libc/src/stdio/generic/fgets.cpp

   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 "hdr/types/FILE.h"
  13 #include "src/__support/macros/config.h"
  14 #include "src/errno/libc_errno.h"
  15 #include <stddef.h>
  16
  17 namespace LIBC_NAMESPACE_DECL {
  18
  19 LLVM_LIBC_FUNCTION(char *, fgets,
  20                    (char *__restrict str, int count,
  21                     ::FILE *__restrict raw_stream)) {
  22   if (count < 1)
  23     return nullptr;
  24
  25   unsigned char c = '\0';
  26   auto stream = reinterpret_cast<LIBC_NAMESPACE::File *__restrict>(raw_stream);
  27   stream->lock();
  28
  29   // i is an int because it's frequently compared to count, which is also int.
  30   int i = 0;
  31
  32   for (; i < (count - 1) && c != '\n'; ++i) {
  33     auto result = stream->read_unlocked(&c, 1);
  34     size_t r = result.value;
  35     if (result.has_error())
  36       libc_errno = result.error;
  37
  38     if (r != 1)
  39       break;
  40     str[i] = c;
  41   }
  42
  43   bool has_error = stream->error_unlocked();
  44   bool has_eof = stream->iseof_unlocked();
  45   stream->unlock();
  46
  47   // If the requested read size makes no sense, an error occured, or no bytes
  48   // were read due to an EOF, then return nullptr and don't write the null byte.
  49   if (has_error || (i == 0 && has_eof))
  50     return nullptr;
  51
  52   str[i] = '\0';
  53   return str;
  54 }
  55
  56 } // namespace LIBC_NAMESPACE_DECL