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FindMimeFromData (urlmon)
.
C# Signature:
[DllImport("urlmon.dll", CharSet = CharSet.Unicode, ExactSpelling = true, SetLastError = false)]
static extern int FindMimeFromData(IntPtr pBC,
[MarshalAs(UnmanagedType.LPWStr)] string pwzUrl,
byte[] pBuffer,
int cbSize,
[MarshalAs(UnmanagedType.LPWStr)] string pwzMimeProposed,
int dwMimeFlags,
out IntPtr ppwzMimeOut,
int dwReserved);
VB Signature:
Declare Function FindMimeFromData Lib "urlmon.dll" (TODO) As TODO
User-Defined Types:
None.
Notes:
None.
Tips & Tricks:
Use Marshal.StringToCoTaskMemUni() to prepare input parameters (IntPtr) declared to receive strings.
Use Marshal.PtrToStringUni() to get the managed string back from the out parameter (IntPtr).
Sample Code:
public string MimeTypeFrom(byte[] dataBytes, string mimeProposed) {
if (dataBytes == null)
throw new ArgumentNullException("dataBytes");
string mimeRet = String.Empty;
IntPtr suggestPtr = IntPtr.Zero, filePtr = IntPtr.Zero, outPtr = IntPtr.Zero;
if (mimeProposed != null && mimeProposed.Length > 0) {
//suggestPtr = Marshal.StringToCoTaskMemUni(mimeProposed); // for your experiments ;-)
mimeRet = mimeProposed;
}
int ret = FindMimeFromData(IntPtr.Zero, null, dataBytes, dataBytes.Length, mimeProposed, 0, out outPtr, 0);
if (ret == 0 && outPtr != IntPtr.Zero) {
//todo: this leaks memory outPtr must be freed
return Marshal.PtrToStringUni(outPtr);
}
return mimeRet;
}
// call it this way:
Trace.Write("MimeType is " + MimeTypeFrom(Encoding.ASCII.GetBytes("%PDF-"), "text/plain"));
Alternative Managed API:
Do you know one? Please contribute it!
/// <summary>
/// Ensures that file exists and retrieves the content type
/// </summary>
/// <param name="file"></param>
/// <returns>Returns for instance "images/jpeg" </returns>
public static string getMimeFromFile(string file)
{
IntPtr mimeout;
if (!System.IO.File.Exists(file))
throw new FileNotFoundException(file + " not found");
int MaxContent = (int)new FileInfo(file).Length;
if (MaxContent > 4096) MaxContent = 4096;
FileStream fs = File.OpenRead(file);
byte[] buf = new byte[MaxContent];
fs.Read(buf, 0, MaxContent);
fs.Close();
int result = FindMimeFromData(IntPtr.Zero, file, buf, MaxContent, null, 0, out mimeout, 0);
An IntPtr is a pointer to a memory location (unmanaged) that adapts to the platform it is running on (64-bit, etc.) UNLIKE a standard int/Integer. You should always use this type for unmanaged calls that require it, even though an int will appear to work on your development machine.
1/13/2008 4:00:13 AM - Damon Carr-72.43.165.29
An IntPtr is a pointer to a memory location (unmanaged) that adapts to the platform it is running on (64-bit, etc.) UNLIKE a standard int/Integer. You should always use this type for unmanaged calls that require it, even though an int will appear to work on your development machine.
1/13/2008 4:00:13 AM - Damon Carr-72.43.165.29
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