126 lines
3.5 KiB
Go
126 lines
3.5 KiB
Go
// Copyright (c) 2020-2021 Shivaram Lingamneni
|
|
// released under the MIT license
|
|
|
|
package ircreader
|
|
|
|
import (
|
|
"bytes"
|
|
"errors"
|
|
"io"
|
|
)
|
|
|
|
/*
|
|
Reader is an optimized line reader for IRC lines containing tags;
|
|
most IRC lines will not approach the maximum line length (8191 bytes
|
|
of tag data, plus 512 bytes of message data), so we want a buffered
|
|
reader that can start with a smaller buffer and expand if necessary,
|
|
while also maintaining a hard upper limit on the size of the buffer.
|
|
*/
|
|
|
|
var (
|
|
ErrReadQ = errors.New("readQ exceeded (read too many bytes without terminating newline)")
|
|
)
|
|
|
|
type Reader struct {
|
|
conn io.Reader
|
|
|
|
initialSize int
|
|
maxSize int
|
|
|
|
buf []byte
|
|
start int // start of valid (i.e., read but not yet consumed) data in the buffer
|
|
end int // end of valid data in the buffer
|
|
searchFrom int // start of valid data in the buffer not yet searched for \n
|
|
eof bool
|
|
}
|
|
|
|
// Returns a new *Reader with sane buffer size limits.
|
|
func NewIRCReader(conn io.Reader) *Reader {
|
|
var reader Reader
|
|
reader.Initialize(conn, 512, 8192+1024)
|
|
return &reader
|
|
}
|
|
|
|
// "Placement new" for a Reader; initializes it with custom buffer size
|
|
// limits.
|
|
func (cc *Reader) Initialize(conn io.Reader, initialSize, maxSize int) {
|
|
*cc = Reader{}
|
|
cc.conn = conn
|
|
cc.initialSize = initialSize
|
|
cc.maxSize = maxSize
|
|
}
|
|
|
|
// Blocks until a full IRC line is read, then returns it. Accepts either \n
|
|
// or \r\n as the line terminator (but not \r in isolation). Passes through
|
|
// errors from the underlying connection. Returns ErrReadQ if the buffer limit
|
|
// was exceeded without a terminating \n.
|
|
func (cc *Reader) ReadLine() ([]byte, error) {
|
|
for {
|
|
// try to find a terminated line in the buffered data already read
|
|
nlidx := bytes.IndexByte(cc.buf[cc.searchFrom:cc.end], '\n')
|
|
if nlidx != -1 {
|
|
// got a complete line
|
|
line := cc.buf[cc.start : cc.searchFrom+nlidx]
|
|
cc.start = cc.searchFrom + nlidx + 1
|
|
cc.searchFrom = cc.start
|
|
// treat \r\n as the line terminator if it was present
|
|
if 0 < len(line) && line[len(line)-1] == '\r' {
|
|
line = line[:len(line)-1]
|
|
}
|
|
return line, nil
|
|
}
|
|
|
|
// are we out of space? we can read more if any of these are true:
|
|
// 1. cc.start != 0, so we can slide the existing data back
|
|
// 2. cc.end < len(cc.buf), so we can read data into the end of the buffer
|
|
// 3. len(cc.buf) < cc.maxSize, so we can grow the buffer
|
|
if cc.start == 0 && cc.end == len(cc.buf) && len(cc.buf) == cc.maxSize {
|
|
return nil, ErrReadQ
|
|
}
|
|
|
|
if cc.eof {
|
|
return nil, io.EOF
|
|
}
|
|
|
|
if len(cc.buf) < cc.maxSize && (len(cc.buf)-(cc.end-cc.start) < cc.initialSize/2) {
|
|
// allocate a new buffer, copy any remaining data
|
|
newLen := roundUpToPowerOfTwo(len(cc.buf) + 1)
|
|
if newLen > cc.maxSize {
|
|
newLen = cc.maxSize
|
|
} else if newLen < cc.initialSize {
|
|
newLen = cc.initialSize
|
|
}
|
|
newBuf := make([]byte, newLen)
|
|
copy(newBuf, cc.buf[cc.start:cc.end])
|
|
cc.buf = newBuf
|
|
} else if cc.start != 0 {
|
|
// slide remaining data back to the front of the buffer
|
|
copy(cc.buf, cc.buf[cc.start:cc.end])
|
|
}
|
|
cc.end = cc.end - cc.start
|
|
cc.start = 0
|
|
|
|
cc.searchFrom = cc.end
|
|
n, err := cc.conn.Read(cc.buf[cc.end:])
|
|
cc.end += n
|
|
if n != 0 && err == io.EOF {
|
|
// we may have received new \n-terminated lines, try to parse them
|
|
cc.eof = true
|
|
} else if err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
}
|
|
|
|
// return n such that v <= n and n == 2**i for some i
|
|
func roundUpToPowerOfTwo(v int) int {
|
|
// http://graphics.stanford.edu/~seander/bithacks.html
|
|
v -= 1
|
|
v |= v >> 1
|
|
v |= v >> 2
|
|
v |= v >> 4
|
|
v |= v >> 8
|
|
v |= v >> 16
|
|
return v + 1
|
|
}
|