116 lines
3.1 KiB
Go
116 lines
3.1 KiB
Go
package common
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/*
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I2P String
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https://geti2p.net/spec/common-structures#string
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Accurate for version 0.9.24
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*/
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import (
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"errors"
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log "github.com/sirupsen/logrus"
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)
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// Maximum number of bytes that can be stored in an I2P string
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const (
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STRING_MAX_SIZE = 255
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)
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type String []byte
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//
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// Look up the length of the string, reporting errors if the string is
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// invalid or the specified length does not match the provided data.
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//
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func (str String) Length() (length int, err error) {
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if len(str) == 0 {
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log.WithFields(log.Fields{
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"at": "(String) Length",
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"reason": "no data",
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}).Error("error parsing string")
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err = errors.New("error parsing string: zero length")
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return
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}
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length = Integer([]byte{byte(str[0])})
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inferred_len := length + 1
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str_len := len(str)
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if inferred_len > str_len {
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log.WithFields(log.Fields{
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"at": "(String) Length",
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"string_bytes_length": str_len,
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"string_length_field": length,
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"expected_bytes_length": inferred_len,
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"reason": "data shorter than specified",
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}).Warn("string format warning")
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err = errors.New("string parsing warning: string data is shorter than specified by length")
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} else if str_len > inferred_len {
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log.WithFields(log.Fields{
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"at": "(String) Length",
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"string_bytes_length": str_len,
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"string_length_field": length,
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"expected_bytes_length": inferred_len,
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"reason": "data longer than specified",
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}).Warn("string format warning")
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err = errors.New("string parsing warning: string contains data beyond length")
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}
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return
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}
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//
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// Return the string data and any errors encountered by Length.
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//
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func (str String) Data() (data string, err error) {
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length, err := str.Length()
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if err != nil {
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switch err.Error() {
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case "error parsing string: zero length":
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return
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case "string parsing warning: string data is shorter than specified by length":
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data = string(str[1:])
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return
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case "string parsing warning: string contains data beyond length":
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data = string(str[1 : length+1])
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return
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}
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}
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data = string(str[1:])
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return
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}
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//
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// This function takes an unformatted Go string and returns a String
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// and any errors encountered during the encoding.
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//
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func ToI2PString(data string) (str String, err error) {
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data_len := len(data)
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if data_len > STRING_MAX_SIZE {
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log.WithFields(log.Fields{
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"at": "ToI2PString",
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"string_len": data_len,
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"max_len": STRING_MAX_SIZE,
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"reason": "too much data",
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}).Error("cannot create I2P string")
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err = errors.New("cannot store that much data in I2P string")
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return
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}
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i2p_string := []byte{byte(data_len)}
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i2p_string = append(i2p_string, []byte(data)...)
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str = String(i2p_string)
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return
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}
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//
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// Read a string from a slice of bytes, returning any extra data on the end
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// of the slice and any errors encountered parsing the String.
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//
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func ReadString(data []byte) (str String, remainder []byte, err error) {
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str = String(data)
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length, err := String(data).Length()
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if err != nil && err.Error() == "string parsing warning: string contains data beyond length" {
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str = String(data[:length+1])
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remainder = data[length+1:]
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err = nil
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}
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return
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}
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