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Docs » Autodocs » iffparse.library » InitIFF
InitIFF -- initialize an IFFHandle structure as a user stream. (V36)
InitIFF(iff, flags, streamHook);
A0 D0 A1
VOID InitIFF(struct IFFHandle *, LONG, struct Hook *);
Initializes an IFFHandle as a general user-defined stream by
allowing the user to declare a hook that the library will call to
accomplish the low-level reading, writing, and seeking of the stream.
Flags are the stream I/O flags for the specified stream; typically a
combination of the IFFF_?SEEK flags.
The stream vector is called with the following arguments:
A0: pointer to streamhook.
A2: pointer to IFFHandle structure.
A1: pointer to IFFStreamCmd structure.
The IFFStreamCmd packet appears as follows:
sc_Command: Contains an IFFCMD_#? value
sc_Buf: Pointer to memory buffer
sc_NBytes: Number of bytes involved in operation
The values taken on by sc_Command, and their meaning, are as follows:
IFFCMD_INIT:
Prepare your stream for reading. This is used for certain
streams that can't be read immediately upon opening, and need
further preparation. (The clipboard.device is an example of
such a stream.) This operation is allowed to fail; any
error code will be returned directly to the client. sc_Buf
and sc_NBytes have no meaning here.
IFFCMD_CLEANUP:
Terminate the transaction with the associated stream. This
is used with streams that can't simply be closed. (Again,
the clipboard is an example of such a stream.) This
operation is not permitted to fail; any error returned will
be ignored (best to return 0, though). sc_Buf and sc_NBytes
have no meaning here.
IFFCMD_READ:
Read from the stream. You are to read sc_NBytes from the
stream and place them in the buffer pointed to by sc_Buf.
Any (non-zero) error returned will be remapped by the parser
into IFFERR_READ.
IFFCMD_WRITE:
Write to the stream. You are to write sc_NBytes to the
stream from the buffer pointed to by sc_Buf. Any (non-zero)
error returned will be remapped by the parser into
IFFERR_WRITE.
IFFCMD_SEEK:
Seek on the stream. You are to perform a seek on the stream
relative to the current position. sc_NBytes is signed;
negative values mean seek backward, positive values mean seek
forward. sc_Buf has no meaning here. Any (non-zero) error
returned will be remapped by the parser into IFFERR_SEEK.
All errors are returned in D0. A return of 0 indicates success.
UNDER NO CIRCUMSTANCES are you permitted to write to the IFFStreamCmd
structure.
iff - pointer to IFFHandle structure to initialize.
flags - stream I/O flags for the IFFHandle.
streamHook - pointer to Hook structure.
<utility/hooks.h>, <libraries/iffparse.h>
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