Adding B3 propagator

api/include/opentelemetry/nostd/string_view.h

@@ -120,6 +120,20 @@ class string_view
     return substr(pos1, count1).compare(string_view(s, count2));
   };
 
+  size_type find(char ch, size_type pos = 0) const noexcept
+  {
+    size_type res = npos;
+    if (pos < length())
+    {
+      auto found = Traits::find(data() + pos, length() - pos, ch);
+      if (found)
+      {
+        res = found - data();
+      }
+    }
+    return res;
+  }
+
   bool operator<(const string_view v) const noexcept { return compare(v) < 0; }
 
   bool operator>(const string_view v) const noexcept { return compare(v) > 0; }

api/include/opentelemetry/trace/propagation/b3_propagator.h

@@ -0,0 +1,276 @@
+#pragma once
+
+#include <array>
+#include <iostream>
+#include <map>
+#include <string>
+#include "opentelemetry/common/key_value_iterable.h"
+#include "opentelemetry/context/context.h"
+#include "opentelemetry/nostd/shared_ptr.h"
+#include "opentelemetry/nostd/span.h"
+#include "opentelemetry/nostd/string_view.h"
+#include "opentelemetry/nostd/variant.h"
+#include "opentelemetry/trace/default_span.h"
+#include "opentelemetry/trace/propagation/http_text_format.h"
+#include "opentelemetry/trace/span.h"
+#include "opentelemetry/trace/span_context.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace trace
+{
+namespace propagation
+{
+
+static const nostd::string_view kB3CombinedHeader = "b3";
+
+static const nostd::string_view kB3TraceIdHeader = "X-B3-TraceId";
+static const nostd::string_view kB3SpanIdHeader  = "X-B3-SpanId";
+static const nostd::string_view kB3SampledHeader = "X-B3-Sampled";
+
+/*
+     B3, single header:
+                   b3: 80f198ee56343ba864fe8b2a57d3eff7-e457b5a2e4d86bd1-1-05e3ac9a4f6e3b90
+                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^ ^ ^^^^^^^^^^^^^^^^
+                       0          TraceId            31 33  SpanId    48 | 52 ParentSpanId 68
+                                                                        50 Debug flag
+     Multiheader version:                                           X-B3-Sampled
+                             X-B3-TraceId                X-B3-SpanId    X-B3-ParentSpanId (ignored)
+*/
+
+static const int kTraceIdHexStrLength   = 32;
+static const int kSpanIdHexStrLength    = 16;
+static const int kTraceFlagHexStrLength = 1;
+
+// The B3PropagatorExtractor class provides an interface that enables extracting context from
+// headers of HTTP requests. HTTP frameworks and clients can integrate with B3Propagator by
+// providing the object  containing the headers, and a getter function for the extraction.
+// Based on:
+// https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/context/api-propagators.md#b3-extract
+template <typename T>
+class B3PropagatorExtractor : public HTTPTextFormat<T>
+{
+public:
+  // Rules that manages how context will be extracted from carrier.
+  using Getter = nostd::string_view (*)(const T &carrier, nostd::string_view trace_type);
+
+  // Returns the context that is stored in the HTTP header carrier with the getter as extractor.
+  context::Context Extract(Getter getter,
+                           const T &carrier,
+                           context::Context &context) noexcept override
+  {
+    SpanContext span_context = ExtractImpl(getter, carrier);
+    nostd::shared_ptr<Span> sp{new DefaultSpan(span_context)};
+    return context.SetValue(kSpanKey, sp);
+  }
+
+  static SpanContext GetCurrentSpan(const context::Context &context)
+  {
+    context::Context ctx(context);
+    context::ContextValue span = ctx.GetValue(kSpanKey);
+    if (nostd::holds_alternative<nostd::shared_ptr<Span>>(span))
+    {
+      return nostd::get<nostd::shared_ptr<Span>>(span).get()->GetContext();
+    }
+    return SpanContext::GetInvalid();
+  }
+
+  static TraceId GenerateTraceIdFromString(nostd::string_view trace_id)
+  {
+    uint8_t buf[kTraceIdHexStrLength / 2];
+    uint8_t *b_ptr = buf;
+    GenerateBuffFromHexStrPad0(trace_id, sizeof(buf), buf);
+    return TraceId(buf);
+  }
+
+  static SpanId GenerateSpanIdFromString(nostd::string_view span_id)
+  {
+    uint8_t buf[kSpanIdHexStrLength / 2];
+    uint8_t *b_ptr = buf;
+    GenerateBuffFromHexStrPad0(span_id, sizeof(buf), buf);
+    return SpanId(buf);
+  }
+
+  static TraceFlags GenerateTraceFlagsFromString(nostd::string_view trace_flags)
+  {
+    if (trace_flags.length() != 1 || (trace_flags[0] != '1' && trace_flags[0] != 'd'))
+    {  // check for invalid length of flags and treat 'd' as sampled
+      return TraceFlags(0);
+    }
+    return TraceFlags(TraceFlags::kIsSampled);
+  }
+
+private:
+  // Converts hex numbers (string_view) into bytes stored in a buffer and pads buffer with 0.
+  static void GenerateBuffFromHexStrPad0(nostd::string_view hexStr, int bufSize, uint8_t *buf)
+  {  // we are doing this starting from "right" side for left-padding
+    nostd::string_view::size_type posInp = hexStr.length();
+    int posOut                           = bufSize;
+    while (posOut--)
+    {
+      int val = 0;
+      if (posInp)
+      {
+        int hexDigit2 = HexToInt(hexStr[--posInp]);  // low nibble
+        int hexDigit1 = 0;
+        if (posInp)
+        {
+          hexDigit1 = HexToInt(hexStr[--posInp]);
+        }
+        if (hexDigit1 < 0 || hexDigit2 < 0)
