/*
* Duktape 1.x compatible module loading framework
*/
#include "duktape.h"
#include "duk_module_duktape.h"
/* (v)snprintf() is missing before MSVC 2015. Note that _(v)snprintf() does
* NOT NUL terminate on truncation, but that's OK here.
* http://stackoverflow.com/questions/2915672/snprintf-and-visual-studio-2010
*/
#if defined(_MSC_VER) && (_MSC_VER < 1900)
#define snprintf _snprintf
#endif
#if 0 /* Enable manually */
#define DUK__ASSERT(x) do { \
if (!(x)) { \
fprintf(stderr, "ASSERTION FAILED at %s:%d: " #x "\n", __FILE__, __LINE__); \
fflush(stderr); \
} \
} while (0)
#define DUK__ASSERT_TOP(ctx,val) do { \
DUK__ASSERT(duk_get_top((ctx)) == (val)); \
} while (0)
#else
#define DUK__ASSERT(x) do { (void) (x); } while (0)
#define DUK__ASSERT_TOP(ctx,val) do { (void) ctx; (void) (val); } while (0)
#endif
static void duk__resolve_module_id(duk_context *ctx, const char *req_id, const char *mod_id) {
duk_uint8_t buf[DUK_COMMONJS_MODULE_ID_LIMIT];
duk_uint8_t *p;
duk_uint8_t *q;
duk_uint8_t *q_last; /* last component */
duk_int_t int_rc;
DUK__ASSERT(req_id != NULL);
/* mod_id may be NULL */
/*
* A few notes on the algorithm:
*
* - Terms are not allowed to begin with a period unless the term
* is either '.' or '..'. This simplifies implementation (and
* is within CommonJS modules specification).
*
* - There are few output bound checks here. This is on purpose:
* the resolution input is length checked and the output is never
* longer than the input. The resolved output is written directly
* over the input because it's never longer than the input at any
* point in the algorithm.
*
* - Non-ASCII characters are processed as individual bytes and
* need no special treatment. However, U+0000 terminates the
* algorithm; this is not an issue because U+0000 is not a
* desirable term character anyway.
*/
/*
* Set up the resolution input which is the requested ID directly
* (if absolute or no current module path) or with current module
* ID prepended (if relative and current module path exists).
*
* Suppose current module is 'foo/bar' and relative path is './quux'.
* The 'bar' component must be replaced so the initial input here is
* 'foo/bar/.././quux'.
*/
if (mod_id != NULL && req_id[0] == '.') {
int_rc = snprintf((char *) buf, sizeof(buf), "%s/../%s", mod_id, req_id);
} else {
int_rc = snprintf((char *) buf, sizeof(buf), "%s", req_id);
}
if (int_rc >= (duk_int_t) sizeof(buf) || int_rc < 0) {
/* Potentially truncated, NUL not guaranteed in any case.
* The (int_rc < 0) case should not occur in practice.
*/
goto resolve_error;
}
DUK__ASSERT(strlen((const char *) buf) < sizeof(buf)); /* at most sizeof(buf) - 1 */
/*
* Resolution loop. At the top of the loop we're expecting a valid
* term: '.', '..', or a non-empty identifier not starting with a period.
*/
p = buf;
q = buf;
for (;;) {
duk_uint_fast8_t c;
/* Here 'p' always points to the start of a term.
*
* We can also unconditionally reset q_last here: if this is
* the last (non-empty) term q_last will have the right value
* on loop exit.
*/
DUK__ASSERT(p >= q); /* output is never longer than input during resolution */
q_last = q;
c = *p++;
if (c == 0) {
goto resolve_error;
} else if (c == '.') {
c = *p++;
if (c == '/') {
/* Term was '.' and is eaten entirely (including dup slashes). */
goto eat_dup_slashes;
}
if (c == '.' && *p == '/') {
/* Term was '..', backtrack resolved name by one component.
