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(scm_string_append_shared): No copying if just one

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non-empty string in args.
This commit is contained in:
Kevin Ryde 2005-11-30 00:26:08 +00:00
parent 606183ba1b
commit a003f3eb60
1 changed files with 23 additions and 9 deletions
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32
libguile/srfi-13.c
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@ -2651,21 +2651,35 @@ SCM_DEFINE (scm_string_reverse_x, "string-reverse!", 1, 2, 0,
SCM_DEFINE (scm_string_append_shared, "string-append/shared", 0, 0, 1, SCM_DEFINE (scm_string_append_shared, "string-append/shared", 0, 0, 1,
(SCM ls), (SCM rest),
"Like @code{string-append}, but the result may share memory\n" "Like @code{string-append}, but the result may share memory\n"
"with the argument strings.") "with the argument strings.")
#define FUNC_NAME s_scm_string_append_shared #define FUNC_NAME s_scm_string_append_shared
{ {
long i; /* If "rest" contains just one non-empty string, return that.
If it's entirely empty strings, then return scm_nullstr.
Otherwise use scm_string_concatenate. */
SCM_VALIDATE_REST_ARGUMENT (ls); SCM ret = scm_nullstr;
int seen_nonempty = 0;
SCM l, s;
/* Optimize the one-argument case. */ SCM_VALIDATE_REST_ARGUMENT (rest);
i = scm_ilength (ls);
if (i == 1) for (l = rest; scm_is_pair (l); l = SCM_CDR (l))
return SCM_CAR (ls); {
else s = SCM_CAR (l);
return scm_string_append (ls); if (scm_c_string_length (s) != 0)
{
if (seen_nonempty)
/* two or more non-empty strings, need full concat */
return scm_string_append (rest);
seen_nonempty = 1;
ret = s;
}
}
return ret;
} }
#undef FUNC_NAME #undef FUNC_NAME