V7 is a C/C++ library that implements Javascript engine. It is intended to be embedded into other programs to allow scripting and configuration, but also it could be used as stand-alone JS interpreter in automation scripts. Main V7 design factors are:
- Small size and simplicity. V7 can fit into resource-constrained environments, like firmware, embedded devices, etc. V7 is under 100kb of compiled x86_64 code.
- Easy C/C++ integration. Exporting existing C/C++ functions into V7 and vice versa is easier then for any other embedded language.
- Simple embedding process. V7 could be embedded into existing project simply
by copying two files,
v7.candv7.hand adding few lines of C/C++ code. - Optional standard library with file IO, Crypto, BSD sockets and more
V7 is targeted to conform to the ECMAScript specification version 5.
- V7 enforces strict mode, even if
use strictis not specified in the source code. Benefits of strict mode are outlined here - All strings passed to
v7_exec()functions must be immutable. This is to simplify memory management and reduce memory usage. V7 stores references to variables and functions without making an internal copy.
Please take a look at Smart.js
// Javascript code
var result = foo(1, 2); // Invokes `exported_foo()` glue function
// C code. exported_foo() glues C function "foo" to Javascript.
static enum v7_err exported_foo(struct v7_c_func_arg *cfa) {
if (cfa->num_args != 2) {
// JavaScript code called us with wrong number of arguments,
// signal error
return V7_ERROR;
} else {
// Extract numeric values from JavaScript arguments
double arg0 = v7_number(cfa->args[0]);
double arg1 = v7_number(cfa->args[1]);
double result = foo(arg0, arg1); // Call real foo() function
v7_push_number(cfa->v7, result); // Push result to JavaScript
return V7_OK; // Signal success
}
}
// Export variable "foo" as C function to the root namespace
struct v7 *v7 = v7_create();
v7_set(v7, v7_rootns(v7), "foo", v7_push_func(v7, &exported_foo));
v7_exec_file(v7, "my_js_code.js");
struct v7 *v7 = v7_create();
v7_exec(v7, "var config = load('config.json');"); // Load JSON config
v7_exec(v7, "config.devices[2].name"); // Lookup value
printf("Device2 name: [%s]\n", v7_top_val(v7)->v.str.buf);
struct v7 *v7_create(void); // Creates and initializes V7 engine
void v7_destroy(struct v7 **); // Cleanes up and deallocates V7 engine
enum v7_err v7_exec(struct v7 *, const char *str); // Executes string
enum v7_err v7_exec_file(struct v7 *, const char *path); // Executes file
struct v7_val *v7_rootns(struct v7 *); // Returns global obj (root namespace)
char *v7_stringify(const struct v7_val *v, char *buf, int bsiz);
const char *v7_get_error_string(const struct v7 *); // Returns error string
int v7_is_true(const struct v7_val *);
void v7_copy(struct v7 *v7, struct v7_val *from, struct v7_val *to);
enum v7_err v7_set(struct v7 *, struct v7_val *, const char *, struct v7_val *);
enum v7_err v7_del(struct v7 *, struct v7_val *obj, const char *key);
struct v7_val *v7_get(struct v7_val *obj, const char *key);
struct v7_val *v7_call(struct v7 *v7, struct v7_val *this_obj, int num_args);
struct v7_val *v7_push_number(struct v7 *, double num);
struct v7_val *v7_push_bool(struct v7 *, int is_true);
struct v7_val *v7_push_string(struct v7 *, const char *str, int len, int own);
struct v7_val *v7_push_new_object(struct v7 *);
struct v7_val *v7_push_val(struct v7 *, struct v7_val *);
struct v7_val *v7_push_func(struct v7 *, v7_func_t);
enum v7_type v7_type(const struct v7_val *);
double v7_number(const struct v7_val *);
const char *v7_string(const struct v7_val *, unsigned long *len);
V7 is released under commercial and GNU GPL v.2 open source licenses. The GPLv2 open source License does not generally permit incorporating this software into non-open source programs. For those customers who do not wish to comply with the GPLv2 open source license requirements, Cesanta Software offers a full, royalty-free commercial license and professional support without any of the GPL restrictions.