Use a read buffer for input in pyrepl

Previously we were reading one byte at a time, which causes much slower IO than necessary. Instead, read in chunks, processing previously read data before asking for more. Signed-off-by: Matt Wozniski <mwozniski@bloomberg.net>
python · pablogsal · Jun 11, 2024 · Jun 7, 2024 · Jun 7, 2024 · Jun 7, 2024
commit 0c4a0ccdcefa368dbb9e6fdc887ba8bc9b9c8ca8
@@ -150,6 +150,8 @@ def __init__(
 
         self.pollob = poll()
         self.pollob.register(self.input_fd, select.POLLIN)
+        self.input_buffer = b""
+        self.input_buffer_pos = 0
         curses.setupterm(term or None, self.output_fd)
         self.term = term
 
@@ -197,6 +199,18 @@ def _my_getstr(cap: str, optional: bool = False) -> bytes | None:
         self.event_queue = EventQueue(self.input_fd, self.encoding)
         self.cursor_visible = 1
 
+    def __read(self, n: int) -> bytes:
+        if not self.input_buffer or self.input_buffer_pos >= len(self.input_buffer):
+            self.input_buffer = os.read(self.input_fd, 10000)
+
+        ret = self.input_buffer[self.input_buffer_pos : self.input_buffer_pos + n]
+        self.input_buffer_pos += len(ret)
+        if self.input_buffer_pos >= len(self.input_buffer):
+            self.input_buffer = b""
+            self.input_buffer_pos = 0
+        return ret
+
+
     def change_encoding(self, encoding: str) -> None:
         """
         Change the encoding used for I/O operations.
@@ -373,7 +387,7 @@ def get_event(self, block: bool = True) -> Event | None:
         while self.event_queue.empty():
             while True:
                 try:
-                    self.push_char(os.read(self.input_fd, 1))
+                    self.push_char(self.__read(1))
                 except OSError as err:
                     if err.errno == errno.EINTR:
                         if not self.event_queue.empty():
@@ -491,7 +505,7 @@ def getpending(self):
                 e.raw += e.raw
 
             amount = struct.unpack("i", ioctl(self.input_fd, FIONREAD, b"\0\0\0\0"))[0]
-            raw = os.read(self.input_fd, amount)
+            raw = self.__read(amount)
             data = str(raw, self.encoding, "replace")
             e.data += data
             e.raw += raw
@@ -514,7 +528,7 @@ def getpending(self):
                 e.raw += e.raw
 
             amount = 10000
-            raw = os.read(self.input_fd, amount)
+            raw = self.__read(amount)
             data = str(raw, self.encoding, "replace")
             e.data += data
             e.raw += raw