func scanFields()

in metric/parse.go [297:393]

• 66 lines of code
• 30 McCabe index (conditional complexity)

func scanFields(buf []byte, i int) (int, []byte, error) {
	start := skipWhitespace(buf, i)
	i = start
	quoted := false

	// tracks how many '=' we've seen
	equals := 0

	// tracks how many commas we've seen
	commas := 0

	for {
		// reached the end of buf?
		if i >= len(buf) {
			break
		}

		// escaped characters?
		if buf[i] == '\\' && i+1 < len(buf) {
			i += 2
			continue
		}

		// If the value is quoted, scan until we get to the end quote
		// Only quote values in the field value since quotes are not significant
		// in the field key
		if buf[i] == '"' && equals > commas {
			quoted = !quoted
			i++
			continue
		}

		// If we see an =, ensure that there is at least on char before and after it
		if buf[i] == '=' && !quoted {
			equals++

			// check for "... =123" but allow "a\ =123"
			if buf[i-1] == ' ' && buf[i-2] != '\\' {
				return i, buf[start:i], makeError("missing field key", buf, i)
			}

			// check for "...a=123,=456" but allow "a=123,a\,=456"
			if buf[i-1] == ',' && buf[i-2] != '\\' {
				return i, buf[start:i], makeError("missing field key", buf, i)
			}

			// check for "... value="
			if i+1 >= len(buf) {
				return i, buf[start:i], makeError("missing field value", buf, i)
			}

			// check for "... value=,value2=..."
			if buf[i+1] == ',' || buf[i+1] == ' ' {
				return i, buf[start:i], makeError("missing field value", buf, i)
			}

			if isNumeric(buf[i+1]) || buf[i+1] == '-' || buf[i+1] == 'N' || buf[i+1] == 'n' {
				var err error
				i, err = scanNumber(buf, i+1)
				if err != nil {
					return i, buf[start:i], err
				}
				continue
			}
			// If next byte is not a double-quote, the value must be a boolean
			if buf[i+1] != '"' {
				var err error
				i, _, err = scanBoolean(buf, i+1)
				if err != nil {
					return i, buf[start:i], err
				}
				continue
			}
		}

		if buf[i] == ',' && !quoted {
			commas++
		}

		// reached end of block?
		if buf[i] == ' ' && !quoted {
			break
		}
		i++
	}

	if quoted {
		return i, buf[start:i], makeError("unbalanced quotes", buf, i)
	}

	// check that all field sections had key and values (e.g. prevent "a=1,b"
	if equals == 0 || commas != equals-1 {
		return i, buf[start:i], makeError("invalid field format", buf, i)
	}

	return i, buf[start:i], nil
}