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//===-- A simple implementation of string stream class ----------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIBC_SRC___SUPPORT_CPP_STRINGSTREAM_H
#define LLVM_LIBC_SRC___SUPPORT_CPP_STRINGSTREAM_H
#include "span.h"
#include "string_view.h"
#include "type_traits.h"
#include "src/__support/integer_to_string.h"
namespace __llvm_libc {
namespace cpp {
// This class is to be used to write simple strings into a user provided buffer
// without any dynamic memory allocation. There is no requirement to mimic the
// C++ standard library class std::stringstream.
class StringStream {
span<char> data;
size_t write_ptr = 0; // The current write pointer
bool err = false; // If an error occurs while writing
void write(const char *bytes, size_t size) {
size_t i = 0;
const size_t data_size = data.size();
for (; write_ptr < data_size && i < size; ++i, ++write_ptr)
data[write_ptr] = bytes[i];
if (i < size) {
// If some of the characters couldn't be written, set error.
err = true;
}
}
public:
static constexpr char ENDS = '\0';
// Create a string stream which will write into |buf|.
constexpr StringStream(const span<char> &buf) : data(buf) {}
// Return a string_view to the current characters in the stream. If a
// null terminator was not explicitly written, then the return value
// will not include one. In order to produce a string_view to a null
// terminated string, write ENDS explicitly.
string_view str() const { return string_view(data.data(), write_ptr); }
// Write the characters from |str| to the stream.
StringStream &operator<<(string_view str) {
write(str.data(), str.size());
return *this;
}
// Write the |val| as string.
template <typename T, enable_if_t<is_integral_v<T>, int> = 0>
StringStream &operator<<(T val) {
const IntegerToString<T> buffer(val);
return *this << buffer.view();
}
template <typename T, enable_if_t<is_floating_point_v<T>, int> = 0>
StringStream &operator<<(T) {
// If this specialization gets activated, then the static_assert will
// trigger a compile error about missing floating point number support.
static_assert(!is_floating_point_v<T>,
"Writing floating point numbers is not yet supported");
return *this;
}
// Write a null-terminated string. The terminating null character is not
// written to allow stremaing to continue.
StringStream &operator<<(const char *str) {
return operator<<(string_view(str));
}
// Write a single character.
StringStream &operator<<(char a) {
write(&a, 1);
return *this;
}
// Return true if any write operation(s) failed due to insufficient size.
bool overflow() const { return err; }
size_t bufsize() const { return data.size(); }
};
} // namespace cpp
} // namespace __llvm_libc
#endif // LLVM_LIBC_SRC___SUPPORT_CPP_STRINGSTREAM_H
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