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Inside Macintosh: Memory /

Chapter 2 - Memory Manager / Memory Manager Reference

Memory Manager Routines / Allocating and Releasing Nonrelocatable Blocks of Memory

NewPtr

You can use the NewPtr function to allocate a nonrelocatable block of memory of a specified size.

FUNCTION NewPtr (logicalSize: Size): Ptr;

logicalSize

The requested size (in bytes) of the nonrelocatable block.

DESCRIPTION

The NewPtr function attempts to allocate, in the current heap zone, a nonrelocatable block with a logical size of logicalSize bytes and then return a pointer to the block. If the requested number of bytes cannot be allocated, NewPtr returns NIL.

The NewPtr function attempts to reserve space as low in the heap zone as possible for the new block. If it is able to reserve the requested amount of space, NewPtr allocates
the nonrelocatable block in the gap ReserveMem creates. Otherwise, NewPtr returns NIL and generates a memFullErr error.

SPECIAL CONSIDERATIONS

Because NewPtr allocates memory, you should not call it at interrupt time.

ASSEMBLY-LANGUAGE INFORMATION

The registers on entry and exit for NewPtr are

Registers on entry
A0	Number of logical bytes requested

Registers on exit
A0	Address of the new block or NIL
D0	Result code

You can specify that the NewPtr function apply to the system heap zone instead of the current zone. To do so, set bit 10 of the routine trap word. In most development systems, you can do this by supplying the word SYS as the second argument to the routine macro, as follows:

_NewPtr ,SYS

If you want to clear the bytes of a block of memory to 0 when you allocate it with the NewPtr function, set bit 9 of the routine trap word. You can usually do this by supplying the word CLEAR as the second argument to the routine macro, as follows:

_NewPtr ,CLEAR

You can combine SYS and CLEAR in the same macro call, but SYS must come first.

_NewPtr ,SYS,CLEAR

RESULT CODES

noErr	0	No error
memFullErr	-108	Not enough memory