tdlight/tdutils/td/utils/StringBuilder.h

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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2018
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#pragma once
#include "td/utils/common.h"
#include "td/utils/Slice-decl.h"
#include "td/utils/StackAllocator.h"
#include <cstdlib>
#include <cstring>
#include <type_traits>
namespace td {
class StringBuilder {
public:
explicit StringBuilder(MutableSlice slice, bool use_buffer = false)
: begin_ptr_(slice.begin()), current_ptr_(begin_ptr_), use_buffer_(use_buffer) {
if (slice.size() <= reserved_size) {
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;
} else {
end_ptr_ = slice.end() - reserved_size;
}
}
void clear() {
current_ptr_ = begin_ptr_;
error_flag_ = false;
}
MutableCSlice as_cslice() {
if (current_ptr_ >= end_ptr_ + reserved_size) {
std::abort(); // shouldn't happen
}
*current_ptr_ = 0;
return MutableCSlice(begin_ptr_, current_ptr_);
}
bool is_error() const {
return error_flag_;
}
StringBuilder &operator<<(const char *str) {
return *this << Slice(str);
}
StringBuilder &operator<<(const wchar_t *str) = delete;
StringBuilder &operator<<(Slice slice) {
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;
}
StringBuilder &operator<<(bool b) {
return *this << (b ? Slice("true") : Slice("false"));
}
StringBuilder &operator<<(char c) {
if (unlikely(!reserve())) {
return on_error();
}
*current_ptr_++ = c;
return *this;
}
StringBuilder &operator<<(unsigned char c) {
return *this << static_cast<unsigned int>(c);
}
StringBuilder &operator<<(signed char c) {
return *this << static_cast<int>(c);
}
StringBuilder &operator<<(int x);
StringBuilder &operator<<(unsigned int x);
StringBuilder &operator<<(long int x);
StringBuilder &operator<<(long unsigned int x);
StringBuilder &operator<<(long long int x);
StringBuilder &operator<<(long long unsigned int x);
struct FixedDouble {
double d;
int precision;
FixedDouble(double d, int precision) : d(d), precision(precision) {
}
};
StringBuilder &operator<<(FixedDouble x);
StringBuilder &operator<<(double x) {
return *this << FixedDouble(x, 6);
}
StringBuilder &operator<<(const void *ptr);
template <class T>
StringBuilder &operator<<(const T *ptr) {
return *this << static_cast<const void *>(ptr);
}
private:
char *begin_ptr_;
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>
std::enable_if_t<std::is_arithmetic<T>::value, string> to_string(const T &x) {
const size_t buf_size = 1000;
auto buf = StackAllocator::alloc(buf_size);
StringBuilder sb(buf.as_slice());
sb << x;
return sb.as_cslice().str();
}
} // namespace td