fix: refactor how c and s track breakpoints

We move state from Server.zig to Emulator.zig (the interface)

src/Packet.zig

@@ -2,6 +2,7 @@ const std = @import("std");
 
 const Allocator = std.mem.Allocator;
 const Emulator = @import("lib.zig").Emulator;
+const State = @import("State.zig");
 
 const target = @import("Server.zig").target;
 const memory_map = @import("Server.zig").memory_map;
@@ -45,7 +46,7 @@ const String = union(enum) {
     }
 };
 
-pub fn parse(self: *Self, allocator: Allocator, emu: Emulator) !String {
+pub fn parse(self: *Self, allocator: Allocator, emu: *Emulator) !String {
     switch (self.contents[0]) {
         // Required
         '?' => {
@@ -76,8 +77,8 @@ pub fn parse(self: *Self, allocator: Allocator, emu: Emulator) !String {
         'G' => @panic("TODO: Register Write"),
         'm' => {
             var tokens = std.mem.tokenize(u8, self.contents[1..], ",");
-            const addr_str = tokens.next() orelse return .{ .static = "E9999" }; // EUNKNOWN
+            const addr_str = tokens.next() orelse return error.InvalidPacket;
-            const length_str = tokens.next() orelse return .{ .static = "E9999" }; // EUNKNOWN
+            const length_str = tokens.next() orelse return error.InvalidPacket;
 
             const addr = try std.fmt.parseInt(u32, addr_str, 16);
             const len = try std.fmt.parseInt(u32, length_str, 16);
@@ -87,9 +88,6 @@ pub fn parse(self: *Self, allocator: Allocator, emu: Emulator) !String {
             {
                 var i: u32 = 0;
                 while (i < len) : (i += 1) {
-                    const value = emu.read(addr + i);
-                    log.debug("read 0x{X:0>2} from 0x{X:0>8}", .{ value, addr + i });
-
                     // writes the formatted integer to the buffer, returns a slice to the buffer but we ignore that
                     _ = std.fmt.bufPrintIntToSlice(ret[i * 2 ..][0..2], emu.read(addr + i), 16, .lower, .{ .fill = '0', .width = 2 });
                 }
@@ -98,15 +96,68 @@ pub fn parse(self: *Self, allocator: Allocator, emu: Emulator) !String {
             return .{ .alloc = ret };
         },
         'M' => @panic("TODO: Memory Write"),
-        'c' => @panic("TODO: Continue"),
+        'c' => {
+            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();
+            switch (emu.step()) {
+                .SingleStep => return .{ .static = "T05" },
+                .Trap => |r| switch (r) {
+                    .HwBkpt => return .{ .static = "T05 hwbreak:;" },
+                    .SwBkpt => return .{ .static = "T05 swbreak:;" },
+                },
+            }
+        },
 
-            const ret = try std.fmt.allocPrint(allocator, "S{x:0>2}", .{@enumToInt(Signal.Trap)});
+        // Breakpoints
-            return .{ .alloc = ret };
+        'z' => switch (self.contents[1]) {
+            '0' => return .{ .static = "" }, //TODO: Remove Software Breakpoint
+            '1' => {
+                var tokens = std.mem.tokenize(u8, self.contents[2..], ",");
+
+                const addr_str = tokens.next() orelse return error.InvalidPacket;
+                const addr = try std.fmt.parseInt(u32, addr_str, 16);
+
+                emu.state.hw_bkpt.remove(addr);
+                return .{ .static = "OK" };
+            },
+            '2' => return .{ .static = "" }, // TODO: Remove Write Watchpoint
+            '3' => return .{ .static = "" }, // TODO: Remove Read Watchpoint
+            '4' => return .{ .static = "" }, // TODO: Remove Access Watchpoint
+            else => return .{ .static = "" },
+        },
+        'Z' => switch (self.contents[1]) {
+            '0' => return .{ .static = "" }, //TODO: Insert Software Breakpoint
+            '1' => {
+                var tokens = std.mem.tokenize(u8, self.contents[2..], ",");
+                const addr_str = tokens.next() orelse return error.InvalidPacket;
+                const kind_str = tokens.next() orelse return error.InvalidPacket;
+
+                const addr = try std.fmt.parseInt(u32, addr_str, 16);
+                const kind = try std.fmt.parseInt(u32, kind_str, 16);
+
+                emu.state.hw_bkpt.add(addr, kind) catch |e| {
+                    switch (e) {
+                        error.OutOfSpace => return .{ .static = "E22" }, // FIXME: Which errno?
+                        else => return e,
+                    }
+                };
+
+                return .{ .static = "OK" };
+            },
+            '2' => return .{ .static = "" }, // TODO: Insert Write Watchpoint
+            '3' => return .{ .static = "" }, // TODO: Insert Read Watchpoint
+            '4' => return .{ .static = "" }, // TODO: Insert Access Watchpoint
+            else => return .{ .static = "" },
         },
 
