README
¶
Colfer 
Colfer is a schema-based binary serialization format optimized for speed and size.
The project's compiler colf(1) generates source code from schema definitions
to marshal and unmarshall data structures.
This is free and unencumbered software released into the public domain. The format is inspired by Protocol Buffer.
Language Support
- C, C99 compliant, C++13 compliant, WIP, API might change
- Go, a.k.a. golang
- Java, Android compatible
- JavaScript, a.k.a. ECMAScript, NodeJS compatible
Features
- Simple and straightforward in use
- No dependencies other than the core library
- Both faster and smaller than: Protocol Buffers, FlatBuffers and MessagePack
- Robust including size protection
- Maximum of 127 fields per data structure
- No support for enumerations
- Framed; suitable for concatenation/streaming
TODO's
- RMI (WIP
) - List type support for integers and timestamps
- Please share your experiences
Use
Download a prebuilt compiler
or run go get -u github.com/pascaldekloe/colfer/cmd/colf to make one yourself.
Without arguments the command prints its manual.
NAME
colf — compile Colfer schemas
SYNOPSIS
colf [ options ] language [ file ... ]
DESCRIPTION
Generates source code for a language. The options are: C, Go,
Java and JavaScript.
The file operands specify the input. Directories are scanned for
files with the colf extension. If file is absent, colf includes
the working directory.
A package can have multiple schema files.
OPTIONS
-b directory
Use a specific destination base directory. (default ".")
-f Normalizes schemas on the fly.
-l expression
Sets the default upper limit for the number of elements in a
list. The expression is applied to the target language under the
name ColferListMax. (default "64 * 1024")
-p prefix
Adds a package prefix. Use slash as a separator when nesting.
-s expression
Sets the default upper limit for serial byte sizes. The
expression is applied to the target language under the name
ColferSizeMax. (default "16 * 1024 * 1024")
-v Enables verbose reporting to the standard error.
EXIT STATUS
The command exits 0 on succes, 1 on compilation failure and 2
when invoked without arguments.
EXAMPLES
Compile ./api/*.colf into ./src/ as Java:
colf -p com/example -b src java api
Compile ./io.colf with compact limits as C:
colf -s 2048 -l 96 c io.colf
BUGS
Report bugs at https://github.com/pascaldekloe/colfer/issues
SEE ALSO
protoc(1)
It is recommended to commit the generated source code to the respective version control. Maven users may disagree.
Schema
Data structures are defined in .colf files. The format is quite conventional.
// Package demo offers a demonstration.
// These comment lines will end up in the generated code.
package demo
// Coarse is the grounds where the game of golf is played.
type coarse struct {
ID uint64
name text
holes []hole
image binary
tags []text
}
type hole struct {
// Lat is the latitude of the cup.
lat float64
// Lon is the longitude of the cup.
lon float64
// Par is the difficulty index.
par uint8
// Water marks the presence of water.
water bool
// Sand marks the presence of sand.
sand bool
}
See what the generated code looks like.
The following table shows how Colfer data types are applied per language.
| Colfer | C | Go | Java | JavaScript |
|---|---|---|---|---|
| bool | bool | bool | boolean | Boolean |
| uint8 | uint8_t | uint8 | byte † | Number |
| uint16 | uint16_t | uint16 | short † | Number |
| uint32 | uint32_t | uint32 | int † | Number |
| uint64 | uint64_t | uint64 | long † | Number ‡ |
| int32 | int32_t | int32 | int | Number |
| int64 | int64_t | int64 | long | Number ‡ |
| float32 | float | float32 | float | Number |
| float64 | double | float64 | double | Number |
| timestamp | 2 × time_t | Time †† | Instant | Date + Number |
| text | char †‡ | string | String ‡‡ | String ‡‡ |
| binary | uint8_t †‡ | []byte | byte[] | Uint8Array |
| list | †‡ | slice | array | Array |
- † signed representation of unsigned data, i.e. may overflow to negative.
- ‡ range limited to (1 - 2⁵³, 2⁵³ - 1)
- †† timezone not preserved
- †‡ struct of pointer + size_t
- ‡‡ characters limited by UTF-16 (
U+0000,U+10FFFF)
Lists may contain floating points, text, binaries or data structures.
Compatibility
Name changes do not affect the serialization format. Deprecated fields can be renamed to clearly discourage its use.
The following changes are backward compatible.
- New fields at the end of Colfer structs
- Change datatype int32 into int64
- Change datatype text into binary
Performance
BenchmarkMarshal/colfer-8 20000000 65.9 ns/op 48 B/op 1 allocs/op
BenchmarkMarshal/protobuf-8 20000000 81.4 ns/op 52 B/op 1 allocs/op
BenchmarkMarshal/flatbuf-8 2000000 701 ns/op 472 B/op 12 allocs/op
BenchmarkUnmarshal/colfer-8 20000000 94.3 ns/op 84 B/op 2 allocs/op
BenchmarkUnmarshal/protobuf-8 10000000 128 ns/op 84 B/op 2 allocs/op
BenchmarkUnmarshal/flatbuf-8 10000000 152 ns/op 84 B/op 2 allocs/op
BenchmarkMarshalReuse/colfer-8 50000000 36.7 ns/op 0 B/op 0 allocs/op
BenchmarkMarshalReuse/protobuf-8 30000000 48.4 ns/op 0 B/op 0 allocs/op
BenchmarkMarshalReuse/flatbuf-8 5000000 294 ns/op 0 B/op 0 allocs/op
BenchmarkUnmarshalReuse/colfer-8 20000000 62.7 ns/op 20 B/op 1 allocs/op
BenchmarkUnmarshalReuse/protobuf-8 20000000 92.5 ns/op 20 B/op 1 allocs/op
BenchmarkUnmarshalReuse/flatbuf-8 10000000 119 ns/op 20 B/op 1 allocs/op
Format
Data structures consist of zero or more field value definitions followed by a
termination byte 0x7f. Only those fields with a value other than the zero
value may be serialized. Fields appear in order as stated by the schema.
