From 82bad92fcf92415f5ee1a1c3c0432c48073a7139 Mon Sep 17 00:00:00 2001
From: Rekai Musuka <rekai@musuka.dev>
Date: Thu, 26 Jan 2023 23:54:33 -0600
Subject: [PATCH] fix: refactor how `c` and `s` track breakpoints

We move state from Server.zig to Emulator.zig (the interface)
---
 src/Packet.zig | 31 ++++++++++++++++---------------
 src/Server.zig |  4 +---
 src/lib.zig    | 32 +++++++++++++++++++++++++++++++-
 3 files changed, 48 insertions(+), 19 deletions(-)

diff --git a/src/Packet.zig b/src/Packet.zig
index f77a728..2ea85ee 100644
--- a/src/Packet.zig
+++ b/src/Packet.zig
@@ -46,7 +46,7 @@ const String = union(enum) {
     }
 };
 
-pub fn parse(self: *Self, allocator: Allocator, state: *State, emu: Emulator) !String {
+pub fn parse(self: *Self, allocator: Allocator, emu: *Emulator) !String {
     switch (self.contents[0]) {
         // Required
         '?' => {
@@ -97,24 +97,25 @@ pub fn parse(self: *Self, allocator: Allocator, state: *State, emu: Emulator) !S
         },
         'M' => @panic("TODO: Memory Write"),
         'c' => {
-            while (true) {
-                emu.step();
-
-                const r = emu.registers();
-                const is_thumb = emu.cpsr() >> 5 & 1 == 1;
-                const r15 = r[15] -| if (is_thumb) @as(u32, 4) else 8;
-
-                if (state.hw_bkpt.isHit(r15)) {
-                    return .{ .static = "T05 hwbreak;" };
-                }
+            switch (emu.contd()) {
+                .SingleStep => unreachable,
+                .Trap => |r| switch (r) {
+                    .HwBkpt => return .{ .static = "T05 hwbreak:;" },
+                    .SwBkpt => return .{ .static = "T05 swbreak:;" },
+                },
             }
         },
         's' => {
             // var tokens = std.mem.tokenize(u8, self.contents[1..], " ");
             // const addr = if (tokens.next()) |s| try std.fmt.parseInt(u32, s, 16) else null;
 
-            emu.step();
-            return .{ .static = "S05" }; // Signal.Trap
+            switch (emu.step()) {
+                .SingleStep => return .{ .static = "T05" },
+                .Trap => |r| switch (r) {
+                    .HwBkpt => return .{ .static = "T05 hwbreak:;" },
+                    .SwBkpt => return .{ .static = "T05 swbreak:;" },
+                },
+            }
         },
 
         // Breakpoints
@@ -126,7 +127,7 @@ pub fn parse(self: *Self, allocator: Allocator, state: *State, emu: Emulator) !S
                 const addr_str = tokens.next() orelse return error.InvalidPacket;
                 const addr = try std.fmt.parseInt(u32, addr_str, 16);
 
-                state.hw_bkpt.remove(addr);
+                emu.state.hw_bkpt.remove(addr);
                 return .{ .static = "OK" };
             },
             '2' => return .{ .static = "" }, // TODO: Remove Write Watchpoint
@@ -144,7 +145,7 @@ pub fn parse(self: *Self, allocator: Allocator, state: *State, emu: Emulator) !S
                 const addr = try std.fmt.parseInt(u32, addr_str, 16);
                 const kind = try std.fmt.parseInt(u32, kind_str, 16);
 
-                state.hw_bkpt.add(addr, kind) catch |e| {
+                emu.state.hw_bkpt.add(addr, kind) catch |e| {
                     switch (e) {
                         error.OutOfSpace => return .{ .static = "E22" }, // FIXME: Which errno?
                         else => return e,
diff --git a/src/Server.zig b/src/Server.zig
index 1be0f65..ac39a23 100644
--- a/src/Server.zig
+++ b/src/Server.zig
@@ -1,7 +1,6 @@
 const std = @import("std");
 const network = @import("network");
 const Packet = @import("Packet.zig");
-const State = @import("State.zig");
 
 const Socket = network.Socket;
 const Allocator = std.mem.Allocator;
@@ -60,7 +59,6 @@ pkt_cache: ?[]const u8 = null,
 client: Socket,
 _socket: Socket,
 
-state: State = .{},
 emu: Emulator,
 
 pub fn init(emulator: Emulator) !Self {
@@ -131,7 +129,7 @@ fn handlePacket(self: *Self, allocator: Allocator, input: []const u8) !Action {
     var packet = Packet.from(allocator, input) catch return .nack;
     defer packet.deinit(allocator);
 
-    var string = packet.parse(allocator, &self.state, self.emu) catch return .nack;
+    var string = packet.parse(allocator, &self.emu) catch return .nack;
     defer string.deinit(allocator);
 
     const reply = string.inner();
diff --git a/src/lib.zig b/src/lib.zig
index cb534c0..f19a982 100644
--- a/src/lib.zig
+++ b/src/lib.zig
@@ -1,10 +1,20 @@
 /// Re-export of the server interface
 pub const Server = @import("Server.zig");
+const State = @import("State.zig");
 
 /// Interface for interacting between GDB and a GBA emu
 pub const Emulator = struct {
     const Self = @This();
 
+    const Signal = union(enum) {
+        const Kind = enum { HwBkpt, SwBkpt };
+
+        Trap: Kind,
+        SingleStep: void,
+    };
+
+    state: State = .{},
+
     ptr: *anyopaque,
 
     readFn: *const fn (*anyopaque, u32) u8,
@@ -75,7 +85,27 @@ pub const Emulator = struct {
         return self.cpsrFn(self.ptr);
     }
 
-    pub inline fn step(self: Self) void {
+    pub inline fn contd(self: *Self) Signal {
+        while (true) {
+            const signal = self.step();
+
+            switch (signal) {
+                .SingleStep => {},
+                .Trap => return signal,
+            }
+        }
+    }
+
+    pub inline fn step(self: *Self) Signal {
         self.stepFn(self.ptr);
+
+        const r = self.registersFn(self.ptr);
+        const is_thumb = self.cpsrFn(self.ptr) >> 5 & 1 == 1;
+
+        const r15 = r[15] -| if (is_thumb) @as(u32, 4) else 8;
+
+        if (self.state.hw_bkpt.isHit(r15)) return .{ .Trap = .HwBkpt };
+
+        return .SingleStep;
     }
 };