bug#24603: [RFC 04/18] Split casify_object into multiple functions

[Michal Nazarewicz <mina86@mina86.com>]

casify_object had three major cases to cover and those were mostly
independent of each other.  Move those branches to separate function
so it’s easier to comprehend each individual case.

While at it, use somewhat more descriptive ch and cased variable names
rather than c and c1.

* src/casefiddle.c (casify_object): Split into…
(do_casify_integer, do_casify_multibyte_string,
do_casify_unibyte_string): …new functions.
---
 src/casefiddle.c | 196 +++++++++++++++++++++++++++++--------------------------
 1 file changed, 104 insertions(+), 92 deletions(-)

diff --git a/src/casefiddle.c b/src/casefiddle.c
index b86f485..47ebdf0 100644
--- a/src/casefiddle.c
+++ b/src/casefiddle.c
@@ -32,108 +32,120 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 enum case_action {CASE_UP, CASE_DOWN, CASE_CAPITALIZE, CASE_CAPITALIZE_UP};
 \f
 static Lisp_Object
-casify_object (enum case_action flag, Lisp_Object obj)
+do_casify_integer (enum case_action flag, Lisp_Object obj)
+{
+  int flagbits = (CHAR_ALT | CHAR_SUPER | CHAR_HYPER
+		  | CHAR_SHIFT | CHAR_CTL | CHAR_META);
+  int flags, ch = XFASTINT (obj), cased;
+  bool multibyte;
+
+  /* If the character has higher bits set above the flags, return it unchanged.
+     It is not a real character.  */
+  if (UNSIGNED_CMP (ch, >, flagbits))
+    return obj;
+
+  flags = ch & flagbits;
+  ch = ch & ~flagbits;
+
+  /* FIXME: Even if enable-multibyte-characters is nil, we may manipulate
+     multibyte chars.  This means we have a bug for latin-1 chars since when we
+     receive an int 128-255 we can't tell whether it's an eight-bit byte or
+     a latin-1 char.  */
+  multibyte = (ch >= 256 ||
+	       !NILP (BVAR (current_buffer, enable_multibyte_characters)));
+  if (! multibyte)
+    MAKE_CHAR_MULTIBYTE (ch);
+  cased = flag == CASE_DOWN ? downcase (ch) : upcase (ch);
+  if (cased == ch)
+    return obj;
+
+  if (! multibyte)
+    MAKE_CHAR_UNIBYTE (cased);
+  XSETFASTINT (obj, cased | flags);
+  return obj;
+}
+
+static Lisp_Object
+do_casify_multibyte_string (enum case_action flag, Lisp_Object obj)
+{
+  ptrdiff_t i, i_byte, size = SCHARS (obj);
+  bool inword = flag == CASE_DOWN;
+  int len, ch, cased;
+  USE_SAFE_ALLOCA;
+  ptrdiff_t o_size;
+  if (INT_MULTIPLY_WRAPV (size, MAX_MULTIBYTE_LENGTH, &o_size))
+    o_size = PTRDIFF_MAX;
+  unsigned char *dst = SAFE_ALLOCA (o_size);
+  unsigned char *o = dst;
+
+  for (i = i_byte = 0; i < size; i++, i_byte += len)
+    {
+      if (o_size - MAX_MULTIBYTE_LENGTH < o - dst)
+	string_overflow ();
+      ch = STRING_CHAR_AND_LENGTH (SDATA (obj) + i_byte, len);
+      if (inword && flag != CASE_CAPITALIZE_UP)
+	cased = downcase (ch);
+      else if (!inword || flag != CASE_CAPITALIZE_UP)
+	cased = upcase (ch);
+      else
+	cased = ch;
+      if ((int) flag >= (int) CASE_CAPITALIZE)
+	inword = (SYNTAX (ch) == Sword);
+      o += CHAR_STRING (cased, o);
+    }
+  eassert (o - dst <= o_size);
+  obj = make_multibyte_string ((char *) dst, size, o - dst);
+  SAFE_FREE ();
+  return obj;
+}
+
+static Lisp_Object
+do_casify_unibyte_string (enum case_action flag, Lisp_Object obj)
 {
-  int c, c1;
+  ptrdiff_t i, size = SCHARS (obj);
   bool inword = flag == CASE_DOWN;
+  int ch, cased;
+
+  obj = Fcopy_sequence (obj);
+  for (i = 0; i < size; i++)
+    {
+      ch = SREF (obj, i);
+      MAKE_CHAR_MULTIBYTE (ch);
+      cased = ch;
+      if (inword && flag != CASE_CAPITALIZE_UP)
+	ch = downcase (ch);
+      else if (!uppercasep (ch)
+	       && (!inword || flag != CASE_CAPITALIZE_UP))
+	ch = upcase (cased);
+      if ((int) flag >= (int) CASE_CAPITALIZE)
+	inword = (SYNTAX (ch) == Sword);
+      if (ch == cased)
+	continue;
+      MAKE_CHAR_UNIBYTE (ch);
+      /* If the char can't be converted to a valid byte, just don't change it */
+      if (ch >= 0 && ch < 256)
+	SSET (obj, i, ch);
+    }
+  return obj;
+}
 
