TestAIFFChunk

Synopsis

result = TestAIFFChunk(data)
D0                     A0

C Prototype

There is no direct C prototype exported for this function. It is called internally from assembly.

Description

Validates whether the data at the current position represents a valid IFF chunk. The function checks that the 4-byte chunk identifier at the given address falls within the valid ASCII range (between “AAAA” and “ZZZZ”). This is a quick sanity check to ensure that the pointer is positioned at a legitimate chunk boundary.

Inputs

• data (A0) — Pointer to the current position in the IFF data, expected to point to a chunk header.

Result

• result (D0) — If non-zero, the data at the position is a valid IFF chunk. If zero, the data is not a valid chunk (the zero flag in the condition codes is set).

See Also

• FindAIFFChunk
• NextIFFChunk

Implementation

The original 68020 assembly implementation:

; Rel.1.1 - Jul 29 1991 --- TestAIFFChunk()
_LVOTestAIFFChunk
        move.l  a1,-(sp)
        move.l  (a0),d0
        lea     "AAAA",a1
        cmp.l   a1,d0
        bmi.s   CheckAChunk_Error
        lea     "ZZZZ",a1
        cmp.l   a1,d0
        bhi.s   CheckAChunk_Error
        move.l  (sp)+,a1
        rts
 
CheckAChunk_Error
        moveq   #0,d0
        move.l  (sp)+,a1
        rts