vendor/github.com/aws/aws-sdk-go/aws/types.go

   1 package aws
   2
   3 import (
   4         "io"
   5         "sync"
   6 )
   7
   8 // ReadSeekCloser wraps a io.Reader returning a ReaderSeekerCloser. Should
   9 // only be used with an io.Reader that is also an io.Seeker. Doing so may
  10 // cause request signature errors, or request body's not sent for GET, HEAD
  11 // and DELETE HTTP methods.
  12 //
  13 // Deprecated: Should only be used with io.ReadSeeker. If using for
  14 // S3 PutObject to stream content use s3manager.Uploader instead.
  15 func ReadSeekCloser(r io.Reader) ReaderSeekerCloser {
  16         return ReaderSeekerCloser{r}
  17 }
  18
  19 // ReaderSeekerCloser represents a reader that can also delegate io.Seeker and
  20 // io.Closer interfaces to the underlying object if they are available.
  21 type ReaderSeekerCloser struct {
  22         r io.Reader
  23 }
  24
  25 // Read reads from the reader up to size of p. The number of bytes read, and
  26 // error if it occurred will be returned.
  27 //
  28 // If the reader is not an io.Reader zero bytes read, and nil error will be returned.
  29 //
  30 // Performs the same functionality as io.Reader Read
  31 func (r ReaderSeekerCloser) Read(p []byte) (int, error) {
  32         switch t := r.r.(type) {
  33         case io.Reader:
  34                 return t.Read(p)
  35         }
  36         return 0, nil
  37 }
  38
  39 // Seek sets the offset for the next Read to offset, interpreted according to
  40 // whence: 0 means relative to the origin of the file, 1 means relative to the
  41 // current offset, and 2 means relative to the end. Seek returns the new offset
  42 // and an error, if any.
  43 //
  44 // If the ReaderSeekerCloser is not an io.Seeker nothing will be done.
  45 func (r ReaderSeekerCloser) Seek(offset int64, whence int) (int64, error) {
  46         switch t := r.r.(type) {
  47         case io.Seeker:
  48                 return t.Seek(offset, whence)
  49         }
  50         return int64(0), nil
  51 }
  52
  53 // IsSeeker returns if the underlying reader is also a seeker.
  54 func (r ReaderSeekerCloser) IsSeeker() bool {
  55         _, ok := r.r.(io.Seeker)
  56         return ok
  57 }
  58
  59 // Close closes the ReaderSeekerCloser.
  60 //
  61 // If the ReaderSeekerCloser is not an io.Closer nothing will be done.
  62 func (r ReaderSeekerCloser) Close() error {
  63         switch t := r.r.(type) {
  64         case io.Closer:
  65                 return t.Close()
  66         }
  67         return nil
  68 }
  69
  70 // A WriteAtBuffer provides a in memory buffer supporting the io.WriterAt interface
  71 // Can be used with the s3manager.Downloader to download content to a buffer
  72 // in memory. Safe to use concurrently.
  73 type WriteAtBuffer struct {
  74         buf []byte
  75         m   sync.Mutex
  76
  77         // GrowthCoeff defines the growth rate of the internal buffer. By
  78         // default, the growth rate is 1, where expanding the internal
  79         // buffer will allocate only enough capacity to fit the new expected
  80         // length.
  81         GrowthCoeff float64
  82 }
  83
  84 // NewWriteAtBuffer creates a WriteAtBuffer with an internal buffer
  85 // provided by buf.
  86 func NewWriteAtBuffer(buf []byte) *WriteAtBuffer {
  87         return &WriteAtBuffer{buf: buf}
  88 }
  89
  90 // WriteAt writes a slice of bytes to a buffer starting at the position provided
  91 // The number of bytes written will be returned, or error. Can overwrite previous
  92 // written slices if the write ats overlap.
  93 func (b *WriteAtBuffer) WriteAt(p []byte, pos int64) (n int, err error) {
  94         pLen := len(p)
  95         expLen := pos + int64(pLen)
  96         b.m.Lock()
  97         defer b.m.Unlock()
  98         if int64(len(b.buf)) < expLen {
  99                 if int64(cap(b.buf)) < expLen {
 100                         if b.GrowthCoeff < 1 {
 101                                 b.GrowthCoeff = 1
 102                         }
 103                         newBuf := make([]byte, expLen, int64(b.GrowthCoeff*float64(expLen)))
 104                         copy(newBuf, b.buf)
 105                         b.buf = newBuf
 106                 }
 107                 b.buf = b.buf[:expLen]
 108         }
 109         copy(b.buf[pos:], p)
 110         return pLen, nil
 111 }
 112
 113 // Bytes returns a slice of bytes written to the buffer.
 114 func (b *WriteAtBuffer) Bytes() []byte {
 115         b.m.Lock()
 116         defer b.m.Unlock()
 117         return b.buf
 118 }