在很长一段时间，我试图用 LVM_GETITEMW 消息 LVIF_TEXT 面膜得到ListView的文本。在32位，但不是在64位架构我的程序工作。

For a long time I tried to use the LVM_GETITEMW message with LVIF_TEXT mask to get the text of a ListView. My program worked in 32 bit but not in 64 bit architecture.

我发现这个问题是在 LVITEM 结构。不久，我的问题是结构是一个合适的64位和为什么。

I discovered that the problem was at the LVITEM struct. Shortly, my question is which struct is the appropriate one for 64 bit and why.

我作为 LVITEMW 结构的结构有以下字段：

The struct I used as the LVITEMW struct had the following fields:

('mask', c_uint32),
('iItem', c_int32),
('iSubItem', c_int32),
('state', c_uint32),
('stateMask', c_uint32),
('pszText', c_uint32),
('cchTextMax', c_int32),
('iImage', c_int32),
('lParam', c_uint64),
('iIndent', c_int32),
('iGroupId', c_int32),
('cColumns', c_uint32),
('puColumns', c_uint32),
('piColFmt', c_int32),
('iGroup', c_int32)

（使用Python编写的2.7 ctypes的，但是这是写作只是一种形式 - 语言实在是无关紧要的）。

(Written with python 2.7 ctypes, but this is just a form of writing - the language is really irrelevant).

这些领域是一样的记载。

很多谷歌上搜索后，我发现这论坛其中有什么我需要的 - 这64位解决方案

After a lot of googling, I found this forum which had exactly what I needed - the 64 bit solution!

因此​​，在64位的结构应该有更多的空间，而应该是这个样子（指针现在的64位，也是 stateMask 是64位。这是从什么论坛上提出了一个有点不同，但工作太）：

So in 64 bit the struct should have more "spaces", and should look something like this (the pointers are now 64 bit and also the stateMask is 64 bit. That's a little bit different from what the forum suggested but works too):

('mask', c_uint32),
('iItem', c_int32),
('iSubItem', c_int32),
('state', c_uint32),
('stateMask', c_uint64), <-- Now 64 bit
('pszText', c_uint64), <-- Now 64 bit which makes sense since this is a pointer
('cchTextMax', c_int32),
('iImage', c_int32),
('lParam', c_uint64),
('iIndent', c_int32),
('iGroupId', c_int32),
('cColumns', c_uint32),
('puColumns', c_uint64), <-- Now 64 bit which makes sense since this is a pointer
('piColFmt', c_int64), <-- Now 64 bit which makes sense since this is a pointer
('iGroup', c_int32)

本次论坛建议有：

The forum suggested having:

('mask', c_uint32),
('iItem', c_int32),
('iSubItem', c_int32),
('state', c_uint32),
('stateMask', c_uint64),
('pszText', c_uint64),
('cchTextMax', c_int32),
('iImage', c_int64), <-- Now 64 bit
('lParam', c_uint32),
('iIndent', c_int32),
('iGroupId', c_int32),
('cColumns', c_uint32),
('puColumns', c_uint32),
('piColFmt', c_int32),
('iGroup', c_int64), <-- Now 128 bit all together
('iGroup2', c_int64) <-- continuation

也可以工作，在名单我需要它是指由pszText文本。

Which also works, at list for my need which is the text pointed by pszText.

和我的问题是：

这个记录任何地方？ 为什么要 stateMask 是 c_uint64 - 应该不是总是相同大小的状态？ 在哪一个才是真正的结构为64位？ Is this documented anywhere? Why should the stateMask be c_uint64 - shouldn't it always be the same size as the state? Which one is the true struct for 64 bit?

感谢您！

推荐答案

由于雷蒙德陈评论我能够找出答案！

Thanks to the comment by Raymond Chen I was able to figure out the answer!

这是关于数据对齐。每个指针应为8字节，并且也应对准于能够由8划分的地址，所以有时应该有指针之前的填充。此外，该结构的大小应该是可分割由分（最大值（sizeof的（在结构中每个字段）），8）这是8中的情况下，由于尺寸一个指针是8。

It's about data alignment. Every pointer should be 8 bytes and should also be aligned to an address that can be divided by 8, so sometimes there should be a padding before the pointer. Also, the size of the struct should be dividable by min(max(sizeof(each field in the struct)), 8) which is 8 in our case since the size of a pointer is 8.

class LVITEMW_explicit(ctypes.Structure):
    _pack_ = 1
    _fields_ = [
        ('mask', c_uint32),         # 0
        ('iItem', c_int32),         # 4
        ('iSubItem', c_int32),      # 8
        ('state', c_uint32),        # 12
        ('stateMask', c_uint32),    # 16
        ('padding1', c_int),
        ('pszText', c_uint64),      # 20 --> 24 after padding (A pointer)
        ('cchTextMax', c_int32),    # 32
        ('iImage', c_int32),        # 36
        ('lParam', c_uint64),       # 40 (On 32 bit should be c_long which is 32 bits)
        ('iIndent', c_int32),       # 48
        ('iGroupId', c_int32),      # 52
        ('cColumns', c_uint32),     # 56
        ('padding2', c_int),
        ('puColumns', c_uint64),    # 60 --> 64 after padding (A pointer)
        ('piColFmt', c_int64),      # 72 (A pointer)
        ('iGroup', c_int32),        # 80
        ('padding3', c_int32),      # The total length was 84 before padding3 was added, which is not dividable by 8
    ]

或者，因为这确实应该写 - 没有 _pack_ = 1 ：

Or as this should really be written - without the _pack_ = 1:

class LVITEMW(ctypes.Structure):
    _fields_ = [
        ('mask', c_uint32),
        ('iItem', c_int32),
        ('iSubItem', c_int32),
        ('state', c_uint32),
        ('stateMask', c_uint32),
        ('pszText', c_uint64),
        ('cchTextMax', c_int32),
        ('iImage', c_int32),
        ('lParam', c_uint64), # On 32 bit should be c_long
        ('iIndent', c_int32),
        ('iGroupId', c_int32),
        ('cColumns', c_uint32),
        ('puColumns', c_uint64),
        ('piColFmt', c_int64),
        ('iGroup', c_int32),
    ]

的确 ctypes.sizeof（LVITEMW）返回88，同 ctypes.sizeof（LVITEMW_explicit）。

再次感谢您的有益的意见！

Thanks again for the helpful comments!