96 lines
2.1 KiB
Go
96 lines
2.1 KiB
Go
package file
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import (
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"encoding/json"
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"strings"
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"unicode/utf8"
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)
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type Source struct {
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contents []rune
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lineOffsets []int32
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}
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func NewSource(contents string) *Source {
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s := &Source{
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contents: []rune(contents),
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}
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s.updateOffsets()
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return s
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}
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func (s *Source) MarshalJSON() ([]byte, error) {
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return json.Marshal(s.contents)
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}
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func (s *Source) UnmarshalJSON(b []byte) error {
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contents := make([]rune, 0)
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err := json.Unmarshal(b, &contents)
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if err != nil {
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return err
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}
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s.contents = contents
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s.updateOffsets()
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return nil
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}
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func (s *Source) Content() string {
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return string(s.contents)
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}
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func (s *Source) Snippet(line int) (string, bool) {
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charStart, found := s.findLineOffset(line)
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if !found || len(s.contents) == 0 {
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return "", false
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}
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charEnd, found := s.findLineOffset(line + 1)
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if found {
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return string(s.contents[charStart : charEnd-1]), true
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}
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return string(s.contents[charStart:]), true
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}
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// updateOffsets compute line offsets up front as they are referred to frequently.
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func (s *Source) updateOffsets() {
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lines := strings.Split(string(s.contents), "\n")
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offsets := make([]int32, len(lines))
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var offset int32
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for i, line := range lines {
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offset = offset + int32(utf8.RuneCountInString(line)) + 1
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offsets[int32(i)] = offset
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}
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s.lineOffsets = offsets
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}
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// findLineOffset returns the offset where the (1-indexed) line begins,
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// or false if line doesn't exist.
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func (s *Source) findLineOffset(line int) (int32, bool) {
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if line == 1 {
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return 0, true
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} else if line > 1 && line <= len(s.lineOffsets) {
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offset := s.lineOffsets[line-2]
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return offset, true
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}
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return -1, false
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}
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// findLine finds the line that contains the given character offset and
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// returns the line number and offset of the beginning of that line.
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// Note that the last line is treated as if it contains all offsets
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// beyond the end of the actual source.
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func (s *Source) findLine(characterOffset int32) (int32, int32) {
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var line int32 = 1
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for _, lineOffset := range s.lineOffsets {
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if lineOffset > characterOffset {
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break
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} else {
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line++
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}
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}
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if line == 1 {
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return line, 0
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}
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return line, s.lineOffsets[line-2]
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}
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