hmmio (HMMIO) - input

The open file handle returned by mmioOpen.

pckinfo (PMMCKINFO) - input

A pointer to the caller-supplied MMCKINFO structure that is to be filled in as follows:

ckid

Set to the chunk ID of the chunk.
ckSize
Set to the size of the data portion of the chunk, including the form type or list type (if any) but not including the 8-byte chunk header or the terminating null (which is present only if chunk size is odd).
fccType
The form type for RIFF chunks, the list type for LIST types, or a NULL value.
ulDataOffset
The file offset of the beginning of the data portion of the chunk, which begins after the 8-byte chunk header. If the chunk is a LIST chunk or a RIFF chunk, then this field must contain the offset of the list type or form type.
ulFlags
Contains other information about the chunk. Currently, mmioDescend zeros this field.

pckinfoParent (PMMCKINFO) - input

Specifies a pointer to the MMCKINFO data structure, which is an optional caller-supplied structure that refers to the parent of the chunk that is being searched for.

A parent of a chunk is the enclosing chunk - only RIFF and LIST chunks can be parents. If pckinfoParent is given, it is assumed that pckinfoParent was filled in when mmioDescend was called to descend into the parent chunk, and mmioDescend will only search for and descend into a chunk within the parent chunk. If pckinfoParent is NULL, this restriction is not imposed. mmioDescend checks only if a chunk is past the end of a given parent chunk, not before the beginning of the parent chunk. Also, mmioDescend checks only if the beginning of a chunk is past the end of the parent chunk.

usFlags (USHORT) - input

Contains 0 or one of the following flags. If none of these flags are specified, mmioDescend descends into the chunk that starts at the current file position.

MMIO_FINDCHUNK

Search for a chunk with a specific ID. The ckid field of MMCKINFO passed in on the pckinfo parameter should contain the ID of the chunk to search for when mmioDescend is called.
MMIO_FINDRIFF
Search for a chunk with an ID of FOURCC_RIFF and with a specific form type. The fccType field of MMCKINFO passed in on the pckinfo parameter contains the form type of the RIFF chunk to search for when mmioDescend is called.
MMIO_FINDLIST
Search for a chunk with an ID of FOURCC_LIST and with a specific list type. The fccType field of MMCKINFO passed in on the pckinfo parameter contains the list type of the LIST chunk to search for when mmioDescend is called.

rc (USHORT) - returns

Return codes indicating success or type of failure:

MMIO_SUCCESS

If the function succeeds, 0 is returned.
MMIOERR_INVALID_HANDLE
The handle passed was not correct.
MMIOERR_INVALID_PARAMETER
A parameter passed was not correct.
MMIOERR_CHUNKNOTFOUND
The end of the file (or the end of the parent chunk, if given) is reached before the desired chunk is found.

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