StringBuilder: allow dynamic resize

GitOrigin-RevId: cd59f013d10f4d8e5911933eeb75384d675fda94
This commit is contained in:
Arseny Smirnov 2018-10-30 14:07:28 +03:00
parent 199194ba42
commit 43ef35eb71
3 changed files with 98 additions and 20 deletions

View File

@ -61,8 +61,34 @@ static char *print_int(char *current_ptr, T x) {
return print_uint(current_ptr, x);
}
bool StringBuilder::reserve_inner(size_t size) {
if (!use_buffer_) {
return false;
}
//TODO: check size_t oveflow
size_t old_data_size = current_ptr_ - begin_ptr_;
size_t need_data_size = old_data_size + size;
size_t old_buffer_size = end_ptr_ - begin_ptr_;
size_t new_buffer_size = (old_buffer_size + 1) * 2;
if (new_buffer_size < need_data_size) {
new_buffer_size = need_data_size;
}
if (new_buffer_size < 100) {
new_buffer_size = 100;
}
new_buffer_size += reserved_size;
auto new_buffer_ = std::make_unique<char[]>(new_buffer_size);
std::memcpy(new_buffer_.get(), begin_ptr_, old_data_size);
buffer_ = std::move(new_buffer_);
begin_ptr_ = buffer_.get();
current_ptr_ = begin_ptr_ + old_data_size;
end_ptr_ = begin_ptr_ + new_buffer_size - reserved_size;
CHECK(end_ptr_ > begin_ptr_);
return true;
}
StringBuilder &StringBuilder::operator<<(int x) {
if (unlikely(end_ptr_ < current_ptr_)) {
if (unlikely(!reserve())) {
return on_error();
}
current_ptr_ = print_int(current_ptr_, x);
@ -70,7 +96,7 @@ StringBuilder &StringBuilder::operator<<(int x) {
}
StringBuilder &StringBuilder::operator<<(unsigned int x) {
if (unlikely(end_ptr_ < current_ptr_)) {
if (unlikely(!reserve())) {
return on_error();
}
current_ptr_ = print_uint(current_ptr_, x);
@ -78,7 +104,7 @@ StringBuilder &StringBuilder::operator<<(unsigned int x) {
}
StringBuilder &StringBuilder::operator<<(long int x) {
if (unlikely(end_ptr_ < current_ptr_)) {
if (unlikely(!reserve())) {
return on_error();
}
current_ptr_ = print_int(current_ptr_, x);
@ -86,7 +112,7 @@ StringBuilder &StringBuilder::operator<<(long int x) {
}
StringBuilder &StringBuilder::operator<<(long unsigned int x) {
if (unlikely(end_ptr_ < current_ptr_)) {
if (unlikely(!reserve())) {
return on_error();
}
current_ptr_ = print_uint(current_ptr_, x);
@ -94,7 +120,7 @@ StringBuilder &StringBuilder::operator<<(long unsigned int x) {
}
StringBuilder &StringBuilder::operator<<(long long int x) {
if (unlikely(end_ptr_ < current_ptr_)) {
if (unlikely(!reserve())) {
return on_error();
}
current_ptr_ = print_int(current_ptr_, x);
@ -102,7 +128,7 @@ StringBuilder &StringBuilder::operator<<(long long int x) {
}
StringBuilder &StringBuilder::operator<<(long long unsigned int x) {
if (unlikely(end_ptr_ < current_ptr_)) {
if (unlikely(!reserve())) {
return on_error();
}
current_ptr_ = print_uint(current_ptr_, x);
@ -110,7 +136,7 @@ StringBuilder &StringBuilder::operator<<(long long unsigned int x) {
}
StringBuilder &StringBuilder::operator<<(FixedDouble x) {
if (unlikely(end_ptr_ < current_ptr_)) {
if (unlikely(!reserve())) {
return on_error();
}
@ -137,7 +163,7 @@ StringBuilder &StringBuilder::operator<<(FixedDouble x) {
}
StringBuilder &StringBuilder::operator<<(const void *ptr) {
if (unlikely(end_ptr_ < current_ptr_)) {
if (unlikely(!reserve())) {
return on_error();
}
current_ptr_ += std::snprintf(current_ptr_, reserved_size, "%p", ptr);

