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Diffstat (limited to 'parser/reader.go')
-rw-r--r--parser/reader.go18
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 {