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  • /* getline.c -- Replacement for GNU C library function getline
    
     *
     * Copyright (C) 1993, 1996, 2001, 2002 Free Software Foundation, Inc.
     *
     * SPDX-License-Identifier:	GPL-2.0+
     */
    
    
    /* Written by Jan Brittenson, bson@gnu.ai.mit.edu.  */
    
    #include <assert.h>
    #include <stdio.h>
    
    /* Always add at least this many bytes when extending the buffer.  */
    #define MIN_CHUNK 64
    
    /* Read up to (and including) a TERMINATOR from STREAM into *LINEPTR
       + OFFSET (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.  Return the number of characters read (not including the
       null terminator), or -1 on error or EOF.
       NOTE: There is another getstr() function declared in <curses.h>.  */
    static int getstr(char **lineptr, size_t *n, FILE *stream,
    		  char terminator, size_t offset)
    {
    	int nchars_avail;	/* Allocated but unused chars in *LINEPTR.  */
    	char *read_pos;		/* Where we're reading into *LINEPTR. */
    	int ret;
    
    	if (!lineptr || !n || !stream)
    		return -1;
    
    	if (!*lineptr) {
    		*n = MIN_CHUNK;
    		*lineptr = malloc(*n);
    		if (!*lineptr)
    			return -1;
    	}
    
    	nchars_avail = *n - offset;
    	read_pos = *lineptr + offset;
    
    	for (;;) {
    		register int c = getc(stream);
    
    		/* We always want at least one char left in the buffer, since we
    		   always (unless we get an error while reading the first char)
    		   NUL-terminate the line buffer.  */
    
    		assert(*n - nchars_avail == read_pos - *lineptr);
    		if (nchars_avail < 2) {
    			if (*n > MIN_CHUNK)
    				*n *= 2;
    			else
    				*n += MIN_CHUNK;
    
    			nchars_avail = *n + *lineptr - read_pos;
    			*lineptr = realloc(*lineptr, *n);
    			if (!*lineptr)
    				return -1;
    			read_pos = *n - nchars_avail + *lineptr;
    			assert(*n - nchars_avail == read_pos - *lineptr);
    		}
    
    		if (c == EOF || ferror (stream)) {
    			/* Return partial line, if any.  */
    			if (read_pos == *lineptr)
    				return -1;
    			else
    				break;
    		}
    
    		*read_pos++ = c;
    		nchars_avail--;
    
    		if (c == terminator)
    			/* Return the line.  */
    			break;
    	}
    
    	/* Done - NUL terminate and return the number of chars read.  */
    	*read_pos = '\0';
    
    	ret = read_pos - (*lineptr + offset);
    	return ret;
    }
    
    int getline (char **lineptr, size_t *n, FILE *stream)
    {
    	return getstr(lineptr, n, stream, '\n', 0);
    }