DosAllocSharedMem - Parameters

ppb (PPVOID) - output

A pointer to a variable that will receive the base address of the allocated range of pages.

OS/2 determines where to allocate the virtual address for the shared memory object.

pszName (PSZ) - input

An optional address of the name string associated with the shared memory object to be allocated.

The name is an ASCIIZ string in the format of an OS/2 file name, and is in the subdirectory, \SHAREMEM\; for example, \SHAREMEM\PUBLIC.DAT.

To allocate unnamed shared memory, set this parameter to NULL. If you want to use unnamed shared memory, the flag parameter must include either OBJ_GETTABLE or OBJ_GIVEABLE.

cb (ULONG) - input

Size, in bytes, of the shared memory object to allocate.

The size is rounded up to the next page-size boundary. The size of a page is 4KB.

flag (ULONG) - input

Allocation attribute and desired access protection flags.

A set of flags describing the allocation attributes and desired access protection for the shared memory object. Possible values are shown in the following lists:

Allocation Attributes

PAG_COMMIT (0x00000010)

All pages in the shared memory object are initially committed.
OBJ_GIVEABLE (0x00000200)
The access to the memory object can be given to another process using the DosGiveSharedMem function.
OBJ_GETTABLE (0x00000100)
The memory object can be accessed by another process that knows the address of the memory and calls the DosGetSharedMem function.
OBJ_TILE (0x00000040)
The shared memory object must be allocated in the first 512MB of virtual-address space, with 16-bit selectors mapping the memory object.

The 16-bit selectors are allocated to map the 32-bit object at 64KB boundaries. The figure in the description of the Parameters for DosAllocMem shows how the 16-bit alias selectors map the 32-bit object. Desired Access Protection

PAG_EXECUTE (0x00000004)
Execute access to the committed pages in the private memory object is desired.
PAG_READ (0x00000001)
Read access is desired.
PAG_WRITE (0x00000002)
Write access is desired.
PAG_GUARD (0x00000008),
Access to the committed pages in the private memory object causes a "guard page entered" condition to be raised in the subject process.
At least one of the bits of PAG_READ, PAG_WRITE, or PAG_EXECUTE must be set.

ulrc (APIRET) - returns

Return Code.

DosAllocSharedMem returns one of the following values:

• NO_ERROR 8
  ERROR_NOT_ENOUGH_MEMORY
  87
  ERROR_INVALID_PARAMETER
  95
  ERROR_INTERRUPT
  123
  ERROR_INVALID_NAME
  183
  ERROR_ALREADY_EXISTS
  For a full list of error codes, see Errors.

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