_getdelim() for MS-Windows compilers

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#pragma warning(disable: 4996)

/* Read up to (and including) a TERMINATOR from STREAM into *LINEPTR
  (and null-terminate it). *LINEPTR is a pointer returned from malloc (or
   NULL), pointing to *N characters of space.  It is realloc'd as
   necessary.  Returns the number of characters read (not including the
   null terminator), or -1 on error or EOF.  */
static __inline void __set_errno(unsigned int no)
{
    errno = no;
}

size_t __getdelim (char** lineptr, size_t* n, int terminator,FILE* stream)
{
    const size_t BLOCKSIZE = 255;
    int c;
    size_t len = 0;
    size_t linesize = 0;
    int newalloc = 0;
    if( lineptr == NULL || stream == NULL || n == NULL)
    {
        _set_errno(EINVAL);
        return -1;
    }
    linesize = BLOCKSIZE;
    if( *lineptr == NULL)
    {
        // allocate new memory if required
        *lineptr = malloc(BLOCKSIZE);
        *n = BLOCKSIZE;
        newalloc = 1;
    }
    else
        linesize = *n;
    while( (c = fgetc(stream)) != EOF && c != terminator)
    {
        // make sure we have enough room for the new character
        // If not, then streatch it out a bit.
        if( (len+1) == linesize)
        {
            linesize += BLOCKSIZE;
            *n = linesize;
            *lineptr = realloc(*lineptr, linesize);
        }
        (*lineptr)[len++] = c;
    }
    if( len == 0 && c != terminator) // check for blank lines
    {
        _set_errno(EINVAL);
        if( newalloc )
        {
            free(*lineptr);
            *lineptr = NULL;
        }
        else
            (*lineptr)[0] = 0; // truncate the string
        return -1;
    }
    (*lineptr)[len] = 0; // null-terminate the string
       
    return len;
}

int main()
{
    unsigned int n = 255;
    char* lineptr = malloc(n);
    FILE* fp = fopen("test3.c", "r");
    if( fp != NULL)
    {
        while(__getdelim(&lineptr, &n, '\n', fp) != -1 )
        {
            printf("%s\n", lineptr);
        }
        free(lineptr);
        lineptr = NULL;
        fclose(fp);
    }

}