* q[-1] = previous slash (or beyond start of buffer)
* q[-2] = last char of previous component (or beyond start of buffer)
*/
p++; /* eat (first) input slash */
DUK__ASSERT(q >= buf);
if (q == buf) {
goto resolve_error;
}
DUK__ASSERT(*(q - 1) == '/');
q--; /* Backtrack to last output slash (dups already eliminated). */
for (;;) {
/* Backtrack to previous slash or start of buffer. */
DUK__ASSERT(q >= buf);
if (q == buf) {
break;
}
if (*(q - 1) == '/') {
break;
}
q--;
}
goto eat_dup_slashes;
}
goto resolve_error;
} else if (c == '/') {
/* e.g. require('/foo'), empty terms not allowed */
goto resolve_error;
} else {
for (;;) {
/* Copy term name until end or '/'. */
*q++ = c;
c = *p++;
if (c == 0) {
/* This was the last term, and q_last was
* updated to match this term at loop top.
*/
goto loop_done;
} else if (c == '/') {
*q++ = '/';
break;
} else {
/* write on next loop */
}
}
}
eat_dup_slashes:
for (;;) {
/* eat dup slashes */
c = *p;
if (c != '/') {
break;
}
p++;
}
}
loop_done:
/* Output #1: resolved absolute name. */
DUK__ASSERT(q >= buf);
duk_push_lstring(ctx, (const char *) buf, (size_t) (q - buf));
/* Output #2: last component name. */
DUK__ASSERT(q >= q_last);
DUK__ASSERT(q_last >= buf);
duk_push_lstring(ctx, (const char *) q_last, (size_t) (q - q_last));
return;
resolve_error:
(void) duk_type_error(ctx, "cannot resolve module id: %s", (const char *) req_id);
}
/* Stack indices for better readability. */
#define DUK__IDX_REQUESTED_ID 0 /* module id requested */
#define DUK__IDX_REQUIRE 1 /* current require() function */
#define DUK__IDX_REQUIRE_ID 2 /* the base ID of the current require() function, resolution base */
#define DUK__IDX_RESOLVED_ID 3 /* resolved, normalized absolute module ID */
#define DUK__IDX_LASTCOMP 4 /* last component name in resolved path */
#define DUK__IDX_DUKTAPE 5 /* Duktape object */
#define DUK__IDX_MODLOADED 6 /* Duktape.modLoaded[] module cache */
#define DUK__IDX_UNDEFINED 7 /* 'undefined', artifact of lookup */
#define DUK__IDX_FRESH_REQUIRE 8 /* new require() function for module, updated resolution base */
#define DUK__IDX_EXPORTS 9 /* default exports table */
#define DUK__IDX_MODULE 10 /* module object containing module.exports, etc */
static duk_ret_t duk__require(duk_context *ctx) {
const char *str_req_id; /* requested identifier */
const char *str_mod_id; /* require.id of current module */
duk_int_t pcall_rc;
/* NOTE: we try to minimize code size by avoiding unnecessary pops,
* so the stack looks a bit cluttered in this function. DUK__ASSERT_TOP()
* assertions are used to ensure stack configuration is correct at each
* step.
*/
/*
* Resolve module identifier into canonical absolute form.
*/
str_req_id = duk_require_string(ctx, DUK__IDX_REQUESTED_ID);
duk_push_current_function(ctx);
duk_get_prop_string(ctx, -1, "id");
str_mod_id = duk_get_string(ctx, DUK__IDX_REQUIRE_ID); /* ignore non-strings */
duk__resolve_module_id(ctx, str_req_id, str_mod_id);
str_req_id = NULL;
str_mod_id = NULL;
/* [ requested_id require require.id resolved_id last_comp ] */
DUK__ASSERT_TOP(ctx, DUK__IDX_LASTCOMP + 1);
/*
* Cached module check.
*
* If module has been loaded or its loading has already begun without
* finishing, return the same cached value (module.exports). The
* value is registered when module load starts so that circular
* references can be supported to some extent.
