80 lines
2.4 KiB
Zig
80 lines
2.4 KiB
Zig
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const std = @import("std");
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const mem = std.mem;
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/// NOTE: This must be mirrored in bytecode.rs.
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pub const Opcode = enum(u8) {
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// Push literal values onto the stack.
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nil,
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false,
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true,
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tag,
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number, // (float: f32)
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rgba, // (r: u8, g: u8, b: u8, a: u8)
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// Duplicate existing values.
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local, // (index: u8) push a value relative to the bottom of the current stack window
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set_local, // (index: u8) set the value of a value relative to the bottom of the current stack window
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capture, // (index: u8) push a value captured by the current closure
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def, // (index: u16) get the value of a definition
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set_def, // (index: u16) set the value of a definition
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// Create lists.
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list, // (len: u16)
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// Create literal functions.
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function, // (params: u8, then: u16), at `then`: (local_count: u8, capture_count: u8, captures: [capture_count](source: u8, index: u8))
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// Control flow.
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jump, // (offset: u16)
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jump_if_not, // (offset: u16)
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field, // (count: u8, tags: [count]u16) look up a closure capture named by a tag. this is used to implement records with fields
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// Function calls.
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call, // (argc: u8)
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system, // (index: u8, argc: u8) fast path for system calls
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ret, // must be the last opcode; opcodes after .ret are treated as invalid
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_, // invalid opcodes
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};
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// Constants used by the .function opcode to indicate capture sources.
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pub const capture_local: u8 = 0;
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pub const capture_capture: u8 = 1;
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pub const Chunk = struct {
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bytecode: []const u8,
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};
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pub const Loc = u16;
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pub const Defs = struct {
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num_defs: usize,
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num_tags: usize,
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// Unlike the Rust version, we currently do not store strings here, because we still don't
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// support stack traces.
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// The VM therefore never needs the names of Defs for any practical purposes.
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pub fn parse(
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a: mem.Allocator,
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// These strings are expected to contain a list of names, where each name is terminated
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// by a newline (LF).
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defs_string: []const u8,
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tags_string: []const u8,
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) !*Defs {
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const d = try a.create(Defs);
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errdefer a.destroy(d);
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d.* = .{
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.num_defs = mem.count(u8, defs_string, "\n"),
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.num_tags = mem.count(u8, tags_string, "\n"),
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};
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return d;
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}
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pub fn destroy(defs: *Defs, a: mem.Allocator) void {
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a.destroy(defs);
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}
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};
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