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Initialize memory segments

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This commit is contained in:
Benjamin Feng 2019-11-27 21:19:08 -06:00
parent eff926b454
commit eb1628b033
1 changed files with 37 additions and 10 deletions
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47
lib/std/heap.zig
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@ -253,7 +253,7 @@ extern fn @"llvm.wasm.memory.size.i32"(u32) u32;
extern fn @"llvm.wasm.memory.grow.i32"(u32, u32) i32;
test "" {
_ = WasmPageAllocator.alloc;
_ = WasmPageAllocator.realloc;
}
const WasmPageAllocator = struct {
@ -261,12 +261,24 @@ const WasmPageAllocator = struct {
offset: usize = 0,
data: []u8 = &[_]u8{},
fn alloc(self: FreeBlock, num_pages: usize) ?[]u8 {
fn initData(self: *FreeBlock, data: []u8) void {
std.mem.set(u8, data, 0);
self.data = data;
}
fn totalPages(self: FreeBlock) usize {
return self.data.len * @typeInfo(usize).Int.bits;
}
fn alloc(self: *FreeBlock, num_pages: usize) ?[]u8 {
return null;
}
fn reclaim(self: *FreeBlock, start_page: usize, end_page: usize) void {}
};
var base = FreeBlock{};
var additional = FreeBlock{};
var conventional = FreeBlock{};
var extended = FreeBlock{};
fn nPages(memsize: usize) usize {
return std.mem.alignForward(memsize, std.mem.page_size) / std.mem.page_size;
@ -278,7 +290,7 @@ const WasmPageAllocator = struct {
}
const n_pages = nPages(n);
return base.alloc(n_pages) orelse additional.alloc(n_pages) orelse {
return conventional.alloc(n_pages) orelse extended.alloc(n_pages) orelse {
const prev_page_count = @"llvm.wasm.memory.grow.i32"(0, @intCast(u32, n_pages));
if (prev_page_count < 0) {
return error.OutOfMemory;
@ -305,13 +317,28 @@ const WasmPageAllocator = struct {
}
pub fn shrink(allocator: *Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) []u8 {
var shrinkage = nPages(old_mem.len) - nPages(new_size);
if (shrinkage > 0) {
const success = base.recycle(old_mem[new_size..old_mem.len]);
if (!success) {
std.debug.assert(additional.recycle(old_mem[new_size..old_mem.len]));
const free_start = nPages(@ptrToInt(old_mem.ptr) + new_size);
var free_end = nPages(@ptrToInt(old_mem.ptr) + old_mem.len);
if (free_end > free_start) {
if (conventional.data.len == 0) {
conventional.initData(__heap_base[0..@intCast(usize, @"llvm.wasm.memory.size.i32"(0) * std.mem.page_size)]);
}
if (free_start < conventional.totalPages()) {
conventional.reclaim(free_start, free_end);
} else {
if (extended.data.len == 0) {
extended.offset = conventional.totalPages();
// Steal the last page from the memory currently being reclaimed
free_end -= 1;
extended.initData(@intToPtr([*]u8, free_end)[0..std.mem.page_size]);
}
conventional.reclaim(free_start, free_end);
}
}
return old_mem[0..new_size];
}
};