Re: Windows CE BinaryCompression
- From: "<ctacke/>" <ctacke[@]opennetcf[dot]com>
- Date: Mon, 15 Jan 2007 08:34:08 -0500
If it must be portable, then it's certainly not the way to go. Use
something like ZIP, GZIP or TAR. SharpZipLib is available and works fine.
And it's a .NET interface.
--
Chris Tacke
OpenNETCF Consulting
Managed Code in the Embedded World
www.opennetcf.com
--
"Wagner Bertolini Junior" <wagnerbertolini@xxxxxxxxxxxxxxxxxx> wrote in
message news:OORizyJOHHA.1872@xxxxxxxxxxxxxxxxxxxxxxx
I will really need a specific format, because i need to decompress this
file in another location sometimes.
but i´m really interested on this API.
See this article:
Save Space Using Windows CE Built-in Compression API's
Jeff Zamora
Buried inside the (undocumented) Windows CE API are BinaryCompress and
BinaryDecompress. These functions offer a built-in way to quickly and
easily compress data, and should meet all your data compression needs.
You can use BinaryCompress and BinaryDecompress to perform buffer
compression. BinaryCompress will take a buffer and return a compressed
buffer. BinaryDecompress will take a compressed buffer and turn it back
into the original. BinaryCompress and BinaryDecompress are defined in
coredll.
I assume the compression API uses the same compression as the object
store. That compression is comparative - Windows CE compresses the buffer
using several methods and takes the winner. And remember, all files kept
in the object store are compressed, so this is redundant if you are just
storing data in a file on your device. On the other hand, these APIs might
be useful if you are saving data to a compact flash card, or if you are
generating backup files that may end up back on the device.
Here's an example:
DWORD BinaryCompress(LPBYTE bufin, DWORD lenin, LPBYTE bufout, DWORD
lenout);
DWORD BinaryDecompress(LPBYTE bufin, DWORD lenin, LPBYTE bufout, DWORD
lenout, DWORD skip);
TCHAR string[] = _T("The quick brown fox jumps over the lazy man who did
not come to the aid of his country in time.");
BYTE buffer[1024];
BYTE inpBuffer[1024];
int length = BinaryCompress((BYTE*)string, wcslen(string) *
sizeof(TCHAR), buffer, 1024);
BinaryDecompress(buffer, length, inpBuffer, 1024, 0);
AfxMessageBox((TCHAR*) inpBuffer);
CString message;
message.Format(_T("%i, %i"), wcslen(string), length);
AfxMessageBox(message);
In this example, the uncompressed buffer is 188 bytes and the compressed
buffer is 148 bytes. Not the best, but it is free.
Coredll also contains StringCompress and StringDecompress. I imagine these
are the same as their binary counterparts, except they stop compressing
when they encouter a terminating \0.
"<ctacke/>" <ctacke[@]opennetcf[dot]com> escreveu na mensagem
news:u1K5tm2NHHA.1252@xxxxxxxxxxxxxxxxxxxxxxx
You are going about this the completely wrong way. That's not what the
function is for, and explaining how to get your data into some format
that would be compatible in all cases would be long and
counterproductive. Get a valid compression library or write something
simple like RLE. You should not be P/Invoking for something like this.
--
Chris Tacke
OpenNETCF Consulting
Managed Code in the Embedded World
www.opennetcf.com
--
"Wagner Bertolini Junior" <wagnerbertolini@xxxxxxxxxxxxxxxxxx> wrote in
message news:B5B8025E-5128-4C25-A038-DECE2F86E711@xxxxxxxxxxxxxxxx
I am just trying to compress a file.
Why, it doesn't work?
I saw someone using it.. but he was using C++ to do it.
But i think that is the same usage.
About the Word Aligned, means that the address of my pointer must be
aligned?
Now i get in trouble... I don´t know if i can do that over .NetCF but i
need
to do a research....
