src/core/transport/transport.h

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 *
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#ifndef GRPC_INTERNAL_CORE_TRANSPORT_TRANSPORT_H
#define GRPC_INTERNAL_CORE_TRANSPORT_TRANSPORT_H

#include <stddef.h>

#include "src/core/iomgr/pollset.h"
#include "src/core/transport/stream_op.h"
#include "src/core/channel/context.h"

/* forward declarations */
typedef struct grpc_transport grpc_transport;
typedef struct grpc_transport_callbacks grpc_transport_callbacks;

/* grpc_stream doesn't actually exist. It's used as a typesafe
   opaque pointer for whatever data the transport wants to track
   for a stream. */
typedef struct grpc_stream grpc_stream;

/* Represents the send/recv closed state of a stream. */
typedef enum grpc_stream_state {
  /* the stream is open for sends and receives */
  GRPC_STREAM_OPEN,
  /* the stream is closed for sends, but may still receive data */
  GRPC_STREAM_SEND_CLOSED,
  /* the stream is closed for receives, but may still send data */
  GRPC_STREAM_RECV_CLOSED,
  /* the stream is closed for both sends and receives */
  GRPC_STREAM_CLOSED
} grpc_stream_state;

/* Transport op: a set of operations to perform on a transport */
typedef struct grpc_transport_op {
  grpc_stream_op_buffer *send_ops;
  int is_last_send;
  void (*on_done_send)(void *user_data, int success);
  void *send_user_data;

  grpc_stream_op_buffer *recv_ops;
  grpc_stream_state *recv_state;
  void (*on_done_recv)(void *user_data, int success);
  void *recv_user_data;

  grpc_pollset *bind_pollset;

  grpc_status_code cancel_with_status;
  grpc_mdstr *cancel_message;

  /* Indexes correspond to grpc_context_index enum values */
  grpc_call_context_element *context;
} grpc_transport_op;

/* Callbacks made from the transport to the upper layers of grpc. */
struct grpc_transport_callbacks {
  /* Initialize a new stream on behalf of the transport.
     Must result in a call to
     grpc_transport_init_stream(transport, ..., request) in the same call
     stack.
     Must not result in any other calls to the transport.

     Arguments:
       user_data     - the transport user data set at transport creation time
       transport     - the grpc_transport instance making this call
       request       - request parameters for this stream (owned by the caller)
       server_data   - opaque transport dependent argument that should be passed
                       to grpc_transport_init_stream
     */
  void (*accept_stream)(void *user_data, grpc_transport *transport,
                        const void *server_data);

  void (*goaway)(void *user_data, grpc_transport *transport,
                 grpc_status_code status, gpr_slice debug);

  /* The transport has been closed */
  void (*closed)(void *user_data, grpc_transport *transport);
};

/* Returns the amount of memory required to store a grpc_stream for this
   transport */
size_t grpc_transport_stream_size(grpc_transport *transport);

/* Initialize transport data for a stream.

   Returns 0 on success, any other (transport-defined) value for failure.

   Arguments:
     transport   - the transport on which to create this stream
     stream      - a pointer to uninitialized memory to initialize
     server_data - either NULL for a client initiated stream, or a pointer
                   supplied from the accept_stream callback function */
int grpc_transport_init_stream(grpc_transport *transport, grpc_stream *stream,
                               const void *server_data,
                               grpc_transport_op *initial_op);

/* Destroy transport data for a stream.

   Requires: a recv_batch with final_state == GRPC_STREAM_CLOSED has been
   received by the up-layer. Must not be called in the same call stack as
   recv_frame.

   Arguments:
     transport - the transport on which to create this stream
     stream    - the grpc_stream to destroy (memory is still owned by the
                 caller, but any child memory must be cleaned up) */
void grpc_transport_destroy_stream(grpc_transport *transport,
                                   grpc_stream *stream);

void grpc_transport_op_finish_with_failure(grpc_transport_op *op);

void grpc_transport_op_add_cancellation(grpc_transport_op *op,
                                        grpc_status_code status,
                                        grpc_mdstr *message);

/* TODO(ctiller): remove this */
void grpc_transport_add_to_pollset(grpc_transport *transport,
                                   grpc_pollset *pollset);

char *grpc_transport_op_string(grpc_transport_op *op);

/* Send a batch of operations on a transport

   Takes ownership of any objects contained in ops.

   Arguments:
     transport - the transport on which to initiate the stream
     stream    - the stream on which to send the operations. This must be
                 non-NULL and previously initialized by the same transport.
     op        - a grpc_transport_op specifying the op to perform */
void grpc_transport_perform_op(grpc_transport *transport, grpc_stream *stream,
                               grpc_transport_op *op);

/* Send a ping on a transport

   Calls cb with user data when a response is received.
   cb *MAY* be called with arbitrary transport level locks held. It is not safe
   to call into the transport during cb. */
void grpc_transport_ping(grpc_transport *transport, void (*cb)(void *user_data),
                         void *user_data);

/* Advise peer of pending connection termination. */
void grpc_transport_goaway(grpc_transport *transport, grpc_status_code status,
                           gpr_slice debug_data);

/* Close a transport. Aborts all open streams. */
void grpc_transport_close(grpc_transport *transport);

/* Destroy the transport */
void grpc_transport_destroy(grpc_transport *transport);

/* Return type for grpc_transport_setup_callback */
typedef struct grpc_transport_setup_result {
  void *user_data;
  const grpc_transport_callbacks *callbacks;
} grpc_transport_setup_result;

/* Given a transport, return callbacks for that transport. Used to finalize
   setup as a transport is being created */
typedef grpc_transport_setup_result (*grpc_transport_setup_callback)(
    void *setup_arg, grpc_transport *transport, grpc_mdctx *mdctx);

typedef struct grpc_transport_setup grpc_transport_setup;
typedef struct grpc_transport_setup_vtable grpc_transport_setup_vtable;

struct grpc_transport_setup_vtable {
  void (*initiate)(grpc_transport_setup *setup);
  void (*cancel)(grpc_transport_setup *setup);
};

/* Transport setup is an asynchronous utility interface for client channels to
   establish connections. It's transport agnostic. */
struct grpc_transport_setup {
  const grpc_transport_setup_vtable *vtable;
};

/* Initiate transport setup: e.g. for TCP+DNS trigger a resolve of the name
   given at transport construction time, create the tcp connection, perform
   handshakes, and call some grpc_transport_setup_result function provided at
   setup construction time.
   This *may* be implemented as a no-op if the setup process monitors something
   continuously. */
void grpc_transport_setup_initiate(grpc_transport_setup *setup);
/* Cancel transport setup. After this returns, no new transports should be
   created, and all pending transport setup callbacks should be completed.
   After this call completes, setup should be considered invalid (this can be
   used as a destruction call by setup). */
void grpc_transport_setup_cancel(grpc_transport_setup *setup);

#endif /* GRPC_INTERNAL_CORE_TRANSPORT_TRANSPORT_H */