Adds B3SinglePropagation for the "b3" header

This will be used for JMS and other propagation formats such as w3c
tracestate entry. It is notably more efficient than multi-header.

Example header: `b3: 4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-1`

To aid in migration, this teaches the normal B3 to attempt to extract
single header variants as well.

See openzipkin/b3-propagation#21

brave-tests/src/test/java/brave/propagation/B3SinglePropagationTest.java

@@ -0,0 +1,93 @@
+package brave.propagation;
+
+import brave.internal.Nullable;
+import brave.test.propagation.PropagationTest;
+import java.util.Map;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class B3SinglePropagationTest extends PropagationTest<String> {
+  @Override protected Propagation<String> propagation() {
+    return Propagation.B3_SINGLE_STRING;
+  }
+
+  @Override protected void inject(Map<String, String> map, @Nullable String traceId,
+      @Nullable String parentId, @Nullable String spanId, @Nullable Boolean sampled,
+      @Nullable Boolean debug) {
+    StringBuilder builder = new StringBuilder();
+    if (traceId == null) {
+      if (sampled != null) {
+        builder.append(sampled ? '1' : '0');
+        if (debug != null) builder.append(debug ? "-1" : "-0");
+      } else if (Boolean.TRUE.equals(debug)) {
+        builder.append("1-1");
+      }
+    } else {
+      builder.append(traceId).append('-').append(spanId);
+      if (sampled != null) builder.append(sampled ? "-1" : "-0");
+      if (parentId != null) builder.append('-').append(parentId);
+      if (debug != null) builder.append(debug ? "-1" : "-0");
+    }
+    if (builder.length() != 0) map.put("b3", builder.toString());
+  }
+
+  @Override protected void inject(Map<String, String> carrier, SamplingFlags flags) {
+    if (flags.debug()) {
+      carrier.put("b3", "1-1");
+    } else if (flags.sampled() != null) {
+      carrier.put("b3", flags.sampled() ? "1" : "0");
+    }
+  }
+
+  @Test public void extractTraceContext_sampledFalse() {
+    MapEntry mapEntry = new MapEntry();
+    map.put("b3", "0");
+
+    SamplingFlags result = propagation().extractor(mapEntry).extract(map).samplingFlags();
+
+    assertThat(result)
+        .isEqualTo(SamplingFlags.NOT_SAMPLED);
+  }
+
+  @Test public void extractTraceContext_sampledFalseUpperCase() {
+    MapEntry mapEntry = new MapEntry();
+    map.put("B3", "0");
+
+    SamplingFlags result = propagation().extractor(mapEntry).extract(map).samplingFlags();
+
+    assertThat(result)
+        .isEqualTo(SamplingFlags.NOT_SAMPLED);
+  }
+
+  @Test public void extractTraceContext_malformed() {
+    MapEntry mapEntry = new MapEntry();
+    map.put("b3", "not-a-tumor");
+
+    SamplingFlags result = propagation().extractor(mapEntry).extract(map).samplingFlags();
+
+    assertThat(result)
+        .isEqualTo(SamplingFlags.EMPTY);
+  }
+
+  @Test public void extractTraceContext_malformed_uuid() {
+    MapEntry mapEntry = new MapEntry();
+    map.put("b3", "b970dafd-0d95-40aa-95d8-1d8725aebe40");
+
+    SamplingFlags result = propagation().extractor(mapEntry).extract(map).samplingFlags();
+
+    assertThat(result)
+        .isEqualTo(SamplingFlags.EMPTY);
+  }
+
+  @Test public void extractTraceContext_debug_with_ids() {
+    MapEntry mapEntry = new MapEntry();
+
+    map.put("b3", "4bf92f3577b34da6a3ce929d0e0e4736-00f067aa0ba902b7-1-1");
+
+    TraceContext result = propagation().extractor(mapEntry).extract(map).context();
+
+    assertThat(result.debug())
+        .isTrue();
+  }
+}

brave/src/main/java/brave/propagation/B3Propagation.java

@@ -1,10 +1,13 @@
 package brave.propagation;
 
+import brave.propagation.B3SinglePropagation.B3SingleExtractor;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 
 import static brave.internal.HexCodec.toLowerHex;
+import static brave.propagation.B3SinglePropagation.LOWER_NAME;
+import static brave.propagation.B3SinglePropagation.UPPER_NAME;
 