*/
duk_push_global_stash(ctx);
duk_get_prop_string(ctx, -1, "\xff" "module:Duktape");
duk_remove(ctx, -2); /* Lookup stashed, original 'Duktape' object. */
duk_get_prop_string(ctx, DUK__IDX_DUKTAPE, "modLoaded"); /* Duktape.modLoaded */
duk_require_type_mask(ctx, DUK__IDX_MODLOADED, DUK_TYPE_MASK_OBJECT);
DUK__ASSERT_TOP(ctx, DUK__IDX_MODLOADED + 1);
duk_dup(ctx, DUK__IDX_RESOLVED_ID);
if (duk_get_prop(ctx, DUK__IDX_MODLOADED)) {
/* [ requested_id require require.id resolved_id last_comp Duktape Duktape.modLoaded Duktape.modLoaded[id] ] */
duk_get_prop_string(ctx, -1, "exports"); /* return module.exports */
return 1;
}
DUK__ASSERT_TOP(ctx, DUK__IDX_UNDEFINED + 1);
/* [ requested_id require require.id resolved_id last_comp Duktape Duktape.modLoaded undefined ] */
/*
* Module not loaded (and loading not started previously).
*
* Create a new require() function with 'id' set to resolved ID
* of module being loaded. Also create 'exports' and 'module'
* tables but don't register exports to the loaded table yet.
* We don't want to do that unless the user module search callbacks
* succeeds in finding the module.
*/
/* Fresh require: require.id is left configurable (but not writable)
* so that is not easy to accidentally tweak it, but it can still be
* done with Object.defineProperty().
*
* XXX: require.id could also be just made non-configurable, as there
* is no practical reason to touch it (at least from Ecmascript code).
*/
duk_push_c_function(ctx, duk__require, 1 /*nargs*/);
duk_push_string(ctx, "name");
duk_push_string(ctx, "require");
duk_def_prop(ctx, DUK__IDX_FRESH_REQUIRE, DUK_DEFPROP_HAVE_VALUE); /* not writable, not enumerable, not configurable */
duk_push_string(ctx, "id");
duk_dup(ctx, DUK__IDX_RESOLVED_ID);
duk_def_prop(ctx, DUK__IDX_FRESH_REQUIRE, DUK_DEFPROP_HAVE_VALUE | DUK_DEFPROP_SET_CONFIGURABLE); /* a fresh require() with require.id = resolved target module id */
/* Module table:
* - module.exports: initial exports table (may be replaced by user)
* - module.id is non-writable and non-configurable, as the CommonJS
* spec suggests this if possible
* - module.filename: not set, defaults to resolved ID if not explicitly
* set by modSearch() (note capitalization, not .fileName, matches Node.js)
* - module.name: not set, defaults to last component of resolved ID if
* not explicitly set by modSearch()
*/
duk_push_object(ctx); /* exports */
duk_push_object(ctx); /* module */
duk_push_string(ctx, "exports");
duk_dup(ctx, DUK__IDX_EXPORTS);
duk_def_prop(ctx, DUK__IDX_MODULE, DUK_DEFPROP_HAVE_VALUE | DUK_DEFPROP_SET_WRITABLE | DUK_DEFPROP_SET_CONFIGURABLE); /* module.exports = exports */
duk_push_string(ctx, "id");
duk_dup(ctx, DUK__IDX_RESOLVED_ID); /* resolved id: require(id) must return this same module */
duk_def_prop(ctx, DUK__IDX_MODULE, DUK_DEFPROP_HAVE_VALUE); /* module.id = resolved_id; not writable, not enumerable, not configurable */
duk_compact(ctx, DUK__IDX_MODULE); /* module table remains registered to modLoaded, minimize its size */
DUK__ASSERT_TOP(ctx, DUK__IDX_MODULE + 1);
/* [ requested_id require require.id resolved_id last_comp Duktape Duktape.modLoaded undefined fresh_require exports module ] */
/* Register the module table early to modLoaded[] so that we can
* support circular references even in modSearch(). If an error
* is thrown, we'll delete the reference.
