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 57