function descends into a chunk of a RIFF file that was opened by using the mmioOpen
function. It can also search for a given chunk.
| HMMIO hmmio,
| LPMMCKINFO lpck,
| LPMMCKINFO lpckParent,
| UINT wFlags
File handle of an open RIFF file.
Address an application-defined MMCKINFO
Address of an optional application-defined MMCKINFO
structure identifying the parent of the chunk being searched for. If this
parameter is not NULL, mmioDescend
assumes the MMCKINFO
structure it refers to was filled when mmioDescend
was called to descend into the parent chunk, and mmioDescend
searches for a chunk within the parent chunk. Set this parameter to NULL if
no parent chunk is being specified.
Search flags. If no flags are specified, mmioDescend
descends into the chunk beginning at the current file position. The following
values are defined:
Searches for a chunk with the specified chunk identifier.
Searches for a chunk with the chunk identifier "LIST" and with the specified
Searches for a chunk with the chunk identifier "RIFF" and with the specified
Returns MMSYSERR_NOERROR if successful or an error otherwise. Possible error
values include the following:
||The end of the file (or the end of the parent chunk, if given) was reached
before the desired chunk was found.
A "RIFF" chunk consists of a four-byte chunk identifier (type FOURCC
), followed by a four-byte chunk size (type DWORD
), followed by the data portion of the chunk, followed by a null pad byte if
the size of the data portion is odd. If the chunk identifier is "RIFF" or
"LIST", the first four bytes of the data portion of the chunk are a form type or list
type (type FOURCC
If you use mmioDescend
to search for a chunk, make sure the file position is at the beginning of a
chunk before calling the function. The search begins at the current file
position and continues to the end of the file. If a parent chunk is specified, the
file position should be somewhere within the parent chunk before calling mmioDescend
. In this case, the search begins at the current file position and continues
to the end of the parent chunk.
is unsuccessful in searching for a chunk, the current file position is
undefined. If mmioDescend
is successful, the current file position is changed. If the chunk is a "RIFF"
or "LIST" chunk, the new file position will be just after the form type or
list type (12 bytes from the beginning of the chunk). For other chunks, the new
file position will be the start of the data portion of the chunk (8 bytes from
the beginning of the chunk).
function fills the MMCKINFO
structure pointed to by the lpck
parameter with the following information:
- The ckid member is the chunk. If the MMIO_FINDCHUNK, MMIO_FINDRIFF, or MMIO_FINDLIST
flag is specified for wFlags, the MMCKINFO structure is also used to pass parameters to mmioDescend. In this case, the ckid member specifies the four-character code of the chunk identifier, form type,
or list type to search for.
- The cksize member is the size, in bytes, of the data portion of the chunk. The size
includes the form type or list type (if any), but does not include the 8-byte chunk
header or the pad byte at the end of the data (if any).
- The fccType member is the form type if ckid is "RIFF", or the list type if ckid is "LIST". Otherwise, it is NULL.
- The dwDataOffset member is the file offset of the beginning of the data portion of the chunk.
If the chunk is a "RIFF" chunk or a "LIST" chunk, this member is the offset of
the form type or list type.
- The dwFlags member contains other information about the chunk. Currently, this
information is not used and is set to zero.
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