[perl #19179] [PATCH] creating string_max_bytes()

[via RT]

# New Ticket Created by  [EMAIL PROTECTED] 
# Please include the string:  [perl #19179]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt2/Ticket/Display.html?id=19179 >


This patch
 (1) Creates a string_max_bytes() function,
     as described in docs/strings.pod.
     Code in string.c, prototype in include/parrot/string_funcs.h.
     It just uses s->encoding->max_bytes.
 (2) Modifies string_grow() in string.c to use string_max_bytes(),
     as described in docs/strings.pod.

That is all.

Apropos the TODO item

   String subsystem
   ----------------
       grep docs/strings.pod for unimplemented functions and implement them

and the docs/strings.pod description

   =head1 Non-user-visible String Manipulation Functions
  [...]
       INTVAL string_compute_strlen(STRING* s)

   and

       INTVAL string_max_bytes(STRING *s, INTVAL iv)

   The first updates the contents of C<< s->strlen >> by contemplating the
   buffer C<bufstart> and working out how many characters it contains. The
   second is given a number of characters which we assume are going to be
   added into the string at some point; it returns the maximum number of
   bytes that need to be allocated to admit that number of characters. For
   fixed-width encodings, this is trivial - the "native" encoding, for
   instance, encodes one byte per character, so C<string_native_max_bytes>
   simply returns the C<INTVAL> it is passed; C<string_utf8_max_bytes>, on the
   other hand, returns three times the value that it is passed because a
   UTF8 character may occupy up to three bytes.

   To grow a string to a specified size, use 

       void string_grow(STRING *s, INTVAL newsize)

   The size is given in characters; C<string_max_bytes> is called to turn
   this into a size in bytes, and then the buffer is grown to accomodate
   (at least) that many bytes.

Mitchell Charity



-- attachment  1 ------------------------------------------------------
url: http://rt.perl.org/rt2/attach/45540/35737/fed377/create_string_max_bytes.patch


diff -ur ./include/parrot/string_funcs.h 
../parrot_strings/include/parrot/string_funcs.h
--- ./include/parrot/string_funcs.h     Sun Dec 15 12:59:51 2002
+++ ../parrot_strings/include/parrot/string_funcs.h     Mon Dec 16 06:53:11 2002
@@ -18,6 +18,7 @@
 /* Declarations of accessors */
 
 INTVAL string_compute_strlen(STRING *);
+INTVAL string_max_bytes(STRING*, INTVAL);
 STRING *string_concat(struct Parrot_Interp *, STRING *, STRING *, UINTVAL);
 STRING *string_append(struct Parrot_Interp *, STRING *, STRING *, UINTVAL);
 STRING *string_from_c_string(struct Parrot_Interp *, const void *, UINTVAL);
diff -ur ./string.c ../parrot_strings/string.c
--- ./string.c  Sun Dec 15 12:59:47 2002
+++ ../parrot_strings/string.c  Mon Dec 16 07:16:04 2002
@@ -275,7 +275,8 @@
     unmake_COW(interpreter,s);
 
     /* Don't check buflen, if we are here, we already checked. */
-    Parrot_reallocate_string(interpreter, s, s->buflen + addlen);
+    Parrot_reallocate_string(interpreter, s,
+                             s->buflen + string_max_bytes(s,addlen));
     return s;
 }
 
@@ -488,6 +489,16 @@
     return s->strlen;
 }
 
+/*=for api string string_max_bytes
+ * returns the number of bytes required to safely contain
+ * n characters in the string's encoding
+ */
+INTVAL
+string_max_bytes(STRING *s, INTVAL nchars)
+{
+    return (nchars * s->encoding->max_bytes);
+}
+
 /*=for api string string_concat
  * concatenate two strings
  */