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 16 namespace LIBC_NAMESPACE { 17 18 LLVM_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(&c, 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