changeset 50400:95acba2c29f6

encoding: avoid quadratic time complexity when json-encoding non-UTF8 strings Apparently the code uses "+=" with a bytes object, which is linear-time, so the whole encoding is quadratic-time. This patch makes us use a bytearray object, instead, which has a(n amortized-)constant-time append operation. The encoding is still not particularly fast, but at least a 10MB file takes tens of seconds, not many hours to encode.
author Arseniy Alekseyev <aalekseyev@janestreet.com>
date Mon, 06 Mar 2023 11:27:57 +0000
parents bcf54837241d
children dd42156b6441
files mercurial/encoding.py
diffstat 1 files changed, 4 insertions(+), 4 deletions(-) [+]
line wrap: on
line diff
--- a/mercurial/encoding.py	Wed Mar 08 11:01:11 2023 +0100
+++ b/mercurial/encoding.py	Mon Mar 06 11:27:57 2023 +0000
@@ -657,7 +657,7 @@
             pass
 
     s = pycompat.bytestr(s)
-    r = b""
+    r = bytearray()
     pos = 0
     l = len(s)
     while pos < l:
@@ -673,7 +673,7 @@
             c = unichr(0xDC00 + ord(s[pos])).encode('utf-8', _utf8strict)
             pos += 1
         r += c
-    return r
+    return bytes(r)
 
 
 def fromutf8b(s):
@@ -712,7 +712,7 @@
     # helper again to walk the string without "decoding" it.
 
     s = pycompat.bytestr(s)
-    r = b""
+    r = bytearray()
     pos = 0
     l = len(s)
     while pos < l:
@@ -722,4 +722,4 @@
         if b"\xed\xb0\x80" <= c <= b"\xed\xb3\xbf":
             c = pycompat.bytechr(ord(c.decode("utf-8", _utf8strict)) & 0xFF)
         r += c
-    return r
+    return bytes(r)