handle reads/writes larger than buffers; add .write_timeout

shared-bindings/usb_cdc/Serial.c

@@ -56,7 +56,7 @@
 //|         :rtype: bytes"""
 //|         ...
 //|
-//|     def readinto(self, buf: WriteableBuffer) -> bytes:
+//|     def readinto(self, buf: WriteableBuffer) -> int:
 //|         """Read bytes into the ``buf``.  If ``nbytes`` is specified then read at most
 //|         that many bytes, subject to `timeout`.  Otherwise, read at most ``len(buf)`` bytes.
 //|
@@ -219,6 +219,33 @@ const mp_obj_property_t usb_cdc_serial_timeout_obj = {
               (mp_obj_t)&mp_const_none_obj},
 };
 
+//|     write_timeout: Optional[float]
+//|     """The initial value of `write_timeout` is ``None``. If ``None``, wait indefinitely to finish
+//|     writing all the bytes passed to ``write()``.If 0, do not wait.
+//|     If > 0, wait only ``write_timeout`` seconds."""
+//|
+STATIC mp_obj_t usb_cdc_serial_get_write_timeout(mp_obj_t self_in) {
+    usb_cdc_serial_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_float_t write_timeout = common_hal_usb_cdc_serial_get_write_timeout(self);
+    return (write_timeout < 0.0f) ? mp_const_none : mp_obj_new_float(self->write_timeout);
+}
+MP_DEFINE_CONST_FUN_OBJ_1(usb_cdc_serial_get_write_timeout_obj, usb_cdc_serial_get_write_timeout);
+
+STATIC mp_obj_t usb_cdc_serial_set_write_timeout(mp_obj_t self_in, mp_obj_t write_timeout_in) {
+    usb_cdc_serial_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    common_hal_usb_cdc_serial_set_write_timeout(self,
+        write_timeout_in == mp_const_none ? -1.0f : mp_obj_get_float(write_timeout_in));
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_2(usb_cdc_serial_set_write_timeout_obj, usb_cdc_serial_set_write_timeout);
+
+const mp_obj_property_t usb_cdc_serial_write_timeout_obj = {
+    .base.type = &mp_type_property,
+    .proxy = {(mp_obj_t)&usb_cdc_serial_get_write_timeout_obj,
+              (mp_obj_t)&usb_cdc_serial_set_write_timeout_obj,
+              (mp_obj_t)&mp_const_none_obj},
+};
+
 
 STATIC const mp_rom_map_elem_t usb_cdc_serial_locals_dict_table[] = {
     // Standard stream methods.
@@ -235,6 +262,7 @@ STATIC const mp_rom_map_elem_t usb_cdc_serial_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_reset_input_buffer),  MP_ROM_PTR(&usb_cdc_serial_reset_input_buffer_obj) },
     { MP_OBJ_NEW_QSTR(MP_QSTR_reset_output_buffer), MP_ROM_PTR(&usb_cdc_serial_reset_output_buffer_obj) },
     { MP_OBJ_NEW_QSTR(MP_QSTR_timeout),             MP_ROM_PTR(&usb_cdc_serial_timeout_obj) },
+    { MP_OBJ_NEW_QSTR(MP_QSTR_write_timeout),       MP_ROM_PTR(&usb_cdc_serial_write_timeout_obj) },
 
     // Not in pyserial protocol.
     { MP_OBJ_NEW_QSTR(MP_QSTR_connected),     MP_ROM_PTR(&usb_cdc_serial_connected_obj) },

shared-bindings/usb_cdc/Serial.h

@@ -47,4 +47,7 @@ extern bool common_hal_usb_cdc_serial_get_connected(usb_cdc_serial_obj_t *self);
 extern mp_float_t common_hal_usb_cdc_serial_get_timeout(usb_cdc_serial_obj_t *self);
 extern void common_hal_usb_cdc_serial_set_timeout(usb_cdc_serial_obj_t *self, mp_float_t timeout);
 
+extern mp_float_t common_hal_usb_cdc_serial_get_write_timeout(usb_cdc_serial_obj_t *self);
+extern void common_hal_usb_cdc_serial_set_write_timeout(usb_cdc_serial_obj_t *self, mp_float_t write_timeout);
+
 #endif  // MICROPY_INCLUDED_SHARED_BINDINGS_USB_CDC_SERIAL_H

shared-module/usb_cdc/Serial.c

@@ -31,32 +31,78 @@
 #include "tusb.h"
 
