add read buffer to improve performance

src/SSHLibrary/client.py

@@ -116,6 +116,7 @@ def __init__(self, host, alias=None, port=22, timeout=3, newline='LF',
         self._scp_all_client = None
         self._shell = None
         self._started_commands = []
+        self._receive_buffer = ""
         self.client = self._get_client()
         self.width = width
         self.height = height
@@ -412,7 +413,9 @@ def read(self, delay=None):
         output = self.shell.read()
         if delay:
             output += self._delayed_read(delay)
-        return self._decode(output)
+        output = self._receive_buffer + self._decode(output)
+        self._receive_buffer = ""
+        return output
 
     def _delayed_read(self, delay):
         delay = TimeEntry(delay).value
@@ -434,6 +437,11 @@ def read_char(self):
 
         :returns: A single char read from the output.
         """
+        if self._receive_buffer:
+            char = self._receive_buffer[0]
+            self._receive_buffer = self._receive_buffer[1:]
+            return char
+
         server_output = b''
         while True:
             try:
@@ -464,18 +472,44 @@ def read_until(self, expected):
         return self._read_until(lambda s: expected in s, expected)
 
     def _read_until(self, matcher, expected, timeout=None):
-        output = ''
         timeout = TimeEntry(timeout) if timeout else self.config.get('timeout')
         max_time = time.time() + timeout.value
         while time.time() < max_time:
-            char = self.read_char()
-            if not char:
-                time.sleep(.00001)  # Release GIL so paramiko I/O thread can run
-            output += char
-            if matcher(output):
+            undecoded = self._single_complete_read_to_buffer(max_time)
+            if undecoded:
+                self._receive_buffer += undecoded.decode(
+                    self.config.encoding, "ignore"
+                )
+            match = matcher(self._receive_buffer)
+            if match:
+                if hasattr(match, "end"):
+                    end = match.end()
+                else:
+                    end = self._receive_buffer.index(expected) + len(expected)
+                output = self._receive_buffer[0:end]
+                self._receive_buffer = self._receive_buffer[end:]
                 return output
+        output = self._receive_buffer
+        self._receive_buffer = ""
         raise SSHClientException(f"No match found for '{expected}' in {timeout}\nOutput:\n{output}.")
 
+    def _single_complete_read_to_buffer(self, max_time):
+        """Fill receive buffer with a single read with completed
+        last character.
+        In case of timeout, leftover bytes are returned.
+        """
+        server_output = self.shell.read()
+        while time.time() < max_time:
+            try:
+                self._receive_buffer += self._decode(server_output)
+                return None
+            except UnicodeDecodeError as e:
+                if e.reason == 'unexpected end of data':
+                    server_output += self.shell.read_byte()
+                else:
+                    raise
+        return server_output
+
     def read_until_newline(self):
         """Reads output from the current shell until a newline character is
         encountered or the timeout expires.
@@ -556,6 +590,7 @@ def read_until_regexp_with_prefix(self, regexp, prefix):
         Read and return from output until regexp matches prefix + output.
 
         :param regexp: a pattern or a compiled regexp object used for matching
+        :param str prefix: The prefix string added to output to be matched against
         :raises SSHClientException: if match is not found in prefix+output when
             timeout expires.
 
@@ -565,15 +600,24 @@ def read_until_regexp_with_prefix(self, regexp, prefix):
             regexp = re.compile(regexp)
         matcher = regexp.search
         expected = regexp.pattern
-        ret = ""
         timeout = self.config.get('timeout')
-        start_time = time.time()
-        while time.time() < float(timeout.value) + start_time:
-            ret += self.read_char()
-            if matcher(prefix + self._encode(ret)):
+        max_time = time.time() + float(timeout.value)
+        while time.time() < max_time:
+            undecoded = self._single_complete_read_to_buffer(max_time)
+            if undecoded:
+                self._receive_buffer += undecoded.decode(
+                    self.config.encoding, "ignore"
+                )
+            match = matcher(prefix + self._receive_buffer)
+            if match:
+                end = match.end() - len(prefix)
+                ret = self._receive_buffer[0:end]
+                self._receive_buffer = self._receive_buffer[end:]
                 return ret
+        output = self._receive_buffer
+        self._receive_buffer = ""
         raise SSHClientException(
-            f"No match found for '{expected}' in {timeout}\nOutput:\n{ret}")
+            f"No match found for '{expected}' in {timeout}\nOutput:\n{output}")
 
     def write_until_expected(self, text, expected, timeout, interval):
         """Writes `text` repeatedly in the current shell until the `expected`
@@ -597,18 +641,17 @@ def write_until_expected(self, text, expected, timeout, interval):
 
         :returns: The read output, including the encountered `expected` text.
         """
-        expected = self._encode(expected)
         interval = TimeEntry(interval)
         timeout = TimeEntry(timeout)
         max_time = time.time() + timeout.value
         while time.time() < max_time:
             self.write(text)
             try:
-                return self._read_until(lambda s: expected in self._encode(s), expected,
+                return self._read_until(lambda s: expected in s, expected,
                                         timeout=interval.value)
             except SSHClientException:
                 pass
-        raise SSHClientException(f"No match found for '{self._decode(expected)}' in {timeout}.")
+        raise SSHClientException(f"No match found for '{expected}' in {timeout}.")
 
     def put_file(self, source, destination='.', mode='0o744', newline='',
                  scp='OFF', scp_preserve_times=False):