File size: 1,540 Bytes
619f93d | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 | package buffer
import (
"errors"
"io"
)
// 用于存储不复用的[]byte
type Reader struct {
bufs [][]byte
size int64
offset int64
}
func (r *Reader) Size() int64 {
return r.size
}
func (r *Reader) Append(buf []byte) {
r.size += int64(len(buf))
r.bufs = append(r.bufs, buf)
}
func (r *Reader) Read(p []byte) (int, error) {
n, err := r.ReadAt(p, r.offset)
if n > 0 {
r.offset += int64(n)
}
return n, err
}
func (r *Reader) ReadAt(p []byte, off int64) (int, error) {
if off < 0 || off >= r.size {
return 0, io.EOF
}
n := 0
readFrom := false
for _, buf := range r.bufs {
if readFrom {
nn := copy(p[n:], buf)
n += nn
if n == len(p) {
return n, nil
}
} else if newOff := off - int64(len(buf)); newOff >= 0 {
off = newOff
} else {
nn := copy(p, buf[off:])
if nn == len(p) {
return nn, nil
}
n += nn
readFrom = true
}
}
return n, io.EOF
}
func (r *Reader) Seek(offset int64, whence int) (int64, error) {
switch whence {
case io.SeekStart:
case io.SeekCurrent:
offset = r.offset + offset
case io.SeekEnd:
offset = r.size + offset
default:
return 0, errors.New("Seek: invalid whence")
}
if offset < 0 || offset > r.size {
return 0, errors.New("Seek: invalid offset")
}
r.offset = offset
return offset, nil
}
func (r *Reader) Reset() {
clear(r.bufs)
r.bufs = nil
r.size = 0
r.offset = 0
}
func NewReader(buf ...[]byte) *Reader {
b := &Reader{
bufs: make([][]byte, 0, len(buf)),
}
for _, b1 := range buf {
b.Append(b1)
}
return b
}
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