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Windows: compare file identity in UTIL_isSameFile #4884

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Windows: compare file identity in UTIL_isSameFile #4884

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54 changes: 44 additions & 10 deletions programs/util.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@
#endif /* #ifdef __FreeBSD__ */

#if defined(_WIN32)
# include <windows.h> /* CreateFileA, GetFileInformationByHandle */
# include <sys/utime.h> /* utime */
# include <io.h> /* _chmod */
# define ZSTD_USE_UTIMENSAT 0
Expand Down Expand Up @@ -381,17 +382,52 @@ int UTIL_compareStr(const void *p1, const void *p2) {
return strcmp(* (char * const *) p1, * (char * const *) p2);
}

#if defined(_WIN32)
/* note : Windows has no inode numbers, but a file's identity is given by
* its volume serial number and file index, which stay the same
* however the path to the file is spelled */
static int UTIL_isSameFileWin32(const char* fName1, const char* fName2)
{
BY_HANDLE_FILE_INFORMATION file1Info;
BY_HANDLE_FILE_INFORMATION file2Info;
HANDLE file1Handle;
HANDLE file2Handle;
int same;

if (!strcmp(fName1, fName2)) return 1;

file1Handle = CreateFileA(fName1, FILE_READ_ATTRIBUTES,
FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
if (file1Handle == INVALID_HANDLE_VALUE) return 0;

file2Handle = CreateFileA(fName2, FILE_READ_ATTRIBUTES,
FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
if (file2Handle == INVALID_HANDLE_VALUE) {
CloseHandle(file1Handle);
return 0;
}

same = GetFileInformationByHandle(file1Handle, &file1Info)
&& GetFileInformationByHandle(file2Handle, &file2Info)
&& file1Info.dwVolumeSerialNumber == file2Info.dwVolumeSerialNumber
&& file1Info.nFileIndexHigh == file2Info.nFileIndexHigh
&& file1Info.nFileIndexLow == file2Info.nFileIndexLow;

CloseHandle(file1Handle);
CloseHandle(file2Handle);
return same;
}
#endif

int UTIL_isSameFile(const char* fName1, const char* fName2)
{
int ret;
assert(fName1 != NULL); assert(fName2 != NULL);
UTIL_TRACE_CALL("UTIL_isSameFile(%s, %s)", fName1, fName2);
#if defined(_MSC_VER) || defined(_WIN32)
/* note : Visual does not support file identification by inode.
* inode does not work on Windows, even with a posix layer, like msys2.
* The following work-around is limited to detecting exact name repetition only,
* aka `filename` is considered different from `subdir/../filename` */
ret = !strcmp(fName1, fName2);
ret = UTIL_isSameFileWin32(fName1, fName2);
#else
{ stat_t file1Stat;
stat_t file2Stat;
Expand All @@ -412,13 +448,11 @@ int UTIL_isSameFileStat(
assert(fName1 != NULL); assert(fName2 != NULL);
UTIL_TRACE_CALL("UTIL_isSameFileStat(%s, %s)", fName1, fName2);
#if defined(_MSC_VER) || defined(_WIN32)
/* note : Visual does not support file identification by inode.
* inode does not work on Windows, even with a posix layer, like msys2.
* The following work-around is limited to detecting exact name repetition only,
* aka `filename` is considered different from `subdir/../filename` */
/* note : stat_t does not carry a usable file identity on Windows,
* so compare the files themselves */
(void)file1Stat;
(void)file2Stat;
ret = !strcmp(fName1, fName2);
ret = UTIL_isSameFileWin32(fName1, fName2);
#else
{
ret = (file1Stat->st_dev == file2Stat->st_dev)
Expand Down
11 changes: 11 additions & 0 deletions tests/playTests.sh
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Expand Up @@ -241,6 +241,17 @@ rm -f tmpCompressed
zstd tmp -o tmpOut -c > tmpCompressed
test -f tmpCompressed # file must be created

println "test : refuse output overwriting input through another spelling"
cp tmp tmpRef
zstd -f tmp -o ./tmp && die "should have refused to overwrite input through ./ prefix"
cmp tmp tmpRef || die "refused ./ output modified the input file"
if [ "$isWindows" = true ] ; then
println "test : refuse output overwriting input through a different case"
zstd -f tmp -o TMP && die "should have refused to overwrite input through a different case"
cmp tmp tmpRef || die "refused differently-cased output modified the input file"
fi
rm -f tmpRef

println "test : forgotten argument"
cp tmp tmp2
zstd tmp2 -fo && die "-o must be followed by filename "
Expand Down