hfp: Implement initiate SLC procedure for HFP-HF

bumble/at.py

@@ -0,0 +1,85 @@
+# Copyright 2023 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from typing import List, Union
+
+
+def tokenize_parameters(buffer: bytes) -> List[bytes]:
+    """Split input parameters into tokens.
+    Removes space characters outside of double quote blocks:
+    T-rec-V-25 - 5.2.1 Command line general format: "Space characters (IA5 2/0)
+    are ignored [..], unless they are embedded in numeric or string constants"
+    Raises ValueError in case of invalid input string."""
+
+    tokens = []
+    in_quotes = False
+    token = bytearray()
+    for b in buffer:
+        char = bytearray([b])
+
+        if in_quotes:
+            token.extend(char)
+            if char == b'\"':
+                in_quotes = False
+                tokens.append(token[1:-1])
+                token = bytearray()
+        else:
+            if char == b' ':
+                pass
+            elif char == b',' or char == b')':
+                tokens.append(token)
+                tokens.append(char)
+                token = bytearray()
+            elif char == b'(':
+                if len(token) > 0:
+                    raise ValueError("open_paren following regular character")
+                tokens.append(char)
+            elif char == b'"':
+                if len(token) > 0:
+                    raise ValueError("quote following regular character")
+                in_quotes = True
+                token.extend(char)
+            else:
+                token.extend(char)
+
+    tokens.append(token)
+    return [bytes(token) for token in tokens if len(token) > 0]
+
+
+def parse_parameters(buffer: bytes) -> List[Union[bytes, list]]:
+    """Parse the parameters using the comma and parenthesis separators.
+    Raises ValueError in case of invalid input string."""
+
+    tokens = tokenize_parameters(buffer)
+    accumulator: List[list] = [[]]
+    current: Union[bytes, list] = bytes()
+
+    for token in tokens:
+        if token == b',':
+            accumulator[-1].append(current)
+            current = bytes()
+        elif token == b'(':
+            accumulator.append([])
+        elif token == b')':
+            if len(accumulator) < 2:
+                raise ValueError("close_paren without matching open_paren")
+            accumulator[-1].append(current)
+            current = accumulator.pop()
+        else:
+            current = token
+
+    accumulator[-1].append(current)
+    if len(accumulator) > 1:
+        raise ValueError("missing close_paren")
+    return accumulator[0]