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const std = @import("std"); | |
// Cache requires a function (lambda) to be called when there's no cache hit and an other function(args_to_u64) that can compute args | |
// of the function to u64 that becomes the identifier to compare same arguments. | |
pub fn Cache(lambda: anytype, args_to_u64: fn (anytype) u64) type { | |
const lambda_info = @typeInfo(@TypeOf(lambda)); | |
if (lambda_info != .@"fn") { | |
@compileError("lambda should be a function type"); | |
} | |
const return_type = lambda_info.@"fn".return_type orelse @compileError("No return type"); | |
const return_type_info = @typeInfo(return_type); | |
const return_error_union_type = if (return_type_info == .error_union) blk: { | |
break :blk .{ return_type_info.error_union.error_set || std.mem.Allocator.Error, return_type_info.error_union.payload }; | |
} else blk: { | |
break :blk .{ std.mem.Allocator, return_type }; | |
}; | |
// @compileLog(@typeName(return_type)); | |
const InnerHashMap = std.HashMap(u64, return_type, struct { | |
pub fn hash(_: @This(), key: u64) u64 { | |
return key; | |
} | |
pub fn eql(_: @This(), a: u64, b: u64) bool { | |
return a == b; | |
} | |
}, 80); | |
return struct { | |
_inner: InnerHashMap, | |
const Self = @This(); | |
pub fn init(allocator: std.mem.Allocator) Self { | |
return Self{ ._inner = InnerHashMap.init(allocator) }; | |
} | |
pub fn deinit(self: *Self) void { | |
self._inner.deinit(); | |
} | |
pub fn get(self: *Self, args: anytype) return_error_union_type[0]!return_error_union_type[1] { | |
const key = args_to_u64(args); | |
if (self._inner.get(key)) |value| { | |
return value; | |
} else { | |
const value = @call(.auto, lambda, args); | |
try self._inner.put(key, value); | |
return value; | |
} | |
} | |
}; | |
} | |
// Below tests to cache addition of two numbers | |
fn _add(a: u64, b: u64) u64 { | |
return a + b; | |
} | |
const HashAdd = struct { | |
var allocator: std.mem.Allocator = undefined; | |
pub fn hash_add(args: anytype) u64 { | |
const temp = std.fmt.allocPrint(allocator, "{}:{}", .{ args[0], args[1] }) catch unreachable; | |
defer allocator.free(temp); | |
return std.hash_map.hashString(temp); | |
} | |
}; | |
test "test_cache" { | |
const allocator = std.testing.allocator; | |
HashAdd.allocator = allocator; | |
var cache = Cache(_add, HashAdd.hash_add).init(allocator); | |
const value: u64 = try cache.get(.{ 1, 2 }); | |
try std.testing.expectEqual(3, value); | |
const cache_value: u64 = try cache.get(.{ 1, 2 }); | |
try std.testing.expectEqual(3, cache_value); | |
cache._inner.deinit(); | |
} | |
fn _add_error(a: u64, b: u64) error{Got5}!u64 { | |
if (a + b == 5) { | |
return error.Got5; | |
} | |
return a + b; | |
} | |
test "test_add_error" { | |
const allocator = std.testing.allocator; | |
HashAdd.allocator = allocator; | |
var cache = Cache(_add_error, HashAdd.hash_add).init(allocator); | |
const value = try cache.get(.{ 1, 2 }); | |
try std.testing.expectEqual(3, value); | |
const cache_value = try cache.get(.{ 1, 2 }); | |
try std.testing.expectEqual(3, cache_value); | |
cache._inner.deinit(); | |
} |
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