*/
duk_dup(ctx, DUK__IDX_RESOLVED_ID);
duk_dup(ctx, DUK__IDX_MODULE);
duk_put_prop(ctx, DUK__IDX_MODLOADED); /* Duktape.modLoaded[resolved_id] = module */
/*
* Call user provided module search function and build the wrapped
* module source code (if necessary). The module search function
* can be used to implement pure Ecmacsript, pure C, and mixed
* Ecmascript/C modules.
*
* The module search function can operate on the exports table directly
* (e.g. DLL code can register values to it). It can also return a
* string which is interpreted as module source code (if a non-string
* is returned the module is assumed to be a pure C one). If a module
* cannot be found, an error must be thrown by the user callback.
*
* Because Duktape.modLoaded[] already contains the module being
* loaded, circular references for C modules should also work
* (although expected to be quite rare).
*/
duk_push_string(ctx, "(function(require,exports,module){");
/* Duktape.modSearch(resolved_id, fresh_require, exports, module). */
duk_get_prop_string(ctx, DUK__IDX_DUKTAPE, "modSearch"); /* Duktape.modSearch */
duk_dup(ctx, DUK__IDX_RESOLVED_ID);
duk_dup(ctx, DUK__IDX_FRESH_REQUIRE);
duk_dup(ctx, DUK__IDX_EXPORTS);
duk_dup(ctx, DUK__IDX_MODULE); /* [ ... Duktape.modSearch resolved_id last_comp fresh_require exports module ] */
pcall_rc = duk_pcall(ctx, 4 /*nargs*/); /* -> [ ... source ] */
DUK__ASSERT_TOP(ctx, DUK__IDX_MODULE + 3);
if (pcall_rc != DUK_EXEC_SUCCESS) {
/* Delete entry in Duktape.modLoaded[] and rethrow. */
goto delete_rethrow;
}
/* If user callback did not return source code, module loading
* is finished (user callback initialized exports table directly).
*/
if (!duk_is_string(ctx, -1)) {
/* User callback did not return source code, so module loading
* is finished: just update modLoaded with final module.exports
* and we're done.
*/
goto return_exports;
}
/* Finish the wrapped module source. Force module.filename as the
* function .fileName so it gets set for functions defined within a
* module. This also ensures loggers created within the module get
* the module ID (or overridden filename) as their default logger name.
* (Note capitalization: .filename matches Node.js while .fileName is
* used elsewhere in Duktape.)
*/
duk_push_string(ctx, "\n})"); /* Newline allows module last line to contain a // comment. */
duk_concat(ctx, 3);
if (!duk_get_prop_string(ctx, DUK__IDX_MODULE, "filename")) {
/* module.filename for .fileName, default to resolved ID if
* not present.
*/
duk_pop(ctx);
duk_dup(ctx, DUK__IDX_RESOLVED_ID);
}
pcall_rc = duk_pcompile(ctx, DUK_COMPILE_EVAL);
if (pcall_rc != DUK_EXEC_SUCCESS) {
goto delete_rethrow;
}
pcall_rc = duk_pcall(ctx, 0); /* -> eval'd function wrapper (not called yet) */
if (pcall_rc != DUK_EXEC_SUCCESS) {
goto delete_rethrow;
}
/* Module has now evaluated to a wrapped module function. Force its
* .name to match module.name (defaults to last component of resolved
* ID) so that it is shown in stack traces too. Note that we must not
* introduce an actual name binding into the function scope (which is
* usually the case with a named function) because it would affect the
* scope seen by the module and shadow accesses to globals of the same name.
* This is now done by compiling the function as anonymous and then forcing
* its .name without setting a "has name binding" flag.
