TODO list for porting from Windows to Linux

[rhalbersma]

Below a list of all Windows specific system calls. In parenthesis the likely replacement in terms of Standard C++ or Linux specific system calls. A checked box means that the replacement has been tested. Memory and File I/O can be tested on Windows under Visual Studio. The rest on Windows under MinGW or on Linux under g++.

Memory

• [x] VirtualAlloc (std::aligned_alloc)
• [x] VirtualFree (std::free)

File I/O

• [x] CreateFile (std::fopen)
• [x] GetFileSize (std::fseek and std::ftell)
• [x] SetFilePointer (std::fseek)
• [x] ReadFile (std::fread)
• [x] CloseHandle (std::fclose)

Bit twiddling

• [x] _BitScanForward (__builtin_ctz)
• [x] _BitScanReverse (__builtin_clz)
• [x] _BitScanForward64 (__builtin_ctzll)
• [x] _BitScanReverse64 (__builtin_clzll)
• [x] __popcnt ( __builtin_popcount)
• [x] __popcnt64 (__builtin_popcountll)

Threading

• [x] InitializeCriticalSection (not used)
• [x] EnterCriticalSection (not used)
• [x] LeaveCriticalSection (not used)
• [x] _InterlockedExchange (std::atomic_flag (members test_and_set and clear), ATOMIC_FLAG_INIT, std::memory_order_acquire, std::memory_order_release )

System information

• [x] SYSTEM_INFO.dwPageSize (sysconf(_SC_PAGESIZE))
• [x] SYSTEM_INFO.dwAllocationGranularity (same as dwPageSize)
• [x] MEMORYSTATUS.dwAvailPhys (sysconf(_SC_PHYS_PAGES) * sysconf(_SC_PAGESIZE))
• [x] __cpuid (__builtin_cpu_supports("popcnt"))

[eygilbert]

I think I can eliminate a few of these issues. The 3 CriticalSection functions are #if'd out and not used. We don't need to port them. get_page_size() is only needed for Windows because of FILE_FLAG_NO_BUFFERING. For Linux it can return 4096.

[eygilbert]

I'm not sure about AllocationGranularity. If it is trying to mimic the behavior of VirtualAlloc then the granularity can be set to 4096.

[eygilbert]

Added solutions to the table for _InterlockedExchange,__cpuid, SYSTEM_INFO.dwPageSize, and MEMORYSTATUS.dwAvailPhys

[rhalbersma]

I have pushed a commit that implements this using std::atomic_flag from <atomic>.