include/grpc/grpc.h

/*
 *
 * Copyright 2014, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#ifndef __GRPC_GRPC_H__
#define __GRPC_GRPC_H__

#include <grpc/status.h>

#include <stddef.h>
#include <grpc/support/slice.h>
#include <grpc/support/time.h>

#ifdef __cplusplus
extern "C" {
#endif

/* Completion Channels enable notification of the completion of asynchronous
   actions. */
typedef struct grpc_completion_queue grpc_completion_queue;

/* The Channel interface allows creation of Call objects. */
typedef struct grpc_channel grpc_channel;

/* A server listens to some port and responds to request calls */
typedef struct grpc_server grpc_server;

/* A Call represents an RPC. When created, it is in a configuration state
   allowing properties to be set until it is invoked. After invoke, the Call
   can have messages written to it and read from it. */
typedef struct grpc_call grpc_call;

/* Type specifier for grpc_arg */
typedef enum {
  GRPC_ARG_STRING,
  GRPC_ARG_INTEGER,
  GRPC_ARG_POINTER
} grpc_arg_type;

/* A single argument... each argument has a key and a value

   A note on naming keys:
     Keys are namespaced into groups, usually grouped by library, and are
     keys for module XYZ are named XYZ.key1, XYZ.key2, etc. Module names must
     be restricted to the regex [A-Za-z][_A-Za-z0-9]{,15}.
     Key names must be restricted to the regex [A-Za-z][_A-Za-z0-9]{,47}.

     GRPC core library keys are prefixed by grpc.

     Library authors are strongly encouraged to #define symbolic constants for
     their keys so that it's possible to change them in the future. */
typedef struct {
  grpc_arg_type type;
  char *key;
  union {
    char *string;
    int integer;
    struct {
      void *p;
      void *(*copy)(void *p);
      void (*destroy)(void *p);
    } pointer;
  } value;
} grpc_arg;

/* An array of arguments that can be passed around */
typedef struct {
  size_t num_args;
  grpc_arg *args;
} grpc_channel_args;

/* Channel argument keys: */
/* Enable census for tracing and stats collection */
#define GRPC_ARG_ENABLE_CENSUS "grpc.census"
/* Maximum number of concurrent incoming streams to allow on a http2
   connection */
#define GRPC_ARG_MAX_CONCURRENT_STREAMS "grpc.max_concurrent_streams"
/* Maximum message length that the channel can receive */
#define GRPC_ARG_MAX_MESSAGE_LENGTH "grpc.max_message_length"

/* Status of a completed call */
typedef struct grpc_status {
  grpc_status_code code;
  char *details;
} grpc_status;

/* Result of a grpc call. If the caller satisfies the prerequisites of a
   particular operation, the grpc_call_error returned will be GRPC_CALL_OK.
   Receiving any other value listed here is an indication of a bug in the
   caller. */
typedef enum grpc_call_error {
  /* everything went ok */
  GRPC_CALL_OK = 0,
  /* something failed, we don't know what */
  GRPC_CALL_ERROR,
  /* this method is not available on the server */
  GRPC_CALL_ERROR_NOT_ON_SERVER,
  /* this method is not available on the client */
  GRPC_CALL_ERROR_NOT_ON_CLIENT,
  /* this method must be called before invoke */
  GRPC_CALL_ERROR_ALREADY_INVOKED,
  /* this method must be called after invoke */
  GRPC_CALL_ERROR_NOT_INVOKED,
  /* this call is already finished
     (writes_done or write_status has already been called) */
  GRPC_CALL_ERROR_ALREADY_FINISHED,
  /* there is already an outstanding read/write operation on the call */
  GRPC_CALL_ERROR_TOO_MANY_OPERATIONS,
  /* the flags value was illegal for this call */
  GRPC_CALL_ERROR_INVALID_FLAGS
} grpc_call_error;

/* Result of a grpc operation */
typedef enum grpc_op_error {
  /* everything went ok */
  GRPC_OP_OK = 0,
  /* something failed, we don't know what */
  GRPC_OP_ERROR
} grpc_op_error;

/* Write Flags: */
/* Hint that the write may be buffered and need not go out on the wire
   immediately. GRPC is free to buffer the message until the next non-buffered
   write, or until writes_done, but it need not buffer completely or at all. */
#define GRPC_WRITE_BUFFER_HINT (0x00000001u)
/* Force compression to be disabled for a particular write
   (start_write/add_metadata). Illegal on invoke/accept. */
#define GRPC_WRITE_NO_COMPRESS (0x00000002u)

/* A buffer of bytes */
struct grpc_byte_buffer;
typedef struct grpc_byte_buffer grpc_byte_buffer;

/* Sample helpers to obtain byte buffers (these will certainly move place */
grpc_byte_buffer *grpc_byte_buffer_create(gpr_slice *slices, size_t nslices);
size_t grpc_byte_buffer_length(grpc_byte_buffer *bb);
void grpc_byte_buffer_destroy(grpc_byte_buffer *byte_buffer);

