strings: store size together with text in memory

ain.c

@@ -28,6 +28,7 @@
 #include "ain.h"
 #include "little_endian.h"
 #include "instructions.h"
+#include "vm_string.h"
 
 static const char *errtab[AIN_MAX_ERROR] = {
 	[AIN_SUCCESS]             = "Success",
@@ -86,6 +87,24 @@ static char **read_strings(struct ain_reader *r, int count)
 	return strings;
 }
 
+static struct string *read_vm_string(struct ain_reader *r)
+{
+	size_t len = strlen((char*)r->buf + r->index);
+	struct string *s = make_string((char*)r->buf + r->index, len);
+	s->literal = true;
+	r->index += len + 1;
+	return s;
+}
+
+static struct string **read_vm_strings(struct ain_reader *r, int count)
+{
+	struct string **strings = calloc(count, sizeof(struct string*));
+	for (int i = 0; i < count; i++) {
+		strings[i] = read_vm_string(r);
+	}
+	return strings;
+}
+
 static struct ain_variable *read_variables(struct ain_reader *r, int count)
 {
 	struct ain_variable *variables = calloc(count, sizeof(struct ain_variable));
@@ -260,7 +279,7 @@ static bool read_tag(struct ain_reader *r, struct ain *ain)
 		int32_t count = read_int32(r);
 		ain->structures = read_structures(r, count);
 	} else if (TAG_EQ("MSG0")) {
-		ain->messages = read_strings(r, read_int32(r));
+		ain->messages = read_vm_strings(r, read_int32(r));
 	} else if (TAG_EQ("MAIN")) {
 		ain->main = read_int32(r);
 	} else if (TAG_EQ("MSGF")) {
@@ -274,7 +293,7 @@ static bool read_tag(struct ain_reader *r, struct ain *ain)
 	} else if (TAG_EQ("GVER")) {
 		ain->game_version = read_int32(r);
 	} else if (TAG_EQ("STR0")) {
-		ain->strings = read_strings(r, read_int32(r));
+		ain->strings = read_vm_strings(r, read_int32(r));
 	} else if (TAG_EQ("FNAM")) {
 		ain->filenames = read_strings(r, read_int32(r));
 	} else if (TAG_EQ("OJMP")) {

ain.h

@@ -21,6 +21,8 @@
 #include <stdbool.h>
 #include <stddef.h>
 
+#include "vm_string.h"
+
 struct ain;
 
 enum ain_error {
@@ -160,13 +162,13 @@ struct ain {
 	struct ain_global *globals;
 	struct ain_initval *global_initvals;
 	struct ain_struct *structures;
-	char **messages;
+	struct string **messages;
 	int32_t main;
 	int32_t msgf;
 	struct ain_library *libraries;
 	struct ain_switch *switches;
 	int32_t game_version;
-	char **strings;
+	struct string **strings;
 	char **filenames;
 	int32_t ojmp;
 	struct ain_function_type *function_types;

string.c

@@ -18,45 +18,42 @@
 #include <stdio.h>
 #include <string.h>
 #include "system4.h"
-#include "sys4_string.h"
+#include "vm_string.h"
 
-struct string make_string(char *str, size_t len)
+struct string *make_string(const char *str, unsigned int len)
 {
-	return (struct string) {
-		.str = str,
-		.len = len,
-		.mutable = false
-	};
+	struct string *s = xmalloc(sizeof(struct string) + len + 1);
+	s->size = len;
+	s->literal = false;
+	memcpy(s->text, str, len);
+	s->text[len] = '\0';
+	return s;
 }
 
 void free_string(struct string *str)
 {
-	if (str->mutable)
-		free(str->str);
+	if (!str->literal)
+		free(str);
 }
 
-void string_add(struct string *a, struct string *b)
+struct string *string_append(struct string *a, struct string *b)
 {
-	if (a->mutable) {
-		a->str = xrealloc(a->str, a->len + b->len + 1);
+	if (!a->literal) {
+		a = xrealloc(a, sizeof(struct string) + a->size + b->size + 1);
 	} else {
-		char *literal = a->str;
-		a->str = xmalloc(a->len + b->len + 1);
-		memcpy(a->str, literal, a->len + 1);
+		struct string *tmp = xmalloc(sizeof(struct string) + a->size + b->size + 1);
+		memcpy(tmp, a, sizeof(struct string) + a->size);
+		a = tmp;
 	}
-	memcpy(a->str + a->len, b->str, b->len + 1);
-	a->len = a->len + b->len;
+	memcpy(a->text + a->size, b->text, b->size + 1);
+	a->size = a->size + b->size;
+	return a;
 }
 
