diff options
| -rw-r--r-- | parser/reader.go | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/parser/reader.go b/parser/reader.go index 6b077fc..28cbe3d 100644 --- a/parser/reader.go +++ b/parser/reader.go @@ -9,16 +9,23 @@ import ( "unicode/utf8" ) +// position represents the current position of the reader in the buffer. It has +// both a row and column, as well as a previous column. We need that previous +// column to figure out our position when backtracking with reader.unreadRune(). type position struct { col uint row uint prevCol uint } +// String returns the position of the last-processed rune in the buffer in the +// standard ‘row:col’ format, while starting at 1:1 to be vim-compatible. func (p position) String() string { return fmt.Sprintf("%d:%d", p.row+1, p.col) } +// reader represents the actual parser. It has both an underlying buffered +// reader, and a position. type reader struct { r *bufio.Reader pos position @@ -39,6 +46,10 @@ func (reader *reader) peekRune() (rune, error) { return r, nil } +// unreadRune moves the parser one rune back, allowing for basic backtracking. +// You can only safely call reader.unreadRune() once before reading again. If +// not you will risk messing up the parsers position tracking if you unread +// multiple newlines. func (reader *reader) unreadRune() error { if reader.pos.col == 0 { reader.pos.col = reader.pos.prevCol @@ -50,6 +61,8 @@ func (reader *reader) unreadRune() error { return reader.r.UnreadRune() } +// readRune reads and returns the next rune in the readers buffer. It is just a +// wrapper around ‘reader.r.ReadRune()’ that updates the readers position. func (reader *reader) readRune() (rune, error) { r, _, err := reader.r.ReadRune() if r == '\n' { @@ -62,6 +75,8 @@ func (reader *reader) readRune() (rune, error) { return r, err } +// readNonSpaceRune is identical to reader.readRune(), except it skips any runes +// representing spaces (as defined by unicode). func (reader *reader) readNonSpaceRune() (rune, error) { if err := reader.skipSpaces(); err != nil { return 0, err @@ -70,6 +85,9 @@ func (reader *reader) readNonSpaceRune() (rune, error) { return reader.readRune() } +// skipSpaces moves the parser forwards so that the next call to +// ‘reader.readRune()’ is guaranteed to read a non-space rune as defined by +// Unicode. func (reader *reader) skipSpaces() error { for { if r, err := reader.readRune(); err != nil { |