[Chapter19&Strings] - Adding strings

clox/compiler.c

@@ -173,6 +173,11 @@ static void number() {
   emitConstant(NUMBER_VAL(value));
 }
 
+static void string() {
+  emitConstant(OBJ_VAL(copyString(parser.previous.start + 1,
+                                  parser.previous.length - 2)));
+}
+
 static void unary() {
   TokenType operatorType = parser.previous.type;
 
@@ -226,7 +231,7 @@ ParseRule rules[] = {
   [TOKEN_LESS]          = {NULL,     binary, PREC_COMPARISON},
   [TOKEN_LESS_EQUAL]    = {NULL,     binary, PREC_COMPARISON},
   [TOKEN_IDENTIFIER]    = {NULL,     NULL,   PREC_NONE},
-  [TOKEN_STRING]        = {NULL,     NULL,   PREC_NONE},
+  [TOKEN_STRING]        = {string,   NULL,   PREC_NONE},
   [TOKEN_NUMBER]        = {number,   NULL,   PREC_NONE},
   [TOKEN_AND]           = {NULL,     NULL,   PREC_NONE},
   [TOKEN_CLASS]         = {NULL,     NULL,   PREC_NONE},

clox/compiler.h

@@ -1,6 +1,7 @@
 #ifndef clox_compiler_h
 #define clox_compiler_h
 
+#include "object.h"
 #include "vm.h"
 
 bool compile(const char* source, Chunk* chunk);

clox/memory.c

@@ -1,6 +1,7 @@
 #include <stdlib.h>
 
 #include "memory.h"
+#include "vm.h"
 
 void* reallocate(void* pointer, size_t oldSize, size_t newSize) {
   if (newSize == 0) {
@@ -12,3 +13,23 @@ void* reallocate(void* pointer, size_t oldSize, size_t newSize) {
   if (result == NULL) exit(1);
   return result;
 }
+static void freeObject(Obj* object) {
+  switch (object->type) {
+    case OBJ_STRING: {
+      ObjString* string = (ObjString*)object;
+      FREE_ARRAY(char, string->chars, string->length + 1);
+      FREE(ObjString, object);
+      break;
+    }
+  }
+}
+void freeObjects() {
+  Obj* object = vm.objects;
+  while (object != NULL) {
+    Obj* next = object->next;
+    freeObject(object);
+    object = next;
+  }
+}
+
+

clox/memory.h

@@ -2,6 +2,12 @@
 #define clox_memory_h
 
 #include "common.h"
+#include "object.h"
+
+#define ALLOCATE(type, count) \
+    (type*)reallocate(NULL, 0, sizeof(type) * (count))
+
+#define FREE(type, pointer) reallocate(pointer, sizeof(type), 0)
 
 #define GROW_CAPACITY(capacity) \
     ((capacity) < 8 ? 8 : (capacity) * 2)
@@ -14,5 +20,6 @@
     reallocate(pointer, sizeof(type) * (oldCount), 0)
 
 void* reallocate(void* pointer, size_t oldSize, size_t newSize);
+void freeObjects();
 
 #endif

clox/object.c

@@ -0,0 +1,43 @@
+#include <stdio.h>
+#include <string.h>
+
+#include "memory.h"
+#include "object.h"
+#include "value.h"
+#include "vm.h"
+
+#define ALLOCATE_OBJ(type, objectType) \
+    (type*)allocateObject(sizeof(type), objectType)
+
+static Obj* allocateObject(size_t size, ObjType type) {
+  Obj* object = (Obj*)reallocate(NULL, 0, size);
+  object->type = type;
+
+  object->next = vm.objects;
+  vm.objects = object;
+  return object;
+}
+
+
+static ObjString* allocateString(char* chars, int length) {
+  ObjString* string = ALLOCATE_OBJ(ObjString, OBJ_STRING);
+  string->length = length;
+  string->chars = chars;
+  return string;
+}
+ObjString* takeString(char* chars, int length) {
+  return allocateString(chars, length);
+}
+ObjString* copyString(const char* chars, int length) {
+  char* heapChars = ALLOCATE(char, length + 1);
+  memcpy(heapChars, chars, length);
+  heapChars[length] = '\0';
+  return allocateString(heapChars, length);
+}
+void printObject(Value value) {
+  switch (OBJ_TYPE(value)) {
+    case OBJ_STRING:
+      printf("%s", AS_CSTRING(value));
+      break;
+  }
+}

clox/object.h

@@ -0,0 +1,33 @@
+#ifndef clox_object_h
+#define clox_object_h
+
+#include "value.h"
+
+#define OBJ_TYPE(value)        (AS_OBJ(value)->type)
+
+#define IS_STRING(value)       isObjType(value, OBJ_STRING)
+
+#define AS_STRING(value)       ((ObjString*)AS_OBJ(value))
+#define AS_CSTRING(value)      (((ObjString*)AS_OBJ(value))->chars)
+
+typedef enum {
+  OBJ_STRING,
+} ObjType;
+
+struct Obj {
+  ObjType type;
+  struct Obj* next;
+};
+struct ObjString {
+  Obj obj;
+  int length;
+  char* chars;
+};
+ObjString* takeString(char* chars, int length);
+ObjString* copyString(const char* chars, int length);
+void printObject(Value value);
+static inline bool isObjType(Value value, ObjType type) {
+  return IS_OBJ(value) && AS_OBJ(value)->type == type;
+}
+
+#endif

clox/tests/test_string.lox

@@ -0,0 +1 @@
+"st" + "ri" + "ng"

clox/value.c

@@ -1,5 +1,7 @@
 #include <stdio.h>
+#include "string.h"
 
