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package sexp
import (
"bufio"
"io"
)
// Value is an S-Expression value
type Value interface {
First() Value
Second() Value
Value() interface{}
String() string
}
func peek(r *bufio.Reader) (c byte, e error) {
c, e = r.ReadByte()
if e != io.EOF {
r.UnreadByte()
}
return
}
// Read will read an S-Expression from the given reader
func Read(r *bufio.Reader) Value {
res, _ := ReadValue(r)
return res
}
// ReadWhitespace will read from the reader until no whitespace is encountered
func ReadWhitespace(r *bufio.Reader) {
c, e := peek(r)
for e != io.EOF && isWhitespace(c) {
r.ReadByte()
c, e = peek(r)
}
}
// ReadValue will read and return an S-Expression value from the reader
func ReadValue(r *bufio.Reader) (Value, bool) {
ReadWhitespace(r)
c, err := peek(r)
if err != nil {
return nil, true
}
switch c {
case '(':
return ReadList(r), false
case ')':
return nil, true
case '"':
return ReadString(r), false
case '#':
return ReadBigNum(r), false
default:
return ReadSymbol(r), false
}
}
func isWhitespace(c byte) bool {
switch c {
case ' ', '\t', '\n', '\r':
return true
default:
return false
}
}
func isNotSymbolCharacter(c byte) bool {
if isWhitespace(c) {
return true
}
switch c {
case '(', ')':
return true
default:
return false
}
}
func expect(r *bufio.Reader, c byte) bool {
ReadWhitespace(r)
res, err := r.ReadByte()
if res != c {
r.UnreadByte()
}
return res == c && err != io.EOF
}
func untilFixed(b byte) func(byte) bool {
return func(until byte) bool {
return until == b
}
}
// ReadDataUntil will read and collect bytes from the reader until it encounters EOF or the given function returns true.
func ReadDataUntil(r *bufio.Reader, until func(byte) bool) []byte {
result := make([]byte, 0, 10)
c, err := peek(r)
for err != io.EOF && !until(c) {
r.ReadByte()
result = append(result, c)
c, err = peek(r)
}
return result
}
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