msgpack neovim c client proof of concept

main.c

#include <stdio.h>
#include <unistd.h>
#include <sys/socket.h>
#include <msgpack.h>

/*
 * $ NVIM_LISTEN_ADDRESS=127.0.0.1:8888 nvim
 *
 */

void unpack_stream(msgpack_sbuffer *sbuf)
{
    msgpack_unpacker unpacker;
    msgpack_unpacker_init(&unpacker, MSGPACK_UNPACKER_INIT_BUFFER_SIZE);

    // Feed the unpacked with data
    msgpack_unpacker_reserve_buffer(&unpacker, sbuf->size);
    memcpy(msgpack_unpacker_buffer(&unpacker), sbuf->data, sbuf->size);
    msgpack_unpacker_buffer_consumed(&unpacker, sbuf->size);

    msgpack_unpacked result;
    msgpack_unpacked_init(&result);

    while (msgpack_unpacker_next(&unpacker, &result)) {
        msgpack_object_print(stdout, result.data);
        puts("");
    }
}

void unpack(msgpack_sbuffer *sbuf)
{
    msgpack_zone mempool;
    msgpack_zone_init(&mempool, 2048);

    msgpack_object deserialized;
    msgpack_unpack(sbuf->data, sbuf->size, NULL, &mempool, &deserialized);

    msgpack_object_print(stdout, deserialized);
    puts("");

    msgpack_zone_destroy(&mempool);
}

void prepare(msgpack_sbuffer *sbuf)
{
    msgpack_packer packer;

    msgpack_packer_init(&packer, sbuf, msgpack_sbuffer_write);

    // [0, id, 0, "method", ["param1", "param2"]]
    msgpack_pack_array(&packer, 4);
    msgpack_pack_int(&packer, 0);
    msgpack_pack_int(&packer, 82);
    char method[] = "vim_command";
    msgpack_pack_str(&packer, sizeof(method) - 1);
    msgpack_pack_str_body(&packer, method, sizeof(method) - 1);
    msgpack_pack_array(&packer, 1);
    char param[] = "echo \"hello world\"";
    msgpack_pack_str(&packer, sizeof(param) - 1);
    msgpack_pack_str_body(&packer, param, sizeof(param) - 1);
}

int connect_nvim(unsigned int port)
{
    int sfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sfd == -1) {
        fprintf(stderr, "Error opening socket\n");
        return -1;
    }

    struct sockaddr_in addr;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = 0;
    addr.sin_addr.s_addr = INADDR_ANY;
    addr.sin_family = AF_INET;

    if (connect(sfd, (struct sockaddr *) &addr, sizeof(addr)) == -1) {
        fprintf(stderr, "Error connecting to socket\n");
        return -1;
    }

    return sfd;
}

int main(int argc, char **argv)
{
    // FIXME Do not hard-code the port
    //char *nvim_listen_addr = getenv("NVIM_LISTEN_ADDRESS");
    //if (nvim_listen_addr)
    //    printf("Detected env var: %s\n", nvim_listen_addr);
    int sfd = connect_nvim(8888);

    msgpack_sbuffer sbuf;
    msgpack_sbuffer_init(&sbuf);
    prepare(&sbuf);
    printf("About to send: ");
    unpack(&sbuf);

    if (write(sfd, sbuf.data, sbuf.size) == -1) {
        fprintf(stderr, "Error sending data\n");
        return 1;
    }

    if (read(sfd, sbuf.data, sbuf.size) == -1) {
        fprintf(stderr, "Error receiving data\n");
        return 1;
    }

    close(sfd);

    printf("Received: ");
    unpack(&sbuf);

    msgpack_sbuffer_destroy(&sbuf);

    return 0;
}

makefile

TARGET=nvim-c-client

CC=gcc
DEBUG=-g
OPT=-O0
WARN=-Wall
PTHREAD=-pthread
CCFLAGS=$(DEBUG) $(OPT) $(WARN) $(PTHREAD) -pipe
MSGPACKLIB=`pkg-config --cflags --libs msgpack`

LD=gcc
#LDFLAGS=$(PTHREAD) $(MSGPACKLIB) -export-dynamic
LDFLAGS=$(MSGPACKLIB)

OBJS=main.o

all: $(OBJS)
	$(LD) -o $(TARGET) $(OBJS) $(LDFLAGS)

main.o: src/main.c
	$(CC) -c $(CCFLAGS) src/main.c $(MSGPACKLIB) -o main.o

clean:
	rm -f *.o $(TARGET)