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authorKaz Kylheku <kaz@kylheku.com>2014-07-19 19:19:21 -0700
committerKaz Kylheku <kaz@kylheku.com>2014-07-19 19:19:21 -0700
commit8fe8e46c6dce8292f2c12660d0c383e521f9233a (patch)
tree347e192c467d2140b61ecc77356e18b544535fef
parent5f9d1d22af102a8e9d2a769ea02243fb5763fe74 (diff)
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* lib.c (search_str): Support negative starting index.
Hoist uselessly repeated c_str operation out of loop. * txr.1: Document negative starting index for search-str.
-rw-r--r--ChangeLog7
-rw-r--r--lib.c18
-rw-r--r--txr.18
3 files changed, 27 insertions, 6 deletions
diff --git a/ChangeLog b/ChangeLog
index d2a40266..906b02b2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
2014-07-19 Kaz Kylheku <kaz@kylheku.com>
+ * lib.c (search_str): Support negative starting index.
+ Hoist uselessly repeated c_str operation out of loop.
+
+ * txr.1: Document negative starting index for search-str.
+
+2014-07-19 Kaz Kylheku <kaz@kylheku.com>
+
* hash.c (hash_construct): Nullify the pairs argument so that
it works correctly with an empty vector.
diff --git a/lib.c b/lib.c
index 0f705211..3f38ab97 100644
--- a/lib.c
+++ b/lib.c
@@ -2145,11 +2145,14 @@ val search_str(val haystack, val needle, val start_num, val from_end)
const wchar_t *n = c_str(needle), *h;
if (!h_is_lazy) {
- do {
- const wchar_t *f;
- h = c_str(haystack);
+ h = c_str(haystack);
+
+ if (start < 0)
+ start += wcslen(h);
- f = wcsstr(h + start, n);
+ nonlazy:
+ do {
+ const wchar_t *f = wcsstr(h + start, n);
if (f)
pos = f - h;
@@ -2159,6 +2162,13 @@ val search_str(val haystack, val needle, val start_num, val from_end)
} else {
size_t ln = c_num(length_str(needle));
+ if (start < 0) {
+ lazy_str_force(haystack);
+ h = c_str(haystack->ls.prefix);
+ start += wcslen(h);
+ goto nonlazy;
+ }
+
do {
lazy_str_force_upto(haystack, plus(num(start + 1), length_str(needle)));
h = c_str(haystack->ls.prefix);
diff --git a/txr.1 b/txr.1
index 666d238c..b3f4b3b8 100644
--- a/txr.1
+++ b/txr.1
@@ -9337,8 +9337,12 @@ The search-str function finds an occurrence of the string <needle> inside
the <haystack> string and returns its position. If no such occurrence exists,
it returns nil.
-If a <start> argument is specified, it gives the starting index for the
-search. If the <from-end> argument is specified and is not nil, it means
+If a <start> argument is not specified, it defaults to zero. If it is
+a non-negative integer, it specifies the starting character position for
+the search. Negative values of <start> indicate positions from the end of the
+string, such that -1 is the last character of the string.
+
+If the <from-end> argument is specified and is not nil, it means
that the search is conducted right-to-left. If multiple matches are possible,
it will find the rightmost one rather than the leftmost one.