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feat: code generation for conditional and switch statements

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Brett Broadhurst 2026-03-03 16:22:35 -07:00
parent 889f678dd8
commit d6ff3a40bd
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7 changed files with 476 additions and 59 deletions
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124
src/Story.zig
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@ -38,7 +38,9 @@ pub const Opcode = enum(u8) {
ret,
/// Pop a value off the stack, discarding it.
pop,
/// Push an object representing the boolean value of "true" to the stack.
true,
/// Push an object representing the boolean value of "false" to the stack.
false,
/// Pop two values off the stack and calculate their sum.
/// The result will be pushed to the stack.
@ -60,8 +62,13 @@ pub const Opcode = enum(u8) {
cmp_gt,
cmp_lte,
cmp_gte,
/// Jump unconditionally to the target address.
jmp,
/// Jump conditionally to the target address if the boolean value at the
/// top of the stack is true.
jmp_t,
/// Jump conditionally to the target address if the boolean value at the
/// top of the stack is false.
jmp_f,
call,
divert,
@ -118,14 +125,14 @@ pub fn trace(story: *Story, writer: *std.Io.Writer, frame: *CallFrame) !void {
if (slot) |object| {
try story_dumper.dumpObject(object);
} else {
try writer.writeAll("NULL");
try writer.writeAll("null");
}
try writer.writeAll(", ");
}
if (last_slot) |object| {
try story_dumper.dumpObject(object);
} else {
try writer.writeAll("NULL");
try writer.writeAll("null");
}
}
@ -198,7 +205,7 @@ fn setGlobal(vm: *Story, key: *const Object.String, value: *Object) !void {
fn execute(vm: *Story) !std.ArrayListUnmanaged(u8) {
const gpa = vm.allocator;
defer {
errdefer {
vm.can_advance = false;
}
if (vm.isCallStackEmpty()) return .empty;
@ -215,11 +222,27 @@ fn execute(vm: *Story) !std.ArrayListUnmanaged(u8) {
switch (code[frame.ip]) {
.exit => {
vm.is_exited = true;
vm.can_advance = false;
return .empty;
},
.true => {
const true_object = try Object.Number.create(vm, .{
.boolean = true,
});
try vm.pushStack(@ptrCast(true_object));
frame.ip += 1;
},
.false => {
const false_object = try Object.Number.create(vm, .{
.boolean = false,
});
try vm.pushStack(@ptrCast(false_object));
frame.ip += 1;
},
.pop => {
const object_top = vm.popStack();
if (object_top == null) return error.InvalidArgument;
if (vm.popStack()) |_| {} else {
return error.InvalidArgument;
}
frame.ip += 1;
},
.add => {
@ -243,12 +266,74 @@ fn execute(vm: *Story) !std.ArrayListUnmanaged(u8) {
frame.ip += 1;
},
.neg => {
const arg_object = vm.peekStack(0);
if (arg_object) |arg| {
if (vm.peekStack(0)) |arg| {
_ = Object.Number.negate(@ptrCast(arg));
} else {
return error.InvalidArgument;
}
frame.ip += 1;
},
.not => {
if (vm.peekStack(0)) |arg| {
const value = try Object.Number.create(vm, .{
.boolean = arg.isFalsey(),
});
_ = vm.popStack();
try vm.pushStack(@ptrCast(value));
} else {
return error.StackOverflow;
}
frame.ip += 1;
},
.cmp_eq => {
const lhs = vm.peekStack(1) orelse return error.Bugged;
const rhs = vm.peekStack(0) orelse return error.Bugged;
const value = try Object.cmpEql(vm, @ptrCast(lhs), @ptrCast(rhs));
_ = vm.popStack();
_ = vm.popStack();
try vm.pushStack(@ptrCast(value));
frame.ip += 1;
},
.cmp_lt, .cmp_gt, .cmp_lte, .cmp_gte => |op| {
const lhs = vm.peekStack(1) orelse return error.Bugged;
const rhs = vm.peekStack(0) orelse return error.Bugged;
const value = try Object.Number.performLogic(vm, op, @ptrCast(lhs), @ptrCast(rhs));
_ = vm.popStack();
_ = vm.popStack();
try vm.pushStack(@ptrCast(value));
frame.ip += 1;
},
.jmp => {
const arg_offset = readAddress(code, frame.ip);
frame.ip += 3 + arg_offset;
},
.jmp_t => {
const arg_offset = readAddress(code, frame.ip);
frame.ip += 3;
if (vm.peekStack(0)) |condition| {
if (!condition.isFalsey()) {
frame.ip += arg_offset;
}
} else {
return error.InvalidArgument;
}
},
.jmp_f => {
const arg_offset = readAddress(code, frame.ip);
frame.ip += 3;
if (vm.peekStack(0)) |condition| {
if (condition.isFalsey()) {
frame.ip += arg_offset;
}
} else {
return error.InvalidArgument;
}
},
.load_const => {
const index: u8 = @intFromEnum(code[frame.ip + 1]);
const value = try vm.getConstant(frame, index);
@ -262,10 +347,11 @@ fn execute(vm: *Story) !std.ArrayListUnmanaged(u8) {
frame.ip += 2;
},
.store => {
const value = vm.peekStack(0);
if (value) |arg| {
if (vm.peekStack(0)) |arg| {
const arg_offset: u8 = @intFromEnum(code[frame.ip + 1]);
vm.setLocal(frame, arg_offset, arg);
} else {
return error.InvalidArgument;
}
frame.ip += 2;
},
@ -283,11 +369,12 @@ fn execute(vm: *Story) !std.ArrayListUnmanaged(u8) {
const global_name = try vm.getConstant(frame, arg_offset);
assert(global_name.tag == .string);
const value = vm.peekStack(0);
if (value) |arg| {
if (vm.peekStack(0)) |arg| {
try vm.setGlobal(@ptrCast(global_name), arg);
_ = vm.popStack();
try vm.pushStack(arg);
} else {
return error.InvalidArgument;
}
frame.ip += 2;
},
@ -297,20 +384,26 @@ fn execute(vm: *Story) !std.ArrayListUnmanaged(u8) {
const string_object = try Object.String.fromObject(vm, object);
const string_bytes = string_object.bytes[0..string_object.length];
try stream_writer.writer.writeAll(string_bytes);
} else {
return error.InvalidArgument;
}
frame.ip += 1;
},
.stream_flush => {
frame.ip += 1;
// FIXME: This is a bit of a hack, but we have to deal with this right now.
const buffered = stream_writer.writer.buffered();
if (buffered.len == 0) continue;
return stream_writer.toArrayList();
},
.br_push => {
const arg_offset = std.mem.bytesToValue(u16, code[frame.ip + 1 ..][0..2]);
const arg_offset = readAddress(code, frame.ip);
try vm.current_choices.append(gpa, .{
.text = stream_writer.toArrayList(),
.dest_offset = std.mem.bigToNative(u16, arg_offset),
.dest_offset = arg_offset,
});
frame.ip += 3;
},
@ -335,6 +428,11 @@ fn execute(vm: *Story) !std.ArrayListUnmanaged(u8) {
}
}
fn readAddress(code: []const Story.Opcode, offset: usize) u16 {
const arg_offset = std.mem.bytesToValue(u16, code[offset + 1 ..][0..2]);
return std.mem.bigToNative(u16, arg_offset);
}
pub fn advance(story: *Story, gpa: std.mem.Allocator) ![]const u8 {
var content = try story.execute();
return content.toOwnedSlice(gpa);