1 files changed, 304 insertions, 0 deletions
diff --git a/src/allocators.zig b/src/allocators.zig
new file mode 100644
index 000000000..b6a13ba47
--- /dev/null
+++ b/src/allocators.zig
@@ -0,0 +1,304 @@
+const std = @import("std");
+
+const Wyhash = std.hash.Wyhash;
+const FixedBufferAllocator = std.heap.FixedBufferAllocator;
+
+// https://en.wikipedia.org/wiki/.bss#BSS_in_C
+pub fn BSSSectionAllocator(comptime size: usize) type {
+    return struct {
+        var backing_buf: [size]u8 = undefined;
+        var fixed_buffer_allocator = FixedBufferAllocator.init(&backing_buf);
+        var buf_allocator = &fixed_buffer_allocator.allocator;
+        const Allocator = std.mem.Allocator;
+        const Self = @This();
+
+        allocator: Allocator,
+        fallback_allocator: *Allocator,
+
+        is_overflowed: bool = false,
+
+        pub fn get(self: *Self) *Allocator {
+            return &self.allocator;
+        }
+
+        pub fn init(fallback_allocator: *Allocator) Self {
+            return Self{ .fallback_allocator = fallback_allocator, .allocator = Allocator{
+                .allocFn = BSSSectionAllocator(size).alloc,
+                .resizeFn = BSSSectionAllocator(size).resize,
+            } };
+        }
+
+        pub fn alloc(
+            allocator: *Allocator,
+            len: usize,
+            ptr_align: u29,
+            len_align: u29,
+            return_address: usize,
+        ) error{OutOfMemory}![]u8 {
+            const self = @fieldParentPtr(Self, "allocator", allocator);
+            return buf_allocator.allocFn(buf_allocator, len, ptr_align, len_align, return_address) catch |err| {
+                self.is_overflowed = true;
+                return self.fallback_allocator.allocFn(self.fallback_allocator, len, ptr_align, len_align, return_address);
+            };
+        }
+
+        pub fn resize(
+            allocator: *Allocator,
+            buf: []u8,
+            buf_align: u29,
+            new_len: usize,
+            len_align: u29,
+            return_address: usize,
+        ) error{OutOfMemory}!usize {
+            const self = @fieldParentPtr(Self, "allocator", allocator);
+            if (fixed_buffer_allocator.ownsPtr(buf.ptr)) {
+                return fixed_buffer_allocator.allocator.resizeFn(&fixed_buffer_allocator.allocator, buf, buf_align, new_len, len_align, return_address);
+            } else {
+                return self.fallback_allocator.resizeFn(self.fallback_allocator, buf, buf_align, new_len, len_align, return_address);
+            }
+        }
+    };
+}
+
+const HashKeyType = u64;
+const IndexMap = std.HashMapUnmanaged(HashKeyType, u32, hash_hashFn, hash_eqlFn, 80);
+pub const Result = struct {
+    hash: HashKeyType,
+    index: u32,
+    status: ItemStatus,
+
+    pub fn hasCheckedIfExists(r: *Result) bool {
+        return r.status != .unknown;
+    }
+};
+const Seed = 999;
+pub const NotFound = std.math.maxInt(u32);
+pub const Unassigned = NotFound - 1;
+
+pub fn hash_hashFn(key: HashKeyType) HashKeyType {
+    return key;
+}
+
+pub fn hash_eqlFn(a: HashKeyType, b: HashKeyType) bool {
+    return a == b;
+}
+
+pub const ItemStatus = packed enum(u3) {
+    unknown,
+    exists,
+    not_found,
+};
+
+const hasDeinit = std.meta.trait.hasFn("deinit")(ValueType);
+
+pub fn BSSMap(comptime ValueType: type, comptime count: anytype, store_keys: bool, estimated_key_length: usize) type {
+    const max_index = count - 1;
+    const BSSMapType = struct {
+        pub var backing_buf: [count]ValueType = undefined;
+        pub var backing_buf_used: u16 = 0;
+        const Allocator = std.mem.Allocator;
+        const Self = @This();
+
+        // const HashTableAllocator = BSSSectionAllocator(@bitSizeOf(HashKeyType) * count * 2);
+
+        index: IndexMap,
+        overflow_list: std.ArrayListUnmanaged(ValueType),
+        allocator: *Allocator,
+
+        pub var instance: Self = undefined;
+
+        pub fn init(allocator: *std.mem.Allocator) *Self {
+            instance = Self{
+                .index = IndexMap{},
+                .allocator = allocator,
+                .overflow_list = std.ArrayListUnmanaged(ValueType){},
+            };
+
+            return &instance;
+        }
+
+        pub fn isOverflowing() bool {
+            return backing_buf_used >= @as(u16, count);
+        }
+
+        pub fn getOrPut(self: *Self, key: []const u8) !Result {
+            const _key = Wyhash.hash(Seed, key);
+            var index = try self.index.getOrPut(self.allocator, _key);
+
+            if (index.found_existing) {
+                return Result{
+                    .hash = _key,
+                    .index = index.entry.value,
+                    .status = switch (index.entry.value) {
+                        NotFound => .not_found,
+                        Unassigned => .unknown,
+                        else => .exists,
+                    },
+                };
+            }
+            index.entry.value = Unassigned;
+
+            return Result{
+                .hash = _key,
+                .index = Unassigned,
+                .status = .unknown,
+            };
+        }
+
+        pub fn get(self: *const Self, key: []const u8) ?*ValueType {
+            const _key = Wyhash.hash(Seed, key);
+            const index = self.index.get(_key) orelse return null;
+            return self.atIndex(index);
+        }
+
+        pub fn markNotFound(self: *Self, result: Result) void {
+            self.index.put(self.allocator, result.hash, NotFound) catch unreachable;
+        }
+
+        pub fn atIndex(self: *const Self, index: u32) ?*ValueType {
