blob: abe073f12b96d917cd984d080788cd1420299aaf (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
|
// SPDX-License-Identifier: GPL-3.0-or-later
package plan
import (
"fmt"
"strconv"
"strings"
)
// MaxIndex returns the highest {N} used in s, 0 when none. It reports the
// same errors Expand does for a malformed placeholder: an unclosed
// placeholder, or {0} (capture groups are numbered from 1). It shares
// Expand's scanner shape: "{{" and "}}" each emit one literal brace, and any
// other "{" opens a placeholder that runs to the next "}".
func MaxIndex(s string) (int, error) {
max := 0
for i := 0; i < len(s); {
switch {
case s[i] == '{' && i+1 < len(s) && s[i+1] == '{':
i += 2
case s[i] == '}' && i+1 < len(s) && s[i+1] == '}':
i += 2
case s[i] == '{':
end := strings.IndexByte(s[i+1:], '}')
if end < 0 {
return 0, fmt.Errorf("unclosed placeholder")
}
body := s[i+1 : i+1+end]
if n, err := strconv.Atoi(body); err == nil {
if n == 0 {
return 0, fmt.Errorf("capture groups are numbered from 1")
}
if n >= 1 && n <= 9 && n > max {
max = n
}
}
i += end + 2
default:
i++
}
}
return max, nil
}
|
