writen.c

unix环境高级编程的源代码

#include    "ourhdr.h"

ssize_t                        /* Write "n" bytes to a descriptor. */
writen(int fd, const void *vptr, size_t n)
{
    size_t        nleft, nwritten;
    const char    *ptr;

    ptr = vptr;    /* can't do pointer arithmetic on void* */
    nleft = n;
    while (nleft > 0) {
        if ( (nwritten = write(fd, ptr, nleft)) <= 0)
            return(nwritten);        /* error */

        nleft -= nwritten;
        ptr   += nwritten;
    }
    return(n);
}