README
¶
protolog
Package protolog implements a simple file format for a sequence of blobs with ability to store a message type with each blob as well as a checksum. It is intended for logging protobuf messages. Unlike other formats, it tries to be simple, so writing a reader/writer in other languages is trivial. This design is a modified form of Eric Lesh's recordio Go implementation (github.com/eclesh/recordio). This package swaps out a single varint header for fixed size headers with support for a uint16 ID of the message type and a CRC-32C checksum.
Example: reading with a Scanner
const fooTypeID uint16 = 13 // ids that tell us type of message
f, _ := os.Open("data.log")
defer f.Close()
scanner := protolog.NewScanner(f)
for scanner.Scan() {
data := scanner.Bytes()
switch scanner.TypeID() {
case fooTypeID:
var foo myFooProtobufType
foo.Unmarshal(data)
// Check other types
}
}
if err := scanner.Error(); err != nil {
// Do error handling
}
Example: reading with a Reader
const fooTypeID uint16 = 13 // ids that tell us type of message
f, _ := os.Open("data.log")
f.Close()
r := protolog.NewReader(f)
for {
data, typeID, err := r.Next()
if err == io.EOF {
break
}
switch typeID {
case fooTypeID:
var foo myFooProtobufType
foo.Unmarshal(data)
// Check other types
}
}
Example: writing one type of message
const fooTypeID uint16 = 13 // ids that tell us type of message
f, _ := os.Create("data.log")
w := protolog.NewTypedWriter(fooTypeID, f)
data, _ := myFooProtobufObj.Marshal()
w.Write(data)
data, _ = my2ndFooProtobufObj.Marshal()
w.Write(data)
f.Close()
Example: writing different messages
const (
fooTypeID uint16 = 13
barTypeID uint16 = 14
)
f, _ := os.Create("data.log")
w := protolog.NewMultiTypeWriter(f)
typebuf := make([]byte, 2)
serialization, _ := myFooProtobufObj.Marshal()
w.Write(fooTypeID, serialization)
serialization, _ = myBarProtobufObj.Marshal()
w.Write(barTypeID, serialization)
f.Close()
File Format
Header 1 (10 bytes)
Message # Bytes excluding fixed header (uint32, 4 bytes)
Checksum (4 bytes)
Message Type ID (uint16, 2 bytes)
Binary Data 1 (variable # bytes)
...
Header N (10 bytes)
Binary Data N (variable # bytes)
License
Copyright (C) 2019 Bill Katz
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Documentation
¶
Overview ¶
Package protolog implements a simple file format for a sequence of blobs with ability to store a message type with each blob as well as a checksum. It is intended for logging protobuf messages. Unlike other formats, it tries to be simple, so writing a reader/writer in other languages is trivial. This design is a modified form of Eric Lesh's recordio Go implementation (github.com/eclesh/recordio). It uses fixed size headers with support for a uint16 ID of the message type and a CRC-32C checksum. Each blob must be less than 4 GiB (2^32 bytes).
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ( // ErrBadChecksum is an error returned when a bad checksum is detected. ErrBadChecksum = fmt.Errorf("bad checksum detected while reading data") )
Functions ¶
This section is empty.
Types ¶
type MultiTypedWriter ¶
type MultiTypedWriter struct {
// contains filtered or unexported fields
}
MultiTypedWriter writes records that can have different optional type identifiers
func NewMultiTypedWriter ¶
func NewMultiTypedWriter(w io.Writer) *MultiTypedWriter
NewMultiTypedWriter returns a new writer that could have different record types.
type Reader ¶
type Reader struct {
// contains filtered or unexported fields
}
Reader allows reading of checksummed binary blobs with optional uint16 type IDs.
type Scanner ¶
type Scanner struct {
// contains filtered or unexported fields
}
A Scanner is a convenient method for reading records sequentially.
func NewScanner ¶
NewScanner creates a new Scanner from reader r.
func (*Scanner) Bytes ¶
Bytes returns the data of the most recently scanned record. Subsequent calls may overwrite the returned data, so you must copy it if not using it immediately.
type TypedWriter ¶
type TypedWriter struct {
// contains filtered or unexported fields
}
TypedWriter writes records that have a single optional type identifier
func NewTypedWriter ¶
func NewTypedWriter(recordType uint16, w io.Writer) *TypedWriter
NewTypedWriter returns a new writer that uses the same record type.
Source Files