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