tcl_server: Support line buffers up to 4M (v3)

Currently, the maximum size of a command sent to the TCL server is
4k. This patch increases this limit up to 4M.

Reasoning:
To get high-speed JTAG data transfers, I'm using a very long shift
register. This reduces the overhead of the state changes, as well as the
latency due to the common USB adapter transfers considerably. In order
to submit those long DRSCAN commands to OpenOCD over the TCL/TCL
interface, long TCL command lines are required. This is enabled by this
patch.

v3:
Address review comments. Drop line instead of connection when realloc()
fails.

Changes in v2 of this patch:
The line buffer is allocated dynamically to avoid an OpenOCD memory
overhead if the large buffers are not used. The buffer starts at 4K and
increases exponentially up to 1M, and then linearly in 1M increments up
to 4M.

Change-Id: Iecaef6a56ed5e18e9de4d912a514031ea78fa3bd
Signed-off-by: Philipp Wagner <philipp.wagner@tum.de>
Reviewed-on: http://openocd.zylin.com/2837
Tested-by: jenkins
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>

1 files changed, 43 insertions, 8 deletions

diff --git a/src/server/tcl_server.c b/src/server/tcl_server.c
index a4270a84..789eee8b 100644
--- a/src/server/tcl_server.c
+++ b/src/server/tcl_server.c
@@ -27,12 +27,14 @@
 #include <helper/binarybuffer.h>
 
 #define TCL_SERVER_VERSION		"TCL Server 0.1"
-#define TCL_MAX_LINE			(4096)
+#define TCL_LINE_INITIAL		(4*1024)
+#define TCL_LINE_MAX			(4*1024*1024)
 
 struct tcl_connection {
 	int tc_linedrop;
 	int tc_lineoffset;
-	char tc_line[TCL_MAX_LINE];
+	int tc_line_size;
+	char *tc_line;
 	int tc_outerror;/* flag an output error */
 	enum target_state tc_laststate;
 	bool tc_notify;
@@ -144,11 +146,17 @@ static int tcl_new_connection(struct connection *connection)
 {
 	struct tcl_connection *tclc;
 
-	tclc = malloc(sizeof(struct tcl_connection));
+	tclc = calloc(1, sizeof(struct tcl_connection));
 	if (tclc == NULL)
 		return ERROR_CONNECTION_REJECTED;
 
-	memset(tclc, 0, sizeof(struct tcl_connection));
+	tclc->tc_line_size = TCL_LINE_INITIAL;
+	tclc->tc_line = malloc(tclc->tc_line_size);
+	if (tclc->tc_line == NULL) {
+		free(tclc);
+		return ERROR_CONNECTION_REJECTED;
+	}
+
 	connection->priv = tclc;
 
 	struct target *target = get_target_by_num(connection->cmd_ctx->current_target);
@@ -175,6 +183,8 @@ static int tcl_input(struct connection *connection)
 	int reslen;
 	struct tcl_connection *tclc;
 	unsigned char in[256];
+	char *tc_line_new;
+	int tc_line_size_new;
 
 	rlen = connection_read(connection, &in, sizeof(in));
 	if (rlen <= 0) {
@@ -191,10 +201,31 @@ static int tcl_input(struct connection *connection)
 	for (i = 0; i < rlen; i++) {
 		/* buffer the data */
 		tclc->tc_line[tclc->tc_lineoffset] = in[i];
-		if (tclc->tc_lineoffset < TCL_MAX_LINE)
+		if (tclc->tc_lineoffset < tclc->tc_line_size) {
 			tclc->tc_lineoffset++;
-		else
+		} else if (tclc->tc_line_size >= TCL_LINE_MAX) {
+			/* maximum line size reached, drop line */
 			tclc->tc_linedrop = 1;
+		} else {
+			/* grow line buffer: exponential below 1 MB, linear above */
+			if (tclc->tc_line_size <= 1*1024*1024)
+				tc_line_size_new = tclc->tc_line_size * 2;
+			else
+				tc_line_size_new = tclc->tc_line_size + 1*1024*1024;
+
+			if (tc_line_size_new > TCL_LINE_MAX)
+				tc_line_size_new = TCL_LINE_MAX;
+
+			tc_line_new = realloc(tclc->tc_line, tc_line_size_new);
+			if (tc_line_new == NULL) {
+				tclc->tc_linedrop = 1;
+			} else {
+				tclc->tc_line = tc_line_new;
+				tclc->tc_line_size = tc_line_size_new;
+				tclc->tc_lineoffset++;
+			}
+
+		}
 
 		/* ctrl-z is end of command. When testing from telnet, just
 		 * press ctrl-z a couple of times first to put telnet into the
@@ -230,9 +261,13 @@ static int tcl_input(struct connection *connection)
 
 static int tcl_closed(struct connection *connection)
 {
+	struct tcl_connection *tclc;
+	tclc = connection->priv;
+
 	/* cleanup connection context */
-	if (connection->priv) {
-		free(connection->priv);
+	if (tclc) {
+		free(tclc->tc_line);
+		free(tclc);
 		connection->priv = NULL;
 	}