1 files changed, 284 insertions, 0 deletions
diff --git a/src/cpp/ext/filters/census/rpc_encoding.h b/src/cpp/ext/filters/census/rpc_encoding.h
new file mode 100644
index 0000000000..ffffa60c46
--- /dev/null
+++ b/src/cpp/ext/filters/census/rpc_encoding.h
@@ -0,0 +1,284 @@
+/*
+ *
+ * Copyright 2018 gRPC 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.
+ *
+ */
+
+#ifndef GRPC_INTERNAL_CPP_EXT_FILTERS_CENSUS_RPC_ENCODING_H
+#define GRPC_INTERNAL_CPP_EXT_FILTERS_CENSUS_RPC_ENCODING_H
+
+#include <grpc/support/port_platform.h>
+
+#include <string.h>
+
+#include "absl/base/internal/endian.h"
+#include "absl/strings/string_view.h"
+#include "opencensus/trace/span_context.h"
+#include "opencensus/trace/span_id.h"
+#include "opencensus/trace/trace_id.h"
+
+namespace grpc {
+
+// TODO: Rename to GrpcTraceContextV0.
+struct GrpcTraceContext {
+  GrpcTraceContext() {}
+
+  explicit GrpcTraceContext(const ::opencensus::trace::SpanContext& ctx) {
+    ctx.trace_id().CopyTo(trace_id);
+    ctx.span_id().CopyTo(span_id);
+    ctx.trace_options().CopyTo(trace_options);
+  }
+
+  ::opencensus::trace::SpanContext ToSpanContext() const {
+    return ::opencensus::trace::SpanContext(
+        ::opencensus::trace::TraceId(trace_id),
+        ::opencensus::trace::SpanId(span_id),
+        ::opencensus::trace::TraceOptions(trace_options));
+  }
+
+  // TODO: For performance:
+  // uint8_t version;
+  // uint8_t trace_id_field_id;
+  uint8_t trace_id[::opencensus::trace::TraceId::kSize];
+  // uint8_t span_id_field_id;
+  uint8_t span_id[::opencensus::trace::SpanId::kSize];
+  // uint8_t trace_options_field_id;
+  uint8_t trace_options[::opencensus::trace::TraceOptions::kSize];
+};
+
+// TraceContextEncoding encapsulates the logic for encoding and decoding of
+// trace contexts.
+class TraceContextEncoding {
+ public:
+  // Size of encoded GrpcTraceContext. (16 + 8 + 1 + 4)
+  static constexpr size_t kGrpcTraceContextSize = 29;
+  // Error value.
+  static constexpr size_t kEncodeDecodeFailure = 0;
+
+  // Deserializes a GrpcTraceContext from the incoming buffer. Returns the
+  // number of bytes deserialized from the buffer. If the incoming buffer is
+  // empty or the encoding version is not supported it will return 0 bytes,
+  // currently only version 0 is supported. If an unknown field ID is
+  // encountered it will return immediately without parsing the rest of the
+  // buffer. Inlined for performance reasons.
+  static size_t Decode(absl::string_view buf, GrpcTraceContext* tc) {
+    if (buf.empty()) {
+      return kEncodeDecodeFailure;
+    }
+    uint8_t version = buf[kVersionIdOffset];
+    // TODO: Support other versions later. Only support version 0 for
+    // now.
+    if (version != kVersionId) {
+      return kEncodeDecodeFailure;
+    }
+
+    size_t pos = kVersionIdSize;
+    while (pos < buf.size()) {
+      size_t bytes_read =
+          ParseField(absl::string_view(&buf[pos], buf.size() - pos), tc);
+      if (bytes_read == 0) {
+        break;
+      } else {
+        pos += bytes_read;
+      }
+    }
+    return pos;
+  }
+
+  // Serializes a GrpcTraceContext into the provided buffer. Returns the number
+  // of bytes serialized into the buffer. If the buffer is not of sufficient
+  // size (it must be at least kGrpcTraceContextSize bytes) it will drop
+  // everything and return 0 bytes serialized. Inlined for performance reasons.
