4.1

1 files changed, 369 insertions, 0 deletions

diff --git a/zen/dst_hack.cpp b/zen/dst_hack.cpp
new file mode 100644
index 00000000..f6579441
--- /dev/null
+++ b/zen/dst_hack.cpp
@@ -0,0 +1,369 @@
+#include "dst_hack.h"
+#include <bitset>
+#include "basic_math.h"
+#include "long_path_prefix.h"
+#include "utf8.h"
+#include "assert_static.h"
+#include "int64.h"
+#include "file_error.h"
+#include "dll.h"
+
+using namespace zen;
+
+
+namespace
+{
+//fast ::GetVolumePathName() clone: let's hope it's not too simple (doesn't honor mount points)
+Zstring getVolumeName(const Zstring& filename)
+{
+    //this call is expensive: ~1.5 ms!
+    //    if (!::GetVolumePathName(applyLongPathPrefix(filename).c_str(), //__in   LPCTSTR lpszFileName,
+    //                             fsName,                                     //__out  LPTSTR lpszVolumePathName,
+    //                             BUFFER_SIZE))                               //__in   DWORD cchBufferLength
+    // ...
+    //    Zstring volumePath = fsName;
+    //    if (!volumePath.EndsWith(FILE_NAME_SEPARATOR)) //a trailing backslash is required
+    //        volumePath += FILE_NAME_SEPARATOR;
+
+    Zstring nameFmt = removeLongPathPrefix(filename); //throw()
+    if (!endsWith(nameFmt, FILE_NAME_SEPARATOR))
+        nameFmt += FILE_NAME_SEPARATOR; //GetVolumeInformation expects trailing backslash
+
+    if (startsWith(nameFmt, Zstr("\\\\"))) //UNC path: "\\ComputerName\SharedFolder\"
+    {
+        size_t nameSize = nameFmt.size();
+        const size_t posFirstSlash = nameFmt.find(Zstr("\\"), 2);
+        if (posFirstSlash != Zstring::npos)
+        {
+            nameSize = posFirstSlash + 1;
+            const size_t posSecondSlash = nameFmt.find(Zstr("\\"), posFirstSlash + 1);
+            if (posSecondSlash != Zstring::npos)
+                nameSize = posSecondSlash + 1;
+        }
+        return Zstring(nameFmt.c_str(), nameSize); //include trailing backslash!
+    }
+    else //local path: "C:\Folder\"
+    {
+        const size_t pos = nameFmt.find(Zstr(":\\"));
+        if (pos == 1) //expect single letter volume
+            return Zstring(nameFmt.c_str(), 3);
+    }
+
+    return Zstring();
+}
+}
+
+
+bool dst::isFatDrive(const Zstring& fileName) //throw()
+{
+    const size_t BUFFER_SIZE = MAX_PATH + 1;
+    wchar_t fsName[BUFFER_SIZE];
+
+    const Zstring volumePath = getVolumeName(fileName);
+    if (volumePath.empty())
+        return false;
+
+    //suprisingly fast: ca. 0.03 ms per call!
+    if (!::GetVolumeInformation(volumePath.c_str(), //__in_opt   LPCTSTR lpRootPathName,
+                                NULL,               //__out      LPTSTR lpVolumeNameBuffer,
+                                0,                  //__in       DWORD nVolumeNameSize,
+                                NULL,               //__out_opt  LPDWORD lpVolumeSerialNumber,
+                                NULL,               //__out_opt  LPDWORD lpMaximumComponentLength,
+                                NULL,               //__out_opt  LPDWORD lpFileSystemFlags,
+                                fsName,             //__out      LPTSTR lpFileSystemNameBuffer,
+                                BUFFER_SIZE))       //__in       DWORD nFileSystemNameSize
+    {
+        assert(false); //shouldn't happen
+        return false;
+    }
+    //DST hack seems to be working equally well for FAT and FAT32 (in particular creation time has 10^-2 s precision as advertised)
+    return fsName == Zstring(L"FAT") ||
+           fsName == Zstring(L"FAT32");
+}
+
+
+bool dst::isFatDrive(HANDLE hFile) //throw()
+{
+    //dynamically load windows API function
+    typedef BOOL (WINAPI *GetVolumeInformationByHandleWFunc)(HANDLE  hFile,
+                                                             LPWSTR  lpVolumeNameBuffer,
+                                                             DWORD   nVolumeNameSize,
