Golang encoding.DecodeString函數代碼示例

func decodeTableKey(valType parser.Datum, key []byte) (parser.Datum, []byte, error) {
	var isNull bool
	if key, isNull = encoding.DecodeIfNull(key); isNull {
		return parser.DNull, key, nil
	}
	switch valType.(type) {
	case parser.DBool:
		rkey, i, err := encoding.DecodeVarint(key)
		return parser.DBool(i != 0), rkey, err
	case parser.DInt:
		rkey, i, err := encoding.DecodeVarint(key)
		return parser.DInt(i), rkey, err
	case parser.DFloat:
		rkey, f, err := encoding.DecodeFloat(key, nil)
		return parser.DFloat(f), rkey, err
	case parser.DString:
		rkey, r, err := encoding.DecodeString(key, nil)
		return parser.DString(r), rkey, err
	case parser.DBytes:
		rkey, r, err := encoding.DecodeString(key, nil)
		return parser.DBytes(r), rkey, err
	case parser.DDate:
		rkey, t, err := encoding.DecodeTime(key)
		return parser.DDate{Time: t}, rkey, err
	case parser.DTimestamp:
		rkey, t, err := encoding.DecodeTime(key)
		return parser.DTimestamp{Time: t}, rkey, err
	case parser.DInterval:
		rkey, d, err := encoding.DecodeVarint(key)
		return parser.DInterval{Duration: time.Duration(d)}, rkey, err
	default:
		return nil, nil, util.Errorf("TODO(pmattis): decoded index key: %s", valType.Type())
	}
}

// decodeKeyVals decodes the values that are part of the key. ValTypes is a
// slice returned from makeKeyVals. The decoded values are stored in the vals
// parameter while the valTypes parameter is unmodified. Note that len(vals) >=
// len(valTypes). The types of the decoded values will match the corresponding
// entry in the valTypes parameter with the exception that a value might also
// be parser.DNull. The remaining bytes in the key after decoding the values
// are returned.
func decodeKeyVals(valTypes, vals []parser.Datum, key []byte) ([]byte, error) {
	for j := range valTypes {
		var isNull bool
		if key, isNull = encoding.DecodeIfNull(key); isNull {
			vals[j] = parser.DNull
			continue
		}

		switch valTypes[j].(type) {
		case parser.DInt:
			var i int64
			key, i = encoding.DecodeVarint(key)
			vals[j] = parser.DInt(i)
		case parser.DFloat:
			var f float64
			key, f = encoding.DecodeFloat(key, nil)
			vals[j] = parser.DFloat(f)
		case parser.DString:
			var r string
			key, r = encoding.DecodeString(key, nil)
			vals[j] = parser.DString(r)
		default:
			return nil, util.Errorf("TODO(pmattis): decoded index key: %s", valTypes[j].Type())
		}
	}

	return key, nil
}

func decodeTableKey(valType parser.Datum, key []byte) (parser.Datum, []byte, error) {
	var isNull bool
	if key, isNull = encoding.DecodeIfNull(key); isNull {
		return parser.DNull, key, nil
	}
	switch valType.(type) {
	case parser.DBool:
		var i int64
		key, i = encoding.DecodeVarint(key)
		return parser.DBool(i != 0), key, nil
	case parser.DInt:
		var i int64
		key, i = encoding.DecodeVarint(key)
		return parser.DInt(i), key, nil
	case parser.DFloat:
		var f float64
		key, f = encoding.DecodeFloat(key, nil)
		return parser.DFloat(f), key, nil
	case parser.DString:
		var r string
		key, r = encoding.DecodeString(key, nil)
		return parser.DString(r), key, nil
	default:
		return nil, nil, util.Errorf("TODO(pmattis): decoded index key: %s", valType.Type())
	}
}

