1//===-- Implementation of fgets -------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "src/stdio/fgets.h"
10#include "src/__support/File/file.h"
11
12#include "src/errno/libc_errno.h"
13#include <stddef.h>
14#include <stdio.h>
15
16namespace LIBC_NAMESPACE {
17
18LLVM_LIBC_FUNCTION(char *, fgets,
19 (char *__restrict str, int count,
20 ::FILE *__restrict raw_stream)) {
21 if (count < 1)
22 return nullptr;
23
24 unsigned char c = '\0';
25 auto stream = reinterpret_cast<LIBC_NAMESPACE::File *__restrict>(raw_stream);
26 stream->lock();
27
28 // i is an int because it's frequently compared to count, which is also int.
29 int i = 0;
30
31 for (; i < (count - 1) && c != '\n'; ++i) {
32 auto result = stream->read_unlocked(data: &c, len: 1);
33 size_t r = result.value;
34 if (result.has_error())
35 libc_errno = result.error;
36
37 if (r != 1)
38 break;
39 str[i] = c;
40 }
41
42 bool has_error = stream->error_unlocked();
43 bool has_eof = stream->iseof_unlocked();
44 stream->unlock();
45
46 // If the requested read size makes no sense, an error occured, or no bytes
47 // were read due to an EOF, then return nullptr and don't write the null byte.
48 if (has_error || (i == 0 && has_eof))
49 return nullptr;
50
51 str[i] = '\0';
52 return str;
53}
54
55} // namespace LIBC_NAMESPACE
56

source code of libc/src/stdio/generic/fgets.cpp