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third/spdlog/details/fmt_helper.h

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+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+#pragma once
+
+#include <chrono>
+#include <iterator>
+#include <spdlog/common.h>
+#include <spdlog/fmt/fmt.h>
+#include <type_traits>
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    #include <charconv>
+    #include <limits>
+#endif
+
+// Some fmt helpers to efficiently format and pad ints and strings
+namespace spdlog {
+namespace details {
+namespace fmt_helper {
+
+inline void append_string_view(spdlog::string_view_t view, memory_buf_t &dest) {
+    auto *buf_ptr = view.data();
+    dest.append(buf_ptr, buf_ptr + view.size());
+}
+
+#ifdef SPDLOG_USE_STD_FORMAT
+template <typename T>
+inline void append_int(T n, memory_buf_t &dest) {
+    // Buffer should be large enough to hold all digits (digits10 + 1) and a sign
+    SPDLOG_CONSTEXPR const auto BUF_SIZE = std::numeric_limits<T>::digits10 + 2;
+    char buf[BUF_SIZE];
+
+    auto [ptr, ec] = std::to_chars(buf, buf + BUF_SIZE, n, 10);
+    if (ec == std::errc()) {
+        dest.append(buf, ptr);
+    } else {
+        throw_spdlog_ex("Failed to format int", static_cast<int>(ec));
+    }
+}
+#else
+template <typename T>
+inline void append_int(T n, memory_buf_t &dest) {
+    fmt::format_int i(n);
+    dest.append(i.data(), i.data() + i.size());
+}
+#endif
+
+template <typename T>
+SPDLOG_CONSTEXPR_FUNC unsigned int count_digits_fallback(T n) {
+    // taken from fmt: https://github.com/fmtlib/fmt/blob/8.0.1/include/fmt/format.h#L899-L912
+    unsigned int count = 1;
+    for (;;) {
+        // Integer division is slow so do it for a group of four digits instead
+        // of for every digit. The idea comes from the talk by Alexandrescu
+        // "Three Optimization Tips for C++". See speed-test for a comparison.
+        if (n < 10) return count;
+        if (n < 100) return count + 1;
+        if (n < 1000) return count + 2;
+        if (n < 10000) return count + 3;
+        n /= 10000u;
+        count += 4;
+    }
+}
+
+template <typename T>
+inline unsigned int count_digits(T n) {
+    using count_type =
+        typename std::conditional<(sizeof(T) > sizeof(uint32_t)), uint64_t, uint32_t>::type;
+#ifdef SPDLOG_USE_STD_FORMAT
+    return count_digits_fallback(static_cast<count_type>(n));
+#else
+    return static_cast<unsigned int>(fmt::
+    // fmt 7.0.0 renamed the internal namespace to detail.
+    // See: https://github.com/fmtlib/fmt/issues/1538
+    #if FMT_VERSION < 70000
+                                         internal
+    #else
+                                         detail
+    #endif
+                                     ::count_digits(static_cast<count_type>(n)));
+#endif
+}
+
+inline void pad2(int n, memory_buf_t &dest) {
+    if (n >= 0 && n < 100)  // 0-99
+    {
+        dest.push_back(static_cast<char>('0' + n / 10));
+        dest.push_back(static_cast<char>('0' + n % 10));
+    } else  // unlikely, but just in case, let fmt deal with it
+    {
+        fmt_lib::format_to(std::back_inserter(dest), SPDLOG_FMT_STRING("{:02}"), n);
+    }
+}
+
+template <typename T>
+inline void pad_uint(T n, unsigned int width, memory_buf_t &dest) {
+    static_assert(std::is_unsigned<T>::value, "pad_uint must get unsigned T");
+    for (auto digits = count_digits(n); digits < width; digits++) {
+        dest.push_back('0');
+    }
+    append_int(n, dest);
+}
+
+template <typename T>
+inline void pad3(T n, memory_buf_t &dest) {
+    static_assert(std::is_unsigned<T>::value, "pad3 must get unsigned T");
+    if (n < 1000) {
+        dest.push_back(static_cast<char>(n / 100 + '0'));
+        n = n % 100;
+        dest.push_back(static_cast<char>((n / 10) + '0'));
+        dest.push_back(static_cast<char>((n % 10) + '0'));
+    } else {
+        append_int(n, dest);
+    }
+}
+
+template <typename T>
+inline void pad6(T n, memory_buf_t &dest) {
+    pad_uint(n, 6, dest);
+}
+
+template <typename T>
+inline void pad9(T n, memory_buf_t &dest) {
+    pad_uint(n, 9, dest);
+}
+
+// return fraction of a second of the given time_point.
+// e.g.
+// fraction<std::milliseconds>(tp) -> will return the millis part of the second
+template <typename ToDuration>
+inline ToDuration time_fraction(log_clock::time_point tp) {
+    using std::chrono::duration_cast;
+    using std::chrono::seconds;
+    auto duration = tp.time_since_epoch();
+    auto secs = duration_cast<seconds>(duration);
+    return duration_cast<ToDuration>(duration) - duration_cast<ToDuration>(secs);
+}
+
+}  // namespace fmt_helper
+}  // namespace details
+}  // namespace spdlog