third_party/fuchsia-sdk/pkg/trace-provider-so/include/lib/trace-provider/provider.h

// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

//
// The API for initializing the trace provider for a process.
//

#ifndef ZIRCON_SYSTEM_ULIB_LIB_TRACE_PROVIDER_PROVIDER_H_
#define ZIRCON_SYSTEM_ULIB_LIB_TRACE_PROVIDER_PROVIDER_H_

#include <assert.h>
#include <zircon/compiler.h>
#include <zircon/types.h>

#include <lib/async/dispatcher.h>

__BEGIN_CDECLS

// Contents of the provider/manager FIFO.
// One important function the FIFO serves is to support TraceHandler and
// TraceProvider having potentially disjoint lifetimes: The trace engine can
// be running (for however brief a time) after the trace provider goes away,
// and therefore the FIDL channel can go away while the engine is still
// running.

// The format of fifo packets for messages passed between the trace manager
// and trace providers.
typedef struct trace_provider_packet {
  // One of TRACE_PROVIDER_*.
  uint16_t request;

  // Optional data for the request.
  // The contents depend on the request.
  // If unused they must be passed as zero.
  uint16_t data16;
  uint32_t data32;
  uint64_t data64;
} trace_provider_packet_t;

// The protocol version we are using.
// This is non-zero to catch initialization bugs.
#define TRACE_PROVIDER_FIFO_PROTOCOL_VERSION 1

// Provider->Manager
// Zero is reserved to catch initialization bugs.

// Indicate the provider successfully started.
// |data32| is TRACE_PROVIDER_FIFO_PROTOCOL_VERSION
// |data16,data64| are unused (must be zero).
#define TRACE_PROVIDER_STARTED (0x1)

// A buffer is full and needs to be saved (streaming mode only).
// |data16| is unused (must be zero).
// |data32| is the "wrapped count", which is a count of the number of times
// a buffer has filled.
// |data64| is current offset in the durable buffer
#define TRACE_PROVIDER_SAVE_BUFFER (0x2)

// Indicate the provider has completely stopped tracing.
// |data16,data32,data64| are unused (must be zero).
#define TRACE_PROVIDER_STOPPED (0x3)

// Sends an alert.
// |data16, data32, data64| contains the alert name, padded with zeros if the name
// is less than 14 characters.
#define TRACE_PROVIDER_ALERT (0x4)

// Next Provider->Manager packet = 0x5

// Manager->Provider
// A buffer has been saved (streaminng mode only).
// |data32| is the "wrapped count", which is a count of the number of times
// a buffer has filled.
// |data16,data64| are unused (must be zero).
#define TRACE_PROVIDER_BUFFER_SAVED (0x100)

// Next Manager->Provider packet = 0x101

// End fifo packet descriptions.

// Represents a trace provider.
typedef struct trace_provider trace_provider_t;

// Creates a trace provider associated with the specified async dispatcher
// and registers it with the tracing system.
//
// The trace provider will start and stop the trace engine in response to requests
// from the tracing system.
//
// |to_service| is the channel to use to connect to the trace manager.
// It is consumed regardless of success/failure.
//
// |dispatcher| is the asynchronous dispatcher which the trace provider and trace
// engine will use for dispatch.  This must outlive the trace provider instance,
// and must be single-threaded.
//
// |name| is the name of the trace provider and is used for diagnostic
// purposes. The maximum supported length is 100 characters.
//
// Returns the trace provider, or null if creation failed.
//
// TODO(ZX-1036): Currently this connects to the trace manager service.
// Switch to passively exporting the trace provider via the "hub" through
// the process's exported directory once that stuff is implemented.  We'll
// probably need to pass some extra parameters to the trace provider then.
trace_provider_t* trace_provider_create_with_name(zx_handle_t to_service,
                                                  async_dispatcher_t* dispatcher, const char* name);

// Wrapper around trace_provider_create_with_name for backward compatibility.
// TODO(DX-422): Update all providers to use create_with_name, then change this
// to also take a name, then update all providers to call this one, and then
// delete trace_provider_create_with_name.
trace_provider_t* trace_provider_create(zx_handle_t to_service, async_dispatcher_t* dispatcher);

