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138 lines
2.2 KiB
138 lines
2.2 KiB
package bufreader
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import (
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"errors"
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"io"
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)
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const (
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maxReadAttempts = 5
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defaultBufSize = 1024
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)
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var (
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// ErrReadOverflow shows 100% bug in the source reader
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ErrReadOverflow = errors.New("bufreader: reader returned 'n' > bufsize")
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// ErrNegativeReadCount shows 100% bug in the source reader
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ErrNegativeReadCount = errors.New("bufreader: reader returned negative 'n'")
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)
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type BufferedReader struct {
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r io.Reader
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buf []byte
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idx int
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end int
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totalRead int
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}
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func New(r io.Reader, bufsize int) *BufferedReader {
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if bufsize == 0 {
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bufsize = defaultBufSize
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}
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return &BufferedReader{
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r: r,
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buf: make([]byte, bufsize),
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}
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}
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func (s *BufferedReader) safeRead(buf []byte) (n int, err error) {
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readAttempts := 0
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for readAttempts < maxReadAttempts {
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n, err = s.r.Read(buf)
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if n > 0 {
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if n > len(buf) {
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return 0, ErrReadOverflow
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}
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if err == io.EOF {
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err = nil
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}
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return
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}
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if n < 0 {
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return 0, ErrNegativeReadCount
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}
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// n == 0
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if err != nil {
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return
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}
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readAttempts++
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}
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return 0, io.ErrNoProgress
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}
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func (s *BufferedReader) fill() error {
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n, err := s.safeRead(s.buf)
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s.idx = 0
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s.end = n
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return err
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}
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func (s *BufferedReader) ReadByte() (b byte, err error) {
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if s.idx == s.end {
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if err = s.fill(); err != nil {
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return
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}
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}
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b = s.buf[s.idx]
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s.idx++
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s.totalRead++
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return
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}
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func (s *BufferedReader) Read(buf []byte) (int, error) {
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size := len(buf)
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buffered := s.end - s.idx
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if size <= buffered {
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for i, b := range s.buf[s.idx : s.idx+size] {
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buf[i] = b
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}
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s.idx += size
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s.totalRead += len(buf)
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return size, nil
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}
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for i, b := range s.buf[s.idx:s.end] {
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buf[i] = b
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}
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s.idx = 0
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s.end = 0
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n := buffered
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rbuf := buf[buffered:]
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var (
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q int
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err error
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)
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for n < size {
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q, err = s.safeRead(rbuf)
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n += q
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rbuf = rbuf[q:]
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if err != nil {
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if err == io.EOF && n == size {
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s.totalRead += len(buf)
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return n, nil
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}
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break
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}
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}
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s.totalRead += len(buf[:n])
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return n, err
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}
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func (s *BufferedReader) ReadN(size int) ([]byte, error) {
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buf := make([]byte, size)
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_, err := s.Read(buf)
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if err != nil {
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return nil, err
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}
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return buf, nil
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}
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func (s *BufferedReader) TotalRead() int {
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return s.totalRead
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}
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