Entry
R0 = reason code :
Reason Action
1 Describe CDA
2 Allocate block
3 Free block
4 Reallocate block
5 Free all blocks
>&1000 Locate block
other registers as appropriate for reason code
This SWI provides access to a CDA management system which resides in the system sprite area on an Archimedes and in a special WimpExt CDA on a Risc PC. Each block is given a block identifier which is a special unique value that is assigned to each block that is created. Unlike the Heap manager, the CDA can shuffle at will (due to it being in the system sprite area) so there is a special call to locate your block.
Most of these calls can return the errors Bad WimpExt_CDA operation (&457A8) and CDA identifier not found (&457AA).
Provided by CDAManager
Describe CDA
Entry
R0 = 1 - Describe CDA
Exit
R0 = Dynamic area number (3=system sprite area)
R1 = size of area
R2 = total free
R3 = number of blocks in use by your task
R4 = pointer to LocateBlock
Returns information about the CDA. If R1=0 then R2,R3 are corrupt. R4 returns a pointer to the CDA find routine that is used when you pass the reason code as a block identifier.
Allocate block
Entry
R0 = 2 - Allocate block
R2 = size of block required
Exit
R0 = pointer to block
R1 = block identifier
Tries to find a block of the required size. Increases the CDA if necessary. If increasing fails then zero will be returned.
R1 is the block identifier and R0 contains the address of the block but this may change over time - pass R1 as the reason code (as explained below) to get the present block pointer.
Can return Not enough memory (&457AB).
Free block
Entry
R0 = 3 - Free block
R1 = block identifier
Frees the memory used by the specified block.
Reallocate block
Entry
R0 = 4 - Reallocate block
R1 = block identifier
R2 = new size required
Exit
R0 = pointer to block
Tries to resize the specified block. Can return Not enough memory (&457AB) if you are increasing the size.
R0 = 5 - Free all blocks
Frees all blocks in the CDA belonging to your task.
Locate block
Entry
R0 = block identifier (>&1000) - Locate block
Exit
R0 = pointer to block
Locates your block in the CDA.
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