Merge pull request #2878 from WarriorOfWire/ujson-stream-protocol

ujson: work with mp stream protocol for fast & easy read

Author: tannewt

extmod/modujson.c

@@ -53,6 +53,10 @@ STATIC mp_obj_t mod_ujson_dumps(mp_obj_t obj) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_ujson_dumps_obj, mod_ujson_dumps);
 
+#define JSON_DEBUG(...) (void)0
+// #define JSON_DEBUG(...) mp_printf(&mp_plat_print __VA_OPT__(,) __VA_ARGS__)
+
+
 // The function below implements a simple non-recursive JSON parser.
 //
 // The JSON specification is at http://www.ietf.org/rfc/rfc4627.txt
@@ -80,6 +84,7 @@ typedef struct _ujson_stream_t {
 
 STATIC byte ujson_stream_next(ujson_stream_t *s) {
     mp_uint_t ret = s->read(s->stream_obj, &s->cur, 1, &s->errcode);
+    JSON_DEBUG("  usjon_stream_next err:%2d cur: %c \n", s->errcode, s->cur);
     if (s->errcode != 0) {
         mp_raise_OSError(s->errcode);
     }
@@ -89,9 +94,10 @@ STATIC byte ujson_stream_next(ujson_stream_t *s) {
     return s->cur;
 }
 
-STATIC mp_obj_t mod_ujson_load(mp_obj_t stream_obj) {
+STATIC mp_obj_t _mod_ujson_load(mp_obj_t stream_obj, bool return_first_json) {
     const mp_stream_p_t *stream_p = mp_get_stream_raise(stream_obj, MP_STREAM_OP_READ);
     ujson_stream_t s = {stream_obj, stream_p->read, 0, 0};
+    JSON_DEBUG("got JSON stream\n");
     vstr_t vstr;
     vstr_init(&vstr, 8);
     mp_obj_list_t stack; // we use a list as a simple stack for nested JSON
@@ -262,13 +268,18 @@ STATIC mp_obj_t mod_ujson_load(mp_obj_t stream_obj) {
         }
     }
     success:
-    // eat trailing whitespace
-    while (unichar_isspace(S_CUR(s))) {
-        S_NEXT(s);
-    }
-    if (!S_END(s)) {
-        // unexpected chars
-        goto fail;
+    // It is legal for a stream to have contents after JSON.
+    // E.g., A UART is not closed after receiving an object; in load() we will
+    //   return the first complete JSON object, while in loads() we will retain
+    //   strict adherence to the buffer's complete semantic.
+    if (!return_first_json) {
+        while (unichar_isspace(S_CUR(s))) {
+            S_NEXT(s);
+        }
+        if (!S_END(s)) {
+            // unexpected chars
+            goto fail;
+        }
     }
     if (stack_top == MP_OBJ_NULL || stack.len != 0) {
         // not exactly 1 object
@@ -280,14 +291,18 @@ STATIC mp_obj_t mod_ujson_load(mp_obj_t stream_obj) {
     fail:
     mp_raise_ValueError(translate("syntax error in JSON"));
 }
+
+STATIC mp_obj_t mod_ujson_load(mp_obj_t stream_obj) {
+    return _mod_ujson_load(stream_obj, true);
+}
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_ujson_load_obj, mod_ujson_load);
 
 STATIC mp_obj_t mod_ujson_loads(mp_obj_t obj) {
     size_t len;
     const char *buf = mp_obj_str_get_data(obj, &len);
     vstr_t vstr = {len, len, (char*)buf, true};
     mp_obj_stringio_t sio = {{&mp_type_stringio}, &vstr, 0, MP_OBJ_NULL};
-    return mod_ujson_load(MP_OBJ_FROM_PTR(&sio));
+    return _mod_ujson_load(MP_OBJ_FROM_PTR(&sio), false);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_ujson_loads_obj, mod_ujson_loads);
 

ports/atmel-samd/common-hal/busio/UART.c

@@ -45,6 +45,9 @@
 
 #include "samd/sercom.h"
 
+#define UART_DEBUG(...) (void)0
+// #define UART_DEBUG(...) mp_printf(&mp_plat_print __VA_OPT__(,) __VA_ARGS__)
+
 // Do-nothing callback needed so that usart_async code will enable rx interrupts.
 // See comment below re usart_async_register_callback()
 static void usart_async_rxc_callback(const struct usart_async_descriptor *const descr) {

shared-bindings/busio/UART.c

@@ -39,6 +39,9 @@
 #include "py/stream.h"
 #include "supervisor/shared/translate.h"
 
+#define STREAM_DEBUG(...) (void)0
+// #define STREAM_DEBUG(...) mp_printf(&mp_plat_print __VA_OPT__(,) __VA_ARGS__)
+
 
 //| .. currentmodule:: busio
 //|
@@ -219,6 +222,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(busio_uart___exit___obj, 4, 4, busio_
 
 // These three methods are used by the shared stream methods.
 STATIC mp_uint_t busio_uart_read(mp_obj_t self_in, void *buf_in, mp_uint_t size, int *errcode) {
+    STREAM_DEBUG("busio_uart_read stream %d\n", size);
     busio_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
     check_for_deinit(self);
     byte *buf = buf_in;