         // Optional
@@ -125,6 +176,7 @@ pub fn parse(self: *Self, allocator: Allocator, emu: Emulator) !String {
         },
         'q' => {
             if (self.contents[1] == 'C' and self.contents.len == 2) return .{ .static = "QC1" };
+
             if (substr(self.contents[1..], "fThreadInfo")) return .{ .static = "m1" };
             if (substr(self.contents[1..], "sThreadInfo")) return .{ .static = "l" };
             if (substr(self.contents[1..], "Attached")) return .{ .static = "1" }; // Tell GDB we're attached to a process
@@ -142,9 +194,10 @@ pub fn parse(self: *Self, allocator: Allocator, emu: Emulator) !String {
                 _ = tokens.next(); // Xfer
                 _ = tokens.next(); // features
                 _ = tokens.next(); // read
-                const annex = tokens.next() orelse return .{ .static = "E9999" };
+
-                const offset_str = tokens.next() orelse return .{ .static = "E99999" };
+                const annex = tokens.next() orelse return error.InvalidPacket;
-                const length_str = tokens.next() orelse return .{ .static = "E9999" };
+                const offset_str = tokens.next() orelse return error.InvalidPacket;
+                const length_str = tokens.next() orelse return error.InvalidPacket;
 
                 if (std.mem.eql(u8, annex, "target.xml")) {
                     const offset = try std.fmt.parseInt(usize, offset_str, 16);
@@ -173,8 +226,8 @@ pub fn parse(self: *Self, allocator: Allocator, emu: Emulator) !String {
                 _ = tokens.next(); // Xfer
                 _ = tokens.next(); // memory-map
                 _ = tokens.next(); // read
-                const offset_str = tokens.next() orelse return .{ .static = "E9999" };
+                const offset_str = tokens.next() orelse return error.InvalidPacket;
-                const length_str = tokens.next() orelse return .{ .static = "E9999" };
+                const length_str = tokens.next() orelse return error.InvalidPacket;
 
                 const offset = try std.fmt.parseInt(usize, offset_str, 16);
                 const length = try std.fmt.parseInt(usize, length_str, 16);

src/Server.zig

@@ -129,7 +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.emu) catch return .nack;
+    var string = packet.parse(allocator, &self.emu) catch return .nack;
     defer string.deinit(allocator);
 
     const reply = string.inner();

src/State.zig

@@ -0,0 +1,68 @@
+const std = @import("std");
+
+hw_bkpt: HwBkpt = .{},
+
+const HwBkpt = struct {
+    const log = std.log.scoped(.HwBkpt);
+
+    list: [2]?Bkpt = .{ null, null },
+
+    pub fn isHit(self: *const @This(), addr: u32) bool {
+        for (self.list) |bkpt_opt| {
+            if (bkpt_opt == null) continue;
+            const bkpt = bkpt_opt.?;
+
+            if (bkpt.addr == addr) return true;
+        }
+
+        return false;
+    }
+
+    pub fn add(self: *@This(), addr: u32, kind: u32) !void {
+        for (self.list) |*bkpt_opt| {
+            if (bkpt_opt.* != null) {
+                const bkpt = bkpt_opt.*.?;
+                if (bkpt.addr == addr) return; // makes this fn indempotent
+
+                continue;
+            }
+
+            bkpt_opt.* = .{ .addr = addr, .kind = try Bkpt.Kind.from(u32, kind) };
+            log.debug("Added Breakpoint at 0x{X:0>8}", .{addr});
+
+            return;
+        }
+
+        return error.OutOfSpace;
+    }
+
+    pub fn remove(self: *@This(), addr: u32) void {
+        for (self.list) |*bkpt_opt| {
+            if (bkpt_opt.* == null) continue;
+            const bkpt = bkpt_opt.*.?; // FIXME: bkpt_opt.?.addr works though?
+
+            log.debug("Removed Breakpoint at 0x{X:0>8}", .{addr});
+            if (bkpt.addr == addr) bkpt_opt.* = null;
+        }
+    }
+};
+
+const Bkpt = struct {
+    addr: u32,
+    kind: Kind,
+
+    const Kind = enum(u3) {
+        Arm = 2,
+        Thumb = 4,
+
+        pub fn from(comptime T: type, num: T) !@This() {
+            comptime std.debug.assert(@typeInfo(T) == .Int);
+
+            return switch (num) {
+                2 => .Arm,
+                4 => .Thumb,
+                else => error.UnknownBkptKind,
+            };
+        }
+    };
+};

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;
     }
 };