perr("expected %s for key %q, got nested value", tipe,
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kpath(key, keytail))
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}
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if len(values) != 1 {
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perr("expected %s for key %q, but key passed %v times", tipe,
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kpath(key, keytail), len(values))
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}
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}
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func keyed(tipe reflect.Type, key, keytail string) (string, string) {
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idx := strings.IndexRune(keytail, ']')
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// Keys must be at least 1 rune wide: we refuse to use the empty string
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// as the key
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if len(keytail) < 3 || keytail[0] != '[' || idx < 2 {
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perr("expected a square bracket delimited index for %q "+
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"(of type %v)", kpath(key, keytail), tipe)
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}
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return keytail[1:idx], keytail[idx+1:]
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}
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func parseTextUnmarshaler(key, keytail string, values []string, target reflect.Value) {
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primitive("encoding.TextUnmarshaler", key, keytail, values)
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tu := target.Addr().Interface().(encoding.TextUnmarshaler)
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err := tu.UnmarshalText([]byte(values[0]))
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if err != nil {
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perr("error while calling UnmarshalText on %v for key %q: %v",
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target.Type(), kpath(key, keytail), err)
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}
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}
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func parseBool(key, keytail string, values []string, target reflect.Value) {
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primitive("bool", key, keytail, values)
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switch values[0] {
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case "true", "1", "on":
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target.SetBool(true)
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case "false", "0", "":
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target.SetBool(false)
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default:
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perr("could not parse key %q as bool", kpath(key, keytail))
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}
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}
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func parseInt(key, keytail string, values []string, target reflect.Value) {
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primitive("int", key, keytail, values)
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t := target.Type()
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i, err := strconv.ParseInt(values[0], 10, t.Bits())
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if err != nil {
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perr("error parsing key %q as int: %v", kpath(key, keytail),
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err)
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}
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target.SetInt(i)
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}
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func parseUint(key, keytail string, values []string, target reflect.Value) {
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primitive("uint", key, keytail, values)
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t := target.Type()
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i, err := strconv.ParseUint(values[0], 10, t.Bits())
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if err != nil {
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perr("error parsing key %q as uint: %v", kpath(key, keytail),
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err)
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}
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target.SetUint(i)
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}
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func parseFloat(key, keytail string, values []string, target reflect.Value) {
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primitive("float", key, keytail, values)
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t := target.Type()
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f, err := strconv.ParseFloat(values[0], t.Bits())
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if err != nil {
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perr("error parsing key %q as float: %v", kpath(key, keytail),
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err)
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}
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target.SetFloat(f)
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}
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func parseString(key, keytail string, values []string, target reflect.Value) {
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primitive("string", key, keytail, values)
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target.SetString(values[0])
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}
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func parseSlice(key, keytail string, values []string, target reflect.Value) {
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// BUG(carl): We currently do not handle slices of nested types. If
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// support is needed, the implementation probably could be fleshed out.
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if keytail != "[]" {
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perr("unexpected array nesting for key %q: %q",
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kpath(key, keytail), keytail)
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}
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t := target.Type()
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slice := reflect.MakeSlice(t, len(values), len(values))
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kp := kpath(key, keytail)
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for i := range values {
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// We actually cheat a little bit and modify the key so we can
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// generate better debugging messages later
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key := fmt.Sprintf("%s[%d]", kp, i)
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parse(key, "", values[i:i+1], slice.Index(i))
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}
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target.Set(slice)
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}
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func parseMap(key, keytail string, values []string, target reflect.Value) {
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t := target.Type()
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mapkey, maptail := keyed(t, key, keytail)
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// BUG(carl): We don't support any map keys except strings, although
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// there's no reason we shouldn't be able to throw the value through our
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// unparsing stack.
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var mk reflect.Value
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if t.Key().Kind() == reflect.String {
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mk = reflect.ValueOf(mapkey).Convert(t.Key())
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} else {
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pebkac("key for map %v isn't a string (it's a %v).", t, t.Key())
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}
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if target.IsNil() {
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target.Set(reflect.MakeMap(t))
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}
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val := target.MapIndex(mk)
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if !val.IsValid() || !val.CanSet() {
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// It's a teensy bit annoying that the value returned by
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// MapIndex isn't Set()table if the key exists.
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val = reflect.New(t.Elem()).Elem()
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}
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parse(key, maptail, values, val)
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target.SetMapIndex(mk, val)
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}
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func parseStruct(key, keytail string, values []string, target reflect.Value) {
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t := target.Type()
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sk, skt := keyed(t, key, keytail)
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cache := cacheStruct(t)
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parseStructField(cache, key, sk, skt, values, target)
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}
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func parsePtr(key, keytail string, values []string, target reflect.Value) {
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t := target.Type()
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if target.IsNil() {
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target.Set(reflect.New(t.Elem()))
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}
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parse(key, keytail, values, target.Elem())
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}
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