as_poll.h

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/*
 * Copyright 2008-2018 Aerospike, Inc.
 *
 * Portions may be licensed to Aerospike, Inc. under one or more contributor
 * license agreements.
 *
 * 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.
 */
#pragma once

#if !defined(_MSC_VER)
#include <sys/select.h>
#endif

#ifdef __cplusplus
extern "C" {
#endif

/******************************************************************************
 * TYPES
 *****************************************************************************/

typedef struct as_poll_s {
#if !defined(_MSC_VER)
    size_t size;
    fd_set* set;
#else
    fd_set set;
#endif
} as_poll;

/******************************************************************************
 * INLINE FUNCTIONS
 *****************************************************************************/

#if !defined(_MSC_VER)

#define AS_STACK_LIMIT (16 * 1024)

// There is a conflict even among various versions of linux,
// because it's common to compile kernels - or set ulimits -
// where the FD_SETSIZE is much greater than a compiled version.
// Thus, we can compute the required size of the fdset and use a reasonable size
// the other option is using epoll, which is a little scary for this kind of
// "I just want a timeout" usage.
//
// The reality is 8 bits per byte, but this calculation is a little more general.
// Roundup fd in increments of FD_SETSIZE and convert to bytes.
#define as_poll_init(_poll, _fd)\
    (_poll)->size = (((_fd) / FD_SETSIZE) + 1) * FD_SETSIZE / 8;\
    (_poll)->set = ((_poll)->size > AS_STACK_LIMIT)? cf_malloc((_poll)->size) : alloca((_poll)->size);

static inline int
as_poll_socket(as_poll* poll, as_socket_fd fd, uint32_t timeout, bool read)
{
    // From glibc-2.15 (ubuntu 12.0.4+), the FD_* functions has a check on the
    // number of fds passed. According to the man page of FD_SET, the behavior
    // is undefined for fd > 1024. But this is enforced from glibc-2.15
    // https://sourceware.org/bugzilla/show_bug.cgi?id=10352
    //
    // So, manipulate the base and the offset of the fd in it.
    memset(poll->set, 0, poll->size);
    FD_SET(fd % FD_SETSIZE, &poll->set[fd / FD_SETSIZE]);

    struct timeval tv;
    struct timeval* tvp;
    int rv;

    if (timeout > 0) {
        tv.tv_sec = timeout / 1000;
        tv.tv_usec = (timeout % 1000) * 1000;
        tvp = &tv;
    }
    else {
        tvp = NULL;
    }

    if (read) {
        rv = select(fd + 1, poll->set /*readfd*/, 0 /*writefd*/, 0/*oobfd*/, tvp);
    }
    else {
        rv = select(fd + 1, 0 /*readfd*/, poll->set /*writefd*/, 0/*oobfd*/, tvp);
    }

    if (rv <= 0) {
        return rv;
    }

    if (! FD_ISSET(fd % FD_SETSIZE, &poll->set[fd / FD_SETSIZE])) {
        return -2;
    }
    return rv;
}

static inline void
as_poll_destroy(as_poll* poll)
{
    if (poll->size > AS_STACK_LIMIT) {
        cf_free(poll->set);
    }
}

#else  // _MSC_VER

#define as_poll_init(_poll, _fd)

static inline int
as_poll_socket(as_poll* poll, as_socket_fd fd, uint32_t timeout, bool read)
{
    FD_ZERO(&poll->set);
    FD_SET(fd, &poll->set);

    struct timeval tv;
    struct timeval* tvp;
    int rv;

    if (timeout > 0) {
        tv.tv_sec = timeout / 1000;
        tv.tv_usec = (timeout % 1000) * 1000;
        tvp = &tv;
    }
    else {
        tvp = NULL;
    }

    if (read) {
        rv = select(0, &poll->set /*readfd*/, 0 /*writefd*/, 0/*oobfd*/, tvp);
    }
    else {
        rv = select(0, 0 /*readfd*/, &poll->set /*writefd*/, 0/*oobfd*/, tvp);
    }

    if (rv <= 0) {
        return rv;
    }

    if (! FD_ISSET(fd, &poll->set)) {
        return -2;
    }
    return rv;
}

#define as_poll_destroy(_poll)

#endif

#ifdef __cplusplus
} // end extern "C"
#endif