crossplatform getline c function.

getline.c

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <stddef.h>

typedef ptrdiff_t ssize_t;
/*******************************************************************************
 * getline -- Stores line of text from stream.                                 *
 *                                                                             *
 * Parameters                                                                  *
 *      lineptr -- Storing address for the line of text. Buffer is NUL         *
 *                 terminated and includes newline character if found.         *
 *                 lineptr is malloc'd and must be free'd by caller.           *
 *      n       -- Buffer size(in bytes) stored in linepter. Reallocates as    *
 *                 necessary capture input stream.                             *
 *      stream  -- Source where line of text originates from.                  *
 *                                                                             *
 * Returns                                                                     *
 *      On success, returns the number of characters read, including newline,  *
 *      but not including the terminating null byte ('\0'). Return -1 on       *
 *      failure to read a line (including end-of-file condition).              *
 *      In the event of an error, errno is set to indicate the cause.          *
 *******************************************************************************/

/* Based on the spec found here 
   http://man7.org/linux/man-pages/man3/getline.3.html */

ssize_t
getline( char   **lineptr, /* input/output - storage address for input stream */
         size_t  *n,       /* input/output - string size in bytes */
         FILE    *stream ) /* input - text stream */
{
        char    *buffer_tmp, *position;
        size_t   block,      offset;
        int      c;

        if( !stream || !lineptr || !n ) {
                errno = EINVAL;
                return -1;
        /* Minimum length for strings is 2 bytes. */
        } else if( *lineptr == NULL || *n <= 1 ) {
                *n = 128;
                if( !(*lineptr = malloc(*n)) ) {
                        errno = ENOMEM;
                        return -1;
                }
        }
        block = *n;
        position = *lineptr;

        while( (c = fgetc(stream)) != EOF \
            && (*position++ = c) != '\n' ) {
                offset = position - *lineptr; /* realloc doesn't guarantee it can keep '*lineptr' in same memory spot. 
                                               * so needs keep track of offset. */
                if( offset >= *n ) {
                        buffer_tmp = realloc(*lineptr, *n += block);
                        if( !buffer_tmp ) { /* Do not free. Return *lineptr. */
                                errno = ENOMEM;
                                return -1;
                        }
                        *lineptr = buffer_tmp;
                        position = *lineptr + offset;
                }
        }
        *position = '\0';
        return (position - *lineptr - 1);
}

Works perfect!