1 files changed, 165 insertions, 0 deletions
diff --git a/api/src/main/java/io/opencensus/trace/SpanContext.java b/api/src/main/java/io/opencensus/trace/SpanContext.java
new file mode 100644
index 00000000..49ed751b
--- /dev/null
+++ b/api/src/main/java/io/opencensus/trace/SpanContext.java
@@ -0,0 +1,165 @@
+/*
+ * Copyright 2016-17, OpenCensus 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 io.opencensus.trace;
+
+import java.util.Arrays;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * A class that represents a span context. A span context contains the state that must propagate to
+ * child {@link Span}s and across process boundaries. It contains the identifiers (a {@link TraceId
+ * trace_id} and {@link SpanId span_id}) associated with the {@link Span} and a set of {@link
+ * TraceOptions options}.
+ *
+ * @since 0.5
+ */
+@Immutable
+public final class SpanContext {
+  private static final Tracestate TRACESTATE_DEFAULT = Tracestate.builder().build();
+  private final TraceId traceId;
+  private final SpanId spanId;
+  private final TraceOptions traceOptions;
+  private final Tracestate tracestate;
+
+  /**
+   * The invalid {@code SpanContext}.
+   *
+   * @since 0.5
+   */
+  public static final SpanContext INVALID =
+      new SpanContext(TraceId.INVALID, SpanId.INVALID, TraceOptions.DEFAULT, TRACESTATE_DEFAULT);
+
+  /**
+   * Creates a new {@code SpanContext} with the given identifiers and options.
+   *
+   * @param traceId the trace identifier of the span context.
+   * @param spanId the span identifier of the span context.
+   * @param traceOptions the trace options for the span context.
+   * @return a new {@code SpanContext} with the given identifiers and options.
+   * @deprecated use {@link #create(TraceId, SpanId, TraceOptions, Tracestate)}.
+   */
+  @Deprecated
+  public static SpanContext create(TraceId traceId, SpanId spanId, TraceOptions traceOptions) {
+    return create(traceId, spanId, traceOptions, TRACESTATE_DEFAULT);
+  }
+
+  /**
+   * Creates a new {@code SpanContext} with the given identifiers and options.
+   *
+   * @param traceId the trace identifier of the span context.
+   * @param spanId the span identifier of the span context.
+   * @param traceOptions the trace options for the span context.
+   * @param tracestate the trace state for the span context.
+   * @return a new {@code SpanContext} with the given identifiers and options.
+   * @since 0.16
+   */
+  public static SpanContext create(
+      TraceId traceId, SpanId spanId, TraceOptions traceOptions, Tracestate tracestate) {
+    return new SpanContext(traceId, spanId, traceOptions, tracestate);
+  }
+
+  /**
+   * Returns the trace identifier associated with this {@code SpanContext}.
+   *
+   * @return the trace identifier associated with this {@code SpanContext}.
+   * @since 0.5
+   */
+  public TraceId getTraceId() {
+    return traceId;
+  }
+
+  /**
+   * Returns the span identifier associated with this {@code SpanContext}.
+   *
+   * @return the span identifier associated with this {@code SpanContext}.
+   * @since 0.5
+   */
+  public SpanId getSpanId() {
+    return spanId;
+  }
+
+  /**
+   * Returns the {@code TraceOptions} associated with this {@code SpanContext}.
+   *
+   * @return the {@code TraceOptions} associated with this {@code SpanContext}.
+   * @since 0.5
+   */
+  public TraceOptions getTraceOptions() {
+    return traceOptions;
+  }
+
+  /**
+   * Returns the {@code Tracestate} associated with this {@code SpanContext}.
+   *
+   * @return the {@code Tracestate} associated with this {@code SpanContext}.
+   * @since 0.5
+   */
+  public Tracestate getTracestate() {
+    return tracestate;
+  }
+
+  /**
+   * Returns true if this {@code SpanContext} is valid.
+   *
+   * @return true if this {@code SpanContext} is valid.
+   * @since 0.5
+   */
+  public boolean isValid() {
+    return traceId.isValid() && spanId.isValid();
+  }
+
+  @Override
+  public boolean equals(@Nullable Object obj) {
+    if (obj == this) {
+      return true;
+    }
+
+    if (!(obj instanceof SpanContext)) {
+      return false;
+    }
+
+    SpanContext that = (SpanContext) obj;
+    return traceId.equals(that.traceId)
+        && spanId.equals(that.spanId)
+        && traceOptions.equals(that.traceOptions);
+  }
+
+  @Override
+  public int hashCode() {
+    return Arrays.hashCode(new Object[] {traceId, spanId, traceOptions});
+  }
+
+  @Override
+  public String toString() {
+    return "SpanContext{traceId="
+        + traceId
+        + ", spanId="
+        + spanId
+        + ", traceOptions="
+        + traceOptions
+        + "}";
+  }
+
+  private SpanContext(
+      TraceId traceId, SpanId spanId, TraceOptions traceOptions, Tracestate tracestate) {
+    this.traceId = traceId;
+    this.spanId = spanId;
+    this.traceOptions = traceOptions;
+    this.tracestate = tracestate;
+  }
+}