Использование High Memory в OS/2

Евгений Коцюба, 2003

int fd = open (filename,mode);
long size_of_file = filesize(fd);
char * input = malloc(size_of_file);
read(fd, input, (unsigned) size_of_file);

VIRTUALADDRESSLIMIT=2048

The smallest value allowed is 512, which provides compatability with previous versions of OS/2 which only allowed access to 512 MB. The largest value supported is 3072 (3 GB). The VIRTUALADDRESSLIMIT parameter may be specified as part of selective install.

Values in excess of 512 will reduce the number of processes that can concurrently run on the system. When memory has been exhausted, OS/2 control program functions will fail with ERROR_NOT_ENOUGH_MEMORY and PM functions will fail with PMERR_INSUFFICIENT_MEMORY.

This information can be found in the SMP programming addendum, shipped as part of the Warp SMP toolkit (SMP.INF).

#include <umalloc.h>

Heap_t _ucreate(void *block, size_t initsz, int clean, int memtype,
 void *(*getmore_fn)(Heap_t, size_t *, int *)
 void (*release_fn)(Heap_t, void *, size_t);

Before you call _ucreate, you must first get the initial block of memory for the heap. You can get this block by calling an OS/2 API (such as DosAllocMem or or DosAllocSharedMem) or by statically allocating it. (See the CP Programming Guide and Reference for more information on the OS/2 APIs.)
Note: You must also return this initial block of memory to the system after you destroy the heap.

• block The pointer to the initial block you obtained.
• initsz The size of the initial block, which must be at least _HEAP_MIN_SIZE bytes (defined in<malloc.h>). If you are creating a fixed-size heap, the size must be large enough to satisfy all memory requests your program will make of it.
• clean The macro _BLOCK_CLEAN, if the memory in the block has been initialized to 0, or !_BLOCK_CLEAN, if the memory has not been touched. This improves the efficiency of _ucalloc; if the memory is already initialized to 0, _ucalloc does not need to initialize it.
• Note: DosAllocMem initializes memory to 0 for you. You can also use memset to initialize the memory; however, memset also commits all the memory at once, an action that could slow overall performance.
• memtype A macro indicating the type of memory in your heap: _HEAP_REGULAR (regular) or _HEAP_TILED (tiled). If you want the memory to be shared, specify _HEAP_SHARED as well (for example, _HEAP_REGULAR | _HEAP_SHARED). Tiled memory blocks will not cross 64K boundaries, so the data in them can be used in 16-bit programs. Shared memory can be shared between different processes. For more information on different types of memory, see the Programming Guide and the Control Program Guide and Reference.
• Note: Make sure that when you get the initial block, you request the same type of memory that you specify for memtype.
• getmore_fn A function you provide to get more memory from the system (typically using OS/2 APIs or static allocation). To create a fixed-size heap, specify NULL for this parameter.
• release_fn A function you provide to return memory to the system (typically using DosFreeMem). To create a fixed-size heap, specify NULL for this parameter.
  

• uh Is the heap to get memory for.
• size Is the size of the allocation request passed by _umalloc. You probably want to return enough memory at a time to satisfy several allocations; otherwise, every subsequent allocation has to call getmore_fn. You should return multiples of 64K (the smallest size that DosAllocMem returns). Make sure you update the size parameter if you return more than the original request.
• clean Within getmore_fn, you must set this variable either to _BLOCK_CLEAN, to indicate that you initialized the memory to 0, or to !_BLOCK_CLEAN, to indicate that the memory is untouched.