Implement output buffering to improve TCP performance

Author: geekfactory

Shell.c

@@ -47,6 +47,7 @@ char shellfmtbuf[CONFIG_SHELL_FMT_BUFFER];
 
 shell_reader_t shell_reader = 0;
 shell_writer_t shell_writer = 0;
+struct shell_outbuffer_data * obhandle = 0;
 bool initialized = false;
 
 /*-------------------------------------------------------------*
@@ -114,6 +115,17 @@ bool shell_init(shell_reader_t reader, shell_writer_t writer, char * msg)
 	return true;
 }
 
+void shell_use_buffered_output(shell_bwriter_t writer)
+{
+	static struct shell_outbuffer_data obd;
+
+	obhandle = &obd;
+
+	obd.shell_bwriter = writer;
+	obd.buffercount = 0;
+	obd.buffertimer = millis();
+}
+
 bool shell_register(shell_program_t program, const char * string)
 {
 	uint8_t i;
@@ -142,6 +154,20 @@ void shell_putc(char c)
 {
 	if (initialized != false && shell_writer != 0)
 		shell_writer(c);
+	if (initialized != false && obhandle != 0) {
+		// Keep track of last byte
+		obhandle->buffertimer = millis();
+		// Empty buffer if it´s full before storing anything else
+		if (obhandle->buffercount >= 30) {
+			// Write output...
+			if (obhandle->shell_bwriter != 0)
+				obhandle->shell_bwriter(obhandle->outbuffer, obhandle->buffercount);
+			// and clear counter
+			obhandle->buffercount = 0;
+		}
+		// Write to buffer always
+		obhandle->outbuffer[obhandle->buffercount++] = c;
+	}
 }
 
 void shell_print(const char * string)
@@ -268,6 +294,17 @@ void shell_task()
 	if (!initialized)
 		return;
 
+	// Process buffered output if enabled
+	if (obhandle != 0) {
+		if (obhandle->buffercount != 0 && millis() - obhandle->buffertimer >= 200) {
+			obhandle->buffertimer = millis();
+			if (obhandle->shell_bwriter != 0)
+				obhandle->shell_bwriter(obhandle->outbuffer, obhandle->buffercount);
+			// and clear counter
+			obhandle->buffercount = 0;
+		}
+	}
+
 	// Process each one of the received characters
 	if (shell_reader(&rxchar)) {
 
@@ -480,6 +517,7 @@ static void shell_prompt()
  *		Shell formatted print support			*
  *-------------------------------------------------------------*/
 #ifdef SHELL_PRINTF_LONG_SUPPORT
+
 static void uli2a(unsigned long int num, unsigned int base, int uc, char * bf)
 {
 	int n = 0;

Shell.h

@@ -73,7 +73,7 @@
 
 /**
  * End of user configurable parameters, do not touch anything below this line
- */ 
+ */
 
 /*-------------------------------------------------------------*
  *		Macros & definitions				*
@@ -120,6 +120,12 @@ typedef void (*shell_writer_t) (char);
  */
 typedef int (*shell_reader_t) (char *);
 
+/*
+ * Type definition for a function that sends multiple chars to the remote
+ * terminal (function pointer)
+ */
+typedef void (*shell_bwriter_t)(char *, uint8_t);
+
 /**
  * This enumeration defines the errors printed by the programs called by the
  * shell.
@@ -151,6 +157,13 @@ struct shell_command_entry {
 	const char * shell_command_string;
 };
 
+struct shell_outbuffer_data {
+	char outbuffer[30];
+	shell_bwriter_t shell_bwriter;
+	uint32_t buffertimer;
+	uint8_t buffercount;
+};
+
 /*-------------------------------------------------------------*
  *		Function prototypes				*
  *-------------------------------------------------------------*/
@@ -172,6 +185,23 @@ extern "C" {
 	 * otherwise.
 	 */
 	bool shell_init(shell_reader_t reader, shell_writer_t writer, char * msg);
+	
+	/**
+	 * @brief Enables internal output buffer for output chars
+	 * 
+	 * Call this function to enable the use of an internal buffer to temporary store
+	 * characters that will be sent to a remote device. This function is meant to be
+	 * used when the communication channel performs better when many characters are 
+	 * written at the same time. For example TCP/IP sockets perform better if a group 
+	 * of characters are sent on a single segment.
+	 * 
+	 * The content of the internal buffer is written when the it is full or if
+	 * 200 milliseconds have elapsed since the last character write on the buffer.
+	 * 
+         * @param writer The callback function used to write a group of characters on the
+	 * stream.
+         */
+	void shell_use_buffered_output(shell_bwriter_t writer);
 
 	/**
 	 * @brief Registers a command with the command line library
@@ -242,7 +272,7 @@ extern "C" {
 	 * @param ... Aditional arguments that are inserted on the string as text
 	 */
 	void shell_printf(const char * fmt, ...);
-	
+
 	/**
 	 * @brief Prints the list of registered commands
 	 *

keywords.txt

@@ -9,19 +9,20 @@
 #######################################
 # Methods and Functions (KEYWORD2)
 #######################################
-shell_init				KEYWORD2
-shell_register			KEYWORD2
-shell_unregister_all	KEYWORD2
-shell_putc				KEYWORD2
-shell_print				KEYWORD2
-shell_println			KEYWORD2
-shell_printf			KEYWORD2
-shell_print_commands	KEYWORD2
-shell_print_error		KEYWORD2
-shell_task				KEYWORD2
-shell_print_pm			KEYWORD2
-shell_println_pm		KEYWORD2
-shell_printf_pm			KEYWORD2
+shell_init					KEYWORD2
+shell_use_buffered_output	KEYWORD2
+shell_register				KEYWORD2
+shell_unregister_all		KEYWORD2
+shell_putc					KEYWORD2
+shell_print					KEYWORD2
+shell_println				KEYWORD2
+shell_printf				KEYWORD2
+shell_print_commands		KEYWORD2
+shell_print_error			KEYWORD2
+shell_task					KEYWORD2
+shell_print_pm				KEYWORD2
+shell_println_pm			KEYWORD2
+shell_printf_pm				KEYWORD2
 
 #######################################
 # Instances (KEYWORD2)

library.properties

@@ -1,5 +1,5 @@
 name=GeekFactory Shell Library
-version=1.1.0
+version=1.2.0
 author=www.geekfactory.mx
 maintainer=Jesus Ruben Santa Anna Zamudio
 sentence=Library to create a simple Command Line Interface (CLI).