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package sqs
/*
* Performs the MD5 algorithm for attribute responses described in
* the AWS documentation here: http://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/SQSMessageAttributes.html#sqs-attrib-md5
*/
import (
"crypto/md5"
"encoding/binary"
"sort"
)
// Returns length of string as an Big Endian byte array
func getStringLengthAsByteArray(s string) []byte {
var res []byte = make([]byte, 4)
binary.BigEndian.PutUint32(res, uint32(len(s)))
return res
}
// How to calculate the MD5 of Attributes
func calculateAttributeMD5(attributes map[string]string) []byte {
// We're going to walk attributes in alpha-sorted order
var keys []string
for k := range attributes {
keys = append(keys, k)
}
sort.Strings(keys)
// Now we'll build our encoded string
var encoded []byte
for _, k := range keys {
v := attributes[k]
t := "String"
encodedItems := [][]byte{
getStringLengthAsByteArray(k),
[]byte(k), // Name
getStringLengthAsByteArray(t),
[]byte(t), // Data Type ("String")
{0x01}, // "String Value" (0x01)
getStringLengthAsByteArray(v),
[]byte(v), // Value
}
// Append each of these to our encoding
for _, item := range encodedItems {
encoded = append(encoded, item...)
}
}
res := md5.Sum(encoded)
// Return MD5 sum
return res[:]
}
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