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file_reader_iter.go
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/
file_reader_iter.go
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// Copyright (c) 2017 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 fs
import (
"bufio"
"io"
"os"
"github.com/m3db/m3/src/m3em/checksum"
)
const (
defaultBufferSize = 1024
)
type bufferedFileReaderIter struct {
currentBytes []byte
checksum checksum.Accumulator
bufferedReader *bufio.Reader
fileHandle *os.File
err error
done bool
init bool
}
// NewFileReaderIter creates a new buffered FileReaderIter
func NewFileReaderIter(
filepath string,
) (FileReaderIter, error) {
return NewSizedFileReaderIter(filepath, defaultBufferSize)
}
// NewSizedFileReaderIter creates a new buffered FileReaderIter
func NewSizedFileReaderIter(
filepath string,
bufferSize int,
) (FileReaderIter, error) {
fhandle, err := os.Open(filepath)
if err != nil {
return nil, err
}
var (
bytes = make([]byte, bufferSize)
buffReader = bufio.NewReaderSize(fhandle, bufferSize)
iter = &bufferedFileReaderIter{
currentBytes: bytes,
checksum: checksum.NewAccumulator(),
bufferedReader: buffReader,
fileHandle: fhandle,
}
)
return iter, nil
}
func (r *bufferedFileReaderIter) Current() []byte {
if r.Err() != nil {
return nil
}
return r.currentBytes
}
func (r *bufferedFileReaderIter) Next() bool {
if !r.init {
r.init = true
}
if r.done || r.err != nil {
return false
}
n, err := r.bufferedReader.Read(r.currentBytes)
if err != nil && err != io.EOF {
r.err = err
r.Close()
return false
}
bytes := r.currentBytes[:n]
r.checksum.Update(bytes)
r.currentBytes = bytes
if err == io.EOF {
r.done = true
r.Close()
}
return true
}
func (r *bufferedFileReaderIter) Close() error {
handle := r.fileHandle
r.fileHandle = nil
r.currentBytes = nil
r.bufferedReader = nil
if handle != nil {
return handle.Close()
}
return nil
}
func (r *bufferedFileReaderIter) Checksum() uint32 {
return r.checksum.Current()
}
func (r *bufferedFileReaderIter) Err() error {
return r.err
}