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reactos/sdk/lib/ucrt/stdio/gets.cpp
2025-01-16 14:18:53 +02:00

149 lines
5.3 KiB
C++

//
// gets.cpp
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// Defines gets() and gets_s(), which read a line from stdin.
//
#include <corecrt_internal_stdio.h>
#include <corecrt_internal_securecrt.h>
// Reads a line of text from stdin, storing it in the 'result' buffer. This
// function supports two modes:
//
// [1] Insecure, which is used by the abominable gets() and _getws() functions.
// In this mode, the buffer is not bounds-checked; it is just assumed that
// the buffer is large enough. Text is read until a newline is reached or
// EOF is reached. This mode is enabled by passing _CRT_UNBOUNDED_BUFFER_SIZE
// as the buffer size.
//
// [2] Secure, which is used by the gets_s() and _getws_s() functions. In this
// mode, the buffer is bound-checked. If there is insufficient space in the
// buffer for the entire line of text, the line is read and discarded, the
// buffer is zero'ed, and nullptr is returned. If the buffer is larger than
// is required, the remaining space of the buffer is zero-filled.
//
// On success, 'result' is returned. On failure, nullptr is returned. If the
// 'return_early_if_eof_is_first' flag is true and the first read encounters EOF,
// the buffer is left unchanged and nullptr is returned.
template <typename Character>
_Success_(return != nullptr)
static Character* __cdecl common_gets(
_Out_writes_z_(result_size_in_characters) Character* const result,
_In_ size_t const result_size_in_characters,
_In_ bool const return_early_if_eof_is_first
) throw()
{
typedef __acrt_stdio_char_traits<Character> stdio_traits;
_VALIDATE_RETURN(result != nullptr, EINVAL, nullptr);
_VALIDATE_RETURN(result_size_in_characters > 0, EINVAL, nullptr);
Character* return_value = result;
_lock_file(stdin);
__try
{
if (!stdio_traits::validate_stream_is_ansi_if_required(stdin))
{
return_value = nullptr;
__leave;
}
// Special case: if the first character is EOF, treat it specially if
// we were asked to do so:
typename stdio_traits::int_type c = stdio_traits::getc_nolock(stdin);
if (c == stdio_traits::eof)
{
return_value = nullptr;
if (return_early_if_eof_is_first)
__leave;
}
// For the insecure version, we do no buffer size check and no debug fill:
if (result_size_in_characters == _CRT_UNBOUNDED_BUFFER_SIZE)
{
#pragma warning(push)
#pragma warning(disable:__WARNING_POTENTIAL_BUFFER_OVERFLOW_HIGH_PRIORITY) // 26015 - knowingly unsafe
Character* result_it = result;
while (c != '\n' && c != stdio_traits::eof)
{
*result_it++ = static_cast<Character>(c);
c = stdio_traits::getc_nolock(stdin);
}
*result_it = '\0';
#pragma warning(pop)
}
// For the secure version, we track the buffer size. If we run out of
// buffer space, we still read in the rest of the current line until we
// reach '\n' or EOF, but we discard the characters and reset the buffer
// to be zero-filled.
else
{
size_t available = result_size_in_characters;
Character* result_it = result;
while (c != '\n' && c != stdio_traits::eof)
{
if (available > 0)
{
--available;
*result_it++ = static_cast<Character>(c);
}
c = stdio_traits::getc_nolock(stdin);
}
// If we ran out of space, clear the buffer and return failure:
if (available == 0)
{
_RESET_STRING(result, result_size_in_characters);
_RETURN_BUFFER_TOO_SMALL_ERROR(result, result_size_in_characters, nullptr);
}
*result_it = '\0';
_FILL_STRING(result, result_size_in_characters, result_size_in_characters - available + 1);
}
}
__finally
{
_unlock_file(stdin);
}
__endtry
return return_value;
}
// Reads a line of text from stdin and stores it in the result buffer. If the
// line is longer than will fit in the buffer, the line is discarded, the buffer
// is reset, and nullptr is returned.
extern "C" char* __cdecl gets_s(char* const result, size_t const result_size_in_characters)
{
return common_gets(result, result_size_in_characters, false);
}
extern "C" wchar_t* __cdecl _getws_s(wchar_t* const result, size_t const result_size_in_characters)
{
return common_gets(result, result_size_in_characters, false);
}
// Reads a line of text from stdin and stores it in the result buffer. This
// function assumes there is sufficient room in the buffer. Do not use this
// function; use gets_s(), fgets(), _getws_s(), or fgetws() instead. If EOF
// is encountered on the first read from the stream, the buffer is left
// unmodified and nullptr is returned.
extern "C" char* __cdecl gets(char* const result)
{
return common_gets(result, _CRT_UNBOUNDED_BUFFER_SIZE, true);
}
extern "C" wchar_t* __cdecl _getws(wchar_t* const result)
{
return common_gets(result, _CRT_UNBOUNDED_BUFFER_SIZE, true);
}