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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-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #ifndef LLVM_LIBC_SRC___SUPPORT_CPP_STRINGSTREAM_H |
| 10 | #define LLVM_LIBC_SRC___SUPPORT_CPP_STRINGSTREAM_H |
| 11 | |
| 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 | |
| 19 | namespace LIBC_NAMESPACE_DECL { |
| 20 | namespace cpp { |
| 21 | |
| 22 | // This class is to be used to write simple strings into a user provided buffer |
| 23 | // without any dynamic memory allocation. There is no requirement to mimic the |
| 24 | // C++ standard library class std::stringstream. |
| 25 | class StringStream { |
| 26 | span<char> data; |
| 27 | size_t write_ptr = 0; // The current write pointer |
| 28 | bool err = false; // If an error occurs while writing |
| 29 | |
| 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 | |
| 41 | public: |
| 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 a |
| 48 | // null terminator was not explicitly written, then the return value |
| 49 | // will not include one. In order to produce a string_view to a null |
| 50 | // 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 will |
| 69 | // 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 not |
| 76 | // 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 cpp |
| 94 | } // namespace LIBC_NAMESPACE_DECL |
| 95 | |
| 96 | #endif // LLVM_LIBC_SRC___SUPPORT_CPP_STRINGSTREAM_H |
| 97 |
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