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(scm_string_filter, scm_string_delete): Strip leading and

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trailing deletions, so as to return a substring if those are the only
changes.
This commit is contained in:
Kevin Ryde 2005-07-11 23:59:57 +00:00
parent f71e4d8c09
commit 8591234398
1 changed files with 50 additions and 9 deletions
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59
libguile/srfi-13.c
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@ -3254,8 +3254,7 @@ SCM_DEFINE (scm_string_split, "string-split", 2, 0, 0,
SCM_DEFINE (scm_string_filter, "string-filter", 2, 2, 0,
(SCM s, SCM char_pred, SCM start, SCM end),
"Filter the string @var{s}, retaining only those characters\n"
"which satisfy @var{char_pred}. The result may share storage\n"
"with @var{s}.\n"
"which satisfy @var{char_pred}.\n"
"\n"
"If @var{char_pred} is a procedure, it is applied to each\n"
"character as a predicate, if it is a character, it is tested\n"
@ -3271,21 +3270,36 @@ SCM_DEFINE (scm_string_filter, "string-filter", 2, 2, 0,
MY_VALIDATE_SUBSTRING_SPEC_COPY (1, s, cstr,
3, start, cstart,
4, end, cend);
/* The explicit loops below stripping leading and trailing non-matches
mean we can return a substring if those are the only deletions, making
string-filter as efficient as string-trim-both in that case. */
if (SCM_CHARP (char_pred))
{
size_t count;
char chr;
/* count chars to keep */
chr = SCM_CHAR (char_pred);
/* strip leading non-matches by incrementing cstart */
while (cstart < cend && cstr[cstart] != chr)
cstart++;
/* strip trailing non-matches by decrementing cend */
while (cend > cstart && cstr[cend-1] != chr)
cend--;
/* count chars to keep */
count = 0;
for (idx = cstart; idx < cend; idx++)
if (cstr[idx] == chr)
count++;
/* if whole of start to end kept then return substring */
if (count == cend - cstart)
{
/* whole of cstart to cend is to be kept, return a copy-on-write
substring */
result_substring:
result = scm_i_substring (s, cstart, cend);
}
@ -3296,6 +3310,14 @@ SCM_DEFINE (scm_string_filter, "string-filter", 2, 2, 0,
{
size_t count;
/* strip leading non-matches by incrementing cstart */
while (cstart < cend && ! SCM_CHARSET_GET (char_pred, cstr[cstart]))
cstart++;
/* strip trailing non-matches by decrementing cend */
while (cend > cstart && ! SCM_CHARSET_GET (char_pred, cstr[cend-1]))
cend--;
/* count chars to be kept */
count = 0;
for (idx = cstart; idx < cend; idx++)
@ -3351,8 +3373,7 @@ SCM_DEFINE (scm_string_filter, "string-filter", 2, 2, 0,
SCM_DEFINE (scm_string_delete, "string-delete", 2, 2, 0,
(SCM s, SCM char_pred, SCM start, SCM end),
"Delete characters satisfying @var{char_pred} from @var{s}. The\n"
"result may share storage with @var{s}.\n"
"Delete characters satisfying @var{char_pred} from @var{s}.\n"
"\n"
"If @var{char_pred} is a procedure, it is applied to each\n"
"character as a predicate, if it is a character, it is tested\n"
@ -3368,6 +3389,11 @@ SCM_DEFINE (scm_string_delete, "string-delete", 2, 2, 0,
MY_VALIDATE_SUBSTRING_SPEC_COPY (1, s, cstr,
3, start, cstart,
4, end, cend);
/* The explicit loops below stripping leading and trailing matches mean we
can return a substring if those are the only deletions, making
string-delete as efficient as string-trim-both in that case. */
if (SCM_CHARP (char_pred))
{
size_t count;
@ -3375,15 +3401,24 @@ SCM_DEFINE (scm_string_delete, "string-delete", 2, 2, 0,
chr = SCM_CHAR (char_pred);
/* strip leading matches by incrementing cstart */
while (cstart < cend && cstr[cstart] == chr)
cstart++;
/* strip trailing matches by decrementing cend */
while (cend > cstart && cstr[cend-1] == chr)
cend--;
/* count chars to be kept */
count = 0;
for (idx = cstart; idx < cend; idx++)
if (cstr[idx] != chr)
count++;
/* if whole of start to end kept then return substring */
if (count == cend - cstart)
{
/* whole of cstart to cend is to be kept, return a copy-on-write
substring */
result_substring:
result = scm_i_substring (s, cstart, cend);
}
@ -3411,14 +3446,20 @@ SCM_DEFINE (scm_string_delete, "string-delete", 2, 2, 0,
{
size_t count;
/* strip leading matches by incrementing cstart */
while (cstart < cend && SCM_CHARSET_GET (char_pred, cstr[cstart]))
cstart++;
/* strip trailing matches by decrementing cend */
while (cend > cstart && SCM_CHARSET_GET (char_pred, cstr[cend-1]))
cend--;
/* count chars to be kept */
count = 0;
for (idx = cstart; idx < cend; idx++)
if (! SCM_CHARSET_GET (char_pred, cstr[idx]))
count++;
/* if whole of start to end kept then return substring, including
possibly s itself */
if (count == cend - cstart)
goto result_substring;
else