python - 如何使用 QDataStream 在 Python 中打开一个 bin 文件

Question

我有一个在应用程序中编码的 bin 文件，我需要访问它并将其转换为 csv 文件。我已获得文档，但不确定如何在 Python 中访问此文件的内容。

这里有一些关于数据集是如何序列化的细节

Datasets.bin is a list of DataSet classes serialized using Qt's QDataStream serialization using version QDataStream::Qt_4_7.

The format of the datasets.bin file is:

quint32 Magic Number    0x46474247
quint32 Version     1
quint32 DataSet Marker  0x44415441
qint32      # of DataSets       n
DataSet DataSet 1
DataSet DataSet 2
     .
     .
     .
     .
DataSet DataSet n


The format of each DataSet is:

quint32     Magic Number    0x53455455  
QString     Name
quint32     Flags           Bit field (Set Table)
QString     Id          [Optional]  
QColor      Color           [Optional]
qint32          Units           [Optional]
QStringList         Creator Ids     [Optional]
bool            Hidden          [Optional]
QList<double>   Thresholds      [Optional]
QString         Source          [Optional]
qint32          Role            [Optional]
QVector<QPointF>    data points

我一直在查看 PyQt4 数据流文档，但似乎找不到任何具体示例。任何指向我正确方向的帮助都会很棒

Answer 1

PyQt 无法以与 C++ 相同的方式读取所有数据，因为它无法处理模板类(如 QList<double> 和 QVector<QPointF> )，这需要特定于语言的支持，而这在 Python 中是不可用的。这意味着必须使用变通方法。幸运的是，datastream format非常简单，因此读取任意模板类可以简化为一个简单的算法:将长度读取为 uint32 , 然后遍历 range并将包含的元素一个一个地读取到 list 中:

points = []
length = stream.readUInt32()
for index in range(length):
    point = QPoint()
    stream >> point
    points.append(point)

下面是一个脚本，展示了如何正确读取整个数据集格式:

from PyQt4 import QtCore, QtGui

FLAG_HASSOURCE = 0x0001
FLAG_HASROLE = 0x0002
FLAG_HASCOLOR = 0x0004
FLAG_HASID = 0x0008
FLAG_COMPRESS = 0x0010
FLAG_HASTHRESHOLDS = 0x0020
FLAG_HASUNITS = 0x0040
FLAG_HASCREATORIDS = 0x0080
FLAG_HASHIDDEN = 0x0100
FLAG_HASMETADATA = 0x0200

MAGIC_NUMBER = 0x46474247
FILE_VERSION = 1
DATASET_MARKER = 0x44415441
DATASET_MAGIC = 0x53455455

def read_data(path):
    infile = QtCore.QFile(path)
    if not infile.open(QtCore.QIODevice.ReadOnly):
        raise IOError(infile.errorString())

    stream = QtCore.QDataStream(infile)
    magic = stream.readUInt32()
    if magic != MAGIC_NUMBER:
        raise IOError('invalid magic number')
    version = stream.readUInt32()
    if version != FILE_VERSION:
        raise IOError('invalid file version')
    marker = stream.readUInt32()
    if marker != DATASET_MARKER:
        raise IOError('invalid dataset marker')
    count = stream.readInt32()
    if count < 1:
        raise IOError('invalid dataset count')

    stream.setVersion(QtCore.QDataStream.Qt_4_7)

    rows = []
    while not stream.atEnd():
        row = []

        magic = stream.readUInt32()
        if magic != DATASET_MAGIC:
            raise IOError('invalid dataset magic number')

        row.append(('Name', stream.readQString()))

        flags = stream.readUInt32()
        row.append(('Flags', flags))

        if flags & FLAG_HASID:
            row.append(('ID', stream.readQString()))
        if flags & FLAG_HASCOLOR:
            color = QtGui.QColor()
            stream >> color
            row.append(('Color', color))
        if flags & FLAG_HASUNITS:
            row.append(('Units', stream.readInt32()))
        if flags & FLAG_HASCREATORIDS:
            row.append(('Creators', stream.readQStringList()))
        if flags & FLAG_HASHIDDEN:
            row.append(('Hidden', stream.readBool()))
        if flags & FLAG_HASTHRESHOLDS:
            thresholds = []
            length = stream.readUInt32()
            for index in range(length):
                thresholds.append(stream.readDouble())
            row.append(('Thresholds', thresholds))
        if flags & FLAG_HASSOURCE:
            row.append(('Source', stream.readQString()))
        if flags & FLAG_HASROLE:
            row.append(('Role', stream.readInt32()))

        points = []
        length = stream.readUInt32()
        for index in range(length):
            point = QtCore.QPointF()
            stream >> point
            points.append(point)
        row.append(('Points', points))
        rows.append(row)

    infile.close()

    return rows

rows = read_data('datasets.bin')

for index, row in enumerate(rows):
    print('Row %s:' % index)
    for key, data in row:
        if isinstance(data, list) and len(data):
            print('  %s = [%s ... ] (%s items)' % (
                  key, repr(data[:3])[1:-1], len(data)))
        else:
            print('  %s = %s' % (key, data))