From 14edad9a88787b0fec63e34ea31235f2b05731be Mon Sep 17 00:00:00 2001
From: overflowerror <mail@overflowerror.com>
Date: Thu, 2 May 2024 14:28:08 +0200
Subject: [PATCH] feat: Add support for array subscripts

---
 compiler/src/ast.c                            | 14 ++++++
 compiler/src/ast.h                            |  4 ++
 compiler/src/band.c                           | 49 ++++++++++++++++---
 compiler/src/band.h                           |  7 ++-
 compiler/src/codegen_expr.c                   | 10 ++++
 compiler/src/parser.y                         | 16 +++---
 compiler/src/scope.c                          |  8 +++
 compiler/src/scope.h                          |  1 +
 .../test/cases/020c-print-array-offset.in     |  4 ++
 .../test/cases/020c-print-array-offset.out    |  3 ++
 10 files changed, 100 insertions(+), 16 deletions(-)
 create mode 100644 compiler/test/cases/020c-print-array-offset.in
 create mode 100644 compiler/test/cases/020c-print-array-offset.out

diff --git a/compiler/src/ast.c b/compiler/src/ast.c
index b2d3ef3..fd1346a 100644
--- a/compiler/src/ast.c
+++ b/compiler/src/ast.c
@@ -135,11 +135,25 @@ struct expression* literal_expression_array_new(size_t length, struct expression
 }
 
 struct expression* variable_expression_new(char* id) {
+    _new(expr, expression);
+    expr->kind = VARIABLE;
+    expr->type = UNKNOWN_TYPE;
+    expr->variable = (struct variable_expression) {
+            .id = id,
+            .is_offset = false,
+            .offset = 0,
+    };
+    return expr;
+}
+
+struct expression* variable_expression_new_offset(char* id, size_t offset) {
 	_new(expr, expression);
 	expr->kind = VARIABLE;
 	expr->type = UNKNOWN_TYPE;
 	expr->variable = (struct variable_expression) {
 		.id = id,
+        .is_offset = true,
+        .offset = offset,
 	};
 	return expr;
 }
diff --git a/compiler/src/ast.h b/compiler/src/ast.h
index abd0f38..ad212eb 100644
--- a/compiler/src/ast.h
+++ b/compiler/src/ast.h
@@ -2,6 +2,7 @@
 #define AST_H
 
 #include <stdlib.h>
+#include <stdbool.h>
 
 enum literal_kind {
 	NUMBER_LITERAL,
@@ -50,6 +51,8 @@ struct literal_expression {
 
 struct variable_expression {
 	char* id;
+    bool is_offset;
+    size_t offset;
 };
 
 struct macro_expression {
@@ -147,6 +150,7 @@ struct expression* literal_expression_str_new(char*);
 struct expression* literal_expression_num_new(long long);
 struct expression* literal_expression_array_new(size_t, struct expression**);
 struct expression* variable_expression_new(char*);
+struct expression* variable_expression_new_offset(char*, size_t);
 struct expression* macro_expression_new(char*, char*);
 struct expression* builtin_call_expression_new(void);
 void builtin_call_expression_add_argument(struct expression*, struct expression*);
diff --git a/compiler/src/band.c b/compiler/src/band.c
index b2a8384..6ffdd0f 100644
--- a/compiler/src/band.c
+++ b/compiler/src/band.c
@@ -60,12 +60,20 @@ size_t band_find_empty_region_index(band_t* band) {
 
 region_t* band_allocate_region(band_t* band, size_t size) {
 	region_t* region = safe_malloc(sizeof(region_t));
-	band_addr_t addr = band_find_gap(band, size);
-	size_t regions_index = band_find_empty_region_index(band);
+    size_t regions_index = band_find_empty_region_index(band);
+
+	band_addr_t addr;
+    if (size != 0) {
+        addr = band_find_gap(band, size);
+    } else {
+        addr = 0;
+    }
 
 	region->start = addr;
 	region->size = size;
 	region->index = regions_index;
+    region->ref_count = 1;
+    region->parent = NULL;
 
 	band->regions[regions_index] = region;
 	for (size_t i = 0; i < size; i++) {
@@ -91,13 +99,38 @@ region_t* band_allocate_tmp(band_t* band, size_t size) {
 	return region;
 }
 
-void band_region_free(band_t* band, region_t* region) {
-	band->regions[region->index] = NULL;
-	for (size_t i = 0; i < region->size; i++) {
-		band->band[region->start + i] = NULL;
-	}
+region_t* band_allocate_ref(band_t* band, region_t* parent) {
+    region_t* region = band_allocate_region(band, 0);
+    region->name = NULL;
+    region->is_temp = true;
 
-	free(region);
+    parent->ref_count++;
+    region->parent = parent;
+
+    region->size = parent->size;
+    region->start = parent->start;
+
+    return region;
+}
+
+void band_region_free(band_t* band, region_t* region) {
+    region->ref_count--;
+
+    if (region->ref_count == 0) {
+        if (region->parent == NULL) {
+            band->regions[region->index] = NULL;
+            for (size_t i = 0; i < region->size; i++) {
+                band->band[region->start + i] = NULL;
+            }
+
+            free(region);
+        } else {
+            band_region_free(band, region->parent);
+
+            band->regions[region->index] = NULL;
+            free(region);
+        }
+    }
 }
 
 void band_region_free_raw(band_t* band, band_addr_t addr) {
diff --git a/compiler/src/band.h b/compiler/src/band.h
index b1bcd3e..5b1c568 100644
--- a/compiler/src/band.h
+++ b/compiler/src/band.h
@@ -8,12 +8,14 @@
 
 typedef size_t band_addr_t;
 