+  static size_t Encode(const GrpcTraceContext& tc, char* buf, size_t buf_size) {
+    if (buf_size < kGrpcTraceContextSize) {
+      return kEncodeDecodeFailure;
+    }
+    buf[kVersionIdOffset] = kVersionId;
+    buf[kTraceIdOffset] = kTraceIdField;
+    memcpy(&buf[kTraceIdOffset + 1], tc.trace_id,
+           opencensus::trace::TraceId::kSize);
+    buf[kSpanIdOffset] = kSpanIdField;
+    memcpy(&buf[kSpanIdOffset + 1], tc.span_id,
+           opencensus::trace::SpanId::kSize);
+    buf[kTraceOptionsOffset] = kTraceOptionsField;
+    memcpy(&buf[kTraceOptionsOffset + 1], tc.trace_options,
+           opencensus::trace::TraceOptions::kSize);
+    return kGrpcTraceContextSize;
+  }
+
+ private:
+  // Parses the next field from the incoming buffer and stores the parsed value
+  // in a GrpcTraceContext struct.  If it does not recognize the field ID it
+  // will return 0, otherwise it returns the number of bytes read.
+  static size_t ParseField(absl::string_view buf, GrpcTraceContext* tc) {
+    // TODO: Add support for multi-byte field IDs.
+    if (buf.empty()) {
+      return 0;
+    }
+    // Field ID is always the first byte in a field.
+    uint32_t field_id = buf[0];
+    size_t bytes_read = kFieldIdSize;
+    switch (field_id) {
+      case kTraceIdField:
+        bytes_read += kTraceIdSize;
+        if (bytes_read > buf.size()) {
+          return 0;
+        }
+        memcpy(tc->trace_id, &buf[kFieldIdSize],
+               opencensus::trace::TraceId::kSize);
+        break;
+      case kSpanIdField:
+        bytes_read += kSpanIdSize;
+        if (bytes_read > buf.size()) {
+          return 0;
+        }
+        memcpy(tc->span_id, &buf[kFieldIdSize],
+               opencensus::trace::SpanId::kSize);
+        break;
+      case kTraceOptionsField:
+        bytes_read += kTraceOptionsSize;
+        if (bytes_read > buf.size()) {
+          return 0;
+        }
+        memcpy(tc->trace_options, &buf[kFieldIdSize],
+               opencensus::trace::TraceOptions::kSize);
+        break;
+      default:  // Invalid field ID
+        return 0;
+    }
+
+    return bytes_read;
+  }
+
+  // Size of Version ID.
+  static constexpr size_t kVersionIdSize = 1;
+  // Size of Field ID.
+  static constexpr size_t kFieldIdSize = 1;
+
+  // Offset and value for currently supported version ID.
+  static constexpr size_t kVersionIdOffset = 0;
+  static constexpr size_t kVersionId = 0;
+
+  // Fixed Field ID values:
+  enum FieldIdValue {
+    kTraceIdField = 0,
+    kSpanIdField = 1,
+    kTraceOptionsField = 2,
+  };
+
+  // Field data sizes in bytes
+  enum FieldSize {
+    kTraceIdSize = 16,
+    kSpanIdSize = 8,
+    kTraceOptionsSize = 1,
+  };
+
+  // Fixed size offsets for field ID start positions during encoding.  Field
+  // data immediately follows.
+  enum FieldIdOffset {
+    kTraceIdOffset = kVersionIdSize,
+    kSpanIdOffset = kTraceIdOffset + kFieldIdSize + kTraceIdSize,
+    kTraceOptionsOffset = kSpanIdOffset + kFieldIdSize + kSpanIdSize,
+  };
+
+  TraceContextEncoding() = delete;
+  TraceContextEncoding(const TraceContextEncoding&) = delete;
+  TraceContextEncoding(TraceContextEncoding&&) = delete;
+  TraceContextEncoding operator=(const TraceContextEncoding&) = delete;
+  TraceContextEncoding operator=(TraceContextEncoding&&) = delete;
+};
+
+// TODO: This may not be needed. Check to see if opencensus requires
+// a trailing server response.
