void cut(string_ptr& into, size_t i, size_t l) const {
/*get the start*/
BYTE const* nstart = start;
repeat(i) utf8_adv(nstart);
/*for the trivial case where we would reach
the end of this string, don't bother
iterating over the rest of the string
*/
if(i + l == len) {
into.reset(
new Utf8Impl(buffer, nstart, end, l)
);
return;
}
/*iterate over the substring. since we are
iterating over the substring anyway, we might
as well check if the substring is pure ascii.
*/
bool nonascii = false;
BYTE const* nend = nstart;
repeat(l) utf8_adv_check(nend, nonascii);
if(nonascii) {
into.reset(
new Utf8Impl(buffer, nstart, nend, l)
);
return;
} else {
into.reset(
new AsciiImpl(buffer, nstart, l)
);
return;
}
}
void RopeImpl::append_string_impl(
string_ptr& dest,
string_ptr const& one,
string_ptr const& two) {
/*trivial cases where one string is empty*/
if(one->length() == 0) {
dest = two;
return;
} else if(two->length() == 0){
dest = one;
return;
}
/*check for catting two short Ascii strings.*/
AsciiImpl* as1 = dynamic_cast<AsciiImpl*>(one.get());
if(as1 && as1->length() < (ASCII_BUFFER_LEVEL / 2)) {
AsciiImpl* as2 = dynamic_cast<AsciiImpl*>(two.get());
if(as2 && as2->length() < (ASCII_BUFFER_LEVEL / 2)) {
size_t l1 = as1->length();
size_t l2 = as2->length();
/*create a single buffer and concat them*/
boost::shared_array<BYTE> nbp(new BYTE(l1 + l2));
std::copy(as2->start, &as2->start[l2],
std::copy(as1->start, &as1->start[l1],
&nbp[0]
)
);
dest.reset(new AsciiImpl(nbp, &nbp[0], l1 + l2));
return;
}
}
size_t d1 = one->rope_depth();
size_t d2 = two->rope_depth();
if(d1 > d2 + 1) {
/*first subtree is pretty heavy, check if:
one two
/\ |
/\ c d
a b
If so, do this:
/\
/ \
/\ /\
a b c d
*/
RopeImpl& r1 = static_cast<RopeImpl&>(*one);
size_t d1_2 = r1.two->rope_depth();
if(d1_2 <= d2 + 1) {
string_ptr tmp;
base_append_string_impl(tmp, r1.two, two, d1_2, d2);
append_string_impl(dest, r1.one, tmp);
return;
}
}
base_append_string_impl(dest, one, two, d1, d2);
}
void RopeImpl::base_append_string_impl(
string_ptr& dest,
string_ptr const& one,
string_ptr const& two,
size_t d1,
size_t d2) {
size_t nd =
d1 > d2 ? d1 + 1 :
/*otherwise*/ d2 + 1 ;
dest.reset(
new RopeImpl(one, two, nd, one->length())
);
}
void cut(string_ptr& into, size_t i, size_t l) const {
into.reset(
new AsciiImpl(buffer, start + i, l)
);
}