FindMimeFromData function

Article
07/13/2016

Determines the MIME type from the data provided.

Syntax

HRESULT FindMimeFromData(
             LPBC    pBC,
             LPCWSTR pwzUrl,
             LPVOID  pBuffer,
             DWORD   cbSize,
             LPCWSTR pwzMimeProposed,
             DWORD   dwMimeFlags,
             LPWSTR  *ppwzMimeOut,
  _Reserved_ DWORD   dwReserved
);

Parameters

pBC

A pointer to the IBindCtx interface. Can be set to NULL.

pwzUrl

A pointer to a string value that contains the URL of the data. Can be set to NULL if pBuffer contains the data to be sniffed.

pBuffer

A pointer to the buffer that contains the data to be sniffed. Can be set to NULL if pwzUrl contains a valid URL.

cbSize

An unsigned long integer value that contains the size of the buffer.

pwzMimeProposed

A pointer to a string value that contains the proposed MIME type. This value is authoritative if type cannot be determined from the data. If the proposed type contains a semi-colon (;) it is removed. This parameter can be set to NULL.

dwMimeFlags

FMFD_DEFAULT (0x00000000)

No flags specified. Use default behavior for the function.

FMFD_URLASFILENAME (0x00000001)

Treat the specified pwzUrl as a file name.

FMFD_ENABLEMIMESNIFFING (0x00000002)

Internet Explorer 6 for Windows XP SP2 and later. Use MIME-type detection even if FEATURE_MIME_SNIFFING is detected. Usually, this feature control key would disable MIME-type detection.

FMFD_IGNOREMIMETEXTPLAIN (0x00000004)

Internet Explorer 6 for Windows XP SP2 and later. Perform MIME-type detection if "text/plain" is proposed, even if data sniffing is otherwise disabled. Plain text may be converted to text/html if HTML tags are detected.

FMFD_SERVERMIME (0x00000008)

Internet Explorer 8. Use the authoritative MIME type specified in pwzMimeProposed. Unless FMFD_IGNOREMIMETEXTPLAIN is specified, no data sniffing is performed.

FMFD_RESPECTTEXTPLAIN (0x00000010)

Internet Explorer 9. Do not perform detection if "text/plain" is specified in pwzMimeProposed.

FMFD_RETURNUPDATEDIMGMIMES (0x00000020)

Internet Explorer 9. Returns image/png and image/jpeg instead of image/x-png and image/pjpeg.

ppwzMimeOut

The address of a string value that receives the suggested MIME type.

dwReserved

Reserved. Must be set to 0.

Return value

This function can return one of these values.

Return code	Description
S_OK	The operation completed successfully.
E_FAIL	The operation failed.
E_INVALIDARG	One or more arguments are invalid.
E_OUTOFMEMORY	There is insufficient memory to complete the operation.

Remarks

MIME type detection, or "data sniffing," refers to the process of determining an appropriate MIME type from binary data. The final result depends on a combination of server-supplied MIME type headers, file name extension, and/or the data itself. Usually, only the first 256 bytes of data are significant. For more information and a complete list of recognized MIME types, see MIME Type Detection in Internet Explorer.

If pwzUrl is specified without data to be sniffed (pBuffer), the file name extension determines the MIME type. If the file name extension cannot be mapped to a MIME type, this method returns E_FAIL unless a proposed MIME type is supplied in pwzMimeProposed.

After ppwzMimeOut returns and is read, the memory allocated for it should be freed with the operator delete function.

Internet Explorer 8 and later. FindMimeFromData will not promote image types to "text/html" even if the data lacks signature bytes.

Requirements

Minimum supported client	Windows XP
Minimum supported server	Windows 2000 Server
Product	Internet Explorer 4.0
Header	Urlmon.h
Library	Urlmon.lib
DLL	Urlmon.dll

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