// Same as trace_provider_create_with_name except does not return until the
// provider is registered with the trace manager.
// On return, if !NULL, |*out_already_started| is true if the trace manager has
// already started tracing, which is a hint to the provider to wait for the
// Start() message before continuing if it wishes to not drop trace records
// before Start() is received.
trace_provider_t* trace_provider_create_synchronously(zx_handle_t to_service,
                                                      async_dispatcher_t* dispatcher,
                                                      const char* name, bool* out_already_started);

// Wrappers on the above functions that use fdio.
trace_provider_t* trace_provider_create_with_name_fdio(async_dispatcher_t* dispatcher,
                                                       const char* name);
trace_provider_t* trace_provider_create_with_fdio(async_dispatcher_t* dispatcher);
trace_provider_t* trace_provider_create_synchronously_with_fdio(async_dispatcher_t* dispatcher,
                                                                const char* name,
                                                                bool* out_already_started);

// Destroys the trace provider.
void trace_provider_destroy(trace_provider_t* provider);

__END_CDECLS

#ifdef __cplusplus

#include <lib/zx/channel.h>

#include <memory>

namespace trace {

// Convenience RAII wrapper for creating and destroying a trace provider.
class TraceProvider {
 public:
  // Create a trace provider synchronously, and return an indicator of
  // whether tracing has started already in |*out_already_started|.
  // Returns a boolean indicating success.
  // This is done with a factory function because it's more complex than
  // the basic constructor.
  static bool CreateSynchronously(zx::channel to_service, async_dispatcher_t* dispatcher,
                                  const char* name, std::unique_ptr<TraceProvider>* out_provider,
                                  bool* out_already_started) {
    auto provider = trace_provider_create_synchronously(to_service.release(), dispatcher, name,
                                                        out_already_started);
    if (!provider)
      return false;
    *out_provider = std::unique_ptr<TraceProvider>(new TraceProvider(provider));
    return true;
  }

  // Creates a trace provider.
  TraceProvider(zx::channel to_service, async_dispatcher_t* dispatcher)
      : provider_(trace_provider_create(to_service.release(), dispatcher)) {}

  // Creates a trace provider.
  TraceProvider(zx::channel to_service, async_dispatcher_t* dispatcher, const char* name)
      : provider_(trace_provider_create_with_name(to_service.release(), dispatcher, name)) {}

  // Destroys a trace provider.
  ~TraceProvider() {
    if (provider_)
      trace_provider_destroy(provider_);
  }

  // Returns true if the trace provider was created successfully.
  bool is_valid() const { return provider_ != nullptr; }

 protected:
  explicit TraceProvider(trace_provider_t* provider) : provider_(provider) {}

 private:
  trace_provider_t* const provider_;
};

class TraceProviderWithFdio : public TraceProvider {
 public:
  static bool CreateSynchronously(async_dispatcher_t* dispatcher, const char* name,
                                  std::unique_ptr<TraceProviderWithFdio>* out_provider,
                                  bool* out_already_started) {
    auto provider =
        trace_provider_create_synchronously_with_fdio(dispatcher, name, out_already_started);
    if (!provider)
      return false;
    *out_provider = std::unique_ptr<TraceProviderWithFdio>(new TraceProviderWithFdio(provider));
    return true;
  }

  // Creates a trace provider.
  explicit TraceProviderWithFdio(async_dispatcher_t* dispatcher)
      : TraceProviderWithFdio(trace_provider_create_with_fdio(dispatcher)) {}

  // Creates a trace provider.
  explicit TraceProviderWithFdio(async_dispatcher_t* dispatcher, const char* name)
      : TraceProviderWithFdio(trace_provider_create_with_name_fdio(dispatcher, name)) {}

 private:
  explicit TraceProviderWithFdio(trace_provider_t* provider) : TraceProvider(provider) {}
};

}  // namespace trace

#endif  // __cplusplus

#endif  // ZIRCON_SYSTEM_ULIB_LIB_TRACE_PROVIDER_PROVIDER_H_