add signature algorithm debug helper

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>

library/ssl_debug_helpers.h

@@ -39,7 +39,7 @@ const char *mbedtls_tls_prf_types_str( mbedtls_tls_prf_types in );
 
 const char *mbedtls_ssl_key_export_type_str( mbedtls_ssl_key_export_type in );
 
-
+const char *mbedtls_ssl_sig_alg_to_str( uint16_t in );
 
 #endif /* MBEDTLS_DEBUG_C */
 

scripts/generate_ssl_debug_helpers.py

@@ -88,7 +88,8 @@ def preprocess_c_source_code(source, *classes):
                 if has_instance is False:
                     has_instance = True
                     yield pair_start, start_line
-                yield instance.span()[0], instance
+                if instance:
+                    yield instance.span()[0], instance
         if has_instance:
             yield start, end_line
 
@@ -234,6 +235,63 @@ class EnumDefinition:
                            prototype=self._prototype)
         return body
 
+class SignatureAlgorithmDefinition:
+    """
+        Generate helper functions for signature algorithms.
+
+        It generates translation function from signature algorithm define to string.
+        Signature algorithm definition looks like:
+        #define MBEDTLS_TLS1_3_SIG_[ upper case signature algorithm ] [ value(hex) ]
+
+        Known limitation:
+        - the definitions SHOULD  exist in same macro blocks.
+    """
+
+    @classmethod
+    def extract(cls, source_code, start=0, end=-1):
+        sig_alg_pattern = re.compile(r'#define\s+(?P<name>MBEDTLS_TLS1_3_SIG_\w+)\s+' +
+                                     r'(?P<value>0[xX][0-9a-fA-F]+)$',
+                                     re.MULTILINE | re.DOTALL)
+        matches = list(sig_alg_pattern.finditer(source_code, start, end))
+        if matches:
+            yield SignatureAlgorithmDefinition(source_code, definitions=matches)
+
+    def __init__(self, source_code, definitions=None):
+        if definitions is None:
+            definitions = []
+        assert isinstance(definitions, list) and definitions
+        self._definitions = definitions
+        self._source = source_code
+
+    def __repr__(self):
+        return 'SigAlgs({})'.format(self._definitions[0].span())
+
+    def span(self):
+        return self._definitions[0].span()
+    def __str__(self):
+        """
+            Generate function for translating value to string
+        """
+        translation_table = []
+        for m in self._definitions:
+            name = m.groupdict()['name']
+            translation_table.append(
+                '\tcase {}:\n\t    return "{}";'.format(name,
+                                                        name[len('MBEDTLS_TLS1_3_SIG_'):].lower())
+                )
+
+        body = textwrap.dedent('''\
+            const char *mbedtls_ssl_sig_alg_to_str( uint16_t in )
+            {{
+                switch( in )
+                {{
+            {translation_table}
+                }};
+
+                return "UNKOWN";
+            }}''')
+        body = body.format(translation_table='\n'.join(translation_table))
+        return body
 
 OUTPUT_C_TEMPLATE = '''\
 /* Automatically generated by generate_ssl_debug_helpers.py. DO NOT EDIT. */
@@ -283,7 +341,9 @@ def generate_ssl_debug_helpers(output_directory, mbedtls_root):
         source_code = remove_c_comments(f.read())
 
     definitions = dict()
-    for start, instance in preprocess_c_source_code(source_code, EnumDefinition):
+    for start, instance in preprocess_c_source_code(source_code,
+                                                    EnumDefinition,
+                                                    SignatureAlgorithmDefinition):
         if start in definitions:
             continue
         if isinstance(instance, EnumDefinition):