| 🛟 Updated. 28d5985 k33g 20h ago | 1 | package buffer |
| 2 | |
| 3 | import "strings" |
| 4 | |
| 5 | // DefaultTabWidth is how many columns a tab character spans on screen unless |
| 6 | // the caller says otherwise. Eight matches gofmt's own assumption. |
| 7 | const DefaultTabWidth = 8 |
| 8 | |
| 9 | // Buffer is the text of one file, held as a slice of lines. |
| 10 | // |
| 11 | // Every buffer has at least one line, so an empty buffer is a single empty |
| 12 | // line rather than no line at all. That invariant removes a special case from |
| 13 | // every method below. |
| 14 | // |
| 15 | // A Buffer is not safe for concurrent use. |
| 16 | type Buffer struct { |
| 17 | lines [][]rune |
| 18 | |
| 19 | path string |
| 20 | modified bool |
| 21 | crlf bool // the file used \r\n line endings when it was read |
| 22 | finalNewline bool // the file ended with a line terminator |
| 23 | |
| 24 | cursor Position |
| 25 | anchor *Position // start of the selection, nil when nothing is selected |
| 26 | |
| 27 | tabWidth int |
| 28 | |
| 29 | undoStack []edit |
| 30 | redoStack []edit |
| 31 | coalesce bool // the next edit may merge into the previous undo entry |
| 32 | |
| 33 | revision int // bumped on every change, so caches know when to rebuild |
| 34 | } |
| 35 | |
| 36 | // New returns an empty buffer holding a single empty line. |
| 37 | // |
| 38 | // Its text is the empty string, not a lone line feed: the buffer holds exactly |
| 39 | // what was put into it, and nothing is put into a new one. Pressing Enter at |
| 40 | // the end of the last line is what gives a file its trailing newline, here as |
| 41 | // in any other editor. |
| 42 | // |
| 43 | // b := buffer.New() |
| 44 | // b.Insert("package main\n") |
| 45 | // fmt.Println(b.LineCount()) // 2 |
| 46 | func New() *Buffer { |
| 47 | return &Buffer{ |
| 48 | lines: [][]rune{{}}, |
| 49 | tabWidth: DefaultTabWidth, |
| 50 | } |
| 51 | } |
| 52 | |
| 53 | // NewFromString returns a buffer holding text, split on line feeds. |
| 54 | // |
| 55 | // A trailing line feed is remembered rather than turned into an extra empty |
| 56 | // line, so that saving the buffer reproduces the input byte for byte. |
| 57 | // |
| 58 | // b := buffer.NewFromString("package main\n\nfunc main() {}\n") |
| 59 | // fmt.Println(b.LineCount()) // 3 |
| 60 | func NewFromString(text string) *Buffer { |
| 61 | b := New() |
| 62 | b.SetText(text) |
| 63 | b.modified = false |
| 64 | b.clearHistory() |
| 65 | return b |
| 66 | } |
| 67 | |
| 68 | // SetText replaces the whole content of the buffer, resets the cursor to the |
| 69 | // start and drops the selection. The undo history is kept, so loading a |
| 70 | // template over a buffer stays undoable. |
| 71 | func (b *Buffer) SetText(text string) { |
| 72 | b.crlf = strings.Contains(text, "\r\n") |
| 73 | if b.crlf { |
| 74 | text = strings.ReplaceAll(text, "\r\n", "\n") |
| 75 | } |
| 76 | |
| 77 | b.finalNewline = strings.HasSuffix(text, "\n") |
| 78 | if b.finalNewline { |
| 79 | text = strings.TrimSuffix(text, "\n") |
| 80 | } |
| 81 | |
| 82 | b.ReplaceRange(b.wholeRange(), text) |
| 83 | b.SetCursor(Position{}) |
| 84 | b.ClearSelection() |
| 85 | } |
| 86 | |
| 87 | // Text returns the whole content of the buffer, with the line endings the file |
| 88 | // was read with and the trailing newline it had, if any. |
| 89 | func (b *Buffer) Text() string { |
| 90 | sep := "\n" |
| 91 | if b.crlf { |
| 92 | sep = "\r\n" |
| 93 | } |
| 94 | |
| 95 | parts := make([]string, len(b.lines)) |
| 96 | for i, line := range b.lines { |
| 97 | parts[i] = string(line) |
| 98 | } |
| 99 | |
| 100 | text := strings.Join(parts, sep) |
| 101 | if b.finalNewline { |
| 102 | text += sep |
| 103 | } |
| 104 | return text |
| 105 | } |
| 106 | |
| 107 | // LineCount returns the number of lines, always at least one. |
| 108 | func (b *Buffer) LineCount() int { |
| 109 | return len(b.lines) |
| 110 | } |
| 111 | |