+        {  // malformed hex sequence. Fill entire buffer with zeroes.
+          for (int j = 0; j < bufSize; j++)
+          {
+            buf[j] = 0;
+          }
+          return;
+        }
+        val = hexDigit1 * 16 + hexDigit2;
+      }
+      buf[posOut] = val;
+    }
+  }
+
+  // Converts a single character to a corresponding integer (e.g. '1' to 1), return -1
+  // if the character is not a valid number in hex.
+  static uint8_t HexToInt(char c)
+  {
+    if (c >= '0' && c <= '9')
+    {
+      return (int)(c - '0');
+    }
+    else if (c >= 'a' && c <= 'f')
+    {
+      return (int)(c - 'a' + 10);
+    }
+    else if (c >= 'A' && c <= 'F')
+    {
+      return (int)(c - 'A' + 10);
+    }
+    else
+    {
+      return -1;
+    }
+  }
+
+  static SpanContext ExtractImpl(Getter getter, const T &carrier)
+  {
+    // all these are hex values
+    nostd::string_view trace_id;
+    nostd::string_view span_id;
+    nostd::string_view trace_flags;
+
+    // first let's try a single-header variant
+    auto singleB3Header = getter(carrier, kB3CombinedHeader);
+    if (!singleB3Header.empty())
+    {
+      // From: https://github.com/openzipkin/b3-propagation/blob/master/RATIONALE.md
+      // trace_id can be 16 or 32 chars
+      auto firstSep = singleB3Header.find('-');
+      trace_id      = singleB3Header.substr(0, firstSep);
+      if (firstSep != nostd::string_view::npos)
+      {  // at least two fields are required
+        auto secondSep = singleB3Header.find('-', firstSep + 1);
+        if (secondSep != nostd::string_view::npos)
+        {  // more than two fields - check also trace_flags
+          span_id = singleB3Header.substr(firstSep + 1, secondSep - firstSep - 1);
+          if (secondSep + 1 < singleB3Header.size())
+          {
+            trace_flags = singleB3Header.substr(secondSep + 1, kTraceFlagHexStrLength);
+          }
+        }
+        else
+        {
+          span_id = singleB3Header.substr(firstSep + 1);
+        }
+      }
+    }
+    else
+    {
+      trace_id    = getter(carrier, kB3TraceIdHeader);
+      span_id     = getter(carrier, kB3SpanIdHeader);
+      trace_flags = getter(carrier, kB3SampledHeader);
+    }
+
+    // now convert hex to objects
+    TraceId trace_id_obj = GenerateTraceIdFromString(trace_id);
+    SpanId span_id_obj   = GenerateSpanIdFromString(span_id);
+    if (!trace_id_obj.IsValid() || !span_id_obj.IsValid())
+    {
+      return SpanContext(false, false);
+    }
+    TraceFlags trace_flags_obj = GenerateTraceFlagsFromString(trace_flags);
+    return SpanContext(trace_id_obj, span_id_obj, trace_flags_obj, true);
+  }
+};
+
+// The B3Propagator class provides interface that enables extracting and injecting context into
+// single header of HTTP Request.
+template <typename T>
+class B3Propagator : public B3PropagatorExtractor<T>
+{
+public:
+  // Rules that manages how context will be injected to carrier.
+  using Setter = void (*)(T &carrier,
+                          nostd::string_view trace_type,
+                          nostd::string_view trace_description);
+  // Sets the context for a HTTP header carrier with self defined rules.
+  void Inject(Setter setter, T &carrier, const context::Context &context) noexcept override
+  {
+    SpanContext span_context = B3PropagatorExtractor<T>::GetCurrentSpan(context);
+    if (!span_context.IsValid())
+    {
+      return;
+    }
+    char trace_id[32];
+    TraceId(span_context.trace_id()).ToLowerBase16(trace_id);
+    char span_id[16];
+    SpanId(span_context.span_id()).ToLowerBase16(span_id);
+    char trace_flags[2];
+    TraceFlags(span_context.trace_flags()).ToLowerBase16(trace_flags);
+    // Note: This is only temporary replacement for appendable string
+    std::string hex_string = "";
+    for (int i = 0; i < 32; i++)
+    {
+      hex_string.push_back(trace_id[i]);
+    }
+    hex_string.push_back('-');
+    for (int i = 0; i < 16; i++)
+    {
+      hex_string.push_back(span_id[i]);
+    }
+    hex_string.push_back('-');
+    hex_string.push_back(trace_flags[1]);
+    setter(carrier, kB3CombinedHeader, hex_string);
+  }
+};
+
+template <typename T>
+class B3PropagatorMultiHeader : public B3PropagatorExtractor<T>
+{
+public:
+  // Rules that manages how context will be injected to carrier.
+  using Setter = void (*)(T &carrier,
+                          nostd::string_view trace_type,
+                          nostd::string_view trace_description);
+  void Inject(Setter setter, T &carrier, const context::Context &context) noexcept override
+  {
+    SpanContext span_context = B3PropagatorExtractor<T>::GetCurrentSpan(context);
+    if (!span_context.IsValid())
+    {
+      return;
+    }
+    char trace_id[32];
+    TraceId(span_context.trace_id()).ToLowerBase16(trace_id);
+    char span_id[16];
+    SpanId(span_context.span_id()).ToLowerBase16(span_id);
+    char trace_flags[2];
+    TraceFlags(span_context.trace_flags()).ToLowerBase16(trace_flags);
+    setter(carrier, kB3TraceIdHeader, nostd::string_view(trace_id, sizeof(trace_id)));
+    setter(carrier, kB3SpanIdHeader, nostd::string_view(span_id, sizeof(span_id)));
+    setter(carrier, kB3SampledHeader, nostd::string_view(trace_flags + 1, 1));
+  }
+};
+
+}  // namespace propagation
+}  // namespace trace
+OPENTELEMETRY_END_NAMESPACE