// prettyKey pretty-prints the specified key, skipping over the first skip
// fields.
func prettyKey(key roachpb.Key, skip int) string {
	if !bytes.HasPrefix(key, keys.TableDataPrefix) {
		return fmt.Sprintf("index key missing table data prefix: %q vs %q",
			key, keys.TableDataPrefix)
	}
	key = key[len(keys.TableDataPrefix):]

	var buf bytes.Buffer
	for k := 0; len(key) > 0; k++ {
		var d interface{}
		var err error
		switch encoding.PeekType(key) {
		case encoding.Null:
			key, _ = encoding.DecodeIfNull(key)
			d = parser.DNull
		case encoding.NotNull:
			key, _ = encoding.DecodeIfNotNull(key)
			d = "#"
		case encoding.Int:
			var i int64
			key, i, err = encoding.DecodeVarint(key)
			d = parser.DInt(i)
		case encoding.Float:
			var f float64
			key, f, err = encoding.DecodeFloat(key, nil)
			d = parser.DFloat(f)
		case encoding.Bytes:
			var s string
			key, s, err = encoding.DecodeString(key, nil)
			d = parser.DString(s)
		case encoding.Time:
			var t time.Time
			key, t, err = encoding.DecodeTime(key)
			d = parser.DTimestamp{Time: t}
		default:
			// This shouldn't ever happen, but if it does let the loop exit.
			key = nil
			d = "unknown"
		}
		if skip > 0 {
			skip--
			continue
		}
		if err != nil {
			fmt.Fprintf(&buf, "/<%v>", err)
			continue
		}
		fmt.Fprintf(&buf, "/%s", d)
	}
	return buf.String()
}

func decodeKeyPrint(key roachpb.Key) string {
	var buf bytes.Buffer
	for k := 0; len(key) > 0; k++ {
		var err error
		switch encoding.PeekType(key) {
		case encoding.Null:
			key, _ = encoding.DecodeIfNull(key)
			fmt.Fprintf(&buf, "/NULL")
		case encoding.NotNull:
			key, _ = encoding.DecodeIfNotNull(key)
			fmt.Fprintf(&buf, "/#")
		case encoding.Int:
			var i int64
			key, i, err = encoding.DecodeVarint(key)
			if err == nil {
				fmt.Fprintf(&buf, "/%d", i)
			}
		case encoding.Float:
			var f float64
			key, f, err = encoding.DecodeFloat(key, nil)
			if err == nil {
				fmt.Fprintf(&buf, "/%f", f)
			}
		case encoding.Bytes:
			var s string
			key, s, err = encoding.DecodeString(key, nil)
			if err == nil {
				fmt.Fprintf(&buf, "/%q", s)
			}
		case encoding.Time:
			var t time.Time
			key, t, err = encoding.DecodeTime(key)
			if err == nil {
				fmt.Fprintf(&buf, "/%s", t.UTC().Format(time.UnixDate))
			}
		default:
			// This shouldn't ever happen, but if it does let the loop exit.
			fmt.Fprintf(&buf, "/%q", []byte(key))
			key = nil
		}

		if err != nil {
			fmt.Fprintf(&buf, "/<%v>", err)
			continue
		}
	}
	return buf.String()
}

// ShowDatabases returns all the databases.
// Privileges: None.
//   Notes: postgres does not have a "show databases"
//          mysql has a "SHOW DATABASES" permission, but we have no system-level permissions.
func (p *planner) ShowDatabases(n *parser.ShowDatabases) (planNode, error) {
	// TODO(pmattis): This could be implemented as:
	//
	//   SELECT id FROM system.namespace WHERE parentID = 0

	prefix := MakeNameMetadataKey(keys.RootNamespaceID, "")
	sr, err := p.txn.Scan(prefix, prefix.PrefixEnd(), 0)
	if err != nil {
		return nil, err
	}
	v := &valuesNode{columns: []string{"Database"}}
	for _, row := range sr {
		_, name := encoding.DecodeString(bytes.TrimPrefix(row.Key, prefix), nil)
		v.rows = append(v.rows, []parser.Datum{parser.DString(name)})
	}
	return v, nil
}

func (p *planner) getTableNames(dbDesc *DatabaseDescriptor) (parser.QualifiedNames, error) {
	prefix := MakeNameMetadataKey(dbDesc.ID, "")
	sr, err := p.txn.Scan(prefix, prefix.PrefixEnd(), 0)
	if err != nil {
		return nil, err
	}

	var qualifiedNames parser.QualifiedNames
	for _, row := range sr {
		_, tableName := encoding.DecodeString(bytes.TrimPrefix(row.Key, prefix), nil)
		qname := &parser.QualifiedName{
			Base:     parser.Name(dbDesc.Name),
			Indirect: parser.Indirection{parser.NameIndirection(tableName)},
		}
		if err := qname.NormalizeTableName(""); err != nil {
			return nil, err
		}
		qualifiedNames = append(qualifiedNames, qname)
	}
	return qualifiedNames, nil
}