wasm: WasmAllocator that uses fixed 64kb pages
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0a280b6062
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45
std/heap.zig
45
std/heap.zig
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@ -318,6 +318,51 @@ pub const FixedBufferAllocator = struct {
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}
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};
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extern fn @"llvm.wasm.memory.grow.i32"(u32, u32) i32;
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/// This allocator tries to allocate the specified number of 64 KB pages and uses FixedBufferAllocator internally
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pub const WasmAllocator = blk: {
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if (builtin.arch != builtin.Arch.wasm32) {
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@compileError("only supported in wasm32");
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} else {
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const mem_grow = @"llvm.wasm.memory.grow.i32";
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const WASM_PAGE_SIZE = 64 * 1024; // 64 kilobytes
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break :blk struct {
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allocator: Allocator,
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fb_allocator: FixedBufferAllocator,
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pub fn init(num_pages: u32) !WasmAllocator {
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const prev_block = mem_grow(0, num_pages);
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if (prev_block == -1) {
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return error.OutOfMemory;
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}
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const buffer_slice = @intToPtr([*]u8, @intCast(usize, prev_block) * WASM_PAGE_SIZE)[0..(WASM_PAGE_SIZE * num_pages)];
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return WasmAllocator{
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.allocator = Allocator{
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.reallocFn = realloc,
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.shrinkFn = shrink,
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},
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.fb_allocator = FixedBufferAllocator.init(buffer_slice),
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};
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}
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fn realloc(allocator: *Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) ![]u8 {
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const self = @fieldParentPtr(WasmAllocator, "allocator", allocator);
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return FixedBufferAllocator.realloc(&self.fb_allocator.allocator, old_mem, old_align, new_size, new_align);
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}
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fn shrink(allocator: *Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) []u8 {
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const self = @fieldParentPtr(WasmAllocator, "allocator", allocator);
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return FixedBufferAllocator.shrink(&self.fb_allocator.allocator, old_mem, old_align, new_size, new_align);
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}
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};
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}
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};
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pub const ThreadSafeFixedBufferAllocator = blk: {
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if (builtin.single_threaded) {
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break :blk FixedBufferAllocator;
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