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mapping.go
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mapping.go
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package common
/*
I2P Mapping
https://geti2p.net/spec/common-structures#mapping
Accurate for version 0.9.24
+----+----+----+----+----+----+----+----+
| size |key_string (len + data) | = |
+----+----+----+----+----+----+----+----+
| val_string (len + data) | ; | ...
+----+----+----+----+----+----+----+
size :: Integer
length -> 2 bytes
Total number of bytes that follow
key_string :: String
A string (one byte length followed by UTF-8 encoded characters)
= :: A single byte containing '='
val_string :: String
A string (one byte length followed by UTF-8 encoded characters)
; :: A single byte containing ';'
*/
import (
"encoding/binary"
"errors"
log "github.com/Sirupsen/logrus"
"sort"
)
type Mapping []byte
// Parsed key-values pairs inside a Mapping.
type MappingValues [][2]String
//
// Returns the values contained in a Mapping in the form of a MappingValues.
//
func (mapping Mapping) Values() (map_values MappingValues, errs []error) {
var str String
var remainder = mapping
var err error
length := Integer(remainder[:2])
inferred_length := length + 2
remainder = remainder[2:]
mapping_len := len(mapping)
if mapping_len > inferred_length {
log.WithFields(log.Fields{
"at": "(Mapping) Values",
"mappnig_bytes_length": mapping_len,
"mapping_length_field": length,
"expected_bytes_length": inferred_length,
"reason": "data longer than expected",
}).Warn("mapping format warning")
errs = append(errs, errors.New("warning parsing mapping: data exists beyond length of mapping"))
} else if inferred_length > mapping_len {
log.WithFields(log.Fields{
"at": "(Mapping) Values",
"mappnig_bytes_length": mapping_len,
"mapping_length_field": length,
"expected_bytes_length": inferred_length,
"reason": "data shorter than expected",
}).Warn("mapping format warning")
errs = append(errs, errors.New("warning parsing mapping: mapping length exceeds provided data"))
}
for {
// Read a key, breaking on fatal errors
// and appending warnings
str, remainder, err = ReadString(remainder)
key_str := str
if err != nil {
if stopValueRead(err) {
errs = append(errs, err)
return
}
}
if !beginsWith(remainder, 0x3d) {
log.WithFields(log.Fields{
"at": "(Mapping) Values",
"reason": "expected =",
}).Warn("mapping format violation")
errs = append(errs, errors.New("mapping format violation, expected ="))
return
}
remainder = remainder[1:]
// Read a value, breaking on fatal errors
// and appending warnings
str, remainder, err = ReadString(remainder)
val_str := str
if err != nil {
if stopValueRead(err) {
errs = append(errs, err)
return
}
}
if !beginsWith(remainder, 0x3b) {
log.WithFields(log.Fields{
"at": "(Mapping) Values",
"reason": "expected ;",
}).Warn("mapping format violation")
errs = append(errs, errors.New("mapping format violation, expected ;"))
return
}
remainder = remainder[1:]
// Append the key-value pair and break if there is no more data to read
map_values = append(map_values, [2]String{key_str, val_str})
if len(remainder) == 0 {
break
}
}
return
}
//
// Return true if two keys in a mapping are identical.
//
func (mapping Mapping) HasDuplicateKeys() bool {
seen_values := make(map[string]bool)
values, _ := mapping.Values()
for _, pair := range values {
key, _ := pair[0].Data()
if _, present := seen_values[key]; present {
return true
} else {
seen_values[key] = true
}
}
return false
}
//
// Convert a MappingValue struct to a Mapping. The values are first
// sorted in the order defined in mappingOrder.
//
func ValuesToMapping(values MappingValues) (mapping Mapping) {
mappingOrder(values)
for _, kv_pair := range values {
key_string := kv_pair[0]
key_string = append(key_string, []byte("=")[0])
key_value := kv_pair[1]
key_value = append(key_value, []byte(";")[0])
mapping = append(append(mapping, key_string...), key_value...)
}
map_len := len(mapping)
len_bytes := make([]byte, 2)
binary.BigEndian.PutUint16(len_bytes, uint16(map_len))
mapping = append(len_bytes, mapping...)
return
}
//
// Convert a Go map of unformatted strings to a sorted Mapping.
//
func GoMapToMapping(gomap map[string]string) (mapping Mapping, err error) {
map_vals := MappingValues{}
for k, v := range gomap {
key_str, kerr := ToI2PString(k)
if kerr != nil {
err = kerr
return
}
val_str, verr := ToI2PString(v)
if verr != nil {
err = verr
return
}
map_vals = append(
map_vals,
[2]String{key_str, val_str},
)
}
mapping = ValuesToMapping(map_vals)
return
}
type byValue MappingValues
func (set byValue) Len() int { return len(set) }
func (set byValue) Swap(i, j int) { set[i], set[j] = set[j], set[i] }
func (set byValue) Less(i, j int) bool {
data1, _ := set[i][1].Data()
data2, _ := set[j][1].Data()
return data1 < data2
}
type byKey MappingValues
func (set byKey) Len() int { return len(set) }
func (set byKey) Swap(i, j int) { set[i], set[j] = set[j], set[i] }
func (set byKey) Less(i, j int) bool {
data1, _ := set[i][0].Data()
data2, _ := set[j][0].Data()
return data1 < data2
}
//
// I2P Mappings require consistent order for for cryptographic signing, and sorting
// by keys. When new Mappings are created, they are stable sorted first by values
// than by keys to ensure a consistent order.
//
func mappingOrder(values MappingValues) {
sort.Stable(byValue(values))
sort.Stable(byKey(values))
}
//
// Check if the string parsing error indicates that the Mapping
// should no longer be parsed.
//
func stopValueRead(err error) bool {
return err.Error() == "error parsing string: zero length"
}
//
// Determine if the first byte in a slice of bytes is the provided byte.
//
func beginsWith(bytes []byte, chr byte) bool {
return len(bytes) != 0 &&
bytes[0] == chr
}