/* Reader for byte buffers. Iterates over slices in the byte buffer */
struct grpc_byte_buffer_reader;
typedef struct grpc_byte_buffer_reader grpc_byte_buffer_reader;

grpc_byte_buffer_reader *grpc_byte_buffer_reader_create(
    grpc_byte_buffer *buffer);
/* At the end of the stream, returns 0. Otherwise, returns 1 and sets slice to
   be the returned slice. Caller is responsible for calling gpr_slice_unref on
   the result. */
int grpc_byte_buffer_reader_next(grpc_byte_buffer_reader *reader,
                                 gpr_slice *slice);
void grpc_byte_buffer_reader_destroy(grpc_byte_buffer_reader *reader);

/* A single metadata element */
typedef struct grpc_metadata {
  char *key;
  char *value;
  size_t value_length;
} grpc_metadata;

typedef enum grpc_completion_type {
  GRPC_QUEUE_SHUTDOWN,       /* Shutting down */
  GRPC_READ,                 /* A read has completed */
  GRPC_INVOKE_ACCEPTED,      /* An invoke call has been accepted by flow
                                control */
  GRPC_WRITE_ACCEPTED,       /* A write has been accepted by
                                flow control */
  GRPC_FINISH_ACCEPTED,      /* writes_done or write_status has been accepted */
  GRPC_CLIENT_METADATA_READ, /* The metadata array sent by server received at
                                client */
  GRPC_FINISHED,             /* An RPC has finished. The event contains status.
                                On the server this will be OK or Cancelled. */
  GRPC_SERVER_RPC_NEW,       /* A new RPC has arrived at the server */
  GRPC_COMPLETION_DO_NOT_USE /* must be last, forces users to include
                                a default: case */
} grpc_completion_type;

typedef struct grpc_event {
  grpc_completion_type type;
  void *tag;
  grpc_call *call;
  /* Data associated with the completion type. Field names match the type of
     completion as listed in grpc_completion_type. */
  union {
    /* Contains a pointer to the buffer that was read, or NULL at the end of a
       stream. */
    grpc_byte_buffer *read;
    grpc_op_error write_accepted;
    grpc_op_error finish_accepted;
    grpc_op_error invoke_accepted;
    struct {
      size_t count;
      grpc_metadata *elements;
    } client_metadata_read;
    grpc_status finished;
    struct {
      const char *method;
      const char *host;
      gpr_timespec deadline;
      size_t metadata_count;
      grpc_metadata *metadata_elements;
    } server_rpc_new;
  } data;
} grpc_event;

/* Initialize the grpc library */
void grpc_init();

/* Shutdown the grpc library */
void grpc_shutdown();

grpc_completion_queue *grpc_completion_queue_create();

/* Blocks until an event is available, the completion queue is being shutdown,
   or deadline is reached. Returns NULL on timeout, otherwise the event that
   occurred. Callers should call grpc_event_finish once they have processed
   the event.

   Callers must not call grpc_completion_queue_next and
   grpc_completion_queue_pluck simultaneously on the same completion queue. */
grpc_event *grpc_completion_queue_next(grpc_completion_queue *cq,
                                       gpr_timespec deadline);

/* Blocks until an event with tag 'tag' is available, the completion queue is
   being shutdown or deadline is reached. Returns NULL on timeout, or a pointer
   to the event that occurred. Callers should call grpc_event_finish once they
   have processed the event.

   Callers must not call grpc_completion_queue_next and
   grpc_completion_queue_pluck simultaneously on the same completion queue. */
grpc_event *grpc_completion_queue_pluck(grpc_completion_queue *cq, void *tag,
                                        gpr_timespec deadline);

/* Cleanup any data owned by the event */
void grpc_event_finish(grpc_event *event);

/* Begin destruction of a completion queue. Once all possible events are
   drained it's safe to call grpc_completion_queue_destroy. */
void grpc_completion_queue_shutdown(grpc_completion_queue *cq);

/* Destroy a completion queue. The caller must ensure that the queue is
   drained and no threads are executing grpc_completion_queue_next */
void grpc_completion_queue_destroy(grpc_completion_queue *cq);

/* Create a call given a grpc_channel, in order to call 'method'. The request
   is not sent until grpc_call_invoke is called. All completions are sent to
   'completion_queue'. */
grpc_call *grpc_channel_create_call(grpc_channel *channel, const char *method,
                                    const char *host, gpr_timespec deadline);

/* Create a client channel */
grpc_channel *grpc_channel_create(const char *target,
                                  const grpc_channel_args *args);

/* Close and destroy a grpc channel */
void grpc_channel_destroy(grpc_channel *channel);

/* THREAD-SAFETY for grpc_call
   The following functions are thread-compatible for any given call:
     grpc_call_add_metadata
     grpc_call_invoke
     grpc_call_start_write
     grpc_call_writes_done
     grpc_call_start_read
     grpc_call_destroy
   The function grpc_call_cancel is thread-safe, and can be called at any
   point before grpc_call_destroy is called. */

/* Error handling for grpc_call
   Most grpc_call functions return a grpc_error. If the error is not GRPC_OK
   then the operation failed due to some unsatisfied precondition.
   If a grpc_call fails, it's guaranteed that no change to the call state
   has been made. */

