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writer.go
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writer.go
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// Copyright (C) 2017 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package text
import "io"
// Writer returns a io writer that collects lines out of a stream and hands
// them to the supplied function.
func Writer(to func(string) error) io.WriteCloser {
return &writer{to: to}
}
type writer struct {
to func(string) error
remains string
}
// Write splits the input into lines, gathering across multiple calls if needed.
// Write implements the io.Writer interface
func (w *writer) Write(p []byte) (n int, err error) {
s := string(p)
start := 0
for i, c := range s {
if c == '\n' {
fragment := s[start:i]
start = i + 1
if len(w.remains) > 0 {
fragment = w.remains + fragment
w.remains = ""
}
if err := w.to(fragment); err != nil {
return 0, err
}
}
}
fragment := s[start:]
if len(w.remains) > 0 {
fragment = w.remains + fragment
}
w.remains = fragment
return len(p), nil
}
// Close flushes any partial lines before closing the stream down.
// The behaviour on Subsequent calles to Write is undefined.
func (w writer) Close() error {
var err error
if w.remains != "" {
err = w.to(w.remains)
w.remains = ""
}
return err
}