Enumerate over text when finding unquoted char

Enumerating rather than using a while loop saves significant CPU when
looking for an unquoted character. This ends up improving the benchmark
~20% on its own.

Signed-off-by: Chris Marchbanks <[email protected]>

Author: csmarchbanks

prometheus_client/parser.py

@@ -139,27 +139,26 @@ def _next_term(text: str, openmetrics: bool) -> Tuple[str, str]:
     return term.strip(), sublabels.strip()
 
 
-def _next_unquoted_char(text: str, chs: str, startidx: int = 0) -> int:
+def _next_unquoted_char(text: str, chs: Optional[str], startidx: int = 0) -> int:
     """Return position of next unquoted character in tuple, or -1 if not found.
     
     It is always assumed that the first character being checked is not already
     inside quotes.
     """
-    i = startidx
     in_quotes = False
     if chs is None:
         chs = string.whitespace
-    while i < len(text):
-        if text[i] == '"' and not _is_character_escaped(text, i):
+
+    for i, c in enumerate(text[startidx:]):
+        if c == '"' and not _is_character_escaped(text, startidx + i):
             in_quotes = not in_quotes
         if not in_quotes:
-            if text[i] in chs:
-                return i
-        i += 1
+            if c in chs:
+                return startidx + i
     return -1
 
 
-def _last_unquoted_char(text: str, chs: str) -> int:
+def _last_unquoted_char(text: str, chs: Optional[str]) -> int:
     """Return position of last unquoted character in list, or -1 if not found."""
     i = len(text) - 1
     in_quotes = False