"<ctacke/>" wrote:
WORD aligned means it falls on a WORD divisible address (address % 2 ==
0).
DWORD aligned means it falls on a DWORD divisible address (address %4
== 0)
What exactly are you trying to do here anyway? I seriously doubt that
you
should be using this undocumented kernel API from an app, let alone a
managed app.
--
Chris Tacke
OpenNETCF Consulting
Managed Code in the Embedded World
www.opennetcf.com
--
"Wagner Bertolini Junior" <wagnerbertolini@xxxxxxxxxxxxxxxxxx> wrote in
message news:uYcWqroNHHA.5016@xxxxxxxxxxxxxxxxxxxxxxx
Can anyone help me with this?
I found at winCe sources this function:
//------------------------------------------------------------------------------
// Compressors - bufin and bufout must be WORD aligned, lenout must
be at
least as
// large as lenin, CECOMPRESS_FAILED is returned if it doesn't fit,
else
compressed length
// CECOMPRESS_ALL_ZEROS returned if buffer entirely zero. If bufout
is
NULL, the output
// length is computed, but the results are not stored. Lenin must be
a
multiple of 2.
//------------------------------------------------------------------------------
DWORD
NKBinaryCompress(
LPBYTE bufin,
DWORD lenin,
LPBYTE bufout,
DWORD lenout
)
{
DWORD retval;
TRUSTED_API (L"NKBinaryCompress", CECOMPRESS_FAILED);
DEBUGMSG(ZONE_ENTRY, (L"NKBinaryCompress entry: %8.8lx %8.8lx
%8.8lx
%8.8lx\r\n", bufin, lenin, bufout, lenout));
retval = CECompress(bufin, lenin, bufout, lenout, 1, 1024);
DEBUGMSG(ZONE_ENTRY, (L"NKBinaryCompress exit: %8.8lx\r\n",
retval));
return retval;
}
But i CAN´T understand the comment, what is WORD aligned?
i'm trying to use it and i'm receving an Error.. i will post the
sample
code:
//DWORD BinaryCompress(LPBYTE bufin, DWORD lenin, LPBYTE bufout,
DWORD
lenout);
//DWORD BinaryDecompress(LPBYTE bufin, DWORD lenin, LPBYTE bufout,
DWORD
lenout, DWORD skip);
[DllImport("coredll.dll", SetLastError=true)]
public static extern unsafe int BinaryCompress(byte* bufferIn, int
lenIn,
byte* bufferOut, ref int lenOut);
[DllImport("coredll.dll", SetLastError = true)]
public static extern unsafe int BinaryDecompress(byte* bufferIn, int
lenIn, byte* bufferOut, ref int lenOut, int skip);
string fileOpen = "\\Temp\\test.bmp";
byte[] bFile;
bFile = OpenFile(fileOpen);
byte[] bufferNew = new byte[bFile.Length];
int iLen = 0;
int ret = 0;
fixed(byte* bLP = bFile)
fixed (byte* bLPNew = bufferNew)
{
ret = BinaryCompress(bLP, (int)bFile.Length, bLPNew,
ref
iLen);
if (ret != 0)
{
ret = Marshal.GetLastWin32Error();
MessageBox.Show(new Win32Exception(ret).Message);
//
this always return 87 / Win32Exception
}
}
if anyone wants to see the OpenFile
private static byte[] OpenFile(string fileOpen)
{
byte[] bFile;
FileStream fs = File.OpenRead(fileOpen);
bFile = new byte[fs.Length];
byte[] bAux = new byte[1024];
int bytToRead = (int)fs.Length;
int count = 0;
int idx = 0;
while (bytToRead > 0)
{
count = fs.Read(bAux, 0, bAux.Length);
idx = (int)fs.Length - bytToRead;
for (int i = 0; i < count; i++)
bFile[idx+i] = bAux[i];
bytToRead -= count;
}
fs.Close();
return bFile;
}
The file length is 307254 bytes.
Any idea??
Thanks a lot.
.
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