1 files changed, 79 insertions, 0 deletions

diff --git a/server/src/trace.cppm b/server/src/trace.cppm
new file mode 100644
index 0000000..00ecd05
--- /dev/null
+++ b/server/src/trace.cppm
@@ -0,0 +1,79 @@
+module;
+
+// Might as well since we're using OpenSSL
+#include <openssl/err.h>
+#include <openssl/rand.h>
+
+export module routemon:trace;
+
+import std;
+import :util;
+
+namespace routemon::trace {
+
+  class uuid7 {
+    std::uint64_t high_ = 0;
+    std::uint64_t low_  = 0;
+
+  public:
+    uuid7() {
+      namespace chrono = std::chrono;
+      auto const unix_time_ms_signed = static_cast<std::int64_t>(chrono::duration_cast<chrono::milliseconds>(chrono::system_clock::now().time_since_epoch()).count());
+      if (unix_time_ms_signed < 0)
+        throw std::runtime_error{"system time before UNIX epoch"};
+      auto const unix_time_ms = static_cast<std::uint64_t>(unix_time_ms_signed);
+      if (std::countl_zero(unix_time_ms) < 16)
+        throw std::runtime_error{"system time too great"};
+
+      auto rand = std::array<unsigned char, 10>{};
+      int s = RAND_bytes(rand.data(), static_cast<int>(rand.size()));
+      if (s != 1) {
+        unsigned long e = ERR_get_error();
+        throw std::runtime_error{std::format("failed to generate UUID(v7): {} ({}, code {})", ERR_reason_error_string(e), ERR_lib_error_string(e), e)};
+      }
+
+      auto version = std::uint64_t{0b0111};
+      auto variant = std::uint64_t{0b10};
+
+      high_ |= unix_time_ms << 16;
+      high_ |= version << 12;
+      high_ |= std::uint64_t{rand[0]} << 4;
+      high_ |= std::uint64_t{rand[1]};
+      low_  |= variant << 62;
+      low_  |= std::uint64_t{rand[2]} << 54;
+      low_  |= std::uint64_t{rand[3]} << 48;
+      low_  |= std::uint64_t{rand[4]} << 40;
+      low_  |= std::uint64_t{rand[5]} << 32;
+      low_  |= std::uint64_t{rand[6]} << 24;
+      low_  |= std::uint64_t{rand[7]} << 16;
+      low_  |= std::uint64_t{rand[8]} <<  8;
+      low_  |= std::uint64_t{rand[9]};
+    }
+
+    auto format(std::array<char, 37>& target) -> void {
+      auto high_high     = (high_ & 0xffff'ffff'0000'0000) >> 32;
+      auto high_low_high = (high_ & 0x0000'0000'ffff'0000) >> 16;
+      auto low_low_high  = (high_ & 0x0000'0000'0000'ffff) >>  0;
+      auto high_low      = (low_  & 0xffff'0000'0000'0000) >> 48;
+      auto low_low       = (low_  & 0x0000'ffff'ffff'ffff) >>  0;
+
+      std::format_to(target.begin(), "{:0>8x}-{:0>4x}-{:0>4x}-{:0>4x}-{:0>12x}",
+                     high_high, high_low_high, low_low_high, high_low, low_low);
+      target.back() = '\0';
+    }
+  };
+
+  export class id {
+    std::array<char, 37> chars_;
+
+  public:
+    id() {
+      uuid7{}.format(chars_);
+    }
+
+    auto as_string() const -> util::zstring_view {
+      return util::zstring_view{chars_.data(), chars_.size() - 1};
+    }
+  };
+
+} // namespace routemon::trace