 /**
  * Implements <a href="https://github.com/openzipkin/b3-propagation">B3 Propagation</a>
@@ -46,6 +49,8 @@ public final class B3Propagation<K> implements Propagation<K> {
    * "1" implies sampled and is a request to override collection-tier sampling policy.
    */
   static final String FLAGS_NAME = "X-B3-Flags";
+  final K lowerKey; // only for extraction
+  final K upperKey; // only for extraction
   final K traceIdKey;
   final K spanIdKey;
   final K parentSpanIdKey;
@@ -54,6 +59,8 @@ public final class B3Propagation<K> implements Propagation<K> {
   final List<K> fields;
 
   B3Propagation(KeyFactory<K> keyFactory) {
+    this.lowerKey = keyFactory.create(LOWER_NAME);
+    this.upperKey = keyFactory.create(UPPER_NAME);
     this.traceIdKey = keyFactory.create(TRACE_ID_NAME);
     this.spanIdKey = keyFactory.create(SPAN_ID_NAME);
     this.parentSpanIdKey = keyFactory.create(PARENT_SPAN_ID_NAME);
@@ -104,15 +111,23 @@ static final class B3Injector<C, K> implements TraceContext.Injector<C> {
 
   static final class B3Extractor<C, K> implements TraceContext.Extractor<C> {
     final B3Propagation<K> propagation;
+    final B3SingleExtractor<C, K> singleExtractor;
     final Getter<C, K> getter;
 
     B3Extractor(B3Propagation<K> propagation, Getter<C, K> getter) {
       this.propagation = propagation;
+      this.singleExtractor =
+          new B3SingleExtractor<>(propagation.lowerKey, propagation.upperKey, getter);
       this.getter = getter;
     }
 
     @Override public TraceContextOrSamplingFlags extract(C carrier) {
       if (carrier == null) throw new NullPointerException("carrier == null");
+
+      // try to extract single-header format
+      TraceContextOrSamplingFlags extracted = singleExtractor.extract(carrier);
+      if (extracted != TraceContextOrSamplingFlags.EMPTY) return extracted;
+
       // Start by looking at the sampled state as this is used regardless
       // Official sampled value is 1, though some old instrumentation send true
       String sampled = getter.get(carrier, propagation.sampledKey);

