1 files changed, 93 insertions, 0 deletions
diff --git a/users/tazjin/rlox/src/bytecode/chunk.rs b/users/tazjin/rlox/src/bytecode/chunk.rs
new file mode 100644
index 000000000000..fc5cd34fdf4f
--- /dev/null
+++ b/users/tazjin/rlox/src/bytecode/chunk.rs
@@ -0,0 +1,93 @@
+use std::ops::Index;
+
+use super::opcode::{CodeIdx, ConstantIdx, OpCode};
+use super::value;
+
+// In the book, this type is a hand-rolled dynamic array
+// implementation in C. The main benefit of following that approach
+// would be avoiding issues with OpCode variants not having equal
+// sizes, but for the purpose of this I'm going to ignore that
+// problem.
+#[derive(Debug, Default)]
+pub struct Chunk {
+    pub code: Vec<OpCode>,
+    lines: Vec<Span>,
+    constants: Vec<value::Value>,
+}
+
+#[derive(Debug)]
+struct Span {
+    /// Source code line
+    line: usize,
+
+    /// Number of instructions derived from this line
+    count: usize,
+}
+
+impl Chunk {
+    pub fn add_op(&mut self, data: OpCode, line: usize) -> CodeIdx {
+        let idx = self.code.len();
+        self.code.push(data);
+        self.add_line(line);
+        CodeIdx(idx)
+    }
+
+    pub fn add_constant(&mut self, data: value::Value) -> usize {
+        let idx = self.constants.len();
+        self.constants.push(data);
+        idx
+    }
+
+    pub fn constant(&self, idx: ConstantIdx) -> &value::Value {
+        self.constants.index(idx.0)
+    }
+
+    fn add_line(&mut self, line: usize) {
+        match self.lines.last_mut() {
+            Some(span) if span.line == line => span.count += 1,
+            _ => self.lines.push(Span { line, count: 1 }),
+        }
+    }
+
+    pub fn get_line(&self, offset: usize) -> usize {
+        let mut pos = 0;
+        for span in &self.lines {
+            pos += span.count;
+            if pos > offset {
+                return span.line;
+            }
+        }
+
+        panic!("invalid chunk state: line missing for offset {}", offset);
+    }
+}
+
+// Disassembler
+
+/// Print a single disassembled instruction at the specified offset.
+/// Some instructions are printed "raw", others have special handling.
+#[cfg(feature = "disassemble")]
+pub fn disassemble_instruction(chunk: &Chunk, offset: usize) {
+    print!("{:04} ", offset);
+
+    let line = chunk.get_line(offset);
+    if offset > 0 && line == chunk.get_line(offset - 1) {
+        print!("   | ");
+    } else {
+        print!("{:4} ", line);
+    }
+
+    match chunk.code.index(offset) {
+        OpCode::OpConstant(idx) => {
+            println!("OpConstant({:?}) '{:?}'", idx, chunk.constant(*idx))
+        }
+        op => println!("{:?}", op),
+    }
+}
+
+#[cfg(feature = "disassemble")]
+pub fn disassemble_chunk(chunk: &Chunk) {
+    for (idx, _) in chunk.code.iter().enumerate() {
+        disassemble_instruction(chunk, idx);
+    }
+}