Add a regular strlcpy implementation

That also works for buffers without a compile time known size.

src/common/utils.cpp

@@ -94,6 +94,19 @@ bool is_watchdog_timer_disabled() {
     return disable_watchdog_env && disable_watchdog_env == "1"sv;
 }
 
+size_t strlcpy_buffer(char* dst, const std::string& src, size_t size) {
+    if (size == 0) {
+        return src.size();
+    }
+
+    // Make sure there's always room for a null terminator
+    const size_t copy_len = std::min(size - 1, src.size());
+    std::copy(src.c_str(), src.c_str() + copy_len, dst);
+    dst[copy_len] = 0;
+
+    return src.size();
+}
+
 ScopedFlushToZero::ScopedFlushToZero() noexcept {
     old_ftz_mode_ = _MM_GET_FLUSH_ZERO_MODE();
     _MM_SET_FLUSH_ZERO_MODE(_MM_FLUSH_ZERO_ON);

src/common/utils.h

@@ -159,6 +159,13 @@ size_t strlcpy_buffer(char dst[N], const std::string& src) {
     return src.size();
 }
 
+/**
+ * An implementation of BSD's `strlcpy()` function specialized for copying C++
+ * strings to char buffers with runtime known lengths.
+ * https://linux.die.net/man/3/strlcpy
+ */
+size_t strlcpy_buffer(char* dst, const std::string& src, size_t size);
+
 /**
  * A RAII wrapper that will temporarily enable the FTZ flag so that denormals
  * are automatically flushed to zero, returning to whatever the flag was