+                                                             LPDWORD lpVolumeSerialNumber,
+                                                             LPDWORD lpMaximumComponentLength,
+                                                             LPDWORD lpFileSystemFlags,
+                                                             LPWSTR  lpFileSystemNameBuffer,
+                                                             DWORD   nFileSystemNameSize);
+
+    const DllFun<GetVolumeInformationByHandleWFunc> getVolumeInformationByHandle(L"kernel32.dll", "GetVolumeInformationByHandleW");
+    if (!getVolumeInformationByHandle)
+    {
+        assert(false);
+        return false;
+    }
+
+    const size_t BUFFER_SIZE = MAX_PATH + 1;
+    wchar_t fsName[BUFFER_SIZE];
+
+    if (!getVolumeInformationByHandle(hFile,        //__in       HANDLE hFile,
+                                      NULL,         //__out      LPTSTR lpVolumeNameBuffer,
+                                      0,            //__in       DWORD nVolumeNameSize,
+                                      NULL,         //__out_opt  LPDWORD lpVolumeSerialNumber,
+                                      NULL,         //__out_opt  LPDWORD lpMaximumComponentLength,
+                                      NULL,         //__out_opt  LPDWORD lpFileSystemFlags,
+                                      fsName,       //__out      LPTSTR lpFileSystemNameBuffer,
+                                      BUFFER_SIZE)) //__in       DWORD nFileSystemNameSize
+    {
+        assert(false); //shouldn't happen
+        return false;
+    }
+    //DST hack seems to be working equally well for FAT and FAT32 (in particular creation time has 10^-2 s precision as advertised)
+    return fsName == Zstring(L"FAT") ||
+           fsName == Zstring(L"FAT32");
+}
+
+
+namespace
+{
+//convert UInt64 and Int64 to FILETIME
+inline
+FILETIME toFiletime(Int64 number)
+{
+    const UInt64 unsig = to<UInt64>(number);
+
+    FILETIME output = {};
+    output.dwLowDateTime  = unsig.getLo();
+    output.dwHighDateTime = unsig.getHi();
+    return output;
+}
+
+FILETIME toFiletime(UInt64 number)
+{
+    FILETIME output = {};
+    output.dwLowDateTime  = number.getLo();
+    output.dwHighDateTime = number.getHi();
+    return output;
+}
+
+inline
+UInt64 toUInt64(const FILETIME& fileTime)
+{
+    return UInt64(fileTime.dwLowDateTime, fileTime.dwHighDateTime);
+}
+
+
+inline
+Int64 toInt64(const FILETIME& fileTime)
+{
+    return to<Int64>(UInt64(fileTime.dwLowDateTime, fileTime.dwHighDateTime));
+}
+
+
+FILETIME utcToLocal(const FILETIME& utcTime) //throw (std::runtime_error)
+{
+    //treat binary local time representation (which is invariant under DST time zone shift) as logical UTC:
+    FILETIME localTime = {};
+    if (!::FileTimeToLocalFileTime(
+            &utcTime,    //__in   const FILETIME *lpFileTime,
+            &localTime)) //__out  LPFILETIME lpLocalFileTime
+    {
+        const std::wstring errorMessage = _("Conversion error:") + " FILETIME -> local FILETIME: " + "(" +
+                                          "High: " + toString<std::wstring>(utcTime.dwHighDateTime) + " " +
+                                          "Low: "  + toString<std::wstring>(utcTime.dwLowDateTime) + ") " + "\n\n" + getLastErrorFormatted();
+        throw std::runtime_error(wideToUtf8<std::string>(errorMessage));
+    }
+    return localTime;
+}
+
+
+FILETIME localToUtc(const FILETIME& localTime) //throw (std::runtime_error)
+{
+    //treat binary local time representation (which is invariant under DST time zone shift) as logical UTC:
+    FILETIME utcTime = {};
+    if (!::LocalFileTimeToFileTime(
+            &localTime, //__in   const FILETIME *lpLocalFileTime,
+            &utcTime))  //__out  LPFILETIME lpFileTime
+    {
+        const std::wstring errorMessage = _("Conversion error:") + " local FILETIME -> FILETIME: " + "(" +
+                                          "High: " + toString<std::wstring>(localTime.dwHighDateTime) + " " +
