mirror of https://bitbucket.org/ausocean/av.git
96 lines
2.2 KiB
Go
96 lines
2.2 KiB
Go
/*
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NAME
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bytescanner.go
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AUTHOR
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Dan Kortschak <dan@ausocean.org>
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LICENSE
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This is Copyright (C) 2017 the Australian Ocean Lab (AusOcean)
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It is free software: you can redistribute it and/or modify them
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under the terms of the GNU General Public License as published by the
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Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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It is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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in gpl.txt. If not, see http://www.gnu.org/licenses.
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*/
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// Package bytescan implements a byte-level scanner.
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package codecutil
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import "io"
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// ByteScanner is a byte scanner.
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type ByteScanner struct {
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buf []byte
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off int
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// r is the source of data for the scanner.
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r io.Reader
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}
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// NewByteScanner returns a scanner initialised with an io.Reader and a read buffer.
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func NewByteScanner(r io.Reader, buf []byte) *ByteScanner {
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return &ByteScanner{r: r, buf: buf[:0]}
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}
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// ScanUntil scans the scanner's underlying io.Reader until a delim byte
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// has been read, appending all read bytes to dst. The resulting appended data,
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// the last read byte and whether the last read byte was the delimiter.
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func (c *ByteScanner) ScanUntil(dst []byte, delim byte) (res []byte, b byte, err error) {
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outer:
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for {
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var i int
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for i, b = range c.buf[c.off:] {
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if b != delim {
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continue
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}
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dst = append(dst, c.buf[c.off:c.off+i+1]...)
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c.off += i + 1
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break outer
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}
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dst = append(dst, c.buf[c.off:]...)
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err = c.reload()
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if err != nil {
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break
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}
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}
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return dst, b, err
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}
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// ReadByte is an unexported ReadByte.
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func (c *ByteScanner) ReadByte() (byte, error) {
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if c.off >= len(c.buf) {
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err := c.reload()
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if err != nil {
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return 0, err
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}
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}
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b := c.buf[c.off]
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c.off++
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return b, nil
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}
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// reload re-fills the scanner's buffer.
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func (c *ByteScanner) reload() error {
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n, err := c.r.Read(c.buf[:cap(c.buf)])
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c.buf = c.buf[:n]
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if err != nil {
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if err != io.EOF {
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return err
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}
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if n == 0 {
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return io.EOF
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}
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}
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c.off = 0
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return nil
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}
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