2024-06-04 12:41:53 +00:00
|
|
|
// -*- mode:c++; indent-tabs-mode:nil; c-basic-offset:4; coding:utf-8 -*-
|
2024-06-06 01:30:39 +00:00
|
|
|
// vi: set et ft=cpp ts=4 sts=4 sw=4 fenc=utf-8 :vi
|
2024-06-04 12:41:53 +00:00
|
|
|
//
|
|
|
|
|
// Copyright 2024 Justine Alexandra Roberts Tunney
|
|
|
|
|
//
|
|
|
|
|
// Permission to use, copy, modify, and/or distribute this software for
|
|
|
|
|
// any purpose with or without fee is hereby granted, provided that the
|
|
|
|
|
// above copyright notice and this permission notice appear in all copies.
|
|
|
|
|
//
|
|
|
|
|
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
|
|
|
|
|
// WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
|
|
|
|
|
// WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
|
|
|
|
|
// AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
|
|
|
|
|
// DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
|
|
|
|
|
// PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
|
|
|
|
|
// TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
|
|
|
|
|
// PERFORMANCE OF THIS SOFTWARE.
|
|
|
|
|
|
|
|
|
|
#include "string.h"
|
|
|
|
|
|
|
|
|
|
#include <stdckdint.h>
|
|
|
|
|
#include <string.h>
|
|
|
|
|
|
|
|
|
|
namespace ctl {
|
|
|
|
|
|
|
|
|
|
string
|
|
|
|
|
strcat(const string_view lhs, const string_view rhs) noexcept
|
|
|
|
|
{
|
|
|
|
|
string res;
|
|
|
|
|
size_t need;
|
|
|
|
|
if (ckd_add(&need, lhs.n, rhs.n))
|
|
|
|
|
__builtin_trap();
|
|
|
|
|
if (ckd_add(&need, need, 1))
|
|
|
|
|
__builtin_trap();
|
|
|
|
|
res.reserve(need);
|
|
|
|
|
if (lhs.n)
|
ctl::string small-string optimization (#1199)
A small-string optimization is a way of reusing inline storage space for
sufficiently small strings, rather than allocating them on the heap. The
current approach takes after an old Facebook string class: it reuses the
highest-order byte for flags and small-string size, in such a way that a
maximally-sized small string will have its last byte zeroed, making it a
null terminator for the C string.
The only flag we have is in the highest-order bit, that says whether the
string is big (set) or small (cleared.) Most of the logic switches based
on the value of this bit; e.g. data() returns big()->p if it's set, else
small()->buf if it's cleared. For a small string, the capacity is always
fixed at sizeof(string) - 1 bytes; we store the length in the last byte,
but we store it as the number of remaining bytes of capacity, so that at
max size, the last byte will read zero and serve as our null terminator.
Morally speaking, our class's storage is a union over two POD C structs.
For now I gravitated towards a slightly more obtuse approach: the string
class itself contains a blob of the right size, and we alias that blob's
pointer for the two structs, taking some care not to run afoul of object
lifetime rules in C++. If anyone wants to improve on this, contributions
are welcome.
This commit also introduces the `ctl::__` namespace. It can't be legally
spelled by library users, and serves as our version of boost's "detail".
We introduced a string::swap function, and we now use that in operator=.
operator= now takes its argument by value, so we never need to check for
the case where the pointers are equal and can just swap the entire store
of the argument with our own, leaving the C++ destructor to free our old
storage afterwards.
There are probably still a few places where our capacity is slightly off
and we grow too fast, although there don't appear to be any where we are
too slow. I will leave these to be fixed in future changes.
2024-06-07 00:50:51 +00:00
|
|
|
memcpy(res.data(), lhs.p, lhs.n);
|
2024-06-04 12:41:53 +00:00
|
|
|
if (rhs.n)
|
ctl::string small-string optimization (#1199)
A small-string optimization is a way of reusing inline storage space for
sufficiently small strings, rather than allocating them on the heap. The
current approach takes after an old Facebook string class: it reuses the
highest-order byte for flags and small-string size, in such a way that a
maximally-sized small string will have its last byte zeroed, making it a
null terminator for the C string.
The only flag we have is in the highest-order bit, that says whether the
string is big (set) or small (cleared.) Most of the logic switches based
on the value of this bit; e.g. data() returns big()->p if it's set, else
small()->buf if it's cleared. For a small string, the capacity is always
fixed at sizeof(string) - 1 bytes; we store the length in the last byte,
but we store it as the number of remaining bytes of capacity, so that at
max size, the last byte will read zero and serve as our null terminator.
Morally speaking, our class's storage is a union over two POD C structs.
