From da7d9cfcc09c560bc4c61861d97e4bce833cfa67 Mon Sep 17 00:00:00 2001
From: kayomn <kayomn@kayomn.net>
Date: Mon, 24 Oct 2022 01:02:07 +0100
Subject: [PATCH] Add additional closures and uses

---
 src/core/io.zig   | 21 +++++++++++++----
 src/core/meta.zig | 57 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+), 4 deletions(-)

diff --git a/src/core/io.zig b/src/core/io.zig
index 770e77f..4418c63 100644
--- a/src/core/io.zig
+++ b/src/core/io.zig
@@ -2,6 +2,11 @@ const meta = @import("./meta.zig");
 const stack = @import("./stack.zig");
 const std = @import("std");
 
+///
+/// Closure for allocating, reallocating, and deallocating dynamic memory resources through itself.
+///
+pub const Allocator = meta.BiFunction(56, ?[]u8, usize, AllocationError![]u8);
+
 ///
 /// File-system agnostic abstraction for manipulating a file.
 ///
@@ -186,16 +191,24 @@ pub const Writer = meta.Function(@sizeOf(usize), []const u8, usize);
 /// Returns `true` if `this` is the same length and contains the same data as `that`, otherwise
 /// `false`.
 ///
-pub fn equalsBytes(this: []const u8, that: []const u8) bool {
-    return std.mem.eql(u8, this, that);
+pub fn equals(comptime Element: type, this: []const Element, that: []const Element) bool {
+    if (this.len != that.len) return false;
+
+    {
+        var i = std.mem.zeroes(usize);
+
+        while (i < this.len) : (i += 1) if (this[i] != that[i]) return false;
+    }
+
+    return true;
 }
 
 test "Equivalence of bytes" {
     const bytes_sequence = &.{69, 42, 0};
     const testing = std.testing;
 
-    try testing.expect(equalsBytes(bytes_sequence, bytes_sequence));
-    try testing.expect(!equalsBytes(bytes_sequence, &.{69, 42}));
+    try testing.expect(equals(u8, bytes_sequence, bytes_sequence));
+    try testing.expect(!equals(u8, bytes_sequence, &.{69, 42}));
 }
 
 ///
diff --git a/src/core/meta.zig b/src/core/meta.zig
index 884c4a4..582176b 100644
--- a/src/core/meta.zig
+++ b/src/core/meta.zig
@@ -11,6 +11,63 @@ pub fn FnReturn(comptime Fn: type) type {
     return type_info.Fn.return_type orelse void;
 }
 
+///
+/// Returns a double-input single-output closure type where `A` represents the first input type, `B`
+/// represents the second, and `Out` represents the output type, and `captures_size` represents the
+/// size of the closure context.
+///
+pub fn BiFunction(comptime captures_size: usize, comptime A: type,
+    comptime B: type, comptime Out: type) type {
+
+    return struct {
+        applyErased: fn (*anyopaque, A, B) Out,
+        context: [captures_size]u8,
+
+        ///
+        /// Function type.
+        ///
+        const Self = @This();
+
+        ///
+        /// Applies `a` and `b` to `self`, producing a result according to the current context data.
+        ///
+        pub fn apply(self: *Self, a: A, b: B) Out {
+            return self.applyErased(&self.context, a, b);
+        }
+
+        ///
+        /// Creates a new [Self] by capturing the `captures` value as the context and `call` as the
+        /// as the behavior executed when [apply] or [applyErased] is called.
+        ///
+        /// The newly created [Self] is returned.
+        ///
+        pub fn capture(captures: anytype, comptime call: fn (@TypeOf(captures), A, B) Out) Self {
+            const Captures = @TypeOf(captures);
+
+            if (@sizeOf(Captures) > captures_size)
+                @compileError("`captures` must be smaller than or equal to " ++
+                    std.fmt.comptimePrint("{d}", .{captures_size}) ++ " bytes");
+
+            const captures_align = @alignOf(Captures);
+
+            var function = Self{
+                .context = undefined,
+
+                .applyErased = struct {
+                    fn do(erased: *anyopaque, a: A, b: B) Out {
+                        return call(@ptrCast(*Captures, @alignCast(
+                            captures_align, erased)).*, a, b);
+                    }
+                }.do,
+            };
+
+            @ptrCast(*Captures, @alignCast(captures_align, &function.context)).* = captures;
+
+            return function;
+        }
+    };
+}
+
 ///
 /// Returns a single-input single-output closure type where `In` represents the input type, `Out`
 /// represents the output type, and `captures_size` represents the size of the closure context.