go.uber.org/yarpc@v1.72.1/transport/tchannel/internal/reader.go (about)

     1  // Copyright (c) 2022 Uber Technologies, Inc.
     2  //
     3  // Permission is hereby granted, free of charge, to any person obtaining a copy
     4  // of this software and associated documentation files (the "Software"), to deal
     5  // in the Software without restriction, including without limitation the rights
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     7  // copies of the Software, and to permit persons to whom the Software is
     8  // furnished to do so, subject to the following conditions:
     9  //
    10  // The above copyright notice and this permission notice shall be included in
    11  // all copies or substantial portions of the Software.
    12  //
    13  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    14  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    15  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    16  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    17  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    18  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    19  // THE SOFTWARE.
    20  
    21  package internal
    22  
    23  import (
    24  	"encoding/binary"
    25  	"io"
    26  	"sync"
    27  )
    28  
    29  // This file lifted almost as-is from tchannel/typed.
    30  
    31  const _maxPoolStringLen = 32
    32  
    33  // Reader is a reader that reads typed values from an io.Reader.
    34  type Reader struct {
    35  	reader io.Reader
    36  	err    error
    37  	buf    [_maxPoolStringLen]byte
    38  }
    39  
    40  var readerPool = sync.Pool{New: func() interface{} { return &Reader{} }}
    41  
    42  // NewReader returns a reader that reads typed values from the reader.
    43  func NewReader(reader io.Reader) *Reader {
    44  	r := readerPool.Get().(*Reader)
    45  	r.reader = reader
    46  	r.err = nil
    47  	return r
    48  }
    49  
    50  // ReadUint16 reads a uint16.
    51  func (r *Reader) ReadUint16() uint16 {
    52  	if r.err != nil {
    53  		return 0
    54  	}
    55  
    56  	buf := r.buf[:2]
    57  
    58  	var readN int
    59  	readN, r.err = io.ReadFull(r.reader, buf)
    60  	if readN < 2 {
    61  		return 0
    62  	}
    63  	return binary.BigEndian.Uint16(buf)
    64  }
    65  
    66  // ReadString reads a string of length n.
    67  func (r *Reader) ReadString(n int) string {
    68  	if r.err != nil {
    69  		return ""
    70  	}
    71  
    72  	var buf []byte
    73  	if n <= _maxPoolStringLen {
    74  		buf = r.buf[:n]
    75  	} else {
    76  		buf = make([]byte, n)
    77  	}
    78  
    79  	var readN int
    80  	readN, r.err = io.ReadFull(r.reader, buf)
    81  	if readN < n {
    82  		return ""
    83  	}
    84  	s := string(buf)
    85  
    86  	return s
    87  }
    88  
    89  // ReadLen16String reads a uint16-length prefixed string.
    90  func (r *Reader) ReadLen16String() string {
    91  	len := r.ReadUint16()
    92  	return r.ReadString(int(len))
    93  }
    94  
    95  // Err returns any errors hit while reading from the underlying reader.
    96  func (r *Reader) Err() error {
    97  	return r.err
    98  }
    99  
   100  // Release puts the Reader back in the pool.
   101  func (r *Reader) Release() {
   102  	readerPool.Put(r)
   103  }