time: avoid autofree parser temporaries

Author: medvednikov

vlib/time/date_time_parser.v

@@ -7,6 +7,20 @@ mut:
 	current_pos_datetime int
 }
 
+@[inline]
+fn (p &DateTimeParser) matches_at(chars string) bool {
+	end := p.current_pos_datetime + chars.len
+	if end > p.datetime.len {
+		return false
+	}
+	for i in 0 .. chars.len {
+		if p.datetime[p.current_pos_datetime + i] != chars[i] {
+			return false
+		}
+	}
+	return true
+}
+
 fn (mut p DateTimeParser) next(length int) !string {
 	if p.current_pos_datetime + length > p.datetime.len {
 		return error('end of string')
@@ -24,38 +38,61 @@ fn (mut p DateTimeParser) peek(length int) !string {
 }
 
 fn (mut p DateTimeParser) must_be_int(length int) !int {
-	val := p.next(length)!
-	if !val.contains_only('0123456789') {
-		return error('expected int, found: ${val}')
+	end := p.current_pos_datetime + length
+	if end > p.datetime.len {
+		return error('end of string')
+	}
+	mut val := 0
+	for i in p.current_pos_datetime .. end {
+		ch := p.datetime[i]
+		if ch < `0` || ch > `9` {
+			return error('expected int, found: ${p.datetime[p.current_pos_datetime..end]}')
+		}
+		val = val * 10 + int(ch - `0`)
 	}
-	return val.int()
+	p.current_pos_datetime = end
+	return val
 }
 
 fn (mut p DateTimeParser) must_be_int_with_minimum_length(min int, max int, allow_leading_zero bool) !int {
-	mut length := max + 1 - min
-	mut val := ''
-	for _ in 0 .. length {
-		tok := p.peek(1) or { break }
-		if !tok.contains_only('0123456789') {
+	max_len := max + 1 - min
+	start := p.current_pos_datetime
+	mut end := start
+	for _ in 0 .. max_len {
+		if end >= p.datetime.len {
 			break
 		}
-		p.next(1)!
-		val += tok
+		ch := p.datetime[end]
+		if ch < `0` || ch > `9` {
+			break
+		}
+		end++
 	}
-	if val.len < min {
-		return error('expected int with a minimum length of ${min}, found: ${val.len}')
+	if end - start < min {
+		return error('expected int with a minimum length of ${min}, found: ${end - start}')
 	}
-	if !allow_leading_zero && val.starts_with('0') {
+	if !allow_leading_zero && p.datetime[start] == `0` {
 		return error('0 is not allowed for this format')
 	}
-	return val.int()
+	mut val := 0
+	for i in start .. end {
+		val = val * 10 + int(p.datetime[i] - `0`)
+	}
+	p.current_pos_datetime = end
+	return val
 }
 
 fn (mut p DateTimeParser) must_be_string(must string) ! {
-	val := p.next(must.len)!
-	if val != must {
-		return error('invalid string: "${val}"!="${must}" at: ${p.current_pos_datetime}')
+	start := p.current_pos_datetime
+	end := p.current_pos_datetime + must.len
+	if end > p.datetime.len {
+		return error('end of string')
+	}
+	if !p.matches_at(must) {
+		p.current_pos_datetime = end
+		return error('invalid string: "${p.datetime[start..end]}"!="${must}" at: ${p.current_pos_datetime}')
 	}
+	p.current_pos_datetime = end
 }
 
 fn (mut p DateTimeParser) must_be_string_one_of(oneof []string) !string {
@@ -70,22 +107,19 @@ fn (mut p DateTimeParser) must_be_string_one_of(oneof []string) !string {
 
 fn (mut p DateTimeParser) must_be_valid_month() !int {
 	for v in long_months {
-		if p.current_pos_datetime + v.len < p.datetime.len {
-			month_name := p.datetime[p.current_pos_datetime..p.current_pos_datetime + v.len]
-			if v == month_name {
-				p.current_pos_datetime += v.len
-				return long_months.index(month_name) + 1
-			}
+		if p.current_pos_datetime + v.len < p.datetime.len && p.matches_at(v) {
+			p.current_pos_datetime += v.len
+			return long_months.index(v) + 1
 		}
 	}
 	return error_invalid_time(0, 'invalid month name, at: ${p.current_pos_datetime}')
 }
 
 fn (mut p DateTimeParser) must_be_valid_three_letter_month() !int {
 	if p.current_pos_datetime + 3 < p.datetime.len {
-		letters := p.datetime[p.current_pos_datetime..p.current_pos_datetime + 3]
 		for m := 1; m <= long_months.len; m++ {
-			if months_string[(m - 1) * 3..m * 3] == letters {
+			token := months_string[(m - 1) * 3..m * 3]
+			if p.matches_at(token) {
 				p.current_pos_datetime += 3
 				return m
 			}
@@ -96,22 +130,19 @@ fn (mut p DateTimeParser) must_be_valid_three_letter_month() !int {
 
 fn (mut p DateTimeParser) must_be_valid_week_day() !string {
 	for v in long_days {
-		if p.current_pos_datetime + v.len < p.datetime.len {
-			weekday := p.datetime[p.current_pos_datetime..p.current_pos_datetime + v.len]
-			if v == weekday {
-				p.current_pos_datetime += v.len
-				return weekday
-			}
+		if p.current_pos_datetime + v.len < p.datetime.len && p.matches_at(v) {
+			p.current_pos_datetime += v.len
+			return v
 		}
 	}
 	return error_invalid_time(0, 'invalid weekday, at: ${p.current_pos_datetime}')
 }
 
 fn (mut p DateTimeParser) must_be_valid_two_letter_week_day() !int {
 	if p.current_pos_datetime + 2 < p.datetime.len {
-		letters := p.datetime[p.current_pos_datetime..p.current_pos_datetime + 2]
 		for d := 1; d <= long_days.len; d++ {
-			if days_string[(d - 1) * 3..d * 3 - 1] == letters {
+			token := days_string[(d - 1) * 3..d * 3 - 1]
+			if p.matches_at(token) {
 				p.current_pos_datetime += 2
 				return d
 			}
@@ -122,9 +153,9 @@ fn (mut p DateTimeParser) must_be_valid_two_letter_week_day() !int {
 
 fn (mut p DateTimeParser) must_be_valid_three_letter_week_day() !int {
 	if p.current_pos_datetime + 3 < p.datetime.len {
-		letters := p.datetime[p.current_pos_datetime..p.current_pos_datetime + 3]
 		for d := 1; d <= long_days.len; d++ {
-			if days_string[(d - 1) * 3..d * 3] == letters {
+			token := days_string[(d - 1) * 3..d * 3]
+			if p.matches_at(token) {
 				p.current_pos_datetime += 3
 				return d
 			}
@@ -135,18 +166,17 @@ fn (mut p DateTimeParser) must_be_valid_three_letter_week_day() !int {
 
 fn extract_tokens(s string) ![]string {
 	mut tokens := []string{}
-	mut current := ''
-	for r in s {
-		if current.contains_only(r.ascii_str()) || current == '' {
-			current += r.ascii_str()
-		} else {
-			tokens << current
-			current = r.ascii_str()
-		}
+	if s.len == 0 {
+		return tokens
 	}
-	if current != '' {
-		tokens << current
+	mut start := 0
+	for i := 1; i < s.len; i++ {
+		if s[i] != s[i - 1] {
+			tokens << s[start..i]
+			start = i
+		}
 	}
+	tokens << s[start..s.len]
 	return tokens
 }