godot/platform/javascript/javascript_eval.cpp

/*************************************************************************/
/*  javascript_eval.cpp                                                  */
/*************************************************************************/
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/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
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#ifdef JAVASCRIPT_EVAL_ENABLED

#include "api/javascript_eval.h"
#include "emscripten.h"

extern "C" EMSCRIPTEN_KEEPALIVE uint8_t *resize_PackedByteArray_and_open_write(PackedByteArray *p_arr, uint8_t **r_write, int p_len) {

	p_arr->resize(p_len);
	*r_write = p_arr->write();
	return r_write->ptr();
}

Variant JavaScript::eval(const String &p_code, bool p_use_global_exec_context) {

	union {
		bool b;
		double d;
		char *s;
	} js_data;

	PackedByteArray arr;
	uint8_t *arr_write;

	/* clang-format off */
	Variant::Type return_type = static_cast<Variant::Type>(EM_ASM_INT({

		const CODE = $0;
		const USE_GLOBAL_EXEC_CONTEXT = $1;
		const PTR = $2;
		const BYTEARRAY_PTR = $3;
		const BYTEARRAY_WRITE_PTR = $4;
		var eval_ret;
		try {
			if (USE_GLOBAL_EXEC_CONTEXT) {
				// indirect eval call grants global execution context
				var global_eval = eval;
				eval_ret = global_eval(UTF8ToString(CODE));
			} else {
				eval_ret = eval(UTF8ToString(CODE));
			}
		} catch (e) {
			err(e);
			eval_ret = null;
		}

		switch (typeof eval_ret) {

			case 'boolean':
				setValue(PTR, eval_ret, 'i32');
				return 1; // BOOL

			case 'number':
				setValue(PTR, eval_ret, 'double');
				return 3; // FLOAT

			case 'string':
				var array_len = lengthBytesUTF8(eval_ret)+1;
				var array_ptr = _malloc(array_len);
				try {
					if (array_ptr===0) {
						throw new Error('String allocation failed (probably out of memory)');
					}
					setValue(PTR, array_ptr , '*');
					stringToUTF8(eval_ret, array_ptr, array_len);
					return 4; // STRING
				} catch (e) {
					if (array_ptr!==0) {
						_free(array_ptr)
					}
					err(e);
					// fall through
				}
				break;

			case 'object':
				if (eval_ret === null) {
					break;
				}

				if (ArrayBuffer.isView(eval_ret) && !(eval_ret instanceof Uint8Array)) {
					eval_ret = new Uint8Array(eval_ret.buffer);
				}
				else if (eval_ret instanceof ArrayBuffer) {
					eval_ret = new Uint8Array(eval_ret);
				}
				if (eval_ret instanceof Uint8Array) {
					var bytes_ptr = ccall('resize_PackedByteArray_and_open_write', 'number', ['number', 'number' ,'number'], [BYTEARRAY_PTR, BYTEARRAY_WRITE_PTR, eval_ret.length]);
					HEAPU8.set(eval_ret, bytes_ptr);
					return 20; // PACKED_BYTE_ARRAY
				}
				break;
		}
		return 0; // NIL

	}, p_code.utf8().get_data(), p_use_global_exec_context, &js_data, &arr, &arr_write));
	/* clang-format on */

	switch (return_type) {
		case Variant::BOOL:
			return js_data.b;
		case Variant::FLOAT:
			return js_data.d;
		case Variant::STRING: {
			String str = String::utf8(js_data.s);
			/* clang-format off */
				EM_ASM_({ _free($0); }, js_data.s);
			/* clang-format on */
			return str;
		}
		case Variant::PACKED_BYTE_ARRAY:
			arr_write = uint8_t * ();
			return arr;
		default:
			return Variant();
	}
}

#endif // JAVASCRIPT_EVAL_ENABLED