+                                          "Low: "  + toString<std::wstring>(localTime.dwLowDateTime) + ") " + "\n\n" + getLastErrorFormatted();
+        throw std::runtime_error(wideToUtf8<std::string>(errorMessage));
+    }
+    return utcTime;
+}
+
+
+//struct FILETIME {DWORD dwLowDateTime; DWORD dwHighDateTime;};
+const FILETIME FAT_MIN_TIME = { 13374976, 27846544 }; //1980 \ both are valid max/min FAT dates for 2 second precision
+const FILETIME FAT_MAX_TIME = { 14487552, 37251238 }; //2107 /
+
+//http://en.wikipedia.org/wiki/File_Allocation_Table
+const size_t PRECISION_WRITE_TIME  = 20000000; //number of 100 ns per step -> 2 s
+const size_t PRECISION_CREATE_TIME =   100000; //                          -> 1/100 s
+
+/*
+Number of bits of information in create time: ln_2((FAT_MAX_TIME - FAT_MIN_TIME) / PRECISION_CREATE_TIME) = 38.55534023
+Number of bits of information in write time: 30.91148404
+*/
+//total size available to store data:
+const size_t CREATE_TIME_INFO_BITS = 38;
+//   I. indicator that offset in II) is present
+const size_t INDICATOR_EXISTING_BITS = 1;
+//  II. local<->UTC time offset
+const size_t UTC_LOCAL_OFFSET_BITS = 7;
+// III. indicator that offset in II) corresponds to current local write time (this could be a hash of the write time)
+const size_t WRITE_TIME_HASH_BITS = CREATE_TIME_INFO_BITS - INDICATOR_EXISTING_BITS - UTC_LOCAL_OFFSET_BITS;
+
+
+template <size_t precision>
+FILETIME encodeRawInformation(UInt64 rawInfo)
+{
+    rawInfo *= precision;
+    rawInfo += toUInt64(FAT_MIN_TIME);
+
+    assert(rawInfo <= toUInt64(FAT_MAX_TIME));
+    return toFiletime(rawInfo);
+}
+
+
+template <size_t precision>
+UInt64 extractRawInformation(const FILETIME& createTime)
+{
+    assert(toUInt64(FAT_MIN_TIME) <= toUInt64(createTime));
+    assert(toUInt64(createTime) <= toUInt64(FAT_MAX_TIME));
+
+    //FAT create time ranges from 1980 - 2107 (2^7 years) with 1/100 seconds precision
+    UInt64 rawInfo = toUInt64(createTime);
+
+    rawInfo -= toUInt64(FAT_MIN_TIME);
+    rawInfo /= precision;        //reduce precision (FILETIME has unit 10^-7 s)
+
+    assert(toUInt64(encodeRawInformation<precision>(rawInfo)) == toUInt64(createTime)); //must be reversible
+    return rawInfo;
+}
+
+
+//convert write time to it's minimal representation (no restriction to FAT range "1980 - 2107")
+UInt64 extractRawWriteTime(const FILETIME& writeTime)
+{
+    UInt64 rawInfo = toUInt64(writeTime);
+    assert(rawInfo % PRECISION_WRITE_TIME == 0U);
+    rawInfo /= PRECISION_WRITE_TIME;        //reduce precision (FILETIME has unit 10^-7 s)
+    return rawInfo;
+}
+
+
+//files with different resolution than 2 seconds are rounded up when written to FAT
+FILETIME roundToFatWriteTime(const FILETIME& writeTime)
+{
+    UInt64 rawData = toUInt64(writeTime);
+
+    if (rawData % PRECISION_WRITE_TIME != 0U)
+        rawData += PRECISION_WRITE_TIME;
+
+    rawData /= PRECISION_WRITE_TIME;
+    rawData *= PRECISION_WRITE_TIME;
+    return toFiletime(rawData);
+}
+
+
+//get 7-bit value representing time shift in number of quarter-hours
+std::bitset<UTC_LOCAL_OFFSET_BITS> getUtcLocalShift()
+{
+    FILETIME utcTime = FAT_MIN_TIME;
+    utcTime.dwHighDateTime += 5000000; //some arbitrary valid time
+
+    const FILETIME localTime = utcToLocal(utcTime);
+
+    const int timeShiftSec = to<int>((toInt64(localTime) - toInt64(utcTime)) / 10000000); //time shift in seconds
+
+    const int timeShiftQuarter = timeShiftSec / (60 * 15); //time shift in quarter-hours
+
+    const int absValue = numeric::abs(timeShiftQuarter); //MSVC C++0x bug: std::bitset<>(unsigned long) is ambiguous
+
+    if (std::bitset < UTC_LOCAL_OFFSET_BITS - 1 > (absValue).to_ulong() != static_cast<unsigned long>(absValue) || //time shifts that big shouldn't be possible!
+        timeShiftSec % (60 * 15) != 0) //all known time shift have at least 15 minute granularity!