-struct string integer_to_string(int n)
+struct string *integer_to_string(int n)
 {
 	char buf[513];
 	int len = snprintf(buf, 512, "%d" ,n);
 	buf[512] = '\0';
-
-	return (struct string) {
-		.str = xstrdup(buf),
-		.len = len,
-		.mutable = true
-	};
+	return make_string(buf, len);
 }

vm.c

@@ -18,7 +18,7 @@
 #include <string.h>
 
 #include "system4.h"
-#include "sys4_string.h"
+#include "vm_string.h"
 #include "ain.h"
 #include "instructions.h"
 #include "little_endian.h"
@@ -35,7 +35,7 @@ static int stack_ptr = 0;
 // Separate stack for strings
 // Not sure exactly how System40.exe handles strings.
 // Further testing required to ensure this approach doesn't break anything.
-static struct string string_stack[1024];
+static struct string *string_stack[1024];
 static int string_stack_ptr = 0;
 
 //static struct frame *frame_stack[1024];
@@ -93,16 +93,15 @@ static int32_t stack_pop_ref(void)
 
 static void stack_push_string_literal(int32_t no)
 {
-	// FIXME: should store string length when reading AIN
-	string_stack[string_stack_ptr++] = make_string(ain->strings[no], strlen(ain->strings[no]));
+	string_stack[string_stack_ptr++] = ain->strings[no];
 }
 
 static void stack_push_string(struct string *str)
 {
-	string_stack[string_stack_ptr++] = *str;
+	string_stack[string_stack_ptr++] = str;
 }
 
-static struct string stack_pop_string(void)
+static struct string *stack_pop_string(void)
 {
 	string_stack_ptr--;
 	return string_stack[string_stack_ptr];
@@ -111,12 +110,12 @@ static struct string stack_pop_string(void)
 static void stack_toss_string(void)
 {
 	string_stack_ptr--;
-	free_string(&string_stack[string_stack_ptr]);
+	free_string(string_stack[string_stack_ptr]);
 }
 
 static struct string *stack_peek_string(void)
 {
-	return &string_stack[string_stack_ptr-1];
+	return string_stack[string_stack_ptr-1];
 }
 
 /*
@@ -158,7 +157,7 @@ static void system_call(int32_t code)
 		sys_exit(stack_pop());
 		break;
 	case 0x6: // system.Output(string szText)
-		sys_message("%s", stack_peek_string()->str);
+		sys_message("%s", stack_peek_string()->text);
 		// XXX: caller S_POPs
 		break;
 	case 0x14: // system.Peek()
@@ -174,7 +173,7 @@ static void system_call(int32_t code)
 static void execute_instruction(int16_t opcode)
 {
 	int32_t index, a, b, v;
-	struct string sa, sb;
+	struct string *sa, *sb;
 	const char *opcode_name = "UNKNOWN";
 	switch (opcode) {
 	//
@@ -396,12 +395,11 @@ static void execute_instruction(int16_t opcode)
 	case S_ADD:
 		sb = stack_pop_string();
 		sa = stack_pop_string();
-		string_add(&sa, &sb);
-		stack_push_string(&sa);
+		sa = string_append(sa, sb);
+		stack_push_string(sa);
 		break;
 	case I_STRING:
-		sa = integer_to_string(stack_pop());
-		stack_push_string(&sa);
+		stack_push_string(integer_to_string(stack_pop()));
 		break;
 	// -- NOOPs ---
 	case FUNC:

vm_string.h

@@ -21,14 +21,14 @@
 #include <stddef.h>
 
 struct string {
-	char *str;
-	size_t len;
-	bool mutable;
+	unsigned int size;
+	bool literal;
+	char text[];
 };
 
-struct string make_string(char *str, size_t len);
+struct string *make_string(const char *str, unsigned int len);
 void free_string(struct string *str);
-void string_add(struct string *a, struct string *b);
-struct string integer_to_string(int n);
+struct string *string_append(struct string *a, struct string *b);
+struct string *integer_to_string(int n);
 
 #endif