Implement fallocate for win32, revert to ftruncate for xcode.

src/memory/map.cpp

@@ -557,8 +557,13 @@ bool map::remap_(size_t size) NOEXCEPT
 // disk_full: space is set but no code is set with false return.
 bool map::resize_(size_t size) NOEXCEPT
 {
-    // Disk full detection is platform common, any other failure is an abort.
+    // Disk full detection, any other failure is an abort.
+#if defined(HAVE_APPLE)
+    // TODO: implement fallocate for macOS (open and write a byte per block).
+    if (::ftruncate(opened_, size) == fail)
+#else
     if (::fallocate(opened_, 0, capacity_, size - capacity_) == fail)
+#endif
     {
         // Disk full is the only restartable store failure (leave mapped).
         if (errno == ENOSPC)

src/memory/mman-win32/mman.cpp

@@ -223,6 +223,11 @@ int fsync(int fd) noexcept
     return 0;
 }
 
+int fallocate(int fd, int mode, oft__ offset, oft__ size) noexcept
+{
+    return ftruncate(fd, offset + size);
+}
+
 int ftruncate(int fd, oft__ size) noexcept
 {
     LARGE_INTEGER big{};

src/memory/mman-win32/mman.hpp

@@ -40,6 +40,7 @@ int msync(void* addr, size_t len, int flags) noexcept;
 int mlock(const void* addr, size_t len) noexcept;
 int munlock(const void* addr, size_t len) noexcept;
 int fsync(int fd) noexcept;
+int fallocate(int fd, int mode, oft__ offset, oft__ size) noexcept;
 int ftruncate(int fd, oft__ size) noexcept;
 
 #endif // _WIN32