OpenEuphoria

poke_pointer

<built-in> procedure poke_pointer(atom addr, object x) 

stores one or more pointers, starting at a memory location.

Parameters:

1. addr : an atom, the address at which to store
2. x : an object, either an integer or a non empty sequence of pointers.

Errors:

Poking in memory you do not own may be blocked by the OS, and cause a machine exception. If you use the define safe these routines will catch these problems with a Euphoria error.

Comments:

There is no point in having poke_pointers or poke_pointersu. For example, both +power(2,31) and -power(2,31) are stored as #F0000000 on a 32-bit architecture. It is up to whoever reads the value to figure it out.

On all 32-bit operating systems, the poke_pointer uses 4-byte integers. On 64-bit architectures using operating systems, poke_pointer uses 8-byte integers.

It is faster to write several pointers at once by poking a sequence of values, than it is to write one double words at a time in a loop.

The 4-byte (or 8-byte) values to be stored can be negative or positive. You can read them back with either peek_pointer or any other peek function of the correctsize. However, the results are unpredictable if you want to store values with a fractional part or a magnitude greater than the size of a native pointer, even though Euphoria represents them all as atoms.

Example 1:

 a = allocate(100)   -- allocate 100 bytes in memory 
 
-- poke one 4-byte value at a time (on a 32-bit operating system): 
poke_pointer(a, 9712345) 
poke_pointer(a+4, #FF00FF00) 
poke_pointer(a+8, -12345) 
 
-- poke 3 long int values at once: 
poke_pointer(a, {9712345, #FF00FF00, -12345}) 

See Also:

Using Data Double Words, peek4s, peek4u, peek8u, peek8s, peek_pointer poke, poke2, allocate, free, call