 size_t common_hal_usb_cdc_serial_read(usb_cdc_serial_obj_t *self, uint8_t *data, size_t len, int *errcode) {
-    if (self->timeout < 0.0f) {
-        while (tud_cdc_n_available(self->idx) < len) {
-            RUN_BACKGROUND_TASKS;
-            if (mp_hal_is_interrupted()) {
-                return 0;
-            }
-        }
-    } else if (self->timeout > 0.0f) {
-        uint64_t timeout_ms = self->timeout * 1000;
+
+    const bool wait_forever = self->timeout < 0.0f;
+    const bool wait_for_timeout = self->timeout > 0.0f;
+
+    // Read up to len bytes immediately.
+    // The number of bytes read will not be larger than what is already in the TinyUSB FIFO.
+    uint32_t total_num_read = tud_cdc_n_read(self->idx, data, len);
+
+    if (wait_forever || wait_for_timeout) {
+        // Read more if we have time.
+        uint64_t timeout_ms = self->timeout * 1000;  // Junk value if timeout < 0.
         uint64_t start_ticks = supervisor_ticks_ms64();
-        while (tud_cdc_n_available(self->idx) < len &&
-               supervisor_ticks_ms64() - start_ticks <= timeout_ms) {
+
+        uint32_t num_read = 0;
+        while (total_num_read < len &&
+               (wait_forever || supervisor_ticks_ms64() - start_ticks <= timeout_ms)) {
+
+            // Wait for a bit, and check for ctrl-C.
             RUN_BACKGROUND_TASKS;
             if (mp_hal_is_interrupted()) {
                 return 0;
             }
+
+            // Advance buffer pointer and reduce number of bytes that need to be read.
+            len -= num_read;
+            data += num_read;
+
+            // Try to read another batch of bytes.
+            num_read = tud_cdc_n_read(self->idx, data, len);
+            total_num_read += num_read;
         }
     }
-    // Timeout of 0.0f falls through to here with no waiting or unnecessary calculation.
-    return tud_cdc_n_read(self->idx, data, len);
+
+    return total_num_read;
 }
 
 size_t common_hal_usb_cdc_serial_write(usb_cdc_serial_obj_t *self, const uint8_t *data, size_t len, int *errcode) {
-    uint32_t num_written = tud_cdc_n_write(self->idx, data, len);
+    const bool wait_forever = self->write_timeout < 0.0f;
+    const bool wait_for_timeout = self->write_timeout > 0.0f;
+
+    // Write as many bytes as possible immediately.
+    // The number of bytes written at once will not be larger than what can fit in the TinyUSB FIFO.
+    uint32_t total_num_written = tud_cdc_n_write(self->idx, data, len);
     tud_cdc_n_write_flush(self->idx);
-    return num_written;
+
+    if (wait_forever || wait_for_timeout) {
+        // Write more if we have time.
+        uint64_t timeout_ms = self->write_timeout * 1000;  // Junk value if write_timeout < 0.
+        uint64_t start_ticks = supervisor_ticks_ms64();
+
+        uint32_t num_written = 0;
+        while (total_num_written < len &&
+               (wait_forever || supervisor_ticks_ms64() - start_ticks <= timeout_ms)) {
+
+            // Wait for a bit, and check for ctrl-C.
+            RUN_BACKGROUND_TASKS;
+            if (mp_hal_is_interrupted()) {
+                return 0;
+            }
+
+            // Advance buffer pointer and reduce number of bytes that need to be written.
+            len -= num_written;
+            data += num_written;
+
+            // Try to write another batch of bytes.
+            num_written = tud_cdc_n_write(self->idx, data, len);
+            tud_cdc_n_write_flush(self->idx);
+            total_num_written += num_written;
+        }
+    }
+
+    return total_num_written;
 }
 
 uint32_t common_hal_usb_cdc_serial_get_in_waiting(usb_cdc_serial_obj_t *self) {
@@ -91,3 +137,11 @@ mp_float_t common_hal_usb_cdc_serial_get_timeout(usb_cdc_serial_obj_t *self) {
 void common_hal_usb_cdc_serial_set_timeout(usb_cdc_serial_obj_t *self, mp_float_t timeout) {
     self->timeout = timeout;
 }
+
+mp_float_t common_hal_usb_cdc_serial_get_write_timeout(usb_cdc_serial_obj_t *self) {
+    return self->write_timeout;
+}
+
+void common_hal_usb_cdc_serial_set_write_timeout(usb_cdc_serial_obj_t *self, mp_float_t write_timeout) {
+    self->write_timeout = write_timeout;
+}

shared-module/usb_cdc/Serial.h

@@ -31,8 +31,9 @@
 
 typedef struct {
     mp_obj_base_t base;
-    mp_float_t timeout;    // if negative, wait forever.
-    uint8_t idx;           // which CDC device?
+    mp_float_t timeout;       // if negative, wait forever.
+    mp_float_t write_timeout; // if negative, wait forever.
+    uint8_t idx;              // which CDC device?
 } usb_cdc_serial_obj_t;
 
 #endif // SHARED_MODULE_USB_CDC_SERIAL_H

shared-module/usb_cdc/__init__.c

@@ -41,10 +41,12 @@
 static usb_cdc_serial_obj_t serial_objs[CFG_TUD_CDC] = {
     {   .base.type = &usb_cdc_serial_type,
         .timeout = -1.0f,
+        .write_timeout = -1.0f,
         .idx = 0,
     }, {
         .base.type = &usb_cdc_serial_type,
         .timeout = -1.0f,
+        .write_timeout = -1.0f,
         .idx = 1,
     }
 };