Initial sketch of span_id, example, and build.

WORKSPACE

@@ -20,6 +20,7 @@ load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 # Only needed for tests, not to build the OpenTelemetry library.
 http_archive(
     name = "com_google_googletest",
+    sha256 = "9dc9157a9a1551ec7a7e43daea9a694a0bb5fb8bec81235d8a1e6ef64c716dcb",
     strip_prefix = "googletest-release-1.10.0",
     urls = ["https://github.com/google/googletest/archive/release-1.10.0.tar.gz"],
 )

api/BUILD

@@ -1,3 +1,17 @@
+# Copyright 2019, OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 package(default_visibility = ["//visibility:public"])
 
 cc_library(

api/include/opentelemetry/trace/span_id.h

@@ -0,0 +1,56 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#pragma once
+
+#include <cstdint>
+#include <cstring>
+#include <string>
+
+namespace opentelemetry
+{
+namespace trace
+{
+
+class SpanId final
+{
+public:
+  // The size in bytes of the SpanId.
+  static constexpr int kSize = 8;
+
+  // An invalid SpanId (all zeros).
+  SpanId() : rep_{0} {}
+
+  // Creates a SpanId by copying the first kSize bytes from the buffer.
+  explicit SpanId(const uint8_t *buf) { memcpy(rep_, buf, kSize); }
+
+  // Returns a 16-char hex string of the SpanId value.
+  std::string ToHex() const
+  {
+    constexpr char kHex[] = "0123456789ABCDEF";
+    std::string s(kSize * 2, ' ');
+    for (int i = 0; i < kSize; ++i)
+    {
+      s[i * 2 + 0] = kHex[(rep_[i] >> 4) & 0xF];
+      s[i * 2 + 1] = kHex[(rep_[i] >> 0) & 0xF];
+    }
+    return s;
+  }
+
+private:
+  uint8_t rep_[kSize];
+};
+
+}  // namespace trace
+}  // namespace opentelemetry

examples/README.md

@@ -0,0 +1,7 @@
+The examples/ directory is a separate bazel workspace, to show how
+to build libraries and binaries that use the OpenTelemetry library.
+
+```
+cd examples/
+bazel build //helloworld
+```

examples/WORKSPACE

@@ -0,0 +1,21 @@
+# Copyright 2019, OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+workspace(name = "io_opentelemetry_cpp_examples")
+
+# OpenTelemetry should be imported via http_archive.
+local_repository(
+    name = "io_opentelemetry_cpp",
+    path = "../",
+)

examples/helloworld/BUILD

@@ -0,0 +1,21 @@
+# Copyright 2019, OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+cc_binary(
+    name = "helloworld",
+    srcs = ["helloworld.cc"],
+    deps = [
+        "@io_opentelemetry_cpp//api",
+    ],
+)

examples/helloworld/helloworld.cc

@@ -0,0 +1,25 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <opentelemetry/trace/span_id.h>
+
+#include <cstdint>
+#include <iostream>
+
+int main()
+{
+  constexpr uint8_t id[] = {1, 2, 3, 4, 0x50, 0x60, 0x70, 0x80};
+  opentelemetry::trace::SpanId span_id(id);
+  std::cout << "Span ID: '" << span_id.ToHex() << "'\n";
+}

tools/setup-buildtools-mac.sh

@@ -5,7 +5,7 @@
 # control of the brew dirs. That causes the brew update to fail.
 # Temporarily allow the user to take over control of brew files.
 
-echo *** 
+echo ***
 echo *** You may need to enter your admin password to update the brew files:
 echo ***