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1//===-- A simple implementation of string stream class ----------*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef LLVM_LIBC_SRC___SUPPORT_CPP_STRINGSTREAM_H10#define LLVM_LIBC_SRC___SUPPORT_CPP_STRINGSTREAM_H11 12#include "span.h"13#include "src/__support/macros/config.h"14#include "string_view.h"15#include "type_traits.h"16 17#include "src/__support/integer_to_string.h"18 19namespace LIBC_NAMESPACE_DECL {20namespace cpp {21 22// This class is to be used to write simple strings into a user provided buffer23// without any dynamic memory allocation. There is no requirement to mimic the24// C++ standard library class std::stringstream.25class StringStream {26 span<char> data;27 size_t write_ptr = 0; // The current write pointer28 bool err = false; // If an error occurs while writing29 30 void write(const char *bytes, size_t size) {31 size_t i = 0;32 const size_t data_size = data.size();33 for (; write_ptr < data_size && i < size; ++i, ++write_ptr)34 data[write_ptr] = bytes[i];35 if (i < size) {36 // If some of the characters couldn't be written, set error.37 err = true;38 }39 }40 41public:42 static constexpr char ENDS = '\0';43 44 // Create a string stream which will write into |buf|.45 constexpr StringStream(const span<char> &buf) : data(buf) {}46 47 // Return a string_view to the current characters in the stream. If a48 // null terminator was not explicitly written, then the return value49 // will not include one. In order to produce a string_view to a null50 // terminated string, write ENDS explicitly.51 string_view str() const { return string_view(data.data(), write_ptr); }52 53 // Write the characters from |str| to the stream.54 StringStream &operator<<(string_view str) {55 write(str.data(), str.size());56 return *this;57 }58 59 // Write the |val| as string.60 template <typename T, enable_if_t<is_integral_v<T>, int> = 0>61 StringStream &operator<<(T val) {62 const IntegerToString<T> buffer(val);63 return *this << buffer.view();64 }65 66 template <typename T, enable_if_t<is_floating_point_v<T>, int> = 0>67 StringStream &operator<<(T) {68 // If this specialization gets activated, then the static_assert will69 // trigger a compile error about missing floating point number support.70 static_assert(!is_floating_point_v<T>,71 "Writing floating point numbers is not yet supported");72 return *this;73 }74 75 // Write a null-terminated string. The terminating null character is not76 // written to allow stremaing to continue.77 StringStream &operator<<(const char *str) {78 return operator<<(string_view(str));79 }80 81 // Write a single character.82 StringStream &operator<<(char a) {83 write(&a, 1);84 return *this;85 }86 87 // Return true if any write operation(s) failed due to insufficient size.88 bool overflow() const { return err; }89 90 size_t bufsize() const { return data.size(); }91};92 93} // namespace cpp94} // namespace LIBC_NAMESPACE_DECL95 96#endif // LLVM_LIBC_SRC___SUPPORT_CPP_STRINGSTREAM_H97