go-tg-screenshot-bot

1
package dbus
2

3
import "net/url"
4

5
// EscapeBusAddressValue implements a requirement to escape the values
6
// in D-Bus server addresses, as defined by the D-Bus specification at
7
// https://dbus.freedesktop.org/doc/dbus-specification.html#addresses.
8
func EscapeBusAddressValue(val string) string {
9
	toEsc := strNeedsEscape(val)
10
	if toEsc == 0 {
11
		// Avoid unneeded allocation/copying.
12
		return val
13
	}
14

15
	// Avoid allocation for short paths.
16
	var buf [64]byte
17
	var out []byte
18
	// Every to-be-escaped byte needs 2 extra bytes.
19
	required := len(val) + 2*toEsc
20
	if required <= len(buf) {
21
		out = buf[:required]
22
	} else {
23
		out = make([]byte, required)
24
	}
25

26
	j := 0
27
	for i := 0; i < len(val); i++ {
28
		if ch := val[i]; needsEscape(ch) {
29
			// Convert ch to %xx, where xx is hex value.
30
			out[j] = '%'
31
			out[j+1] = hexchar(ch >> 4)
32
			out[j+2] = hexchar(ch & 0x0F)
33
			j += 3
34
		} else {
35
			out[j] = ch
36
			j++
37
		}
38
	}
39

40
	return string(out)
41
}
42

43
// UnescapeBusAddressValue unescapes values in D-Bus server addresses,
44
// as defined by the D-Bus specification at
45
// https://dbus.freedesktop.org/doc/dbus-specification.html#addresses.
46
func UnescapeBusAddressValue(val string) (string, error) {
47
	// Looks like url.PathUnescape does exactly what is required.
48
	return url.PathUnescape(val)
49
}
50

51
// hexchar returns an octal representation of a n, where n < 16.
52
// For invalid values of n, the function panics.
53
func hexchar(n byte) byte {
54
	const hex = "0123456789abcdef"
55

56
	// For n >= len(hex), runtime will panic.
57
	return hex[n]
58
}
59

60
// needsEscape tells if a byte is NOT one of optionally-escaped bytes.
61
func needsEscape(c byte) bool {
62
	if 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z' || '0' <= c && c <= '9' {
63
		return false
64
	}
65
	switch c {
66
	case '-', '_', '/', '\\', '.', '*':
67
		return false
68
	}
69

70
	return true
71
}
72

73
// strNeedsEscape tells how many bytes in the string need escaping.
74
func strNeedsEscape(val string) int {
75
	count := 0
76

77
	for i := 0; i < len(val); i++ {
78
		if needsEscape(val[i]) {
79
			count++
80
		}
81
	}
82

83
	return count
84
}
85