DosAllocShrSeg

Description

This call allocates a named shared memory segment to a process.

Syntax

 DosAllocShrSeg

    (Size, Name, Selector)

Parameters

Size (USHORT) - input

Number of bytes requested. The value specified must be less than or equal to 65535. A value of 0 indicates 65536 bytes.

Name (PSZ) - input

Address of the name string associated with the shared memory segment to be allocated. Name specifies the symbolic name for the shared memory segment. The name string is an ASCIIZ string in the format of an OS/2 file name in a subdirectory called \SHAREMEM\. The name string must include the prefix \SHAREMEM\. For example \SHAREMEM\name.

Selector (PSEL) - output

Address where the selector of the allocated segment is returned.

Return Code

rc (USHORT) - return

Return code descriptions are:

• 0 NO_ERROR
• 8 ERROR_NOT_ENOUGH_MEMORY
• 123 ERROR_INVALID_NAME
• 183 ERROR_ALREADY_EXISTS

Remarks

DosAllocShrSeg allocates a named segment of up to 64KB in size, which is movable and swappable. The segment can be shared by any process that knows the name of the segment.

To access the shared segment, another process issues DosGetShrSeg, specifying the segment name. The selector returned by DosGetShrSeg is the same as the one returned by DosAllocShrSeg.

The maximum number of segments a process can define with DosAllocShrSeg or access with DosGetShrSeg is 256.

Note: This request may be issued from privilege level 2. However, the segment is allocated as a privilege level 3 segment.

Example Code

C Binding

#define INCL_DOSMEMMGR

USHORT  rc = DosAllocShrSeg(Size, Name, Selector);

USHORT           Size;          /* Number of bytes requested */
PSZ              Name;          /* Name string */
PSEL             Selector;      /* Selector allocated (returned) */

USHORT           rc;            /* return code */

This example requests a segment of memory with 27 bytes named "stock.dat".

#define INCL_DOSMEMMGR

#define NUMBER_OF_BYTES 27
#define NAME_SEG "\\SHAREMEM\\stock.dat"

SEL    Selector;
USHORT rc;

   rc = DosAllocShrSeg(NUMBER_OF_BYTES,   /* # of bytes requested */
                       NAME_SEG,          /* Name string */
                       &Selector);        /* Selector allocated */

MASM Binding

EXTRN  DosAllocShrSeg:FAR
INCL_DOSMEMMGR      EQU 1

PUSH   WORD    Size          ;Number of bytes requested
PUSH@  ASCIIZ  Name          ;Name string
PUSH@  WORD    Selector      ;Selector allocated (returned)
CALL   DosAllocShrSeg

Returns WORD