Moved fmt helpers to new file

include/spdlog/details/fmt_helper.h

+//
+// Created by gabi on 6/15/18.
+//
+
+#pragma once
+
+// Some fmt helpers to efficiently format and pad ints and strings
+namespace spdlog {
+namespace details {
+namespace fmt_helper {
+inline void append_str(const std::string &str, fmt::memory_buffer &dest)
+{
+    const char *str_ptr = str.data();
+    dest.append(str_ptr, str_ptr + str.size());
+}
+
+inline void append_buf(const fmt::memory_buffer &buf, fmt::memory_buffer &dest)
+{
+    const char *buf_ptr = buf.data();
+    dest.append(buf_ptr, buf_ptr + buf.size());
+}
+
+inline void append_int(int n, fmt::memory_buffer &dest)
+{
+    fmt::format_int i(n);
+    dest.append(i.data(), i.data() + i.size());
+}
+
+inline void append_size_t(size_t n, fmt::memory_buffer &dest)
+{
+    fmt::format_int i(n);
+    dest.append(i.data(), i.data() + i.size());
+}
+
+inline void append_and_pad2(int n, fmt::memory_buffer &dest)
+{
+    if (n > 9)
+    {
+        append_int(n, dest);
+        return;
+    }
+    if (n >= 0) // 0-9
+    {
+        dest.push_back('0');
+        append_int(n, dest);
+        return;
+    }
+    // negatives (unlikely but just in case, let fmt deal with it)
+    fmt::format_to(dest, "{:02}", n);
+}
+
+inline void append_and_pad3(int n, fmt::memory_buffer &dest)
+{
+    if (n > 99)
+    {
+        append_int(n, dest);
+        return;
+    }
+    if (n > 9) // 10-99
+    {
+        dest.push_back('0');
+    }
+    else if (n >= 0)
+    {
+        dest.push_back('0');
+        dest.push_back('0');
+    }
+    // negatives (unlikely, but just in case let fmt deal with it)
+    else
+    {
+        fmt::format_to(dest, "{:03}", n);
+        return;
+    }
+    append_int(n, dest);
+}
+
+void append_and_pad6(int n, fmt::memory_buffer &dest)
+{
+    if (n > 99999)
+    {
+        append_int(n, dest);
+        return;
+    }
+    if (n > 9999)
+    {
+        dest.push_back('0');
+    }
+    else if (n > 999)
+    {
+        dest.push_back('0');
+        dest.push_back('0');
+    }
+    else if (n > 99)
+    {
+        dest.push_back('0');
+        dest.push_back('0');
+        dest.push_back('0');
+    }
+    else if (n > 9)
+    {
+        dest.push_back('0');
+        dest.push_back('0');
+        dest.push_back('0');
+        dest.push_back('0');
+    }
+    else if (n >= 0)
+    {
+        dest.push_back('0');
+        dest.push_back('0');
+        dest.push_back('0');
+        dest.push_back('0');
+        dest.push_back('0');
+    }
+    else // negatives (unlikely, but just in case let fmt deal with it)
+    {
+        fmt::format_to(dest, "{:06}", n);
+        return;
+    }
+    append_int(n, dest);
+}
+
+} // namespace fmt_helper
+} // namespace details
+} // namespace spdlog
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