+// RpcServerStatsEncoding encapsulates the logic for encoding and decoding of
+// rpc server stats messages. Rpc server stats consists of a uint64_t time
+// value (server latency in nanoseconds).
+class RpcServerStatsEncoding {
+ public:
+  // Size of encoded RPC server stats.
+  static constexpr size_t kRpcServerStatsSize = 10;
+  // Error value.
+  static constexpr size_t kEncodeDecodeFailure = 0;
+
+  // Deserializes rpc server stats from the incoming 'buf' into *time.  Returns
+  // number of bytes decoded. If the buffer is of insufficient size (it must be
+  // at least kRpcServerStatsSize bytes) or the encoding version or field ID are
+  // unrecognized, *time will be set to 0 and it will return
+  // kEncodeDecodeFailure. Inlined for performance reasons.
+  static size_t Decode(absl::string_view buf, uint64_t* time) {
+    if (buf.size() < kRpcServerStatsSize) {
+      *time = 0;
+      return kEncodeDecodeFailure;
+    }
+
+    uint8_t version = buf[kVersionIdOffset];
+    uint32_t fieldID = buf[kServerElapsedTimeOffset];
+    if (version != kVersionId || fieldID != kServerElapsedTimeField) {
+      *time = 0;
+      return kEncodeDecodeFailure;
+    }
+    *time = absl::little_endian::Load64(
+        &buf[kServerElapsedTimeOffset + kFieldIdSize]);
+    return kRpcServerStatsSize;
+  }
+
+  // Serializes rpc server stats into the provided buffer.  It returns the
+  // number of bytes written to the buffer. If the buffer is smaller than
+  // kRpcServerStatsSize bytes it will return kEncodeDecodeFailure. Inlined for
+  // performance reasons.
+  static size_t Encode(uint64_t time, char* buf, size_t buf_size) {
+    if (buf_size < kRpcServerStatsSize) {
+      return kEncodeDecodeFailure;
+    }
+
+    buf[kVersionIdOffset] = kVersionId;
+    buf[kServerElapsedTimeOffset] = kServerElapsedTimeField;
+    absl::little_endian::Store64(&buf[kServerElapsedTimeOffset + kFieldIdSize],
+                                 time);
+    return kRpcServerStatsSize;
+  }
+
+ private:
+  // Size of Version ID.
+  static constexpr size_t kVersionIdSize = 1;
+  // Size of Field ID.
+  static constexpr size_t kFieldIdSize = 1;
+
+  // Offset and value for currently supported version ID.
+  static constexpr size_t kVersionIdOffset = 0;
+  static constexpr size_t kVersionId = 0;
+
+  enum FieldIdValue {
+    kServerElapsedTimeField = 0,
+  };
+
+  enum FieldSize {
+    kServerElapsedTimeSize = 8,
+  };
+
+  enum FieldIdOffset {
+    kServerElapsedTimeOffset = kVersionIdSize,
+  };
+
+  RpcServerStatsEncoding() = delete;
+  RpcServerStatsEncoding(const RpcServerStatsEncoding&) = delete;
+  RpcServerStatsEncoding(RpcServerStatsEncoding&&) = delete;
+  RpcServerStatsEncoding operator=(const RpcServerStatsEncoding&) = delete;
+  RpcServerStatsEncoding operator=(RpcServerStatsEncoding&&) = delete;
+};
+
+}  // namespace grpc
+
+#endif /* GRPC_INTERNAL_CPP_EXT_FILTERS_CENSUS_RPC_ENCODING_H */