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gh-153568: Skip newline translation for source without carriage returns #153584

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Merged
pablogsal merged 1 commit into from
Sep 14, 2026
+16 −7
Merged

gh-153568: Skip newline translation for source without carriage returns #153584

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2 changes: 2 additions & 0 deletions .../NEWS.d/next/Core_and_Builtins/2026-07-11-16-53-21.gh-issue-153568.newlines.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Speed up the tokenizer by copying source text verbatim when it contains no
carriage returns.
21 changes: 14 additions & 7 deletions Parser/tokenizer/decoder.c
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Original file line number Diff line number Diff line change
Expand Up @@ -87,15 +87,22 @@ _PyTok_NormalizeNewlines(const char *data, Py_ssize_t len, int preserve_crlf,
return NULL;
}
Py_ssize_t write = 0;
for (Py_ssize_t read = 0; read < len; read++) {
char c = data[read];
if (!preserve_crlf && c == '\r') {
if (read + 1 < len && data[read + 1] == '\n') {
read++;
if (memchr(data, '\r', len) == NULL) {
// No carriage returns: nothing to translate, copy verbatim.
memcpy(result, data, len);
write = len;
}
else {
for (Py_ssize_t read = 0; read < len; read++) {
char c = data[read];
if (!preserve_crlf && c == '\r') {
if (read + 1 < len && data[read + 1] == '\n') {
read++;
}
c = '\n';
}
c = '\n';
result[write++] = c;
}
result[write++] = c;
}
int implicit = add_final_newline && write > 0 && result[write - 1] != '\n';
if (implicit) {
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