api/test/nostd/string_view_test.cc

@@ -75,6 +75,24 @@ TEST(StringViewTest, SubstrOutOfRange)
 #endif
 }
 
+TEST(StringViewTest, FindSingleCharacter)
+{
+  string_view s = "abc";
+
+  // starting from 0-th position (default)
+  EXPECT_EQ(s.find('a'), 0);
+  EXPECT_EQ(s.find('b'), 1);
+  EXPECT_EQ(s.find('c'), 2);
+  EXPECT_EQ(s.find('d'), -1);  // FIXME: string_view:npos - problem with linker
+
+  // starting from given index
+  EXPECT_EQ(s.find('a', 1), -1);
+  EXPECT_EQ(s.find('b', 1), 1);
+
+  // out of index
+  EXPECT_EQ(s.find('a', 10), -1);
+}
+
 TEST(StringViewTest, Compare)
 {
   string_view s1 = "aaa";

api/test/trace/propagation/CMakeLists.txt

@@ -1,4 +1,4 @@
-foreach(testname http_text_format_test)
+foreach(testname http_text_format_test b3_propagation_test)
   add_executable(${testname} "${testname}.cc")
   target_link_libraries(
     ${testname} ${GTEST_BOTH_LIBRARIES} ${CORE_RUNTIME_LIBS}