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Minor make-string optimization

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* libguile/strings.c (STRINGBUF_SET_MUTABLE): New helper.
  (scm_i_string_ensure_mutable_x): Use new helper.
  (scm_make_string): Mark stringbuf as mutable.
This commit is contained in:
Andy Wingo 2017-02-17 11:29:31 +01:00
parent 2864f11d34
commit 9ee21f3e97
1 changed files with 11 additions and 3 deletions
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14
libguile/strings.c
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@ -83,6 +83,10 @@ SCM_SYMBOL (sym_error, "error");
#define STRINGBUF_WIDE(buf) (SCM_CELL_WORD_0(buf) & STRINGBUF_F_WIDE)
#define STRINGBUF_MUTABLE(buf) (SCM_CELL_WORD_0(buf) & STRINGBUF_F_MUTABLE)
#define STRINGBUF_SET_MUTABLE(buf) \
SCM_SET_CELL_WORD_0 (buf, SCM_CELL_WORD_0 (buf) | STRINGBUF_F_MUTABLE)
#define STRINGBUF_CONTENTS(buf) ((void *) \
SCM_CELL_OBJECT_LOC (buf, \
STRINGBUF_HEADER_SIZE))
@ -433,8 +437,7 @@ scm_i_string_ensure_mutable_x (SCM str)
memcpy (STRINGBUF_CHARS (new_buf), STRINGBUF_CHARS (buf), len);
}
SCM_SET_CELL_WORD_0 (new_buf,
SCM_CELL_WORD_0 (new_buf) | STRINGBUF_F_MUTABLE);
STRINGBUF_SET_MUTABLE (new_buf);
SET_STRING_STRINGBUF (str, new_buf);
}
}
@ -1119,7 +1122,12 @@ SCM_DEFINE (scm_make_string, "make-string", 1, 1, 0,
"of the string are all set to @code{#\nul}.")
#define FUNC_NAME s_scm_make_string
{
return scm_c_make_string (scm_to_size_t (k), chr);
SCM ret = scm_c_make_string (scm_to_size_t (k), chr);
/* Given that make-string is mostly used by Scheme to prepare a
mutable string buffer, let's go ahead and mark this as mutable to
avoid a copy when this buffer is next written to. */
STRINGBUF_SET_MUTABLE (STRING_STRINGBUF (ret));
return ret;
}
#undef FUNC_NAME