# HG changeset patch
# User Manuel Jacob <me@manueljacob.de>
# Date 1653171058 -7200
#      Sun May 22 00:10:58 2022 +0200
# Node ID 5207225239557efd1d7d0bb5d5093763dca5191b
# Parent  4c57ce494a4e7ddd561a637abee09b2a9e680eb2
worker: implement _blockingreader.readinto() (issue6444)

The core logic for readinto() was already implemented in read(), so this is
mostly extracting that code into its own method.

Another fix for issue6444 was committed to the stable branch: 2fe4efaa59af.
That is a minimal fix that implements readinto() only on Python versions that
require readinto() (3.8.0 and 3.8.1), which is the right approach for the
stable branch. However, I think that this changeset has its value. It improves
performance in cases when pickle can use readinto(), it reduces code
duplication compared to the other patch, and by defining readinto() on all
Python versions, it makes behavior more consistent across all Python versions.
This changesets reverts the other change.

diff --git a/mercurial/worker.py b/mercurial/worker.py
--- a/mercurial/worker.py
+++ b/mercurial/worker.py
@@ -79,35 +79,12 @@
     def __init__(self, wrapped):
         self._wrapped = wrapped
 
-    # Do NOT implement readinto() by making it delegate to
-    # _wrapped.readinto(), since that is unbuffered. The unpickler is fine
-    # with just read() and readline(), so we don't need to implement it.
-
-    if (3, 8, 0) <= sys.version_info[:3] < (3, 8, 2):
-
-        # This is required for python 3.8, prior to 3.8.2.  See issue6444.
-        def readinto(self, b):
-            pos = 0
-            size = len(b)
-
-            while pos < size:
-                ret = self._wrapped.readinto(b[pos:])
-                if not ret:
-                    break
-                pos += ret
-
-            return pos
-
     def readline(self):
         return self._wrapped.readline()
 
-    # issue multiple reads until size is fulfilled (or EOF is encountered)
-    def read(self, size=-1):
-        if size < 0:
-            return self._wrapped.readall()
-
-        buf = bytearray(size)
+    def readinto(self, buf):
         pos = 0
+        size = len(buf)
 
         with memoryview(buf) as view:
             while pos < size:
@@ -117,7 +94,16 @@
                     break
                 pos += ret
 
-        del buf[pos:]
+        return pos
+
+    # issue multiple reads until size is fulfilled (or EOF is encountered)
+    def read(self, size=-1):
+        if size < 0:
+            return self._wrapped.readall()
+
+        buf = bytearray(size)
+        n_read = self.readinto(buf)
+        del buf[n_read:]
         return bytes(buf)