// Copyright 2022 The Abseil Authors

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#ifndef ABSL_LOG_INTERNAL_APPEND_TRUNCATED_H_

#define ABSL_LOG_INTERNAL_APPEND_TRUNCATED_H_

#include <cstddef>

#include <cstring>

#include <string_view>

#include "absl/base/config.h"

#include "absl/strings/internal/utf8.h"

#include "absl/strings/string_view.h"

#include "absl/types/span.h"

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace log_internal {

// Copies into `dst` as many bytes of `src` as will fit, then truncates the

// copied bytes from the front of `dst` and returns the number of bytes written.

inline size_t AppendTruncated(absl::string_view src, absl::Span<char> &dst) {

  if (src.size() > dst.size()) src = src.substr(0, dst.size());

  memcpy(dst.data(), src.data(), src.size());

  dst.remove_prefix(src.size());

  return src.size();

}

// Likewise, but it also takes a wide character string and transforms it into a

// UTF-8 encoded byte string regardless of the current locale.

// - On platforms where `wchar_t` is 2 bytes (e.g., Windows), the input is

//   treated as UTF-16.

// - On platforms where `wchar_t` is 4 bytes (e.g., Linux, macOS), the input

//   is treated as UTF-32.

inline size_t AppendTruncated(std::wstring_view src, absl::Span<char> &dst) {

  absl::strings_internal::ShiftState state;

  size_t total_bytes_written = 0;

  for (const wchar_t wc : src) {

    // If the destination buffer might not be large enough to write the next

    // character, stop.

    if (dst.size() < absl::strings_internal::kMaxEncodedUTF8Size) break;

    size_t bytes_written =

        absl::strings_internal::WideToUtf8(wc, dst.data(), state);

    if (bytes_written == static_cast<size_t>(-1)) {

      // Invalid character. Encode REPLACEMENT CHARACTER (U+FFFD) instead.

      constexpr wchar_t kReplacementCharacter = L'\uFFFD';

      bytes_written = absl::strings_internal::WideToUtf8(kReplacementCharacter,

                                                         dst.data(), state);

    }

    dst.remove_prefix(bytes_written);

    total_bytes_written += bytes_written;

  }

  return total_bytes_written;

}

// Likewise, but `n` copies of `c`.

inline size_t AppendTruncated(char c, size_t n, absl::Span<char> &dst) {

  if (n > dst.size()) n = dst.size();

  memset(dst.data(), c, n);

  dst.remove_prefix(n);

  return n;

}

}  // namespace log_internal

ABSL_NAMESPACE_END

}  // namespace absl

#endif  // ABSL_LOG_INTERNAL_APPEND_TRUNCATED_H_