[USB CDC] Some speed improvements

Added bulk read method readBytes and improved read and peek methods.

Author: makarenya

cores/arduino/Stream.h

@@ -94,7 +94,7 @@ class Stream : public Print
   float parseFloat(LookaheadMode lookahead = SKIP_ALL, char ignore = NO_IGNORE_CHAR);
   // float version of parseInt
 
-  size_t readBytes( char *buffer, size_t length); // read chars from stream into buffer
+  virtual size_t readBytes( char *buffer, size_t length); // read chars from stream into buffer
   size_t readBytes( uint8_t *buffer, size_t length) { return readBytes((char *)buffer, length); }
   // terminates if length characters have been read or timeout (see setTimeout)
   // returns the number of characters placed in the buffer (0 means no valid data found)

cores/arduino/USBSerial.cpp

@@ -24,7 +24,6 @@
 #include "usbd_desc.h"
 #include "wiring.h"
 
-#define USB_TIMEOUT 50
 /* USB Device Core handle declaration */
 extern USBD_HandleTypeDef hUSBD_Device_CDC;
 extern __IO  uint32_t lineState;
@@ -91,24 +90,26 @@ int USBSerial::available(void) {
 }
 
 int USBSerial::read(void) {
-  // Empty ReceiveQueue - nothing to return
-  if (CDC_ReceiveQueue_ReadSize(&ReceiveQueue) <= 0) {
-    return -1;
-  }
   // Dequeue only one char from queue
   // TS: it safe, because only main thread affects ReceiveQueue->read pos
-  char ch = CDC_ReceiveQueue_Dequeue(&ReceiveQueue);
+  auto ch = CDC_ReceiveQueue_Dequeue(&ReceiveQueue);
   // Resume receive process, if possible
   CDC_resume_receive();
   return ch;
 }
 
+size_t USBSerial::readBytes(char *buffer, size_t length) {
+  auto rest = static_cast<uint16_t>(length);
+  _startMillis = millis();
+  do {
+    rest -= CDC_ReceiveQueue_Read(&ReceiveQueue, reinterpret_cast<uint8_t*>(buffer), rest);
+    if (rest == 0) return length;
+  } while(millis() - _startMillis < _timeout);
+  return length - rest;
+}
+
 int USBSerial::peek(void)
 {
-  // Empty ReceiveQueue - nothing to return
-  if (CDC_ReceiveQueue_ReadSize(&ReceiveQueue) <= 0) {
-    return -1;
-  }
   // Peek one symbol, it can't change receive avaiablity
   return CDC_ReceiveQueue_Peek(&ReceiveQueue);
 }

cores/arduino/USBSerial.h

@@ -36,6 +36,7 @@ class USBSerial : public Stream {
     virtual int availableForWrite(void);
     virtual int peek(void);
     virtual int read(void);
+    virtual size_t readBytes( char *buffer, size_t length); // read chars from stream into buffer
     virtual void flush(void);
     virtual size_t write(uint8_t);
     virtual size_t write(const uint8_t *buffer, size_t size);

cores/arduino/stm32/usb/cdc/cdc_queue.c

@@ -128,7 +128,8 @@ int CDC_ReceiveQueue_ReadSize(CDC_ReceiveQueue_TypeDef *queue) {
 }
 
 // Read one byte from queue.
-uint8_t CDC_ReceiveQueue_Dequeue(CDC_ReceiveQueue_TypeDef *queue) {
+int CDC_ReceiveQueue_Dequeue(CDC_ReceiveQueue_TypeDef *queue) {
+  if (queue->write == queue->read) return -1;
   uint8_t ch = queue->buffer[queue->read++];
   if (queue->read >= queue->length) {
     queue->read = 0;
@@ -137,9 +138,25 @@ uint8_t CDC_ReceiveQueue_Dequeue(CDC_ReceiveQueue_TypeDef *queue) {
 }
 
 // Peek byte from queue.
-uint8_t CDC_ReceiveQueue_Peek(CDC_ReceiveQueue_TypeDef *queue) {
+int CDC_ReceiveQueue_Peek(CDC_ReceiveQueue_TypeDef *queue) {
+  if (queue->write == queue->read) return -1;
   return queue->buffer[queue->read];
 }
 
+uint16_t CDC_ReceiveQueue_Read(CDC_ReceiveQueue_TypeDef *queue, uint8_t *buffer, uint16_t size) {
+  volatile uint16_t write = queue->write;
+  uint16_t available;
+  if (write >= queue->read) {
+    available = write - queue->read;
+  } else {
+    available = CDC_RECEIVE_QUEUE_BUFFER_SIZE - queue->read;
+  }
+  if (available < size) {
+    size = available;
+  }
+  memcpy(buffer, &queue->buffer[queue->read], size);
+  queue->read = (queue->read + size) % CDC_RECEIVE_QUEUE_BUFFER_SIZE;
+  return size;
+}
 #endif /* USBD_USE_CDC */
 #endif /* USBCON */

cores/arduino/stm32/usb/cdc/cdc_queue.h

@@ -78,8 +78,9 @@ void CDC_TransmitQueue_CommitRead(CDC_TransmitQueue_TypeDef *queue);
 
 void CDC_ReceiveQueue_Init(CDC_ReceiveQueue_TypeDef* queue);
 int CDC_ReceiveQueue_ReadSize(CDC_ReceiveQueue_TypeDef* queue);
-uint8_t CDC_ReceiveQueue_Dequeue(CDC_ReceiveQueue_TypeDef* queue);
-uint8_t CDC_ReceiveQueue_Peek(CDC_ReceiveQueue_TypeDef* queue);
+int CDC_ReceiveQueue_Dequeue(CDC_ReceiveQueue_TypeDef* queue);
+int CDC_ReceiveQueue_Peek(CDC_ReceiveQueue_TypeDef* queue);
+uint16_t CDC_ReceiveQueue_Read(CDC_ReceiveQueue_TypeDef* queue, uint8_t* buffer, uint16_t size);
 uint8_t* CDC_ReceiveQueue_ReserveBlock(CDC_ReceiveQueue_TypeDef* queue);
 void CDC_ReceiveQueue_CommitBlock(CDC_ReceiveQueue_TypeDef* queue, uint16_t size);