*/
duk_push_string(ctx, "name");
if (!duk_get_prop_string(ctx, DUK__IDX_MODULE, "name")) {
/* module.name for .name, default to last component if
* not present.
*/
duk_pop(ctx);
duk_dup(ctx, DUK__IDX_LASTCOMP);
}
duk_def_prop(ctx, -3, DUK_DEFPROP_HAVE_VALUE | DUK_DEFPROP_FORCE);
/*
* Call the wrapped module function.
*
* Use a protected call so that we can update Duktape.modLoaded[resolved_id]
* even if the module throws an error.
*/
/* [ requested_id require require.id resolved_id last_comp Duktape Duktape.modLoaded undefined fresh_require exports module mod_func ] */
DUK__ASSERT_TOP(ctx, DUK__IDX_MODULE + 2);
duk_dup(ctx, DUK__IDX_EXPORTS); /* exports (this binding) */
duk_dup(ctx, DUK__IDX_FRESH_REQUIRE); /* fresh require (argument) */
duk_get_prop_string(ctx, DUK__IDX_MODULE, "exports"); /* relookup exports from module.exports in case it was changed by modSearch */
duk_dup(ctx, DUK__IDX_MODULE); /* module (argument) */
DUK__ASSERT_TOP(ctx, DUK__IDX_MODULE + 6);
/* [ requested_id require require.id resolved_id last_comp Duktape Duktape.modLoaded undefined fresh_require exports module mod_func exports fresh_require exports module ] */
pcall_rc = duk_pcall_method(ctx, 3 /*nargs*/);
if (pcall_rc != DUK_EXEC_SUCCESS) {
/* Module loading failed. Node.js will forget the module
* registration so that another require() will try to load
* the module again. Mimic that behavior.
*/
goto delete_rethrow;
}
/* [ requested_id require require.id resolved_id last_comp Duktape Duktape.modLoaded undefined fresh_require exports module result(ignored) ] */
DUK__ASSERT_TOP(ctx, DUK__IDX_MODULE + 2);
/* fall through */
return_exports:
duk_get_prop_string(ctx, DUK__IDX_MODULE, "exports");
duk_compact(ctx, -1); /* compact the exports table */
return 1; /* return module.exports */
delete_rethrow:
duk_dup(ctx, DUK__IDX_RESOLVED_ID);
duk_del_prop(ctx, DUK__IDX_MODLOADED); /* delete Duktape.modLoaded[resolved_id] */
(void) duk_throw(ctx); /* rethrow original error */
return 0; /* not reachable */
}
void duk_module_duktape_init(duk_context *ctx) {
/* Stash 'Duktape' in case it's modified. */
duk_push_global_stash(ctx);
duk_get_global_string(ctx, "Duktape");
duk_put_prop_string(ctx, -2, "\xff" "module:Duktape");
duk_pop(ctx);
/* Register `require` as a global function. */
duk_eval_string(ctx,
"(function(req){"
"var D=Object.defineProperty;"
"D(req,'name',{value:'require'});"
"D(this,'require',{value:req,writable:true,configurable:true});"
"D(Duktape,'modLoaded',{value:Object.create(null),writable:true,configurable:true});"
"})");
duk_push_c_function(ctx, duk__require, 1 /*nargs*/);
duk_call(ctx, 1);
duk_pop(ctx);
}
#undef DUK__ASSERT
#undef DUK__ASSERT_TOP
#undef DUK__IDX_REQUESTED_ID
#undef DUK__IDX_REQUIRE
#undef DUK__IDX_REQUIRE_ID
#undef DUK__IDX_RESOLVED_ID
#undef DUK__IDX_LASTCOMP
#undef DUK__IDX_DUKTAPE
#undef DUK__IDX_MODLOADED
#undef DUK__IDX_UNDEFINED
#undef DUK__IDX_FRESH_REQUIRE
#undef DUK__IDX_EXPORTS
#undef DUK__IDX_MODULE