+#include "object.h"
 #include "memory.h"
 #include "value.h"
 
@@ -30,6 +32,7 @@ void printValue(Value value) {
       break;
     case VAL_NIL: printf("nil"); break;
     case VAL_NUMBER: printf("%g", AS_NUMBER(value)); break;
+    case VAL_OBJ: printObject(value); break;
   }
 }
 
@@ -39,6 +42,13 @@ bool valuesEqual(Value a, Value b) {
     case VAL_BOOL:   return AS_BOOL(a) == AS_BOOL(b);
     case VAL_NIL:    return true;
     case VAL_NUMBER: return AS_NUMBER(a) == AS_NUMBER(b);
+    case VAL_OBJ: {
+      ObjString* aString = AS_STRING(a);
+      ObjString* bString = AS_STRING(b);
+      return aString->length == bString->length &&
+          memcmp(aString->chars, bString->chars,
+                 aString->length) == 0;
+    }
     default:         return false; // Unreachable.
   }
 }

clox/value.h

@@ -3,13 +3,15 @@
 
 #include "common.h"
 
-
+typedef struct Obj Obj;
+typedef struct ObjString ObjString;
 //typedef double Value;
 
 typedef enum {
   VAL_BOOL,
   VAL_NIL, 
   VAL_NUMBER,
+  VAL_OBJ
 } ValueType;
 
 typedef struct {
@@ -17,19 +19,22 @@ typedef struct {
   union {
     bool boolean;
     double number;
-  } as; 
+    Obj* obj;
+  } as;
 } Value;
 
 #define IS_BOOL(value)    ((value).type == VAL_BOOL)
 #define IS_NIL(value)     ((value).type == VAL_NIL)
 #define IS_NUMBER(value)  ((value).type == VAL_NUMBER)
+#define IS_OBJ(value) ((value).type == VAL_OBJ)
 
 #define AS_BOOL(value)    ((value).as.boolean)
 #define AS_NUMBER(value)  ((value).as.number)
-
 #define BOOL_VAL(value)   ((Value){VAL_BOOL, {.boolean = value}})
 #define NIL_VAL           ((Value){VAL_NIL, {.number = 0}})
 #define NUMBER_VAL(value) ((Value){VAL_NUMBER, {.number = value}})
+#define OBJ_VAL(object)   ((Value){VAL_OBJ, {.obj = (Obj*)object}})
+
 
 typedef struct {
   int capacity;

clox/vm.c

@@ -1,9 +1,12 @@
 #include <stdarg.h>
 #include <stdio.h>
+#include <string.h>
 #include "common.h"
 #include "compiler.h"
-#include "vm.h"
 #include "debug.h"
+#include "object.h"
+#include "memory.h"
+#include "vm.h"
 VM vm; 
 static void resetStack() {
   vm.stackTop = vm.stack;
@@ -24,10 +27,11 @@ static void runtimeError(const char* format, ...) {
 
 void initVM() {
   resetStack();
+  vm.objects = NULL;
 }
 
 void freeVM() {
-
+  freeObjects();
 }
 void push(Value value) {
   *vm.stackTop = value;
@@ -45,6 +49,20 @@ static Value peek(int distance) {
 static bool isFalsey(Value value) {
   return IS_NIL(value) || (IS_BOOL(value) && !AS_BOOL(value));
 }
+static void concatenate() {
+  ObjString* b = AS_STRING(pop());
+  ObjString* a = AS_STRING(pop());
+
+  int length = a->length + b->length;
+  char* chars = ALLOCATE(char, length + 1);
+  memcpy(chars, a->chars, a->length);
+  memcpy(chars + a->length, b->chars, b->length);
+  chars[length] = '\0';
+
+  ObjString* result = takeString(chars, length);
+  push(OBJ_VAL(result));
+}
+
 
 static InterpretResult run() {
 #define READ_BYTE() (*vm.ip++)
@@ -91,7 +109,20 @@ static InterpretResult run() {
       }
       case OP_GREATER:  BINARY_OP(BOOL_VAL, >); break;
       case OP_LESS:     BINARY_OP(BOOL_VAL, <); break;
-      case OP_ADD:      BINARY_OP(NUMBER_VAL, +); break;
+      case OP_ADD: {
+        if (IS_STRING(peek(0)) && IS_STRING(peek(1))) {
+          concatenate();
+        } else if (IS_NUMBER(peek(0)) && IS_NUMBER(peek(1))) {
+          double b = AS_NUMBER(pop());
+          double a = AS_NUMBER(pop());
+          push(NUMBER_VAL(a + b));
+        } else {
+          runtimeError(
+              "Operands must be two numbers or two strings.");
+          return INTERPRET_RUNTIME_ERROR;
+        }
+        break;
+      }
       case OP_SUBTRACT: BINARY_OP(NUMBER_VAL, -); break;
       case OP_MULTIPLY: BINARY_OP(NUMBER_VAL, *); break;
       case OP_DIVIDE:   BINARY_OP(NUMBER_VAL, /); break;

clox/vm.h

@@ -11,6 +11,7 @@ typedef struct {
   uint8_t* ip;
   Value stack[STACK_MAX];
   Value* stackTop;
+  Obj* objects;
 } VM;
 typedef enum {
   INTERPRET_OK,
@@ -20,7 +21,8 @@ typedef enum {
 
 void initVM();
 void freeVM();
-InterpretResult interpret(const char* source);
+InterpretResult interpret(const char* chunk);
+extern VM vm;
 void push(Value value);
 Value pop();