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const std = @import("std");
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
// 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.
// 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 {
pub fn Cache(lambda: anytype, args_to_u64: fn (anytype) u64) type {
const lambda_info = @typeInfo(@TypeOf(lambda));
const lambda_info = @typeInfo(@TypeOf(lambda));
if (lambda_info != .@"fn") {
if (lambda_info != .Fn) {
@compileError("lambda should be a function type");
@compileError("lambda should be a function type");
}
}
const return_type = lambda_info.@"fn".return_type orelse @compileError("No return type");
const return_type = lambda_info.Fn.return_type orelse @compileError("No return type");
const InnerHashMap = std.HashMap(u64, return_type, struct {
const InnerHashMap = std.HashMap(u64, return_type, struct {
pub fn hash(_: @This(), key: u64) u64 {
pub fn hash(_: @This(), key: u64) u64 {
return key;
return key;
}
}
pub fn eql(_: @This(), a: u64, b: u64) bool {
pub fn eql(_: @This(), a: u64, b: u64) bool {
return a == b;
return a == b;
}
}
}, 80);
}, 80);
return struct {
return struct {
_inner: InnerHashMap,
_inner: InnerHashMap,
const Self = @This();
const Self = @This();
fn init(allocator: std.mem.Allocator) Cache(lambda, args_to_u64) {
fn init(allocator: std.mem.Allocator) Self {
return Self{ ._inner = InnerHashMap.init(allocator) };
return Self{ ._inner = InnerHashMap.init(allocator) };
}
}
fn get(self: *Self, args: anytype) !return_type {
fn get(self: *Self, args: anytype) !return_type {
const key = args_to_u64(args);
const key = args_to_u64(args);
if (self._inner.get(key)) |value| {
if (self._inner.get(key)) |value| {
std.debug.print("Rertrieving from cache for the key: {d}\n", .{key});
std.debug.print("Rertrieving from cache for the key: {d}\n", .{key});
return value;
return value;
} else {
} else {
std.debug.print("Computing function and storing in cache for the key: {d}\n", .{key});
std.debug.print("Computing function and storing in cache for the key: {d}\n", .{key});
const value = @call(.auto, lambda, args);
const value = @call(.auto, lambda, args);
try self._inner.put(key, value);
try self._inner.put(key, value);
return value;
return value;
}
}
}
}
};
};
}
}
// Below tests to cache addition of two numbers
// Below tests to cache addition of two numbers
fn _add(a: u64, b: u64) u64 {
fn _add(a: u64, b: u64) u64 {
return a + b;
return a + b;
}
}
const HashAdd = struct {
const HashAdd = struct {
var allocator: std.mem.Allocator = undefined;
var allocator: std.mem.Allocator = undefined;
pub fn hash_add(args: anytype) u64 {
pub fn hash_add(args: anytype) u64 {
const temp = std.fmt.allocPrint(allocator, "{}:{}", .{ args[0], args[1] }) catch unreachable;
const temp = std.fmt.allocPrint(allocator, "{}:{}", .{ args[0], args[1] }) catch unreachable;
defer allocator.free(temp);
defer allocator.free(temp);
return std.hash_map.hashString(temp);
return std.hash_map.hashString(temp);
}
}
};
};
test "test_cache" {
test "test_cache" {
const allocator = std.testing.allocator;
const allocator = std.testing.allocator;
HashAdd.allocator = allocator;
HashAdd.allocator = allocator;
var cache = Cache(_add, HashAdd.hash_add).init(allocator);
var cache = Cache(_add, HashAdd.hash_add).init(allocator);
const value: u64 = try cache.get(.{ 1, 2 });
const value: u64 = try cache.get(.{ 1, 2 });
try std.testing.expectEqual(3, value);
try std.testing.expectEqual(3, value);
const cache_value: u64 = try cache.get(.{ 1, 2 });
const cache_value: u64 = try cache.get(.{ 1, 2 });
try std.testing.expectEqual(3, cache_value);
try std.testing.expectEqual(3, cache_value);
cache._inner.deinit();
cache._inner.deinit();
}
}