在VBA中将big-endian转换为little-endian，反之亦然 [英] Converting big-endian into little-endian and vice-versa in VBA

问题描述

我的机器是低位字节序(Intel字节顺序).我需要读取一个以Motorola/IEEE字节顺序("big-endian")包含16位带符号整数数据的二进制文件，然后进行一些计算，最后将生成的integer数据写入big-endian二进制文件中.

My machine is little-endian (Intel byte order). I need to read a binary file containing 16-bit signed integer data in Motorola/IEEE byte order ("big-endian"), then do some calculations, and finally write the resulting integer data in a big-endian binary file.

我如何在VBA中执行上述操作，即将大端转换为小端，反之亦然?

How do I do the above in VBA, i.e. convert big-endian into little-endian and vice-versa?

原因是，我正在处理NASA 航天飞机雷达地形任务数据( HGT文件格式).

The reason is, I'm processing NASA Shuttle Radar Topography Mission data (HGT file format).

推荐答案

下面是一个子例程，可以帮助您入门:

Here is a subroutine that may get you started:

Public Sub ProcessData()
  Dim inputFileName As String
  Dim outputFileName As String
  Dim wordCount As Integer
  Dim i As Integer
  Dim msb As Byte
  Dim lsb As Byte
  Dim unsignedWord As Long
  Dim word As Integer

  inputFileName = "C:\Input.bin"
  outputFileName = "C:\Output.bin"

  wordCount = FileLen(inputFileName) / 2

  Open inputFileName For Binary Access Read As #1
  Open outputFileName For Binary Access Write As #2

  For i = 1 To wordCount
    Get #1, , msb
    Get #1, , lsb

    unsignedWord = CLng(msb) * 256 + lsb
    If unsignedWord > 32768 Then
      word = -CInt(65536 - unsignedWord)
    Else
      word = CInt(unsignedWord)
    End If

    ' Do something with each word.
    word = -word

    If word < 0 Then
      unsignedWord = 65536 + word
    Else
      unsignedWord = word
    End If
    msb = CByte(unsignedWord / 256)
    lsb = CByte(unsignedWord Mod 256)

    Put #2, , msb
    Put #2, , lsb
  Next

  Close #1
  Close #2
End Sub

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