Implement slab map data structure
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This commit is contained in:
kayomn 2023-06-03 19:55:59 +00:00
parent 55d281bdfa
commit 713f9bb08c
4 changed files with 170 additions and 35 deletions

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@ -79,8 +79,8 @@ pub fn Stack(comptime Value: type) type {
/// internal buffer by `growth_amount`, leaving `self` in the same state that it was in prior to starting the /// internal buffer by `growth_amount`, leaving `self` in the same state that it was in prior to starting the
/// grow. /// grow.
/// ///
/// Growing ahead of pushing operations is useful when the upper bound of pushes is well-understood, as it can /// Growing ahead of multiple push operations is useful when the upper bound of pushes is well-understood, as it
/// reduce the number of allocations required per push. /// can reduce the number of allocations required per push.
/// ///
/// *Note* if the `capacity` field of `self` is a non-zero value, `allocator` must reference the same allocation /// *Note* if the `capacity` field of `self` is a non-zero value, `allocator` must reference the same allocation
/// strategy as the one originally used to allocate the current internal buffer. /// strategy as the one originally used to allocate the current internal buffer.

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@ -2,44 +2,166 @@ const debug = @import("./debug.zig");
const io = @import("./io.zig"); const io = @import("./io.zig");
// TODO: Finish implementing. const math = @import("./math.zig");
pub fn Map(comptime Index: type, comptime Element: type) type { const std = @import("std");
///
/// Addressable mapping of integer values of type described by `index_int` to values of type `Value`.
///
/// Slab maps are similar to slot maps in that they have O(1) insertion and removal, use a fragmented flat table
/// structure instead. This reduces memory usage in some cases and can be useful for data that does not need to be
/// quickly iterated over, as values ordering is not guaranteed.
///
/// *Note* `index_int` values may be as big or as small as desired per the use-case of the consumer, however, integers
/// smaller than `usize` may result in the map reporting it is out of memory due to exhausting the addressable space
/// provided by the integer.
///
pub fn Map(comptime index_int: std.builtin.Type.Int, comptime Value: type) type {
return struct { return struct {
free_index: Index = 0, free_index: Index = 0,
entries: []Entry = &.{}, count: Index = 0,
table: []Entry = &.{},
///
/// Table entry which may either store an inserted value or an index to the next free entry in the table.
///
const Entry = union (enum) { const Entry = union (enum) {
free_index: usize, free_index: Index,
element: Element, value: Value,
}; };
///
/// Used for indexing into the slab map.
///
const Index = math.Int(index_int);
///
/// Slab type.
///
const Self = @This(); const Self = @This();
pub fn fetch(self: *Self, index: Index) *Element { ///
const entry = &self.entries[index]; /// Overwrites the value referenced by `index` in `self`.
///
pub fn assign(self: *Self, index: Index, value: Value) void {
const entry = &self.table[index];
debug.assert(entry.* == .element); debug.assert(entry.* == .value);
return &entry.element; entry.value = value;
} }
///
/// Fetches the value referenced by `index` in `self`, returning it.
///
pub fn fetch(self: *Self, index: Index) Value {
const entry = &self.table[index];
debug.assert(entry.* == .value);
return entry.value;
}
///
/// Deinitializes `self` and sets it to an invalid state, freeing all memory allocated by `allocator`.
///
/// *Note* if the `table` field of `self` is an allocated slice, `allocator` must reference the same allocation
/// strategy as the one originally used to allocate the current table.
///
pub fn deinit(self: *Self, allocator: io.Allocator) void { pub fn deinit(self: *Self, allocator: io.Allocator) void {
io.deallocate(allocator, self.entries); if (self.table.len == 0) {
return;
} }
pub fn insert(self: *Self, allocator: io.Allocator, value: Element) io.AllocationError!Index { io.deallocate(allocator, self.table);
_ = self;
_ = allocator;
_ = value;
return 0; self.table = &.{};
self.count = 0;
} }
///
/// Attempts to grow the internal buffer of `self` by `growth_amount` using `allocator`.
///
/// The function returns [io.AllocatorError] if `allocator` could not commit the memory required to grow the
/// table by `growth_amount`, leaving `self` in the same state that it was in prior to starting the grow.
///
/// Growing ahead of multiple insertion operations is useful when the upper bound of insertions is well-
/// understood, as it can reduce the number of allocations required per insertion.
///
/// *Note* if the `table` field of `self` is an allocated slice, `allocator` must reference the same allocation
/// strategy as the one originally used to allocate the current table.
///
pub fn grow(self: *Self, allocator: io.Allocator, growth_amount: usize) io.AllocationError!void {
const grown_capacity = self.table.len + growth_amount;
const entries = try io.allocate_many(Entry, grown_capacity, allocator);
errdefer io.deallocate(allocator, entries);
if (self.table.len != 0) {
for (0 .. self.table.len) |index| {
entries[index] = self.table[index];
}
for (self.table.len .. entries.len) |index| {
entries[index] = .{.free_index = 0};
}
io.deallocate(allocator, self.table);
}
self.table = entries;
}
///
/// Attempts to insert `value` into `self` as a new entry using `allocator` as the allocation strategy,
/// returning an index value representing a reference to the inserted value that may be queried through `self`
/// after.
///
/// The function returns [io.AllocationError] if `allocator` could not commit the memory required to grow the
/// internal buffer of `self` when necessary.
///
/// *Note* if the `table` field of `self` is an allocated slice, `allocator` must reference the same allocation
/// strategy as the one originally used to allocate the current table.
///
pub fn insert(self: *Self, allocator: io.Allocator, value: Value) io.AllocationError!Index {
if (self.count == self.table.len) {
try self.grow(allocator, math.max(1, self.count));
}
if (self.free_index == self.count) {
const entry_index = self.count;
const entry = &self.table[entry_index];
entry.* = .{.value = value};
self.count += 1;
self.free_index += 1;
return entry_index;
}
const entry_index = self.free_index;
const entry = &self.table[self.free_index];
debug.assert(entry.* == .free_index);
self.free_index = entry.free_index;
entry.* = .{.value = value};
return entry_index;
}
///
/// Removes the value referenced by `index` from `self`.
///
pub fn remove(self: *Self, index: Index) void { pub fn remove(self: *Self, index: Index) void {
const entry = &self.entries[index]; const entry = &self.table[index];
debug.assert(entry.* == .element); debug.assert(entry.* == .value);
entry.* = .{.free_index = self.free_index};
self.free_index = index;
} }
}; };
} }