For now I gravitated towards a slightly more obtuse approach: the string
class itself contains a blob of the right size, and we alias that blob's
pointer for the two structs, taking some care not to run afoul of object
lifetime rules in C++. If anyone wants to improve on this, contributions
are welcome.
This commit also introduces the `ctl::__` namespace. It can't be legally
spelled by library users, and serves as our version of boost's "detail".
We introduced a string::swap function, and we now use that in operator=.
operator= now takes its argument by value, so we never need to check for
the case where the pointers are equal and can just swap the entire store
of the argument with our own, leaving the C++ destructor to free our old
storage afterwards.
There are probably still a few places where our capacity is slightly off
and we grow too fast, although there don't appear to be any where we are
too slow. I will leave these to be fixed in future changes.
2024-06-07 00:50:51 +00:00
|
|
|
memcpy(res.data() + lhs.n, rhs.p, rhs.n);
|
|
|
|
|
if (res.isbig()) {
|
2024-06-29 02:07:35 +00:00
|
|
|
res.__b.n = lhs.n + rhs.n;
|
ctl::string small-string optimization (#1199)
A small-string optimization is a way of reusing inline storage space for
sufficiently small strings, rather than allocating them on the heap. The
current approach takes after an old Facebook string class: it reuses the
highest-order byte for flags and small-string size, in such a way that a
maximally-sized small string will have its last byte zeroed, making it a
null terminator for the C string.
The only flag we have is in the highest-order bit, that says whether the
string is big (set) or small (cleared.) Most of the logic switches based
on the value of this bit; e.g. data() returns big()->p if it's set, else
small()->buf if it's cleared. For a small string, the capacity is always
fixed at sizeof(string) - 1 bytes; we store the length in the last byte,
but we store it as the number of remaining bytes of capacity, so that at
max size, the last byte will read zero and serve as our null terminator.
Morally speaking, our class's storage is a union over two POD C structs.
For now I gravitated towards a slightly more obtuse approach: the string
class itself contains a blob of the right size, and we alias that blob's
pointer for the two structs, taking some care not to run afoul of object
lifetime rules in C++. If anyone wants to improve on this, contributions
are welcome.
This commit also introduces the `ctl::__` namespace. It can't be legally
spelled by library users, and serves as our version of boost's "detail".
We introduced a string::swap function, and we now use that in operator=.
operator= now takes its argument by value, so we never need to check for
the case where the pointers are equal and can just swap the entire store
of the argument with our own, leaving the C++ destructor to free our old
storage afterwards.
There are probably still a few places where our capacity is slightly off
and we grow too fast, although there don't appear to be any where we are
too slow. I will leave these to be fixed in future changes.
2024-06-07 00:50:51 +00:00
|
|
|
} else {
|
2024-06-29 02:07:35 +00:00
|
|
|
res.__s.rem = __::sso_max - lhs.n - rhs.n;
|
ctl::string small-string optimization (#1199)
A small-string optimization is a way of reusing inline storage space for
sufficiently small strings, rather than allocating them on the heap. The
current approach takes after an old Facebook string class: it reuses the
highest-order byte for flags and small-string size, in such a way that a
maximally-sized small string will have its last byte zeroed, making it a
null terminator for the C string.
The only flag we have is in the highest-order bit, that says whether the
string is big (set) or small (cleared.) Most of the logic switches based
on the value of this bit; e.g. data() returns big()->p if it's set, else
small()->buf if it's cleared. For a small string, the capacity is always
fixed at sizeof(string) - 1 bytes; we store the length in the last byte,
but we store it as the number of remaining bytes of capacity, so that at
max size, the last byte will read zero and serve as our null terminator.
Morally speaking, our class's storage is a union over two POD C structs.
For now I gravitated towards a slightly more obtuse approach: the string
class itself contains a blob of the right size, and we alias that blob's
pointer for the two structs, taking some care not to run afoul of object
lifetime rules in C++. If anyone wants to improve on this, contributions
are welcome.
This commit also introduces the `ctl::__` namespace. It can't be legally
spelled by library users, and serves as our version of boost's "detail".
We introduced a string::swap function, and we now use that in operator=.
operator= now takes its argument by value, so we never need to check for
the case where the pointers are equal and can just swap the entire store
of the argument with our own, leaving the C++ destructor to free our old
storage afterwards.
There are probably still a few places where our capacity is slightly off
and we grow too fast, although there don't appear to be any where we are
too slow. I will leave these to be fixed in future changes.
2024-06-07 00:50:51 +00:00
|
|
|
}
|
|
|
|
|
res.data()[res.size()] = 0;
|
2024-06-04 12:41:53 +00:00
|
|
|
return res;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
} // namespace ctl
|