/* Add a single metadata element to the call, to be sent upon invocation.
   flags is a bit-field combination of the write flags defined above.
   REQUIRES: grpc_call_start_invoke/grpc_call_accept have not been called on
             this call.
   Produces no events. */
grpc_call_error grpc_call_add_metadata(grpc_call *call, grpc_metadata *metadata,
                                       gpr_uint32 flags);

/* Invoke the RPC. Starts sending metadata and request headers on the wire.
   flags is a bit-field combination of the write flags defined above.
   REQUIRES: Can be called at most once per call.
             Can only be called on the client.
   Produces a GRPC_INVOKE_ACCEPTED event with invoke_accepted_tag when the
       call has been invoked (meaning bytes can start flowing to the wire).
   Produces a GRPC_CLIENT_METADATA_READ event with metadata_read_tag when
       the servers initial metadata has been read.
   Produces a GRPC_FINISHED event with finished_tag when the call has been
       completed (there may be other events for the call pending at this
       time) */
grpc_call_error grpc_call_start_invoke(grpc_call *call,
                                       grpc_completion_queue *cq,
                                       void *invoke_accepted_tag,
                                       void *metadata_read_tag,
                                       void *finished_tag, gpr_uint32 flags);

/* Accept an incoming RPC, binding a completion queue to it.
   To be called after adding metadata to the call, but before sending
   messages.
   flags is a bit-field combination of the write flags defined above.
   REQUIRES: Can be called at most once per call.
             Can only be called on the server.
   Produces a GRPC_FINISHED event with finished_tag when the call has been
       completed (there may be other events for the call pending at this
       time) */
grpc_call_error grpc_call_accept(grpc_call *call, grpc_completion_queue *cq,
                                 void *finished_tag, gpr_uint32 flags);

/* Called by clients to cancel an RPC on the server.
   Can be called multiple times, from any thread. */
grpc_call_error grpc_call_cancel(grpc_call *call);

/* Queue a byte buffer for writing.
   flags is a bit-field combination of the write flags defined above.
   A write with byte_buffer null is allowed, and will not send any bytes on the
   wire. If this is performed without GRPC_WRITE_BUFFER_HINT flag it provides
   a mechanism to flush any previously buffered writes to outgoing flow control.
   REQUIRES: No other writes are pending on the call. It is only safe to
             start the next write after the corresponding write_accepted event
             is received.
             GRPC_INVOKE_ACCEPTED must have been received by the application
             prior to calling this on the client. On the server,
             grpc_call_accept must have been called successfully.
   Produces a GRPC_WRITE_ACCEPTED event. */
grpc_call_error grpc_call_start_write(grpc_call *call,
                                      grpc_byte_buffer *byte_buffer, void *tag,
                                      gpr_uint32 flags);

/* Queue a status for writing.
   REQUIRES: No other writes are pending on the call.
             grpc_call_accept must have been called on the call prior to calling
             this.
             Only callable on the server.
   Produces a GRPC_FINISH_ACCEPTED event when the status is sent. */
grpc_call_error grpc_call_start_write_status(grpc_call *call,
                                             grpc_status status, void *tag);

/* No more messages to send.
   REQUIRES: No other writes are pending on the call.
             Only callable on the client.
   Produces a GRPC_FINISH_ACCEPTED event when all bytes for the call have passed
       outgoing flow control. */
grpc_call_error grpc_call_writes_done(grpc_call *call, void *tag);

/* Initiate a read on a call. Output event contains a byte buffer with the
   result of the read.
   REQUIRES: No other reads are pending on the call. It is only safe to start
             the next read after the corresponding read event is received.
             GRPC_INVOKE_ACCEPTED must have been received by the application
             prior to calling this.
   Produces a single GRPC_READ event. */
grpc_call_error grpc_call_start_read(grpc_call *call, void *tag);

/* Destroy a call. */
void grpc_call_destroy(grpc_call *call);

/* Request a call on a server.
   Allows the server to create a single GRPC_SERVER_RPC_NEW event, with tag
   tag_new.
   If the call is subsequently cancelled, the cancellation will occur with tag
   tag_cancel.
   REQUIRES: Server must not have been shutdown.
   NOTE: calling this is the only way to obtain GRPC_SERVER_RPC_NEW events. */
grpc_call_error grpc_server_request_call(grpc_server *server, void *tag_new);

/* Create a server */
grpc_server *grpc_server_create(grpc_completion_queue *cq,
                                const grpc_channel_args *args);

/* Add a http2 over tcp listener; returns 1 on success, 0 on failure
   REQUIRES: server not started */
int grpc_server_add_http2_port(grpc_server *server, const char *addr);

/* Add a secure port to server; returns 1 on success, 0 on failure
   REQUIRES: server not started */
int grpc_server_add_secure_http2_port(grpc_server *server, const char *addr);

/* Start a server - tells all listeners to start listening */
void grpc_server_start(grpc_server *server);

/* Begin shutting down a server. */
void grpc_server_shutdown(grpc_server *server);

/* Destroy a server */
void grpc_server_destroy(grpc_server *server);

#ifdef __cplusplus
}
#endif

#endif  /* __GRPC_GRPC_H__ */