feat(trace-utils): serialize v04 spans to OTLP

.github/CODEOWNERS

@@ -46,6 +46,7 @@ libdd-dogstatsd-client               @DataDog/apm-common-components-core
 libdd-library-config*/               @DataDog/apm-sdk-capabilities
 libdd-log*/                          @DataDog/apm-common-components-core
 libdd-profiling*/                    @DataDog/libdatadog-profiling
+libdd-proto-codec                    @DataDog/apm-common-components-core
 libdd-telemetry*/                    @DataDog/apm-common-components-core
 libdd-tinybytes                      @DataDog/apm-common-components-core
 libdd-trace-normalization            @DataDog/serverless @DataDog/libdatadog-apm

Cargo.toml

@@ -46,7 +46,7 @@ members = [
   "libdd-tinybytes",
   "libdd-dogstatsd-client",
   "libdd-log",
-  "libdd-log-ffi",
+  "libdd-log-ffi", "libdd-proto-codec",
 ]
 
 # https://doc.rust-lang.org/cargo/reference/resolver.html

libdd-proto-codec/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "libdd-proto-codec"
+rust-version.workspace = true
+edition.workspace = true
+version.workspace = true
+license.workspace = true
+authors.workspace = true
+
+[dependencies]
+bytes = { version = "1.4" }
+
+[dev-dependencies]
+prost = { version = "0.13", features = ["derive"] }
+arbitrary = { version = "1", features = ["derive"] }
+rand = "0.9"
+criterion = { version = "0.5", features = ["html_reports"] }

libdd-proto-codec/src/constants.rs

@@ -0,0 +1,33 @@
+use core::hash;
+
+#[repr(u8)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, hash::Hash, PartialOrd, Ord)]
+pub enum WireType {
+    Varint = 0,
+    Fixed64 = 1,
+    LengthDelimited = 2,
+    StartGroup = 3, // Deprecated in proto3, but still used in proto2.
+    EndGroup = 4,   // Deprecated in proto3, but still used in proto2.
+    Fixed32 = 5,
+}
+
+impl WireType {
+    #[inline]
+    #[allow(unused)]
+    pub(crate) const fn from_u32(value: u32) -> Option<Self> {
+        match value {
+            0 => Some(WireType::Varint),
+            1 => Some(WireType::Fixed64),
+            2 => Some(WireType::LengthDelimited),
+            3 => Some(WireType::StartGroup),
+            4 => Some(WireType::EndGroup),
+            5 => Some(WireType::Fixed32),
+            _ => None,
+        }
+    }
+
+    #[inline]
+    pub(crate) const fn to_u32(self) -> u32 {
+        self as u32
+    }
+}