Peek-A-Buf

Peek-A-Buf is a Go library for a buffered reader with side effect free peeking capability.

At the moment, a buffered reader for runes is implemented meant for things like scanners.

Why is this useful if bufio.Reader exists? Well, the Peek function is sadly not side effect free there:

Calling Peek prevents a UnreadByte or UnreadRune call from succeeding until the next read operation.

But this is something needed within the SQL parser of the SQLSplitter. So this little library was created basically wrapping bufio.Reader and re-implementing small parts of it.

In addition to the side effect free peek function, it returns an EOF rune instead of an error if it reaches the end of the buffer.

Have a look at the documentation.

Installation

Just go get it:

go get github.com/philiplb/peekabuf

Usage

First, import it:

import "github.com/philiplb/peekabuf"

Then, create a new RuneReader with a io.Reader as source, in this case, simply a bytes.BufferString is used:

r := peekabuf.NewRuneReader(bytes.NewBufferString("pab"))

Now, you can read, unread, peek on it. Note the returned EOF rune if the end of the buffer is reached:

// read a bit in the buffer
read := r.Read() // read == 'p'
read = r.Read() // read == 'a'

// unread the last rune
r.Unread()
read = r.Read() // read == 'a'

// peek a bit in the buffer
r.Unread() // unread the last rune so we have a bit to peek
peeked, err := r.Peek(2) // peeked == {'a', 'b'}
peeked, err := r.Peek(4) // peeked == {'a', 'b', peekabuf.EOF}, note that four runes were requested

// read the rest of the buffer
read = r.Read() // read == 'a'
read = r.Read() // read == 'b'
read = r.Read() // read == peekabuf.EOF
read = r.Read() // read == peekabuf.EOF

License

MIT