brave/src/main/java/brave/propagation/B3SingleFormat.java

@@ -0,0 +1,168 @@
+package brave.propagation;
+
+import brave.internal.Nullable;
+import java.util.Collections;
+import java.util.logging.Logger;
+
+import static brave.internal.HexCodec.lenientLowerHexToUnsignedLong;
+import static brave.internal.HexCodec.writeHexLong;
+import static brave.internal.TraceContexts.FLAG_DEBUG;
+import static brave.internal.TraceContexts.FLAG_SAMPLED;
+import static brave.internal.TraceContexts.FLAG_SAMPLED_SET;
+import static java.util.logging.Level.FINE;
+
+/** Implements the progation format described in {@link B3SinglePropagation}. */
+final class B3SingleFormat {
+  static final Logger logger = Logger.getLogger(B3SingleFormat.class.getName());
+  static final int FORMAT_MAX_LENGTH = 32 + 1 + 16 + 2 + 16 + 2; // traceid128-spanid-1-parentid-1
+
+  static String writeB3SingleFormat(TraceContext context) {
+    char[] result = getCharBuffer();
+    int pos = 0;
+    long traceIdHigh = context.traceIdHigh();
+    if (traceIdHigh != 0L) {
+      writeHexLong(result, pos, traceIdHigh);
+      pos += 16;
+    }
+    writeHexLong(result, pos, context.traceId());
+    pos += 16;
+    result[pos++] = '-';
+    writeHexLong(result, pos, context.spanId());
+    pos += 16;
+
+    Boolean sampled = context.sampled();
+    if (sampled != null) {
+      result[pos++] = '-';
+      result[pos++] = (sampled == Boolean.TRUE) ? '1' : '0';
+    }
+
+    long b3Id = context.parentIdAsLong();
+    if (b3Id != 0) {
+      result[pos++] = '-';
+      writeHexLong(result, pos, b3Id);
+      pos += 16;
+    }
+
+    if (context.debug()) {
+      result[pos++] = '-';
+      result[pos++] = '1';
+    }
+    return new String(result, 0, pos);
+  }
+
+  static @Nullable TraceContextOrSamplingFlags maybeB3SingleFormat(String b3) {
+    int length = b3.length();
+    if (length == 1) {
+      int flags = parseSampledFlag(b3, 0);
+      if (flags == 0) return null;
+      return TraceContextOrSamplingFlags.create(SamplingFlags.toSamplingFlags(flags));
+    } else if (length == 3) {
+      int flags = parseSampledFlag(b3, 0);
+      if (flags == 0) return null;
+      flags = parseDebugFlag(b3, 2, flags);
+      if (flags == 0) return null;
+      return TraceContextOrSamplingFlags.create(SamplingFlags.toSamplingFlags(flags));
+    }
+
+    // At this point we minimally expect a traceId-spanId pair
+    if (length < 16 + 1 + 16 /* traceid64-spanid */) {
+      logger.fine("Invalid input: truncated");
+      return null;
+    } else if (length > FORMAT_MAX_LENGTH) {
+      logger.fine("Invalid input: too long");
+      return null;
+    }
+
+    int pos = 0;
+    long traceIdHigh, traceId;
+    if (b3.charAt(32) == '-') {
+      traceIdHigh = lenientLowerHexToUnsignedLong(b3, 0, 16);
+      traceId = lenientLowerHexToUnsignedLong(b3, 16, 32);
+      pos += 33; // traceid128-
+    } else {
+      traceIdHigh = 0L;
+      traceId = lenientLowerHexToUnsignedLong(b3, 0, 16);
+      pos += 17; // traceid64-
+    }
+
+    if (traceIdHigh == 0L && traceId == 0L) {
+      logger.fine("Invalid input: expected a 16 or 32 lower hex trace ID at offset 0");
+      return null;
+    }
+
+    long spanId = lenientLowerHexToUnsignedLong(b3, pos, pos + 16);
+    if (spanId == 0L) {
+      logger.log(FINE, "Invalid input: expected a 16 lower hex span ID at offset {0}", pos);
+      return null;
+    }
+    pos += 17; // spanid-
+
+    int flags = 0;
+    if (length == pos + 1 || (length > pos + 2 && b3.charAt(pos + 1) == '-')) {
+      flags = parseSampledFlag(b3, pos++);
+      if (flags == 0) return null;
+      pos++; // skip the dash
+    }
+
+    long parentId = 0L;
+    if (length >= pos + 17) {
+      parentId = lenientLowerHexToUnsignedLong(b3, pos, pos + 16);
+      if (parentId == 0L) {
+        logger.log(FINE, "Invalid input: expected a 16 lower hex parent ID at offset {0}", pos);
+        return null;
+      }
+      pos += 17;
+    }
+
+    if (length == pos + 1) {
+      flags = parseDebugFlag(b3, pos, flags);
+      if (flags == 0) return null;
+    }
+
+    return TraceContextOrSamplingFlags.create(new TraceContext(
+        flags,
+        traceIdHigh,
+        traceId,
+        parentId,
+        spanId,
+        Collections.emptyList()
+    ));
+  }
+
+
+  static int parseSampledFlag(String b3, int pos) {
+    int flags;
+    char sampledChar = b3.charAt(pos);
+    if (sampledChar == '1') {
+      flags = FLAG_SAMPLED_SET | FLAG_SAMPLED;
+    } else if (sampledChar == '0') {
+      flags = FLAG_SAMPLED_SET;
+    } else {
+      logger.log(FINE, "Invalid input: expected 0 or 1 for sampled at offset {0}", pos);
+      flags = 0;
+    }
+    return flags;
+  }
+
+  static int parseDebugFlag(String b3, int pos, int flags) {
+    char lastChar = b3.charAt(pos);
+    if (lastChar == '1') {
+      flags = FLAG_DEBUG | FLAG_SAMPLED_SET | FLAG_SAMPLED;
+    } else if (lastChar != '0') { // redundant to say debug false, but whatev
+      logger.log(FINE, "Invalid input: expected 1 for debug at offset {0}", pos);
+      flags = 0;
+    }
+    return flags;
+  }
+
+  static final ThreadLocal<char[]> CHAR_BUFFER = new ThreadLocal<>();
+
+  static char[] getCharBuffer() {
+    char[] charBuffer = CHAR_BUFFER.get();
+    if (charBuffer == null) {
+      charBuffer = new char[FORMAT_MAX_LENGTH];
+      CHAR_BUFFER.set(charBuffer);
+    }
+    return charBuffer;
+  }
+}