Repository: uber-go/zap
File: encoder.go (Go)

Code before:
// Copyright (c) 2016 Uber Technologies, Inc.
//
// 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.

package zap

import (
	"io"
	"time"
)

// Encoder is a format-agnostic interface for all log entry marshalers. Since
// log encoders don't need to support the same wide range of use cases as
// general-purpose marshalers, it's possible to make them much faster and
// lower-allocation.
//
// Encoders need not be fully safe for concurrent use, but it should be safe to
// call the Clone and WriteEntry methods concurrently (as long as fields aren't
// simultaneously being added). Concretely, the following code should be safe:
//   enc := NewExoticEncoder() // your Encoder implementation
//   enc.AddString("foo", "bar")
//   for i := 0; i < 10; i++ {
//     go func() {
//       enc.WriteEntry(os.Stdout, "Safe!", zap.InfoLevel, time.Now().UTC())
//       enc.Clone()
//     }()
//   }
// See the JSON encoder for an example implementation.
type Encoder interface {
	KeyValue

	// Copy the encoder, ensuring that adding fields to the copy doesn't affect
	// the original.
	Clone() Encoder
	// Return the encoder to the appropriate sync.Pool. Unpooled encoder
	// implementations can no-op this method.
	Free()
	// Write the supplied message, level, and timestamp to the writer, along with
	// any accumulated context.
	WriteEntry(io.Writer, string, Level, time.Time) error
}


Review comment (suggestion):
Now that this is documented, it seems very strange to require some methods to work concurrently, but not others. Should we actually have 2 interfaces here that separate a mutable state compared to the immutable state that is safe for concurrent use? E.g., breaking out the `WriteEntry` into a separate interface that is safe for concurrent use, while adding fields and `Clone` are not safe for concurrent use.


Code after:
// Copyright (c) 2016 Uber Technologies, Inc.
//
// 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.

package zap

import (
	"io"
	"time"
)

// Encoder is a format-agnostic interface for all log entry marshalers. Since
// log encoders don't need to support the same wide range of use cases as
// general-purpose marshalers, it's possible to make them much faster and
// lower-allocation.
//
// Implementations of the KeyValue interface's methods can, of course, freely
// modify the receiver. However, the Clone and WriteEntry methods will be
// called concurrently and shouldn't modify the receiver.
type Encoder interface {
	KeyValue

	// Copy the encoder, ensuring that adding fields to the copy doesn't affect
	// the original.
	Clone() Encoder
	// Return the encoder to the appropriate sync.Pool. Unpooled encoder
	// implementations can no-op this method.
	Free()
	// Write the supplied message, level, and timestamp to the writer, along with
	// any accumulated context.
	WriteEntry(io.Writer, string, Level, time.Time) error
}