From 19c48f9d58e790f631379750ada9c5c647240ee4 Mon Sep 17 00:00:00 2001
From: Thomas Lindner <tom@dl6tom.de>
Date: Sun, 6 Feb 2022 20:41:28 +0100
Subject: [PATCH] solve Challenge 2 of Set 1

---
 set1/challenge2_fixed_xor/build.zig    | 27 ++++++++++++++
 set1/challenge2_fixed_xor/src/main.zig | 50 ++++++++++++++++++++++++++
 2 files changed, 77 insertions(+)
 create mode 100644 set1/challenge2_fixed_xor/build.zig
 create mode 100644 set1/challenge2_fixed_xor/src/main.zig

diff --git a/set1/challenge2_fixed_xor/build.zig b/set1/challenge2_fixed_xor/build.zig
new file mode 100644
index 0000000..727e5b0
--- /dev/null
+++ b/set1/challenge2_fixed_xor/build.zig
@@ -0,0 +1,27 @@
+const std = @import("std");
+
+pub fn build(b: *std.build.Builder) void {
+    // Standard target options allows the person running `zig build` to choose
+    // what target to build for. Here we do not override the defaults, which
+    // means any target is allowed, and the default is native. Other options
+    // for restricting supported target set are available.
+    const target = b.standardTargetOptions(.{});
+
+    // Standard release options allow the person running `zig build` to select
+    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall.
+    const mode = b.standardReleaseOptions();
+
+    const exe = b.addExecutable("challenge2_fixed_xor", "src/main.zig");
+    exe.setTarget(target);
+    exe.setBuildMode(mode);
+    exe.install();
+
+    const run_cmd = exe.run();
+    run_cmd.step.dependOn(b.getInstallStep());
+    if (b.args) |args| {
+        run_cmd.addArgs(args);
+    }
+
+    const run_step = b.step("run", "Run the app");
+    run_step.dependOn(&run_cmd.step);
+}
diff --git a/set1/challenge2_fixed_xor/src/main.zig b/set1/challenge2_fixed_xor/src/main.zig
new file mode 100644
index 0000000..b9251ae
--- /dev/null
+++ b/set1/challenge2_fixed_xor/src/main.zig
@@ -0,0 +1,50 @@
+const std = @import("std");
+
+fn readHex(allocator: std.mem.Allocator, max_size: usize) ![]u8 {
+    const stdin = std.io.bufferedReader(std.io.getStdIn().reader()).reader();
+
+    var inputbuffer = std.ArrayList(u8).init(allocator);
+    defer inputbuffer.deinit();
+    var resultbuffer = std.ArrayList(u8).init(allocator);
+    defer resultbuffer.deinit();
+
+    while (true) {
+        try stdin.readUntilDelimiterArrayList(&inputbuffer, '\n', max_size * 2);
+        try resultbuffer.resize(inputbuffer.items.len / 2);
+        _ = std.fmt.hexToBytes(resultbuffer.items, inputbuffer.items) catch {
+            std.log.err("not a valid hexadecimal", .{});
+            continue;
+        };
+        return resultbuffer.toOwnedSlice();
+    }
+}
+
+pub fn main() anyerror!void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer _ = gpa.deinit();
+    const allocator = gpa.allocator();
+    const stdout = std.io.getStdOut().writer();
+
+    while (true) {
+        const input1 = try readHex(allocator, 4096);
+        defer allocator.free(input1);
+
+        const input2 = try readHex(allocator, 4096);
+        defer allocator.free(input2);
+
+        if (input1.len != input2.len) {
+            std.log.err("not the same length", .{});
+            continue;
+        }
+
+        var output = try std.ArrayList(u8).initCapacity(allocator, input1.len);
+        defer output.deinit();
+
+        var i: usize = 0;
+        while (i < input1.len) : (i += 1) {
+            try output.append(input1[i] ^ input2[i]);
+        }
+
+        try stdout.print("{}\n", .{std.fmt.fmtSliceHexLower(output.items)});
+    }
+}