From 9e3ced0f2e2247c0d999d39f970dc926a831e0cb Mon Sep 17 00:00:00 2001
From: Patrick MARIE <pm@mkz.me>
Date: Sat, 24 Aug 2024 15:11:45 +0200
Subject: [PATCH] implementing constants

---
 src/main.zig   | 44 +++++++++++++++++++++++++++++++++-----------
 src/utils.zig  |  6 ++++++
 src/values.zig | 43 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+), 11 deletions(-)
 create mode 100644 src/utils.zig
 create mode 100644 src/values.zig

diff --git a/src/main.zig b/src/main.zig
index 2524f58..baabf78 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -2,18 +2,25 @@ const std = @import("std");
 const debug = std.debug;
 const Allocator = std.mem.Allocator;
 
-const OpCode = enum(u8) { OP_RETURN };
+const utils = @import("./utils.zig");
+const values = @import("./values.zig");
+const Value = values.Value;
+const ValueArray = values.ValueArray;
+
+const OpCode = enum(u8) { OP_CONSTANT, OP_RETURN };
 
 const Chunk = struct {
     count: usize,
     capacity: usize,
     code: []u8,
+    constants: ValueArray,
 
     pub fn new() Chunk {
         return Chunk{
             .count = 0,
             .capacity = 0,
             .code = &.{},
+            .constants = ValueArray.new(),
         };
     }
 
@@ -23,12 +30,13 @@ const Chunk = struct {
         self.count = 0;
         self.capacity = 0;
         self.code = &.{};
+        self.constants = ValueArray.new();
     }
 
     pub fn write(self: *Chunk, allocator: Allocator, byte: u8) !void {
         if (self.capacity < self.count + 1) {
             const old_capacity = self.capacity;
-            self.capacity = grow_capacity(old_capacity);
+            self.capacity = utils.grow_capacity(old_capacity);
             self.code = try allocator.realloc(self.code, self.capacity);
         }
 
@@ -43,9 +51,10 @@ const Chunk = struct {
     pub fn dissassemble(self: Chunk, name: []const u8) void {
         debug.print("== {s} ==\n", .{name});
 
-        for (0..self.count) |idx| {
-            const offset = self.dissassemble_instruction(idx);
-            _ = offset;
+        var offset: usize = 0;
+
+        while (offset < self.count) {
+            offset += self.dissassemble_instruction(offset);
         }
     }
 
@@ -56,6 +65,7 @@ const Chunk = struct {
 
         switch (instruction) {
             @intFromEnum(OpCode.OP_RETURN) => return simple_instruction("OP_RETURN", offset),
+            @intFromEnum(OpCode.OP_CONSTANT) => return constant_instruction("OP_CONSTANT", self, offset),
             else => {
                 debug.print("unknown opcode {d}\n", .{instruction});
                 return offset + 1;
@@ -64,23 +74,31 @@ const Chunk = struct {
     }
 
     pub fn deinit(self: *Chunk, allocator: Allocator) void {
+        self.constants.free(allocator);
+
         if (self.capacity > 0) {
             allocator.free(self.code);
         }
     }
+
+    pub fn add_constant(self: *Chunk, allocator: Allocator, value: Value) !usize {
+        try self.constants.write(allocator, value);
+        return self.constants.count - 1;
+    }
 };
 
 pub fn simple_instruction(opcode_name: []const u8, offset: usize) usize {
-    debug.print("{s}\n", .{opcode_name});
+    debug.print("{s:16}\n", .{opcode_name});
 
     return offset + 1;
 }
 
-pub fn grow_capacity(capacity: usize) usize {
-    if (capacity < 8) {
-        return 8;
-    }
-    return capacity * 2;
+pub fn constant_instruction(opcode_name: []const u8, chunk: Chunk, offset: usize) usize {
+    const constant = chunk.code[offset + 1];
+    debug.print("{s:16} {d:4} ", .{ opcode_name, constant });
+    values.print_value(chunk.constants.values[constant]);
+    debug.print("\n", .{});
+    return offset + 2;
 }
 
 pub fn main() !void {
@@ -92,6 +110,10 @@ pub fn main() !void {
     try chunk.init(allocator);
 
     try chunk.write(allocator, @intFromEnum(OpCode.OP_RETURN));
+    const constant = try chunk.add_constant(allocator, 1.2);
+    try chunk.write(allocator, @intFromEnum(OpCode.OP_CONSTANT));
+    try chunk.write(allocator, @intCast(constant));
+
     chunk.dissassemble("test chunk");
 
     chunk.deinit(allocator);
diff --git a/src/utils.zig b/src/utils.zig
new file mode 100644
index 0000000..bd758bc
--- /dev/null
+++ b/src/utils.zig
@@ -0,0 +1,6 @@
+pub fn grow_capacity(capacity: usize) usize {
+    if (capacity < 8) {
+        return 8;
+    }
+    return capacity * 2;
+}
diff --git a/src/values.zig b/src/values.zig
new file mode 100644
index 0000000..7075031
--- /dev/null
+++ b/src/values.zig
@@ -0,0 +1,43 @@
+const std = @import("std");
+const debug = std.debug;
+
+const Allocator = std.mem.Allocator;
+
+const utils = @import("./utils.zig");
+
+pub const Value = f64;
+
+pub const ValueArray = struct {
+    capacity: usize,
+    count: usize,
+    values: []Value,
+
+    pub fn new() ValueArray {
+        return ValueArray{
+            .capacity = 0,
+            .count = 0,
+            .values = &.{},
+        };
+    }
+
+    pub fn write(self: *ValueArray, allocator: Allocator, value: Value) !void {
+        if (self.capacity < self.count + 1) {
+            const old_capacity = self.capacity;
+            self.capacity = utils.grow_capacity(old_capacity);
+            self.values = try allocator.realloc(self.values, self.capacity);
+        }
+
+        self.values[self.count] = value;
+        self.count += 1;
+    }
+
+    pub fn free(self: *ValueArray, allocator: Allocator) void {
+        if (self.capacity > 0) {
+            allocator.free(self.values);
+        }
+    }
+};
+
+pub fn print_value(value: Value) void {
+    debug.print("{any}", .{value});
+}