From 8362c28e3a7bf27324ddb0a85fa2147399ac1273 Mon Sep 17 00:00:00 2001
From: Nathael Pajani <nathael.pajani@ed3l.fr>
Date: Sat, 25 Aug 2012 22:45:41 +0200
Subject: [PATCH] Modifications to drop input buffer content rather than trying
 to read the axact amount of data.

---
 isp_commands.c |  6 +++---
 isp_utils.c    | 39 +++++++++++++++++++++++++++++++++++++++
 isp_utils.h    |  1 +
 3 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/isp_commands.c b/isp_commands.c
index e43f518..7ee167a 100644
--- a/isp_commands.c
+++ b/isp_commands.c
@@ -126,7 +126,7 @@ int isp_connect(unsigned int crystal_freq, int quiet)
 		return -3;
 	}
 	/* Empty read buffer (echo is on) */
-	isp_serial_read(buf, strlen(SYNCHRO), strlen(SYNCHRO));
+	isp_serial_empty_buffer();
 	/* Read reply (OK) */
 	isp_serial_read(buf, REP_BUFSIZE, strlen(SYNCHRO_OK));
 	if (strncmp(SYNCHRO_OK, buf, strlen(SYNCHRO_OK)) != 0) {
@@ -137,7 +137,7 @@ int isp_connect(unsigned int crystal_freq, int quiet)
 	/* Documentation says we should send crystal frequency .. sending anything is OK */
 	isp_serial_write(freq, strlen(freq));
 	/* Empty read buffer (echo is on) */
-	isp_serial_read(buf, strlen(freq), strlen(freq));
+	isp_serial_empty_buffer();
 	/* Read reply (OK) */
 	isp_serial_read(buf, REP_BUFSIZE, strlen(SYNCHRO_OK));
 	if (strncmp(SYNCHRO_OK, buf, strlen(SYNCHRO_OK)) != 0) {
@@ -148,7 +148,7 @@ int isp_connect(unsigned int crystal_freq, int quiet)
 	/* Turn off echo */
 	isp_serial_write(SYNCHRO_ECHO_OFF, strlen(SYNCHRO_ECHO_OFF));
 	/* Empty read buffer (echo still on) */
-	isp_serial_read(buf, strlen(SYNCHRO_ECHO_OFF), strlen(SYNCHRO_ECHO_OFF));
+	isp_serial_empty_buffer();
 	/* Read eror code for command */
 	isp_serial_read(buf, REP_BUFSIZE, 3);
 
diff --git a/isp_utils.c b/isp_utils.c
index 6409375..4bd075d 100644
--- a/isp_utils.c
+++ b/isp_utils.c
@@ -143,6 +143,41 @@ int isp_serial_write(const char* buf, unsigned int buf_size)
 	return nb;
 }
 
+static char next_read_char = 0;
+void isp_serial_empty_buffer()
+{
+	int nb = 0;
+	char unused = 0;
+	unsigned int loops = 0; /* Used to create a timeout */
+
+	do {
+		nb = read(serial_fd, &unused, 1);
+		if (nb < 0) {
+			if ((errno == EAGAIN) || (errno == EWOULDBLOCK)) {
+				if (loops++ > 100) {
+					break; /* timeout at 500ms */
+				}
+				usleep( 5000 );
+				continue;
+			}
+			perror("Serial read error");
+			return;
+		} else if (nb == 0) {
+			printf("serial_read: end of file !!!!\n");
+			return;
+		}
+	} while ((unused != '\r') && (unused != '\n'));
+
+	/* This should be improved by reading ALL \r and \n */
+	if (unused == '\r') {
+		nb = read(serial_fd, &unused, 1);
+	}
+	if (unused == '\n') {
+		return;
+	}
+	next_read_char = unused;
+}
+
 /* Try to read at least "min_read" characters from the serial line.
  * Returns -1 on error, 0 on end of file, or read count otherwise.
  */
@@ -156,6 +191,10 @@ int isp_serial_read(char* buf, unsigned int buf_size, unsigned int min_read)
 		printf("serial_read: buffer too small for min read value.\n");
 		return -3;
 	}
+	if (next_read_char != 0) {
+		buf[count++] = next_read_char;
+		next_read_char = 0;
+	}
 
 	do {
 		nb = read(serial_fd, &buf[count], (buf_size - count));
diff --git a/isp_utils.h b/isp_utils.h
index 5a59186..521ae69 100644
--- a/isp_utils.h
+++ b/isp_utils.h
@@ -30,6 +30,7 @@ void isp_serial_close(void);
 /* Simple write() wrapper, with trace if enabled */
 int isp_serial_write(const char* buf, unsigned int buf_size);
 
+void isp_serial_empty_buffer();
 /* Try to read at least "min_read" characters from the serial line.
  * Returns -1 on error, 0 on end of file, or read count otherwise.
  */
-- 
2.43.0