go-i2p/lib/common/string.go

package common

import (
	"errors"
)

type String []byte

//
// Look up the length of the string, reporting
// errors if the string is invalid or the specified
// length does not match the provided data.
//
func (str String) Length() (int, error) {
	if len(str) == 0 {
		// log
		return 0, errors.New("error parsing string: zero length")
	}
	length := Integer([]byte{byte(str[0])})
	inferred_len := length + 1
	str_len := len(str)
	if inferred_len > str_len {
		// log
		return length, errors.New("string parsing warning: string data is shorter than specified by length")
	} else if str_len > inferred_len {
		//log
		return length, errors.New("string parsing warning: string contains data beyond length")
	}
	return length, nil
}

//
// Return the string data and any errors
// encountered by Length.
//
func (str String) Data() (string, error) {
	length, err := str.Length()
	if err != nil {
		switch err.Error() {
		case "error parsing string: zero length":
			return "", err
		case "string parsing warning: string data is shorter than specified by length":
			return string(str[1:]), err
		case "string parsing warning: string contains data beyond length":
			return string(str[1 : length+1]), err
		}
	}
	return string(str[1:]), nil
}

//
// This function takes an unformatted go string
// and returns a String and any errors encountered
// during the encoding.
//
func ToI2PString(data string) (String, error) {
	data_len := len(data)
	if data_len >= 256 {
		return make([]byte, 0), errors.New("cannot store that much data in I2P string")
	}
	i2p_string := []byte{byte(data_len)}
	i2p_string = append(i2p_string, []byte(data)...)
	return String(i2p_string), nil
}

//
// Read a string from a slice of bytes, returning
// any extra data on the end of the slice.
//
func ReadString(data []byte) (String, []byte, error) {
	str := String(data)
	length, err := String(data).Length()
	if err != nil {
		switch err.Error() {
		case "error parsing string: zero length":
			return String{}, make([]byte, 0), err
		case "string parsing warning: string data is shorter than specified by length":
			return str, make([]byte, 0), err
		case "string parsing warning: string contains data beyond length":
			return String(str[:length+1]), str[length+1:], nil //err
		}
	}
	return str, make([]byte, 0), nil
}