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/*
* Implementation of open_for_write_would_lose_data for Windows.
*/
#include "putty.h"
/*
* This is slightly fiddly because we want to be backwards-compatible
* with systems too old to have GetFileAttributesEx. The next best
* thing is FindFirstFile, which will return a different data
* structure, but one that also contains the fields we want. (But it
* will behave more unhelpfully - for this application - in the
* presence of wildcards, so we'd prefer to use GFAE if we can.)
*/
static inline bool open_for_write_would_lose_data_impl(
DWORD dwFileAttributes, DWORD nFileSizeHigh, DWORD nFileSizeLow)
{
if (dwFileAttributes & (FILE_ATTRIBUTE_DEVICE|FILE_ATTRIBUTE_DIRECTORY)) {
/*
* File is something other than an ordinary disk file, so
* opening it for writing will not cause truncation. (It may
* not _succeed_ either, but that's not our problem here!)
*/
return false;
}
if (nFileSizeHigh == 0 && nFileSizeLow == 0) {
/*
* File is zero-length (or may be a named pipe, which
* dwFileAttributes can't tell apart from a regular file), so
* opening it for writing won't truncate any data away because
* there's nothing to truncate anyway.
*/
return false;
}
return true;
}
bool open_for_write_would_lose_data(const Filename *fn)
{
static HMODULE kernel32_module;
DECL_WINDOWS_FUNCTION(static, BOOL, GetFileAttributesExA,
(LPCSTR, GET_FILEEX_INFO_LEVELS, LPVOID));
if (!kernel32_module) {
kernel32_module = load_system32_dll("kernel32.dll");
GET_WINDOWS_FUNCTION(kernel32_module, GetFileAttributesExA);
}
if (p_GetFileAttributesExA) {
WIN32_FILE_ATTRIBUTE_DATA attrs;
if (!p_GetFileAttributesExA(fn->path, GetFileExInfoStandard, &attrs)) {
/*
* Generally, if we don't identify a specific reason why we
* should return true from this function, we return false, and
* let the subsequent attempt to open the file for real give a
* more useful error message.
*/
return false;
}
return open_for_write_would_lose_data_impl(
attrs.dwFileAttributes, attrs.nFileSizeHigh, attrs.nFileSizeLow);
} else {
WIN32_FIND_DATA fd;
HANDLE h = FindFirstFile(fn->path, &fd);
if (h == INVALID_HANDLE_VALUE) {
/*
* As above, if we can't find the file at all, return false.
*/
return false;
}
CloseHandle(h);
return open_for_write_would_lose_data_impl(
fd.dwFileAttributes, fd.nFileSizeHigh, fd.nFileSizeLow);
}
}
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