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@ -154,6 +154,10 @@ pub fn Hashed(comptime Key: type, comptime Value: type, comptime keyer: Keyer(Ke
/// `self`. /// `self`.
/// ///
pub fn deinit(self: *Self, allocator: io.Allocator) void { pub fn deinit(self: *Self, allocator: io.Allocator) void {
if (self.table.len == 0) {
return;
}
io.deallocate(allocator, self.table); io.deallocate(allocator, self.table);
self.table = &.{}; self.table = &.{};
@ -196,7 +200,6 @@ pub fn Hashed(comptime Key: type, comptime Value: type, comptime keyer: Keyer(Ke
return null; return null;
} }
{
const hash_max = math.min(math.max_int(hash_info), self.table.len); const hash_max = math.min(math.max_int(hash_info), self.table.len);
var hashed_key = math.wrap(keyer.hasher(key), math.min_int(hash_info), hash_max); var hashed_key = math.wrap(keyer.hasher(key), math.min_int(hash_info), hash_max);
var iterations = @as(usize, 0); var iterations = @as(usize, 0);
@ -210,7 +213,6 @@ pub fn Hashed(comptime Key: type, comptime Value: type, comptime keyer: Keyer(Ke
hashed_key = (hashed_key +% 1) % hash_max; hashed_key = (hashed_key +% 1) % hash_max;
} }
}
return null; return null;
} }

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@ -143,7 +143,7 @@ pub const ObjectInfo = struct {
} }
}; };
const ObjectSlab = coral.slab.Map(u32, Object); const ObjectSlab = coral.slab.Map(@typeInfo(u32).Int, Object);
pub const Reporter = coral.io.Functor(void, []const u8); pub const Reporter = coral.io.Functor(void, []const u8);
@ -192,8 +192,12 @@ pub fn deinit(self: *Self) void {
pub fn discard(self: *Self, val: types.Val) void { pub fn discard(self: *Self, val: types.Val) void {
switch (val) { switch (val) {
.object => |object| { .object => |object| {
if (!self.heap.fetch(object).release(self)) { var data = self.heap.fetch(object);
if (data.release(self)) {
self.heap.remove(object); self.heap.remove(object);
} else {
self.heap.assign(object, data);
} }
}, },
@ -267,12 +271,19 @@ pub fn get_field(self: *Self, indexable: types.Ref, field: types.Ref) !types.Val
try self.check(indexable == .object, "invalid type conversion: object"); try self.check(indexable == .object, "invalid type conversion: object");
try self.check(field == .object, "invalid type conversion: object"); try self.check(field == .object, "invalid type conversion: object");
const value = self.heap.fetch(indexable.object).state.fields.lookup(self.heap.fetch(field.object)) orelse { const value = get_value: {
var field_data = self.heap.fetch(field.object);
break: get_value self.heap.fetch(indexable.object).state.fields.lookup(&field_data) orelse {
return .nil; return .nil;
}; };
};
if (value == .object) { if (value == .object) {
self.heap.fetch(value.object).acquire(); var value_data = self.heap.fetch(value.object);
value_data.acquire();
self.heap.assign(value.object, value_data);
} }
return value; return value;