42 lines
1.2 KiB
Go
42 lines
1.2 KiB
Go
package parsekit
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import "fmt"
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// Cursor represents the position of a cursor in various ways.
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type Cursor struct {
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Byte int // The cursor offset in bytes, relative to start of file
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Rune int // The cursor offset in UTF8 runes, relative to start of file
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Column int // The column at which the cursor is (0-indexed)
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Line int // The line at which the cursor is (0-indexed)
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}
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// String produces a string representation of the cursor position.
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func (c Cursor) String() string {
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if c.Line == 0 && c.Column == 0 {
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return fmt.Sprintf("start of file")
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}
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return fmt.Sprintf("line %d, column %d", c.Line+1, c.Column+1)
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}
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// Move updates the position of the cursor, based on the provided input string.
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// The input string represents the runes that has been skipped over. This
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// method will take newlines into account to keep track of line numbers and
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// column positions automatically.
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//
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// Note: when you are writing a parser using parsekit, it's unlikely
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// that you will use this method directly. The parsekit package takes care
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// of calling it at the correct time.
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func (c *Cursor) Move(input string) *Cursor {
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c.Byte += len(input)
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for _, r := range input {
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c.Rune++
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if r == '\n' {
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c.Column = 0
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c.Line++
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} else {
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c.Column++
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}
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}
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return c
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}
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