From e74cbddb0463e93f5d9742accc20bbed027d0b9b Mon Sep 17 00:00:00 2001
From: Tom Willemse
Date: Tue, 31 May 2022 23:02:18 -0700
Subject: Chapter 25.2

---
 clox/src/compiler.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

(limited to 'clox/src/compiler.c')

diff --git a/clox/src/compiler.c b/clox/src/compiler.c
index 7500005..6e98b5e 100644
--- a/clox/src/compiler.c
+++ b/clox/src/compiler.c
@@ -44,6 +44,11 @@ typedef struct {
   int depth;
 } Local;
 
+typedef struct {
+  uint8_t index;
+  bool isLocal;
+} Upvalue;
+
 typedef enum { TYPE_FUNCTION, TYPE_SCRIPT } FunctionType;
 
 typedef struct Compiler {
@@ -53,9 +58,12 @@ typedef struct Compiler {
 
   Local locals[UINT8_COUNT];
   int localCount;
+  Upvalue upvalues[UINT8_COUNT];
   int scopeDepth;
 } Compiler;
 
+static int resolveUpvalue(Compiler *, Token *);
+
 Parser parser;
 Compiler *current = NULL;
 Chunk *compilingChunk;
@@ -340,6 +348,11 @@ static void function(FunctionType type) {
 
   ObjFunction *function = endCompiler();
   emitBytes(OP_CLOSURE, makeConstant(OBJ_VAL(function)));
+
+  for (int i = 0; i < function->upvalueCount; i++) {
+    emitByte(compiler.upvalues[i].isLocal ? 1 : 0);
+    emitByte(compiler.upvalues[i].index);
+  }
 }
 
 static void markInitialized() {
@@ -567,6 +580,9 @@ static void namedVariable(Token name, bool canAssign) {
   if (arg != -1) {
     getOp = OP_GET_LOCAL;
     setOp = OP_SET_LOCAL;
+  } else if ((arg = resolveUpvalue(current, &name)) != -1) {
+    getOp = OP_GET_UPVALUE;
+    setOp = OP_SET_UPVALUE;
   } else {
     arg = identifierConstant(&name);
     getOp = OP_GET_GLOBAL;
@@ -698,6 +714,43 @@ static int resolveLocal(Compiler *compiler, Token *name) {
   return -1;
 }
 
+static int addUpvalue(Compiler *compiler, uint8_t index, bool isLocal) {
+  int upvalueCount = compiler->function->upvalueCount;
+
+  for (int i = 0; i < upvalueCount; i++) {
+    Upvalue *upvalue = &compiler->upvalues[i];
+    if (upvalue->index == index && upvalue->isLocal == isLocal) {
+      return i;
+    }
+  }
+
+  if (upvalueCount == UINT8_COUNT) {
+    error("Too many closure variables in function.");
+    return 0;
+  }
+
+  compiler->upvalues[upvalueCount].isLocal = isLocal;
+  compiler->upvalues[upvalueCount].index = index;
+  return compiler->function->upvalueCount++;
+}
+
+static int resolveUpvalue(Compiler *compiler, Token *name) {
+  if (compiler->enclosing == NULL)
+    return -1;
+
+  int local = resolveLocal(compiler->enclosing, name);
+  if (local != -1) {
+    return addUpvalue(compiler, (uint8_t)local, true);
+  }
+
+  int upvalue = resolveUpvalue(compiler->enclosing, name);
+  if (upvalue != -1) {
+    return addUpvalue(compiler, (uint8_t)upvalue, false);
+  }
+
+  return -1;
+}
+
 static void addLocal(Token name) {
   if (current->localCount == UINT8_COUNT) {
     error("Too many local variables in function.");
-- 
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