+static Lisp_Object
+casify_object (enum case_action flag, Lisp_Object obj)
+{
   /* If the case table is flagged as modified, rescan it.  */
   if (NILP (XCHAR_TABLE (BVAR (current_buffer, downcase_table))->extras[1]))
     Fset_case_table (BVAR (current_buffer, downcase_table));
 
   if (INTEGERP (obj))
-    {
-      int flagbits = (CHAR_ALT | CHAR_SUPER | CHAR_HYPER
-		      | CHAR_SHIFT | CHAR_CTL | CHAR_META);
-      int flags = XINT (obj) & flagbits;
-      bool multibyte = ! NILP (BVAR (current_buffer,
-				     enable_multibyte_characters));
-
-      /* If the character has higher bits set
-	 above the flags, return it unchanged.
-	 It is not a real character.  */
-      if (UNSIGNED_CMP (XFASTINT (obj), >, flagbits))
-	return obj;
-
-      c1 = XFASTINT (obj) & ~flagbits;
-      /* FIXME: Even if enable-multibyte-characters is nil, we may
-	 manipulate multibyte chars.  This means we have a bug for latin-1
-	 chars since when we receive an int 128-255 we can't tell whether
-	 it's an eight-bit byte or a latin-1 char.  */
-      if (c1 >= 256)
-	multibyte = 1;
-      if (! multibyte)
-	MAKE_CHAR_MULTIBYTE (c1);
-      c = flag == CASE_DOWN ? downcase (c1) : upcase (c1);
-      if (c != c1)
-	{
-	  if (! multibyte)
-	    MAKE_CHAR_UNIBYTE (c);
-	  XSETFASTINT (obj, c | flags);
-	}
-      return obj;
-    }
-
-  if (!STRINGP (obj))
+    return do_casify_integer (flag, obj);
+  else if (!STRINGP (obj))
     wrong_type_argument (Qchar_or_string_p, obj);
-  else if (!STRING_MULTIBYTE (obj))
-    {
-      ptrdiff_t i;
-      ptrdiff_t size = SCHARS (obj);
-
-      obj = Fcopy_sequence (obj);
-      for (i = 0; i < size; i++)
-	{
-	  c = SREF (obj, i);
-	  MAKE_CHAR_MULTIBYTE (c);
-	  c1 = c;
-	  if (inword && flag != CASE_CAPITALIZE_UP)
-	    c = downcase (c);
-	  else if (!uppercasep (c)
-		   && (!inword || flag != CASE_CAPITALIZE_UP))
-	    c = upcase (c1);
-	  if ((int) flag >= (int) CASE_CAPITALIZE)
-	    inword = (SYNTAX (c) == Sword);
-	  if (c != c1)
-	    {
-	      MAKE_CHAR_UNIBYTE (c);
-	      /* If the char can't be converted to a valid byte, just don't
-		 change it.  */
-	      if (c >= 0 && c < 256)
-		SSET (obj, i, c);
-	    }
-	}
-      return obj;
-    }
+  else if (!SCHARS (obj))
+    return obj;
+  else if (STRING_MULTIBYTE (obj))
+    return do_casify_multibyte_string (flag, obj);
   else
-    {
-      ptrdiff_t i, i_byte, size = SCHARS (obj);
-      int len;
-      USE_SAFE_ALLOCA;
-      ptrdiff_t o_size;
-      if (INT_MULTIPLY_WRAPV (size, MAX_MULTIBYTE_LENGTH, &o_size))
-	o_size = PTRDIFF_MAX;
-      unsigned char *dst = SAFE_ALLOCA (o_size);
-      unsigned char *o = dst;
-
-      for (i = i_byte = 0; i < size; i++, i_byte += len)
-	{
-	  if (o_size - MAX_MULTIBYTE_LENGTH < o - dst)
-	    string_overflow ();
-	  c = STRING_CHAR_AND_LENGTH (SDATA (obj) + i_byte, len);
-	  if (inword && flag != CASE_CAPITALIZE_UP)
-	    c = downcase (c);
-	  else if (!inword || flag != CASE_CAPITALIZE_UP)
-	    c = upcase (c);
-	  if ((int) flag >= (int) CASE_CAPITALIZE)
-	    inword = (SYNTAX (c) == Sword);
-	  o += CHAR_STRING (c, o);
-	}
-      eassert (o - dst <= o_size);
-      obj = make_multibyte_string ((char *) dst, size, o - dst);
-      SAFE_FREE ();
-      return obj;
-    }
+    return do_casify_unibyte_string (flag, obj);
 }
 
 DEFUN ("upcase", Fupcase, Supcase, 1, 1, 0,
-- 
2.8.0.rc3.226.g39d4020