+    {
+        const std::wstring errorMessage = _("Conversion error:") + " Unexpected UTC <-> local time shift: " +
+                                          "(" + toString<std::wstring>(timeShiftSec) + ") " + "\n\n" + getLastErrorFormatted();
+        throw std::runtime_error(wideToUtf8<std::string>(errorMessage));
+    }
+
+    std::bitset<UTC_LOCAL_OFFSET_BITS> output(absValue);
+    output[UTC_LOCAL_OFFSET_BITS - 1] = timeShiftQuarter < 0; //sign bit
+    return output;
+}
+
+
+//get time-zone shift in seconds
+inline
+int convertUtcLocalShift(std::bitset<UTC_LOCAL_OFFSET_BITS> rawShift)
+{
+    const bool hasSign = rawShift[UTC_LOCAL_OFFSET_BITS - 1];
+    rawShift[UTC_LOCAL_OFFSET_BITS - 1] = false;
+
+    assert_static(UTC_LOCAL_OFFSET_BITS <= sizeof(unsigned long) * 8);
+    return hasSign ?
+           static_cast<int>(rawShift.to_ulong()) * 15 * 60 * -1 :
+           static_cast<int>(rawShift.to_ulong()) * 15 * 60;
+}
+}
+
+
+bool dst::fatHasUtcEncoded(const RawTime& rawTime) //"createTimeRaw" as retrieved by ::FindFirstFile() and ::GetFileAttributesEx(); throw (std::runtime_error)
+{
+    if (toUInt64(rawTime.createTimeRaw) < toUInt64(FAT_MIN_TIME) ||
+        toUInt64(FAT_MAX_TIME) < toUInt64(rawTime.createTimeRaw))
+    {
+        assert(false); //shouldn't be possible according to FAT specification
+        return false;
+    }
+
+    const UInt64 rawInfo = extractRawInformation<PRECISION_CREATE_TIME>(utcToLocal(rawTime.createTimeRaw));
+
+    assert_static(WRITE_TIME_HASH_BITS == 30);
+    return (extractRawWriteTime(utcToLocal(rawTime.writeTimeRaw)) & 0x3FFFFFFFU) == (rawInfo & 0x3FFFFFFFU) && //ensure write time wasn't changed externally
+           rawInfo >> (CREATE_TIME_INFO_BITS - INDICATOR_EXISTING_BITS) == 1U; //extended data available
+}
+
+
+dst::RawTime dst::fatEncodeUtcTime(const FILETIME& writeTimeRealUtc) //throw (std::runtime_error)
+{
+    const FILETIME fatWriteTimeUtc = roundToFatWriteTime(writeTimeRealUtc); //writeTimeRealUtc may have incompatible precision (NTFS)
+
+    //create time lets us store 40 bit of information
+
+    //indicator that utc time is encoded -> hopefully results in a date long way in the future; but even if this bit is accidentally set, we still have the hash!
+    UInt64 data = 1U;
+
+    const std::bitset<UTC_LOCAL_OFFSET_BITS> utcShift = getUtcLocalShift();
+    data <<= UTC_LOCAL_OFFSET_BITS;
+    data |= utcShift.to_ulong();
+
+    data <<= WRITE_TIME_HASH_BITS;
+    data |= extractRawWriteTime(utcToLocal(fatWriteTimeUtc)) & 0x3FFFFFFFU; //trim to last 30 bit of information
+    assert_static(WRITE_TIME_HASH_BITS == 30);
+
+    const FILETIME encodedData = localToUtc(encodeRawInformation<PRECISION_CREATE_TIME>(data)); //localToUtc: make sure data is physically saved as FAT local time
+    assert(toUInt64(FAT_MIN_TIME) <= toUInt64(encodedData));
+    assert(toUInt64(encodedData) <= toUInt64(FAT_MAX_TIME));
+
+    return RawTime(encodedData, fatWriteTimeUtc); //keep compatible with other applications, at least until DST shift actually occurs
+}
+
+
+FILETIME dst::fatDecodeUtcTime(const RawTime& rawTime) //return real UTC time; throw (std::runtime_error)
+{
+    if (!fatHasUtcEncoded(rawTime))
+        return rawTime.writeTimeRaw;
+
+    const UInt64 rawInfo = extractRawInformation<PRECISION_CREATE_TIME>(utcToLocal(rawTime.createTimeRaw));
+
+    const std::bitset<UTC_LOCAL_OFFSET_BITS> rawShift(to<int>((rawInfo >> WRITE_TIME_HASH_BITS) & 0x7FU));  //static_cast<int>: a shame MSC... "unsigned long" should be supported instead!
+    assert_static(UTC_LOCAL_OFFSET_BITS == 7);
+
+    const int timeShiftSec = convertUtcLocalShift(rawShift);
+    const FILETIME writeTimeLocal = utcToLocal(rawTime.writeTimeRaw);
+
+    const Int64 realUTC = toInt64(writeTimeLocal) - Int64(timeShiftSec) * 10000000;
+    return toFiletime(realUTC);
+}