1 [![Build Status](https://travis-ci.org/lunixbochs/struc.svg?branch=master)](https://travis-ci.org/lunixbochs/struc)
6 Struc exists to pack and unpack C-style structures from bytes, which is useful for binary files and network protocols. It could be considered an alternative to `encoding/binary`, which requires massive boilerplate for some similar operations.
8 Take a look at an [example comparing `struc` and `encoding/binary`](https://bochs.info/p/cxvm9)
10 Struc considers usability first. That said, it does cache reflection data and aims to be competitive with `encoding/binary` struct packing in every way, including performance.
17 Var int `struc:"int32,sizeof=Str"`
19 Weird []byte `struc:"[8]int64"`
20 Var []int `struc:"[]int32,little"`
27 - ```Var []int `struc:"[]int32,little,sizeof=StringField"` ``` will pack Var as a slice of little-endian int32, and link it as the size of `StringField`.
28 - `sizeof=`: Indicates this field is a number used to track the length of a another field. `sizeof` fields are automatically updated on `Pack()` based on the current length of the tracked field, and are used to size the target field during `Unpack()`.
29 - Bare values will be parsed as type and endianness.
40 - `pad` - this type ignores field contents and is backed by a `[length]byte` containing nulls
50 Types can be indicated as arrays/slices using `[]` syntax. Example: `[]int64`, `[8]int32`.
52 Bare slice types (those with no `[size]`) must have a linked `Sizeof` field.
54 Private fields are ignored when packing and unpacking.
64 "github.com/lunixbochs/struc"
70 // B will be encoded/decoded as a 16-bit int (a "short")
71 // but is stored as a native int in the struct
74 // the sizeof key links a buffer's size to any int field
75 Size int `struc:"int8,little,sizeof=Str"`
78 // you can get freaky if you want
79 Str2 string `struc:"[5]int64"`
84 t := &Example{1, 2, 0, "test", "test2"}
85 err := struc.Pack(&buf, t)
87 err = struc.Unpack(&buf, o)
94 `BenchmarkEncode` uses struc. `Stdlib` benchmarks use equivalent `encoding/binary` code. `Manual` encodes without any reflection, and should be considered an upper bound on performance (which generated code based on struc definitions should be able to achieve).
97 BenchmarkEncode 1000000 1265 ns/op
98 BenchmarkStdlibEncode 1000000 1855 ns/op
99 BenchmarkManualEncode 5000000 284 ns/op
100 BenchmarkDecode 1000000 1259 ns/op
101 BenchmarkStdlibDecode 1000000 1656 ns/op
102 BenchmarkManualDecode 20000000 89.0 ns/op