View File

@ -18,10 +18,17 @@ namespace td {
class StringBuilder {
public:
explicit StringBuilder(MutableSlice slice)
: begin_ptr_(slice.begin()), current_ptr_(begin_ptr_), end_ptr_(slice.end() - reserved_size) {
explicit StringBuilder(MutableSlice slice, bool use_buffer = false)
: begin_ptr_(slice.begin())
, current_ptr_(begin_ptr_)
, end_ptr_(slice.end() - reserved_size)
, use_buffer_(use_buffer) {
if (slice.size() <= reserved_size) {
std::abort(); // shouldn't happen
auto buffer_size = reserved_size + 100;
buffer_ = std::make_unique<char[]>(buffer_size);
begin_ptr_ = buffer_.get();
current_ptr_ = begin_ptr_;
end_ptr_ = begin_ptr_ + buffer_size - reserved_size;
}
}
@ -49,15 +56,18 @@ class StringBuilder {
StringBuilder &operator<<(const wchar_t *str) = delete;
StringBuilder &operator<<(Slice slice) {
if (unlikely(end_ptr_ < current_ptr_)) {
return on_error();
}
auto size = static_cast<size_t>(end_ptr_ + reserved_size - 1 - current_ptr_);
if (unlikely(slice.size() > size)) {
error_flag_ = true;
} else {
size = slice.size();
size_t size = slice.size();
if (unlikely(!reserve(size))) {
if (end_ptr_ < current_ptr_) {
return on_error();
}
auto available_size = static_cast<size_t>(end_ptr_ + reserved_size - 1 - current_ptr_);
if (size > available_size) {
error_flag_ = true;
size = available_size;
}
}
std::memcpy(current_ptr_, slice.begin(), size);
current_ptr_ += size;
return *this;
@ -68,7 +78,7 @@ class StringBuilder {
}
StringBuilder &operator<<(char c) {
if (unlikely(end_ptr_ < current_ptr_)) {
if (unlikely(!reserve())) {
return on_error();
}
*current_ptr_++ = c;
@ -120,12 +130,28 @@ class StringBuilder {
char *current_ptr_;
char *end_ptr_;
bool error_flag_ = false;
bool use_buffer_ = false;
std::unique_ptr<char[]> buffer_;
static constexpr size_t reserved_size = 30;
StringBuilder &on_error() {
error_flag_ = true;
return *this;
}
bool reserve() {
if (end_ptr_ > current_ptr_) {
return true;
}
return reserve_inner(reserved_size);
}
bool reserve(size_t size) {
if (end_ptr_ > current_ptr_ && static_cast<size_t>(end_ptr_ - current_ptr_) >= size) {
return true;
}
return reserve_inner(size);
}
bool reserve_inner(size_t size);
};
template <class T>

View File

@ -492,3 +492,29 @@ TEST(Misc, full_split) {
test_full_split(" ab cd ef ", {"", "ab", "cd", "ef", ""});
test_full_split(" ab cd ef ", {"", "", "ab", "", "cd", "", "ef", "", ""});
}
TEST(Misc, StringBuilder) {
auto small = std::string{"abcdefghij"};
auto big = std::string(1000, 'a');
using V = std::vector<std::string>;
for (auto use_buf : {false, true}) {
for (size_t initial_buffer_size : {0, 1, 5, 10, 100, 1000, 2000}) {
for (auto test : {V{small}, {small, big, big, small}, {big, small, big}}) {
std::string buf(initial_buffer_size, '\0');
td::StringBuilder sb(buf, use_buf);
std::string res;
for (auto x : test) {
res += x;
sb << x;
}
if (use_buf) {
ASSERT_EQ(res, sb.as_cslice());
} else {
auto got = sb.as_cslice();
res.resize(got.size());
ASSERT_EQ(res, got);
}
}
}
}
}