The zero value for booleans is false, integers: 0, floating points: 0.0,
timestamps: 1970-01-01T00:00:00.000000000Z, text & binary: the empty
string, nested data structures: null and an empty list for data structure
lists.
Data is represented in a big-endian manner. The format relies on varints also known as a variable-length quantity. Bits reserved for future use (RFU) must be set to 0.
Value Definiton
Each definition starts with an 8-bit header. The 7 least significant bits identify the field by its (0-based position) index in the schema. The most significant bit is used as a flag.
Boolean occurrences set the value to true. The flag is RFU.
Unsigned 8-bit integer values just follow the header byte and the flag is RFU. Unsigned 16-bit integer values greather than 255 also follow the header byte. Smaller values are encoded in one byte with the header flag set. Unsigned 32-bit integer values less than 1<<21 are encoded as varints and larger values set the header flag for fixed length encoding. Unsigned 64-bit integer values less than 1<<49 are encoded as varints and larger values set the header flag for fixed length encoding.
Signed 32- and 64-bit integers are encoded as varints. The flag stands for
negative. The tenth byte for 64-bit integers is skipped for encoding since its
value is fixed to 0x01.
Floating points are encoded conform IEEE 754. The flag is RFU.
Timestamps are encoded as a 32-bit unsigned integer for the number of seconds that have elapsed since 00:00:00 UTC, Thursday, 1 January 1970, not counting leap seconds. When the header flag is set then the number of seconds is encoded as a 64-bit two's complement integer. In both cases the value is followed with 32 bits for the nanosecond fraction. Note that the first two bits are RFU.
The data for text and binaries is prefixed with a varint byte size declaration. Text is encoded as UTF-8. The flag is RFU.
Lists of floating points, text, binaries and data structures are prefixed with a varint element size declaration. The flag is RFU.
Documentation
¶
Overview ¶
Package colfer provides schema definitions.
Index ¶
- func Format(file string) (changed bool, err error)
- func GenerateECMA(basedir string, packages []*Package) error
- func GenerateGo(basedir string, packages []*Package) error
- func GenerateJava(basedir string, packages []*Package) error
- func IsECMAKeyword(s string) bool
- func IsJavaKeyword(s string) bool
- type Field
- type Package
- type Struct
- func (s *Struct) DocText(indent string) string
- func (s *Struct) HasBinary() bool
- func (s *Struct) HasBinaryList() bool
- func (s *Struct) HasFloat() bool
- func (s *Struct) HasList() bool
- func (s *Struct) HasText() bool
- func (s *Struct) HasTimestamp() bool
- func (s *Struct) NameTitle() string
- func (s *Struct) String() string
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Format ¶
Format normalizes the file's content. The content of file is expected to be syntactically correct.
func GenerateECMA ¶
GenerateECMA writes the code into file "Colfer.js".
func GenerateGo ¶
GenerateGo writes the code into file "Colfer.go".
func GenerateJava ¶
GenerateJava writes the code into the respective ".java" files.
func IsECMAKeyword ¶
IsECMAKeyword returs whether s is a reserved word in ECMAScript code.
func IsJavaKeyword ¶
IsJavaKeyword returs whether s is a reserved word in Java code.
Types ¶
type Field ¶
type Field struct {
// Struct is the parent.
Struct *Struct
// Index is the Struct.Fields position.
Index int
// Name is the identification token.
Name string
// NameNative is the language specific identification token
NameNative string
// Docs are the documentation texts.
Docs []string
// Type is the datatype.
Type string
// TypeNative is the language specific datatype placeholder.
TypeNative string
// TypeRef is the Colfer data structure reference.
TypeRef *Struct
// TypeList flags whether the datatype is a list.
TypeList bool
}
Field is a Struct member definition.
type Package ¶
type Package struct {
// Name is the identification token.
Name string
// NameNative is the language specific identification token
NameNative string
// Docs are the documentation texts.
Docs []string
// Structs are the type definitions.
Structs []*Struct
// SchemaFiles are the source filenames.
SchemaFiles []string
// SizeMax is the uper limit expression.
SizeMax string
// ListMax is the uper limit expression.
ListMax string
}
Package is a named definition bundle.
func ParseFiles ¶
ParseFiles returns the schema definitions.
func (*Package) HasTimestamp ¶
HasTimestamp returns whether p has one or more timestamp fields.
func (*Package) SchemaFileList ¶
SchemaFileList returns a listing text.
type Struct ¶
type Struct struct {
Pkg *Package
// Name is the identification token.
Name string
// Docs are the documentation texts.
Docs []string
// Fields are the elements in order of appearance.
Fields []*Field
// SchemaFile is the source filename.
SchemaFile string
}
Struct is a data structure definition.
func (*Struct) HasBinaryList ¶
HasBinaryList returns whether s has one or more binary list fields.
func (*Struct) HasTimestamp ¶
HasTimestamp returns whether s has one or more timestamp fields.
Source Files
Directories