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rb_str_{partition,rpartition}_m: Handle /\K/ in pattern

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When the pattern given to String#partition and String#rpartition
contain a /\K/ (lookbehind) operator, the methods return strings
sliced at incorrect positions.

```
# without patch
"abcdbce".partition(/b\Kc/)  # => ["a", "c", "cdbce"]
"abcdbce".rpartition(/b\Kc/)  # => ["abcd", "c", "ce"]
```

This patch fixes the problem by using BEG(0) instead of the return
value of rb_reg_search.

```
# with patch
"abcdbce".partition(/b\Kc/)  # => ["ab", "c", "dbce"]
"abcdbce".rpartition(/b\Kc/)  # => ["abcdb", "c", "e"]
```

As a side-effect this patch makes String#partition 2x faster when the
pattern is a costly Regexp by performing Regexp search only once,
which was unexpectedly done twice in the original implementation.

Fixes [Bug #17119]
This commit is contained in:
Kasumi Hanazuki 2020-08-13 03:37:32 +00:00 committed by Nobuyoshi Nakada
parent 69b5241c36
commit 5d71eed1a7
Notes: git 2020-08-13 20:51:24 +09:00 
Merged: https://github.com/ruby/ruby/pull/3413
2 changed files with 26 additions and 23 deletions
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45
string.c
View File

@ -9940,11 +9940,14 @@ rb_str_partition(VALUE str, VALUE sep)
sep = get_pat_quoted(sep, 0);
if (RB_TYPE_P(sep, T_REGEXP)) {
pos = rb_reg_search(sep, str, 0, 0);
if (pos < 0) {
if (rb_reg_search(sep, str, 0, 0) < 0) {
goto failed;
}
sep = rb_str_subpat(str, sep, INT2FIX(0));
VALUE match = rb_backref_get();
struct re_registers *regs = RMATCH_REGS(match);
pos = BEG(0);
sep = rb_str_subseq(str, pos, END(0) - pos);
}
else {
pos = rb_str_index(str, sep, 0);
@ -9978,37 +9981,33 @@ static VALUE
rb_str_rpartition(VALUE str, VALUE sep)
{
long pos = RSTRING_LEN(str);
int regex = FALSE;
sep = get_pat_quoted(sep, 0);
if (RB_TYPE_P(sep, T_REGEXP)) {
pos = rb_reg_search(sep, str, pos, 1);
regex = TRUE;
if (rb_reg_search(sep, str, pos, 1) < 0) {
goto failed;
}
VALUE match = rb_backref_get();
struct re_registers *regs = RMATCH_REGS(match);
pos = BEG(0);
sep = rb_str_subseq(str, pos, END(0) - pos);
}
else {
VALUE tmp;
tmp = rb_check_string_type(sep);
if (NIL_P(tmp)) {
rb_raise(rb_eTypeError, "type mismatch: %s given",
rb_obj_classname(sep));
}
sep = tmp;
pos = rb_str_sublen(str, pos);
pos = rb_str_rindex(str, sep, pos);
if(pos < 0) {
goto failed;
}
pos = rb_str_offset(str, pos);
}
if (pos < 0) {
return rb_ary_new3(3, str_new_empty(str), str_new_empty(str), rb_str_dup(str));
}
if (regex) {
sep = rb_reg_nth_match(0, rb_backref_get());
}
else {
pos = rb_str_offset(str, pos);
}
return rb_ary_new3(3, rb_str_subseq(str, 0, pos),
sep,
rb_str_subseq(str, pos+RSTRING_LEN(sep),
RSTRING_LEN(str)-pos-RSTRING_LEN(sep)));
failed:
return rb_ary_new3(3, str_new_empty(str), str_new_empty(str), rb_str_dup(str));
}
/*

4
test/ruby/test_string.rb
View File

@ -2603,6 +2603,8 @@ CODE
assert_equal("hello", hello, bug)
assert_equal(["", "", "foo"], "foo".partition(/^=*/))
assert_equal([S("ab"), S("c"), S("dbce")], S("abcdbce").partition(/b\Kc/))
end
def test_rpartition
@ -2627,6 +2629,8 @@ CODE
hello = "hello"
hello.rpartition("hi").map(&:upcase!)
assert_equal("hello", hello, bug)
assert_equal([S("abcdb"), S("c"), S("e")], S("abcdbce").rpartition(/b\Kc/))
end
def test_setter