gotosocial/vendor/github.com/tdewolff/parse/v2/input.go

174 lines
4.1 KiB
Go
Raw Normal View History

package parse
import (
"io"
"io/ioutil"
)
var nullBuffer = []byte{0}
// Input is a buffered reader that allows peeking forward and shifting, taking an io.Input.
// It keeps data in-memory until Free, taking a byte length, is called to move beyond the data.
type Input struct {
buf []byte
pos int // index in buf
start int // index in buf
err error
restore func()
}
// NewInput returns a new Input for a given io.Input and uses ioutil.ReadAll to read it into a byte slice.
// If the io.Input implements Bytes, that is used instead. It will append a NULL at the end of the buffer.
func NewInput(r io.Reader) *Input {
var b []byte
if r != nil {
if buffer, ok := r.(interface {
Bytes() []byte
}); ok {
b = buffer.Bytes()
} else {
var err error
b, err = ioutil.ReadAll(r)
if err != nil {
return &Input{
buf: nullBuffer,
err: err,
}
}
}
}
return NewInputBytes(b)
}
// NewInputString returns a new Input for a given string and appends NULL at the end.
func NewInputString(s string) *Input {
return NewInputBytes([]byte(s))
}
// NewInputBytes returns a new Input for a given byte slice and appends NULL at the end.
// To avoid reallocation, make sure the capacity has room for one more byte.
func NewInputBytes(b []byte) *Input {
z := &Input{
buf: b,
}
n := len(b)
if n == 0 {
z.buf = nullBuffer
} else {
// Append NULL to buffer, but try to avoid reallocation
if cap(b) > n {
// Overwrite next byte but restore when done
b = b[:n+1]
c := b[n]
b[n] = 0
z.buf = b
z.restore = func() {
b[n] = c
}
} else {
z.buf = append(b, 0)
}
}
return z
}
// Restore restores the replaced byte past the end of the buffer by NULL.
func (z *Input) Restore() {
if z.restore != nil {
z.restore()
z.restore = nil
}
}
// Err returns the error returned from io.Input or io.EOF when the end has been reached.
func (z *Input) Err() error {
return z.PeekErr(0)
}
// PeekErr returns the error at position pos. When pos is zero, this is the same as calling Err().
func (z *Input) PeekErr(pos int) error {
if z.err != nil {
return z.err
} else if z.pos+pos >= len(z.buf)-1 {
return io.EOF
}
return nil
}
// Peek returns the ith byte relative to the end position.
// Peek returns 0 when an error has occurred, Err returns the erroz.
func (z *Input) Peek(pos int) byte {
pos += z.pos
return z.buf[pos]
}
// PeekRune returns the rune and rune length of the ith byte relative to the end position.
func (z *Input) PeekRune(pos int) (rune, int) {
// from unicode/utf8
c := z.Peek(pos)
if c < 0xC0 || z.Peek(pos+1) == 0 {
return rune(c), 1
} else if c < 0xE0 || z.Peek(pos+2) == 0 {
return rune(c&0x1F)<<6 | rune(z.Peek(pos+1)&0x3F), 2
} else if c < 0xF0 || z.Peek(pos+3) == 0 {
return rune(c&0x0F)<<12 | rune(z.Peek(pos+1)&0x3F)<<6 | rune(z.Peek(pos+2)&0x3F), 3
}
return rune(c&0x07)<<18 | rune(z.Peek(pos+1)&0x3F)<<12 | rune(z.Peek(pos+2)&0x3F)<<6 | rune(z.Peek(pos+3)&0x3F), 4
}
// Move advances the position.
func (z *Input) Move(n int) {
z.pos += n
}
// Pos returns a mark to which can be rewinded.
func (z *Input) Pos() int {
return z.pos - z.start
}
// Rewind rewinds the position to the given position.
func (z *Input) Rewind(pos int) {
z.pos = z.start + pos
}
// Lexeme returns the bytes of the current selection.
func (z *Input) Lexeme() []byte {
return z.buf[z.start:z.pos:z.pos]
}
// Skip collapses the position to the end of the selection.
func (z *Input) Skip() {
z.start = z.pos
}
// Shift returns the bytes of the current selection and collapses the position to the end of the selection.
func (z *Input) Shift() []byte {
b := z.buf[z.start:z.pos:z.pos]
z.start = z.pos
return b
}
// Offset returns the character position in the buffez.
func (z *Input) Offset() int {
return z.pos
}
// Bytes returns the underlying buffez.
func (z *Input) Bytes() []byte {
return z.buf[: len(z.buf)-1 : len(z.buf)-1]
}
// Len returns the length of the underlying buffez.
func (z *Input) Len() int {
return len(z.buf) - 1
}
// Reset resets position to the underlying buffez.
func (z *Input) Reset() {
z.start = 0
z.pos = 0
}