nwrite.h

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#ifndef LIBNAGIOS_NWRITE_H_INCLUDED
#define LIBNAGIOS_NWRITE_H_INCLUDED

/**
 * @file nwrite.h
 * @brief Functions that properly handle incomplete write()'s
 *
 * Some functions simply use write() to send data through a socket.
 * These calls are sometimes interrupted, especially in the case of
 * an overly large buffer. Even though the write() _could_ finish,
 * the incomplete write is treated as an error. The functions here
 * properly handle those cases.
 *
 * @{
 */

/**
 * Send data through a socket
 * This function will send data through a socket and return
 * the number of bytes written.
 * @param sock The socket to write to
 * @param data The data to write
 * @param lth The length of the data
 * @param sent The number of bytes written (can be NULL)
 * @return The number of bytes written or -1 if error
 */
static inline ssize_t nwrite(int fd, const void *buf, size_t count, ssize_t *written)
{
    /*
     * Given the API we have to assume (unsigned) size_t 'count' fits into
     * a (signed) ssize_t because we can't return a larger value.
     * https://stackoverflow.com/questions/29722999/will-write2-always-write-less-than-or-equal-to-ssize-max
     */
    ssize_t out, tot = 0;

    if (!buf || count == 0)
        return 0;

    while ((size_t) tot < count) {
        out = write(fd, (const char *) buf + tot, count - tot);
        if (out > 0)
            tot += out;
        else if(errno == EAGAIN || errno == EINTR)
            continue;
        else {
            if (written)
                *written = tot;
            return out;
        }
    }
    if (written)
        *written = tot;
    return tot;
}

/** @} */
#endif /* LIBNAGIOS_NWRITE_H_INCLUDED */