python/qmp: add parse_address classmethod

This takes the place of qmp-shell's __get_address function. It also
allows other utilities to share the same parser and syntax for
specifying QMP locations.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 20210603003719.1321369-4-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

python/qemu/qmp/__init__.py

@@ -92,6 +92,12 @@ class QMPResponseError(QMPError):
         self.reply = reply
 
 
+class QMPBadPortError(QMPError):
+    """
+    Unable to parse socket address: Port was non-numerical.
+    """
+
+
 class QEMUMonitorProtocol:
     """
     Provide an API to connect to QEMU via QEMU Monitor Protocol (QMP) and then
@@ -219,6 +225,26 @@ class QEMUMonitorProtocol:
         # Implement context manager exit function.
         self.close()
 
+    @classmethod
+    def parse_address(cls, address: str) -> SocketAddrT:
+        """
+        Parse a string into a QMP address.
+
+        Figure out if the argument is in the port:host form.
+        If it's not, it's probably a file path.
+        """
+        components = address.split(':')
+        if len(components) == 2:
+            try:
+                port = int(components[1])
+            except ValueError:
+                msg = f"Bad port: '{components[1]}' in '{address}'."
+                raise QMPBadPortError(msg) from None
+            return (components[0], port)
+
+        # Treat as filepath.
+        return address
+
     def connect(self, negotiate: bool = True) -> Optional[QMPMessage]:
         """
         Connect to the QMP Monitor and perform capabilities negotiation.