+            return switch (index) {
+                NotFound, Unassigned => null,
+                0...max_index => &backing_buf[index],
+                else => &self.overflow_list.items[index - count],
+            };
+        }
+
+        pub fn put(self: *Self, result: *Result, value: ValueType) !*ValueType {
+            var index: u32 = @intCast(u32, backing_buf_used + 1);
+            if (index >= max_index) {
+                const real_index = self.overflow_list.items.len;
+                index += @truncate(u32, real_index);
+                try self.overflow_list.append(self.allocator, value);
+                result.index = index;
+                self.index.putAssumeCapacity(result.hash, index);
+                return &self.overflow_list.items[real_index];
+            } else {
+                backing_buf_used += 1;
+                backing_buf[index] = value;
+                result.index = index;
+                self.index.putAssumeCapacity(result.hash, index);
+                if (backing_buf_used >= max_index - 1) {
+                    self.overflow_list = try @TypeOf(self.overflow_list).initCapacity(self.allocator, count);
+                }
+                return &backing_buf[index];
+            }
+        }
+
+        pub fn remove(self: *Self, key: string) u32 {
+            const _key = Wyhash.hash(Seed, key);
+            const index = self.index.get(_key) orelse return;
+            switch (index) {
+                Unassigned => {
+                    self.index.remove(_key);
+                },
+                NotFound => {
+                    self.index.remove(_key);
+                },
+                0...max_index => {
+                    if (hasDeinit(ValueType)) {
+                        backing_buf[index].deinit();
+                    }
+                    backing_buf[index] = undefined;
+                },
+                else => {
+                    const i = index - count;
+                    if (hasDeinit(ValueType)) {
+                        self.overflow_list.items[i].deinit();
+                    }
+                    self.overflow_list.items[index - count] = undefined;
+                },
+            }
+
+            return index;
+        }
+    };
+    if (!store_keys) {
+        return BSSMapType;
+    }
+
+    return struct {
+        map: *BSSMapType,
+        const Self = @This();
+        pub var instance: Self = undefined;
+        var key_list_buffer: [count * estimated_key_length]u8 = undefined;
+        var key_list_buffer_used: usize = 0;
+        var key_list_slices: [count][]u8 = undefined;
+        var key_list_overflow: std.ArrayListUnmanaged([]u8) = undefined;
+
+        pub fn init(allocator: *std.mem.Allocator) *Self {
+            instance = Self{
+                .map = BSSMapType.init(allocator),
+            };
+
+            return &instance;
+        }
+
+        pub fn isOverflowing() bool {
+            return instance.map.backing_buf_used >= count;
+        }
+        pub fn getOrPut(self: *Self, key: []const u8) !Result {
+            return try self.map.getOrPut(key);
+        }
+        pub fn get(self: *Self, key: []const u8) ?*ValueType {
+            return @call(.{ .modifier = .always_inline }, BSSMapType.get, .{ self.map, key });
+        }
+
+        pub fn atIndex(self: *Self, index: u32) ?*ValueType {
+            return @call(.{ .modifier = .always_inline }, BSSMapType.atIndex, .{ self.map, index });
+        }
+
+        pub fn keyAtIndex(self: *Self, index: u32) ?[]const u8 {
+            return switch (index) {
+                Unassigned, NotFound => null,
+                0...max_index => {
+                    return key_list_slices[index];
+                },
+                else => {
+                    return key_list_overflow.items[index - count];
+                },
+            };
+        }
+
+        pub fn put(self: *Self, key: anytype, comptime store_key: bool, result: *Result, value: ValueType) !*ValueType {
+            var ptr = try self.map.put(result, value);
+            if (store_key) {
+                try self.putKey(key, result);
+            }
+
+            return ptr;
+        }
+
+        pub fn putKey(self: *Self, key: anytype, result: *Result) !void {
+            if (key_list_buffer_used + key.len < key_list_buffer.len) {
+                const start = key_list_buffer_used;
+                key_list_buffer_used += key.len;
+                var slice = key_list_buffer[start..key_list_buffer_used];
+                std.mem.copy(u8, slice, key);
+
+                if (result.index < count) {
+                    key_list_slices[result.index] = slice;
+                } else {
+                    try key_list_overflow.append(self.map.allocator, slice);
+                }
+            } else if (result.index > key_list_overflow.items.len) {
+                try key_list_overflow.append(self.map.allocator, try self.map.allocator.dupe(u8, key));
+            } else {
+                const real_index = result.index - count;
+                if (key_list_overflow.items[real_index].len > 0) {
+                    self.map.allocator.free(key_list_overflow.items[real_index]);
+                }
+
+                key_list_overflow.items[real_index] = try self.map.allocator.dupe(u8, key);
+            }
+        }
+
+        pub fn markNotFound(self: *Self, result: Result) void {
+            self.map.markNotFound(result);
+        }
+
+        // For now, don't free the keys.
+        pub fn remove(self: *Self, key: string) u32 {
+            return self.map.remove(key);
+        }
+    };
+}