README
¶
structhash 
structhash is a Go library for generating hash strings of arbitrary data structures.
Features
- fields may be ignored or renamed (like in
json.Marshal, but using different struct tag) - fields may be serialized
- fields may be versioned
- fields order in struct doesn't matter (unlike
json.Marshal) - nil values are treated equally to zero values
Installation
Standard go get:
$ go get github.com/cnf/structhash
Documentation
For usage and examples see the Godoc.
Quick start
package main
import (
"fmt"
"crypto/md5"
"crypto/sha1"
"github.com/cnf/structhash"
)
type S struct {
Str string
Num int
}
func main() {
s := S{"hello", 123}
hash, err := structhash.Hash(s, 1)
if err != nil {
panic(err)
}
fmt.Println(hash)
// Prints: v1_41011bfa1a996db6d0b1075981f5aa8f
fmt.Println(structhash.Version(hash))
// Prints: 1
fmt.Printf("%x\n", structhash.Md5(s, 1))
// Prints: 41011bfa1a996db6d0b1075981f5aa8f
fmt.Printf("%x\n", structhash.Sha1(s, 1))
// Prints: 5ff72df7212ce8c55838fb3ec6ad0c019881a772
fmt.Printf("%x\n", md5.Sum(structhash.Dump(s, 1)))
// Prints: 41011bfa1a996db6d0b1075981f5aa8f
fmt.Printf("%x\n", sha1.Sum(structhash.Dump(s, 1)))
// Prints: 5ff72df7212ce8c55838fb3ec6ad0c019881a772
}
Struct tags
structhash supports struct tags in the following forms:
hash:"-", orhash:"name:{string} version:{number} lastversion:{number} method:{string}"
All fields are optional and may be ommitted. Their semantics is:
-- ignore fieldname:{string}- rename field (may be useful when you want to rename field but keep hashes unchanged for backward compatibility)version:{number}- ignore field if version passed to structhash is smaller than given numberlastversion:{number}- ignore field if version passed to structhash is greater than given numbermethod:{string}- use the return value of a field's method instead of the field itself
Example:
type MyStruct struct {
Ignored string `hash:"-"`
Renamed string `hash:"name:OldName version:1"`
Legacy string `hash:"version:1 lastversion:2"`
Serialized error `hash:"method:Error"`
}
Nil values
When hash is calculated, nil pointers, nil slices, and nil maps are treated equally to zero values of corresponding type. E.g., nil pointer to string is equivalent to empty string, and nil slice is equivalent to empty slice.
Documentation
¶
Overview ¶
Package structhash creates hash strings from arbitrary go data structures.
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Dump ¶
Dump takes a data structure and returns its byte representation. This can be useful if you need to use your own hashing function or formatter.
Example ¶
type Person struct {
Name string
Age int
Emails []string
Extra map[string]string
Spouse *Person
}
bill := &Person{
Name: "Bill",
Age: 24,
Emails: []string{"bob@foo.org", "bob@bar.org"},
Extra: map[string]string{
"facebook": "Bob42",
},
}
bob := &Person{
Name: "Bob",
Age: 42,
Emails: []string{"bob@foo.org", "bob@bar.org"},
Extra: map[string]string{
"facebook": "Bob42",
},
Spouse: bill,
}
fmt.Printf("md5: %x\n", md5.Sum(Dump(bob, 1)))
fmt.Printf("sha1: %x\n", sha1.Sum(Dump(bob, 1)))
Output: md5: 6a50d73f3bd0b9ebd001a0b610f387f0 sha1: c45f097a37366eaaf6ffbc7357c2272cd8fb64f6
func Hash ¶
Hash takes a data structure and returns a hash string of that data structure at the version asked.
This function uses md5 hashing function and default formatter. See also Dump() function.
Example ¶
type Person struct {
Name string
Age int
Emails []string
Extra map[string]string
Spouse *Person
}
bill := &Person{
Name: "Bill",
Age: 24,
Emails: []string{"bob@foo.org", "bob@bar.org"},
Extra: map[string]string{
"facebook": "Bob42",
},
}
bob := &Person{
Name: "Bob",
Age: 42,
Emails: []string{"bob@foo.org", "bob@bar.org"},
Extra: map[string]string{
"facebook": "Bob42",
},
Spouse: bill,
}
hash, err := Hash(bob, 1)
if err != nil {
panic(err)
}
fmt.Printf("%s", hash)
Output: v1_6a50d73f3bd0b9ebd001a0b610f387f0
Example (Tags) ¶
type Person struct {
Ignored string `hash:"-"`
NewName string `hash:"name:OldName version:1"`
Age int `hash:"version:1"`
Emails []string `hash:"version:1"`
Extra map[string]string `hash:"version:1 lastversion:2"`
Spouse *Person `hash:"version:2"`
}
bill := &Person{
NewName: "Bill",
Age: 24,
Emails: []string{"bob@foo.org", "bob@bar.org"},
Extra: map[string]string{
"facebook": "Bob42",
},
}
bob := &Person{
NewName: "Bob",
Age: 42,
Emails: []string{"bob@foo.org", "bob@bar.org"},
Extra: map[string]string{
"facebook": "Bob42",
},
Spouse: bill,
}
hashV1, err := Hash(bob, 1)
if err != nil {
panic(err)
}
hashV2, err := Hash(bob, 2)
if err != nil {
panic(err)
}
hashV3, err := Hash(bob, 3)
if err != nil {
panic(err)
}
fmt.Printf("%s\n", hashV1)
fmt.Printf("%s\n", hashV2)
fmt.Printf("%s\n", hashV3)
Output: v1_45d8a54c5f5fd287f197b26d128882cd v2_babd7618f29036f5564816bee6c8a037 v3_012b06239f942549772c9139d66c121e
func Md5 ¶
Md5 takes a data structure and returns its md5 hash. This is a shorthand for md5.Sum(Dump(c, version)).
func Sha1 ¶
Sha1 takes a data structure and returns its sha1 hash. This is a shorthand for sha1.Sum(Dump(c, version)).
func Version ¶
Version returns the version of the supplied hash as an integer or -1 on failure
Example ¶
// A hash string gotten from Hash(). Returns the version as an int.
i := Version("v1_55743877f3ffd5fc834e97bc43a6e7bd")
fmt.Printf("%d", i)
Output: 1
Example (Errors) ¶
// A hash string gotten from Hash(). Returns -1 on error.
i := Version("va_55743877f3ffd5fc834e97bc43a6e7bd")
fmt.Printf("%d", i)
Output: -1
Types ¶
This section is empty.
Source Files