added get_page_size() to core:mem/virtual

core/mem/virtual/virtual.odin

@@ -45,6 +45,17 @@ release :: proc "contextless" (data: rawptr, size: uint) {
 	_release(data, size)
 }
 
+get_page_size :: proc() -> int {
+	// NOTE(tetra): The page size never changes, so why do anything complicated
+	// if we don't have to.
+	@static page_size := -1
+	if page_size != -1 {
+		return page_size
+	}
+	page_size = _get_page_size()
+	return page_size
+}
+
 Protect_Flag :: enum u32 {
 	Read,
 	Write,

core/mem/virtual/virtual_linux.odin

@@ -3,6 +3,7 @@
 package mem_virtual
 
 import "core:sys/linux"
+import "core:sys/posix"
 
 _reserve :: proc "contextless" (size: uint) -> (data: []byte, err: Allocator_Error) {
 	addr, errno := linux.mmap(0, size, {}, {.PRIVATE, .ANONYMOUS})
@@ -33,6 +34,10 @@ _release :: proc "contextless" (data: rawptr, size: uint) {
 	_ = linux.munmap(data, size)
 }
 
+_get_page_size :: proc() -> int {
+	return int(posix.sysconf(._PAGE_SIZE))
+}
+
 _protect :: proc "contextless" (data: rawptr, size: uint, flags: Protect_Flags) -> bool {
 	pflags: linux.Mem_Protection
 	pflags = {}

core/mem/virtual/virtual_other.odin

@@ -21,6 +21,10 @@ _decommit :: proc "contextless" (data: rawptr, size: uint) {
 _release :: proc "contextless" (data: rawptr, size: uint) {
 }
 
+_get_page_size :: proc() -> int {
+	return 0
+}
+
 _protect :: proc "contextless" (data: rawptr, size: uint, flags: Protect_Flags) -> bool {
 	return false
 }

core/mem/virtual/virtual_posix.odin

@@ -20,6 +20,10 @@ _release :: proc "contextless" (data: rawptr, size: uint) {
 	posix.munmap(data, size)
 }
 
+_get_page_size :: proc() -> int {
+	return int(posix.sysconf(._PAGE_SIZE))
+}
+
 _protect :: proc "contextless" (data: rawptr, size: uint, flags: Protect_Flags) -> bool {
 	#assert(i32(posix.Prot_Flag_Bits.READ)  == i32(Protect_Flag.Read))
 	#assert(i32(posix.Prot_Flag_Bits.WRITE) == i32(Protect_Flag.Write))

core/mem/virtual/virtual_windows.odin

@@ -123,6 +123,13 @@ _release :: proc "contextless" (data: rawptr, size: uint) {
 	VirtualFree(data, 0, MEM_RELEASE)
 }
 
+_get_page_size :: proc() -> int {
+	info: SYSTEM_INFO
+	GetSystemInfo(&info)
+
+	return int(info.dwPageSize)
+}
+
 @(no_sanitize_address)
 _protect :: proc "contextless" (data: rawptr, size: uint, flags: Protect_Flags) -> bool {
 	pflags: u32