libcpp: add function to check XID properties

This commit adds a new function intended for checking the XID properties
of a possibly unicode character, as well as the accompanying enum
describing the possible properties.

libcpp/ChangeLog:

	* charset.cc (cpp_check_xid_property): New.
	* include/cpplib.h
	(cpp_check_xid_property): New.
	(enum cpp_xid_property): New.

Signed-off-by: Raiki Tamura <[email protected]>

Author: tamaroning

libcpp/charset.cc

@@ -1332,6 +1332,42 @@ _cpp_uname2c_uax44_lm2 (const char *name, size_t len, char *canon_name)
   return result;
 }
 
+/* Returns flags representing the XID properties of the given codepoint.  */
+unsigned int
+cpp_check_xid_property (cppchar_t c)
+{
+  // fast path for ASCII
+  if (c < 0x80)
+    {
+      if (('A' <= c && c <= 'Z') || ('a' <= c && c <= 'z'))
+	return CPP_XID_START | CPP_XID_CONTINUE;
+      if (('0' <= c && c <= '9') || c == '_')
+	return CPP_XID_CONTINUE;
+    }
+
+  if (c > UCS_LIMIT)
+    return 0;
+
+  int mn, mx, md;
+  mn = 0;
+  mx = ARRAY_SIZE (ucnranges) - 1;
+  while (mx != mn)
+    {
+      md = (mn + mx) / 2;
+      if (c <= ucnranges[md].end)
+	mx = md;
+      else
+	mn = md + 1;
+    }
+
+  unsigned short flags = ucnranges[mn].flags;
+
+  if (flags & CXX23)
+    return CPP_XID_START | CPP_XID_CONTINUE;
+  if (flags & NXX23)
+    return CPP_XID_CONTINUE;
+  return 0;
+}
 
 /* Returns 1 if C is valid in an identifier, 2 if C is valid except at
    the start of an identifier, and 0 if C is not valid in an

libcpp/include/cpplib.h

@@ -1631,4 +1631,11 @@ bool cpp_valid_utf8_p (const char *data, size_t num_bytes);
 bool cpp_is_combining_char (cppchar_t c);
 bool cpp_is_printable_char (cppchar_t c);
 
+enum cpp_xid_property {
+  CPP_XID_START = 1,
+  CPP_XID_CONTINUE = 2
+};
+
+unsigned int cpp_check_xid_property (cppchar_t c);
+
 #endif /* ! LIBCPP_CPPLIB_H */