[cexpr] Support array indexing

The index is currently limited to ints, and is bounds checked (the array
type has a size field indicating the number of elements).

include/QF/cexpr.h

@@ -87,6 +87,11 @@ typedef struct exprtab_s {
 	struct hashtab_s *tab;
 } exprtab_t;
 
+typedef struct exprarray_s {
+	exprtype_t *type;
+	unsigned    size;
+} exprarray_t;
+
 typedef struct exprctx_s {
 	exprval_t  *result;
 	exprtab_t  *symtab;				// directly accessible symbols
@@ -111,6 +116,8 @@ exprval_t *cexpr_value_reference (exprtype_t *type, void *data, exprctx_t *ctx);
 int cexpr_eval_string (const char *str, exprctx_t *context);
 void cexpr_error(exprctx_t *ctx, const char *fmt, ...) __attribute__((format(PRINTF,2,3)));
 
+void cexpr_array_getelement (const exprval_t *a, const exprval_t *b,
+							 exprval_t *c, exprctx_t *ctx);
 void cexpr_struct_getfield (const exprval_t *a, const exprval_t *b,
 							exprval_t *c, exprctx_t *ctx);
 void cexpr_struct_pointer_getfield (const exprval_t *a, const exprval_t *b,
@@ -137,6 +144,7 @@ extern exprtype_t cexpr_field;
 extern exprtype_t cexpr_function;
 extern exprtype_t cexpr_plitem;
 
+extern binop_t cexpr_array_binops[];
 extern binop_t cexpr_struct_binops[];
 extern binop_t cexpr_struct_pointer_binops[];
 

libs/util/cexpr-vars.c

@@ -37,6 +37,29 @@
 
 #include "libs/util/cexpr-parse.h"
 
+VISIBLE void
+cexpr_array_getelement (const exprval_t *a, const exprval_t *b, exprval_t *c,
+						exprctx_t *ctx)
+{
+	__auto_type array = (exprarray_t *) a->type->data;
+	unsigned    index = *(const unsigned *) b->value;
+	exprval_t *val = 0;
+	if (index < array->size) {
+		val = cmemalloc (ctx->memsuper, sizeof (exprval_t));
+		val->type = array->type;
+		val->value = a->value + array->type->size * index;
+	} else {
+		cexpr_error (ctx, "index %d out of bounds for %s", index,
+					 a->type->name);
+	}
+	*(exprval_t **) c->value = val;
+}
+
+VISIBLE binop_t cexpr_array_binops[] = {
+	{ '[', &cexpr_int, &cexpr_exprval, cexpr_array_getelement },
+	{}
+};
+
 VISIBLE void
 cexpr_struct_getfield (const exprval_t *a, const exprval_t *b, exprval_t *c,
 					   exprctx_t *ctx)

libs/util/test/test-cexpr.c

@@ -32,17 +32,31 @@
 #include "QF/cmem.h"
 #include "QF/hash.h"
 #include "QF/mathlib.h"
+#include "QF/va.h"
 #include "QF/simd/vec4f.h"
 
 int a = 5;
 int b = 6;
 int c;
+int array[4] = { 9, 16, 25, 36 };
 vec4f_t point = { 2, 3, 4, 1 };		// a point, so w = 1
 vec4f_t normal = { 1, 2, 3, 0 };	// a vector, so w = 0
 vec4f_t direction = { 4, 5, 6, 0 };	// a vector, so w = 0
 vec4f_t plane;
 vec4f_t intercept;
 
+exprarray_t int_array_4_data = {
+	&cexpr_int,
+	sizeof (array) / sizeof (array[0]),
+};
+exprtype_t int_array_4 = {
+	"int[4]",
+	4 * sizeof (int),
+	cexpr_array_binops,
+	0,
+	&int_array_4_data,
+};
+
 exprtype_t *vector_params[] = {
 	&cexpr_vector,
 	&cexpr_vector,
@@ -117,6 +131,7 @@ exprfunc_t double_func[] = {
 exprsym_t symbols[] = {
 	{ "a", &cexpr_int, &a },
 	{ "b", &cexpr_int, &b },
+	{ "array", &int_array_4, &array },
 	{ "point", &cexpr_vector, &point },
 	{ "normal", &cexpr_vector, &normal },
 	{ "plane", &cexpr_vector, &plane },
@@ -147,6 +162,7 @@ exprctx_t context = { &test_result, &symtab };
 #define TEST_BINOP(op)													\
 	do {																\
 		c = -4096;														\
+		context.result = &test_result;									\
 		cexpr_eval_string ("a " #op " b", &context);					\
 		printf ("c = a %s b -> %d = %d %s %d\n", #op, c, a, #op, b);	\
 		if (c != (a op b)) {											\
@@ -154,6 +170,17 @@ exprctx_t context = { &test_result, &symtab };
 		}																\
 	} while (0)
 
+#define TEST_ARRAY(ind)													\
+	do {																\
+		c = -4096;														\
+		context.result = &test_result;									\
+		cexpr_eval_string (va (0, "array[%d]", ind), &context);			\
+		printf ("c = array[%d] -> %d = %d\n", ind, c, array[ind]);		\
+		if (c != array[ind]) {											\
+			ret |= 1;													\
+		}																\
+	} while (0)
+
 int
 main(int argc, const char **argv)
 {
@@ -173,6 +200,11 @@ main(int argc, const char **argv)
 	TEST_BINOP (^);
 	TEST_BINOP (%);
 
+	TEST_ARRAY (0);
+	TEST_ARRAY (1);
+	TEST_ARRAY (2);
+	TEST_ARRAY (3);
+
 	context.result = &plane_result;
 	cexpr_eval_string ("point.wzyx", &context);
 	if (plane[0] != point[3] || plane[1] != point[2]