| 112 | // Line returns line i as a string, or the empty string if i is out of range. |
| 113 | func (b *Buffer) Line(i int) string { |
| 114 | if i < 0 || i >= len(b.lines) { |
| 115 | return "" |
| 116 | } |
| 117 | return string(b.lines[i]) |
| 118 | } |
| 119 | |
| 120 | // LineRunes returns a copy of line i. Callers may modify the result freely; it |
| 121 | // is disconnected from the buffer. |
| 122 | func (b *Buffer) LineRunes(i int) []rune { |
| 123 | if i < 0 || i >= len(b.lines) { |
| 124 | return nil |
| 125 | } |
| 126 | out := make([]rune, len(b.lines[i])) |
| 127 | copy(out, b.lines[i]) |
| 128 | return out |
| 129 | } |
| 130 | |
| 131 | // LineLen returns the number of runes on line i, or zero if i is out of range. |
| 132 | func (b *Buffer) LineLen(i int) int { |
| 133 | if i < 0 || i >= len(b.lines) { |
| 134 | return 0 |
| 135 | } |
| 136 | return len(b.lines[i]) |
| 137 | } |
| 138 | |
| 139 | // Path returns the file this buffer was read from, or the empty string for a |
| 140 | // buffer that has never been associated with a file. |
| 141 | func (b *Buffer) Path() string { return b.path } |
| 142 | |
| 143 | // SetPath records the file this buffer belongs to, as Save As does. |
| 144 | func (b *Buffer) SetPath(path string) { b.path = path } |
| 145 | |
| 146 | // Modified reports whether the buffer has unsaved changes. Undoing back to the |
| 147 | // state that was last saved still counts as modified: the flag errs towards |
| 148 | // offering to save rather than towards losing work. |
| 149 | func (b *Buffer) Modified() bool { return b.modified } |
| 150 | |
| 151 | // Revision is a counter bumped on every change to the text. Two reads that |
| 152 | // return the same number are guaranteed to have seen the same text, which is |
| 153 | // what lets the syntax highlighter skip work between redraws. |
| 154 | func (b *Buffer) Revision() int { return b.revision } |
| 155 | |
| 156 | // TabWidth returns how many columns a tab character spans on screen. |
| 157 | func (b *Buffer) TabWidth() int { return b.tabWidth } |
| 158 | |
| 159 | // SetTabWidth sets how many columns a tab character spans on screen. Values |
| 160 | // below one are ignored, since a zero-width tab would make columns ambiguous. |
| 161 | func (b *Buffer) SetTabWidth(width int) { |
| 162 | if width > 0 { |
| 163 | b.tabWidth = width |
| 164 | } |
| 165 | } |
| 166 | |
| 167 | // wholeRange returns the range covering every character in the buffer. |
| 168 | func (b *Buffer) wholeRange() Range { |
| 169 | last := len(b.lines) - 1 |
| 170 | return Range{ |
| 171 | Start: Position{}, |
| 172 | End: Position{Line: last, Col: len(b.lines[last])}, |
| 173 | } |
| 174 | } |
| 175 | |
| 176 | // lineAt returns line i, clamped into range. A buffer always holds at least |
| 177 | // one line, so the result is never nil. |
| 178 | func (b *Buffer) lineAt(i int) []rune { |
| 179 | if i < 0 { |
| 180 | return b.lines[0] |
| 181 | } |
| 182 | if i >= len(b.lines) { |
| 183 | return b.lines[len(b.lines)-1] |
| 184 | } |
| 185 | return b.lines[i] |
| 186 | } |
| 187 | |
| 188 | // clamp moves p to the nearest position that actually exists in the buffer. |
| 189 | func (b *Buffer) clamp(p Position) Position { |
| 190 | if p.Line < 0 { |
| 191 | return Position{} |
| 192 | } |
| 193 | if p.Line >= len(b.lines) { |
| 194 | last := len(b.lines) - 1 |
| 195 | return Position{Line: last, Col: len(b.lines[last])} |
| 196 | } |
| 197 | if p.Col < 0 { |
| 198 | p.Col = 0 |
| 199 | } |
| 200 | if p.Col > len(b.lines[p.Line]) { |
| 201 | p.Col = len(b.lines[p.Line]) |
| 202 | } |
| 203 | return p |
| 204 | } |
| 205 | |
| 206 | // splitLines turns text into lines of runes, always returning at least one. |
| 207 | func splitLines(text string) [][]rune { |
| 208 | parts := strings.Split(text, "\n") |
| 209 | lines := make([][]rune, len(parts)) |
| 210 | for i, part := range parts { |
| 211 | lines[i] = []rune(part) |
| 212 | } |
| 213 | return lines |
| 214 | } |