-typedef struct {
+typedef struct region {
 	band_addr_t start;
 	size_t index;
 	size_t size;
 	const char* name;
-	bool is_temp;	
+	bool is_temp;
+    size_t ref_count;
+    struct region* parent;
 } region_t;
 
 typedef struct {
@@ -28,6 +30,7 @@ region_t* band_region_for_addr(band_t*, band_addr_t);
 
 region_t* band_allocate(band_t*, size_t);
 region_t* band_allocate_tmp(band_t*, size_t);
+region_t* band_allocate_ref(band_t*, region_t*);
 
 void band_region_free(band_t*, region_t*);
 void band_region_free_raw(band_t*, band_addr_t);
diff --git a/compiler/src/codegen_expr.c b/compiler/src/codegen_expr.c
index a485d40..8c21bbc 100644
--- a/compiler/src/codegen_expr.c
+++ b/compiler/src/codegen_expr.c
@@ -67,6 +67,16 @@ static region_t* codegen_variable_expr(FILE* _, scope_t* scope, struct variable_
         fprintf(stderr, "unknown variable: %s\n", expr.id);
         exit(1);
     }
+
+    if (expr.is_offset) {
+        if (expr.offset >= region->size) {
+            fprintf(stderr, "index out of bounds (%zu >= %zu)\n", expr.offset, region->size);
+            exit(1);
+        }
+
+        region = scope_add_ref(scope, region, expr.offset, 1);
+    }
+
     return region;
 }
 
diff --git a/compiler/src/parser.y b/compiler/src/parser.y
index e72811e..8c6aa42 100644
--- a/compiler/src/parser.y
+++ b/compiler/src/parser.y
@@ -260,6 +260,16 @@ literal:  NUM
 	| arrayliteral
 ;
 
+variable: ID
+		{
+			$$ = variable_expression_new($1);
+		}
+    | ID OPENING_SQ_BRACKETS NUM CLOSING_SQ_BRACKETS
+        {
+            $$ = variable_expression_new_offset($1, $3);
+        }
+;
+
 arrayliteral: OPENING_SQ_BRACKETS NUM CLOSING_SQ_BRACKETS
                 {
                     $$ = literal_expression_array_new($2, NULL);
@@ -273,12 +283,6 @@ arrayliteral: OPENING_SQ_BRACKETS NUM CLOSING_SQ_BRACKETS
                 }
 ;
 
-variable: ID
-		{
-			$$ = variable_expression_new($1);
-		}
-;
-
 macroexpr: ID MACRO_CONTENT
         {
             $$ = macro_expression_new($1, $2);
diff --git a/compiler/src/scope.c b/compiler/src/scope.c
index aa6c486..1ebbc25 100644
--- a/compiler/src/scope.c
+++ b/compiler/src/scope.c
@@ -46,6 +46,14 @@ region_t* scope_add_tmp(scope_t* scope, size_t size) {
     return region;
 }
 
+region_t* scope_add_ref(scope_t* scope, region_t* parent, size_t offset, size_t size) {
+    region_t* region = band_allocate_ref(scope->band, parent);
+    region->start += offset;
+    region->size = size;
+
+    return region;
+}
+
 region_t* scope_get(scope_t* scope, const char* name) {
     region_t* region = dict_get(scope->variables, name);
 
diff --git a/compiler/src/scope.h b/compiler/src/scope.h
index 73bc397..ad7c1b5 100644
--- a/compiler/src/scope.h
+++ b/compiler/src/scope.h
@@ -17,6 +17,7 @@ scope_t* scope_new(scope_t*);
 region_t* scope_add(scope_t*, const char*, size_t);
 region_t* scope_existing(scope_t*, region_t*, const char*);
 region_t* scope_add_tmp(scope_t*, size_t);
+region_t* scope_add_ref(scope_t*, region_t*, size_t, size_t);
 
 region_t* scope_get(scope_t*, const char*);
 
diff --git a/compiler/test/cases/020c-print-array-offset.in b/compiler/test/cases/020c-print-array-offset.in
new file mode 100644
index 0000000..a6b1897
--- /dev/null
+++ b/compiler/test/cases/020c-print-array-offset.in
@@ -0,0 +1,4 @@
+var a = []{'a', 'b', 'c'};
+
+print(a[0], '\n');
+print(a[1], '\n');
\ No newline at end of file
diff --git a/compiler/test/cases/020c-print-array-offset.out b/compiler/test/cases/020c-print-array-offset.out
new file mode 100644
index 0000000..e703ff4
--- /dev/null
+++ b/compiler/test/cases/020c-print-array-offset.out
@@ -0,0 +1,3 @@
+>>>[-]+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>[-]<[-<<<+>>>>+<]>[-<+>]<[-]++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>[-]<[-<<+>>>+<]>[-<+>]<[-]+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>[-]<[-<+>>+<]>[-<+>]
+<[-]++++++++++<<<.>>>.
+[-]++++++++++<<.>>.