Switch to using OS pipes

07/src/main.zig

@@ -136,42 +136,74 @@ pub fn main() anyerror!void {
     // 5 intcode computers act as the amps
     var machines: [5]intcode.Machine = undefined;
 
+    // Allocate memory once only.
+    for (machines) |*machine| {
+        machine.alloc = alloc;
+        machine.memory = try alloc.alloc(i32, program.len);
+    }
+
+    // Now wire up the machines correctly. The output of each machine should be
+    // the input to the next.
+    const pipes: [6]intcode.CharDev = .{
+        try std.os.pipe(),
+        try std.os.pipe(),
+        try std.os.pipe(),
+        try std.os.pipe(),
+        try std.os.pipe(),
+        try std.os.pipe(),
+    };
+
+    machines[0].input = pipes[0];
+    machines[0].output = pipes[1];
+
+    machines[1].input = machines[0].output;
+    machines[1].output = pipes[2];
+
+    machines[2].input = machines[1].output;
+    machines[2].output = pipes[3];
+
+    machines[3].input = machines[2].output;
+    machines[3].output = pipes[4];
+
+    machines[4].input = machines[3].output;
+    machines[4].output = pipes[5];
+
     // 120 phase permutations. Find the highest.
     var max: i32 = 0;
     for (perm1) |inputs| {
         for (machines) |*machine| {
-            var copy = try alloc.alloc(i32, program.len);
-            std.mem.copy(i32, copy, program);
-
-            machine.* = try intcode.Machine.init(alloc, copy);
+            std.mem.copy(i32, machine.memory, program);
+            machine.ip = 0;
         }
 
-        // Phase input
+        // Phase inputs
         for (inputs) |input, i| {
             try machines[i].writeToInput(input);
         }
 
-        // amplifier input
-        for (machines) |*machine, i| {
-            var ampInput: i32 = 0;
-            if (i > 0) ampInput = try machines[i - 1].readFromOutput(false);
+        // Provide starting value of 0
+        try machines[0].writeToInput(0);
 
-            try machine.writeToInput(ampInput);
+        // run the program
+        for (machines) |*machine, i| {
             try machine.run();
         }
 
-        const final = try machines[4].readFromOutput(false);
+        const final = try machines[4].readFromOutput();
         if (final > max)
             max = final;
 
         // Don't forget to free everything!
         for (machines) |*machine, i| {
             alloc.free(machine.memory);
-            machine.deinit();
         }
     }
 
     std.debug.warn("Day 7, Part 1: {}\n", max);
 
-    // In part 2, the machines need to be wired into a feedback loop
+    // In part 2, the machines need to be wired into a feedback loop.
+    // To do this, drop pipe 6 and replace it with pipe 0
+    std.os.close(pipes[5][0]);
+    std.os.close(pipes[5][1]);
+    machines[4].output = machines[0].input;
 }