webassembly: Use POSIX write for output and add stderr.

All output is now handled by Emscripten's stdio facility.

Signed-off-by: Damien George <damien@micropython.org>

ports/webassembly/library.js

@@ -25,16 +25,6 @@
  */
 
 mergeInto(LibraryManager.library, {
-    mp_js_write: function(ptr, len) {
-        const buffer = HEAPU8.subarray(ptr, ptr + len)
-        if (ENVIRONMENT_IS_NODE) {
-            process.stdout.write(buffer);
-        } else {
-            const printEvent = new CustomEvent('micropython-print', { detail: buffer });
-            document.dispatchEvent(printEvent);
-        }
-    },
-
     // This string will be emitted directly into the output file by Emscripten.
     mp_js_ticks_ms__postset: "var MP_JS_EPOCH = Date.now()",
 

ports/webassembly/mpconfigport.h

@@ -46,6 +46,7 @@
 #define MICROPY_LONGINT_IMPL        (MICROPY_LONGINT_IMPL_MPZ)
 #define MICROPY_ENABLE_DOC_STRING   (1)
 #define MICROPY_WARNINGS            (1)
+#define MICROPY_ERROR_PRINTER       (&mp_stderr_print)
 #define MICROPY_FLOAT_IMPL          (MICROPY_FLOAT_IMPL_DOUBLE)
 #define MICROPY_USE_INTERNAL_ERRNO  (1)
 #define MICROPY_USE_INTERNAL_PRINTF (0)
@@ -60,7 +61,6 @@
 #endif
 #define MICROPY_VFS_POSIX           (MICROPY_VFS)
 #define MICROPY_PY_SYS_PLATFORM     "webassembly"
-#define MICROPY_PY_SYS_STDFILES     (0)
 
 #define MICROPY_EVENT_POLL_HOOK \
     do { \
@@ -102,4 +102,6 @@ typedef long mp_off_t;
 #define _GNU_SOURCE
 #endif
 
+extern const struct _mp_print_t mp_stderr_print;
+
 uint32_t mp_js_random_u32(void);

ports/webassembly/mphalport.c

@@ -24,12 +24,19 @@
  * THE SOFTWARE.
  */
 
+#include <unistd.h>
 #include "library.h"
 #include "mphalport.h"
 
+static void stderr_print_strn(void *env, const char *str, size_t len) {
+    (void)env;
+    write(2, str, len);
+}
+
+const mp_print_t mp_stderr_print = {NULL, stderr_print_strn};
+
 mp_uint_t mp_hal_stdout_tx_strn(const char *str, size_t len) {
-    mp_js_write(str, len);
-    return len;
+    return write(1, str, len);
 }
 
 void mp_hal_delay_ms(mp_uint_t ms) {