qtemporaryfile.cpp File Reference

#include "qtemporaryfile.h"
#include "qplatformdefs.h"
#include "private/qfile_p.h"
#include "private/qfsfileengine_p.h"
#include "private/qsystemerror_p.h"
#include "private/qfilesystemengine_p.h"

Go to the source code of this file.

Classes
class	QTemporaryFileEngine
class	QTemporaryFilePrivate

Typedefs
typedef ushort	Char
typedef HANDLE	NativeFileHandle

Functions
static bool	createFileFromTemplate (NativeFileHandle &file, QFileSystemEntry::NativePath &path, size_t pos, size_t length, QSystemError &error)
	Generates a unique file path and returns a native handle to the open file. More...
static Char	Latin1Char (char ch)

Typedef Documentation

Char

typedef ushort Char

Definition at line 68 of file qtemporaryfile.cpp.

NativeFileHandle

typedef HANDLE NativeFileHandle

Definition at line 76 of file qtemporaryfile.cpp.

Function Documentation

createFileFromTemplate()

static bool createFileFromTemplate ( NativeFileHandle &  file, QFileSystemEntry::NativePath &  path, size_t  pos, size_t  length, QSystemError &  error  )

static

Generates a unique file path and returns a native handle to the open file.

Warning

This function is not part of the public interface.

path is used as a template when generating unique paths, pos identifies the position of the first character that will be replaced in the template and length the number of characters that may be substituted.

Returns an open handle to the newly created file if successful, an invalid handle otherwise. In both cases, the string in path will be changed and contain the generated path name.

Definition at line 135 of file qtemporaryfile.cpp.

Referenced by QTemporaryFileEngine::open().

{
    Q_ASSERT(length != 0);
    Q_ASSERT(pos < size_t(path.length()));
    Q_ASSERT(length <= size_t(path.length()) - pos);

    Char *const placeholderStart = (Char *)path.data() + pos;
    Char *const placeholderEnd = placeholderStart + length;

    // Initialize placeholder with random chars + PID.
    {
        Char *rIter = placeholderEnd;

#if defined(QT_BUILD_CORE_LIB)
        quint64 pid = quint64(QCoreApplication::applicationPid());
        do {
            *--rIter = Latin1Char((pid % 10) + '0');
            pid /= 10;
        } while (rIter != placeholderStart && pid != 0);
#endif

        while (rIter != placeholderStart) {
            char ch = char((qrand() & 0xffff) % (26 + 26));
            if (ch < 26)
                *--rIter = Latin1Char(ch + 'A');
            else
                *--rIter = Latin1Char(ch - 26 + 'a');
        }
    }

#ifdef Q_OS_SYMBIAN
    RFs& fs = qt_s60GetRFs();
#endif

    for (;;) {
        // Atomically create file and obtain handle
#if defined(Q_OS_WIN)
        file = CreateFile((const wchar_t *)path.constData(),
                GENERIC_READ | GENERIC_WRITE,
                FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, CREATE_NEW,
                FILE_ATTRIBUTE_NORMAL, NULL);

        if (file != INVALID_HANDLE_VALUE)
            return true;

        DWORD err = GetLastError();
        if (err != ERROR_FILE_EXISTS) {
            error = QSystemError(err, QSystemError::NativeError);
            return false;
        }
#elif defined(Q_OS_SYMBIAN)
        TInt err = file.Create(fs, qt_QString2TPtrC(path),
                EFileRead | EFileWrite | EFileShareReadersOrWriters);

        if (err == KErrNone)
            return true;

        if (err != KErrAlreadyExists) {
            error = QSystemError(err, QSystemError::NativeError);
            return false;
        }
#else // POSIX
        file = QT_OPEN(path.constData(),
                QT_OPEN_CREAT | O_EXCL | QT_OPEN_RDWR | QT_OPEN_LARGEFILE,
                0600);

        if (file != -1)
            return true;

        int err = errno;
        if (err != EEXIST) {
            error = QSystemError(err, QSystemError::NativeError);
            return false;
        }
#endif

        /* tricky little algorwwithm for backward compatibility */
        for (Char *iter = placeholderStart;;) {
            // Character progression: [0-9] => 'a' ... 'z' => 'A' .. 'Z'
            // String progression: "ZZaiC" => "aabiC"
            switch (char(*iter)) {
                case 'Z':
                    // Rollover, advance next character
                    *iter = Latin1Char('a');
                    if (++iter == placeholderEnd) {
                        // Out of alternatives. Return file exists error, previously set.
                        error = QSystemError(err, QSystemError::NativeError);
                        return false;
                    }

                    continue;

                case '0': case '1': case '2': case '3': case '4':
                case '5': case '6': case '7': case '8': case '9':
                    *iter = Latin1Char('a');
                    break;

                case 'z':
                    // increment 'z' to 'A'
                    *iter = Latin1Char('A');
                    break;

                default:
                    ++*iter;
                    break;
            }
            break;
        }
    }

    Q_ASSERT(false);
}

Latin1Char()

static Char Latin1Char ( char  ch )

inlinestatic

Definition at line 70 of file qtemporaryfile.cpp.

Referenced by createFileFromTemplate(), and QTemporaryFileEngine::open().

{
    return ushort(uchar(ch));
}