1// SPDX-License-Identifier: GPL-2.0+
2/* getline.c -- Replacement for GNU C library function getline
3 *
4 * Copyright (C) 1993, 1996, 2001, 2002 Free Software Foundation, Inc.
5 */
6
7/* Written by Jan Brittenson, bson@gnu.ai.mit.edu.  */
8
9#include <assert.h>
10#include <stdio.h>
11
12/* Always add at least this many bytes when extending the buffer.  */
13#define MIN_CHUNK 64
14
15/* Read up to (and including) a TERMINATOR from STREAM into *LINEPTR
16   + OFFSET (and null-terminate it). *LINEPTR is a pointer returned from
17   malloc (or NULL), pointing to *N characters of space.  It is realloc'd
18   as necessary.  Return the number of characters read (not including the
19   null terminator), or -1 on error or EOF.
20   NOTE: There is another getstr() function declared in <curses.h>.  */
21static int getstr(char **lineptr, size_t *n, FILE *stream,
22		  char terminator, size_t offset)
23{
24	int nchars_avail;	/* Allocated but unused chars in *LINEPTR.  */
25	char *read_pos;		/* Where we're reading into *LINEPTR. */
26	int ret;
27
28	if (!lineptr || !n || !stream)
29		return -1;
30
31	if (!*lineptr) {
32		*n = MIN_CHUNK;
33		*lineptr = malloc(*n);
34		if (!*lineptr)
35			return -1;
36	}
37
38	nchars_avail = *n - offset;
39	read_pos = *lineptr + offset;
40
41	for (;;) {
42		register int c = getc(stream);
43
44		/* We always want at least one char left in the buffer, since we
45		   always (unless we get an error while reading the first char)
46		   NUL-terminate the line buffer.  */
47
48		assert(*n - nchars_avail == read_pos - *lineptr);
49		if (nchars_avail < 2) {
50			if (*n > MIN_CHUNK)
51				*n *= 2;
52			else
53				*n += MIN_CHUNK;
54
55			nchars_avail = *n + *lineptr - read_pos;
56			*lineptr = realloc(*lineptr, *n);
57			if (!*lineptr)
58				return -1;
59			read_pos = *n - nchars_avail + *lineptr;
60			assert(*n - nchars_avail == read_pos - *lineptr);
61		}
62
63		if (c == EOF || ferror (stream)) {
64			/* Return partial line, if any.  */
65			if (read_pos == *lineptr)
66				return -1;
67			else
68				break;
69		}
70
71		*read_pos++ = c;
72		nchars_avail--;
73
74		if (c == terminator)
75			/* Return the line.  */
76			break;
77	}
78
79	/* Done - NUL terminate and return the number of chars read.  */
80	*read_pos = '\0';
81
82	ret = read_pos - (*lineptr + offset);
83	return ret;
84}
85
86int getline (char **lineptr, size_t *n, FILE *stream)
87{
88	return getstr(lineptr, n, stream, '\n', 0);
89}
90