VirtualAlloc2 Function Memoryapi.h
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Reserves, commits, or adjustments the state of a area of memory inside the digital address house of a specified process (allotted memory is initialized to zero). The handle to a course of. The perform allocates Memory Wave Workshop inside the virtual address area of this process. OPERATION access proper. For more information, see Process Safety and Access Rights. If Process is NULL, the function allocates memory for the calling process. The pointer that specifies a desired starting deal with for the area of pages that you want to allocate. If BaseAddress is NULL, the operate determines where to allocate the area. Necessities structure must encompass all zeroes, and the bottom address have to be a a number of of the system allocation granularity. To find out the allocation granularity, use the GetSystemInfo operate. If this tackle is within an enclave that you have not initialized by calling InitializeEnclave, Memory Wave Workshop VirtualAlloc2 allocates a page of zeros for the enclave at that address. The web page should be previously uncommitted, and will not be measured with the EEXTEND instruction of the Intel Software program Guard Extensions programming mannequin.
Handle error. That is true for enclaves that do not support dynamic memory administration (i.e. SGX1). SGX2 enclaves will permit allocation, and the page have to be accepted by the enclave after it has been allotted. The scale of the region of memory to allocate, in bytes. The scale must at all times be a multiple of the web page size. Measurement. This implies, for example, that a 2-byte range that straddles a page boundary causes the operate to allocate each pages. The kind of memory allocation. This parameter must comprise one of the next values. RESERVE and a non-NULL BaseAddress fails until the complete range has already been reserved. An try and commit a web page that is already committed doesn't trigger the operate to fail. This means which you can commit pages without first determining the current dedication state of each web page. Other memory allocation functions, equivalent to malloc and LocalAlloc, can not use reserved memory till it has been launched.
After you substitute a placeholder with a non-public allocation, to free that allocation again to a placeholder, see the dwFreeType parameter of VirtualFree and VirtualFreeEx. A placeholder is a sort of reserved Memory Wave region. A placeholder is a kind of reserved memory area. RESET will contain zeros. If you want the range to include zeros, decommit the memory and then recommit it. RESET, the VirtualAlloc2 function ignores the worth of fProtect. RESET and the range of memory is mapped to a file. A shared view is simply acceptable if it is mapped to a paging file. This worth cannot be used with every other value. RESET earlier, the conduct is undefined. RESET, the VirtualAlloc2 perform ignores the worth of PageProtection. This parameter also can specify the following values as indicated. The dimensions and alignment should be a multiple of the big-web page minimal. To acquire this value, use the GetLargePageMinimum perform. A 64K web page is a area of memory that is 64K in size, nearly and bodily contiguous, and just about and bodily aligned on a 64K boundary.
PAGES is pageable, and bodily pages backing the memory are allocated on demand (on the time of access). PAGES allocation may be mapped utilizing non-contiguous small pages instead. NONPAGED attribute, the allocation might be mapped utilizing non-paged 64K pages. In that case, if contiguous 64K pages can't be obtained, the allocation will fail. PAGES is specified, the size and BaseAddress parameters should each be multiples of 64K (BaseAddress could also be NULL). RESERVE and no other values. The memory safety for the area of pages to be allotted. If the pages are being committed, Memory Wave you may specify any one of the memory safety constants. PARAMETER. Each of these extended parameter values can itself have a sort area of either MemExtendedParameterAddressRequirements or MemExtendedParameterNumaNode. If no MemExtendedParameterNumaNode extended parameter is provided, then the habits is the same as for the VirtualAlloc/MapViewOfFile functions (that is, the preferred NUMA node for the bodily pages is determined primarily based on the ideal processor of the thread that first accesses the memory).
The number of extended parameters pointed to by ExtendedParameters. If the operate succeeds, the return value is the base tackle of the allotted area of pages. If the operate fails, the return value is NULL. To get extended error info, name GetLastError. This API supplies specialized techniques for managing digital memory in assist of high-efficiency video games and server functions. For example, placeholders allow a reserved memory range to be explicitly partitioned, overlaid, and re-mapped; this can be utilized to implement arbitrarily extendable areas or virtual memory ring buffers. VirtualAlloc2 additionally permits for allocating memory with a specific memory-alignment. Each page has an related page state. VirtualAlloc2 can commit pages which are already committed, but cannot reserve pages which can be already reserved. This means you may commit a spread of pages, no matter whether or not they have already been dedicated, and the perform won't fail. On the whole nevertheless, solely a minimal range of principally uncommitted pages must be specified, because committing a lot of pages which can be already dedicated could cause the VirtualAlloc2 name to take for much longer.