output/text: Fix memory leak of internal state buffers.

The text output module keeps buffers for internal state, upon receiving a DF_END
packet it frees the internal context but the buffers are never freed.

This adds a text_cleanup() helper function and registers it as the cleanup
function within all the text output modules.

output/text/ascii.c

@@ -133,4 +133,5 @@ SR_PRIV struct sr_output_format output_text_ascii = {
 	.init = init_ascii,
 	.data = data_ascii,
 	.event = event,
+	.cleanup = text_cleanup,
 };

output/text/bits.c

@@ -116,4 +116,5 @@ SR_PRIV struct sr_output_format output_text_bits = {
 	.init = init_bits,
 	.data = data_bits,
 	.event = event,
+	.cleanup = text_cleanup,
 };

output/text/hex.c

@@ -109,4 +109,5 @@ SR_PRIV struct sr_output_format output_text_hex = {
 	.init = init_hex,
 	.data = data_hex,
 	.event = event,
+	.cleanup = text_cleanup,
 };

output/text/text.c

@@ -171,6 +171,31 @@ err:
 	return ret;
 }
 
+SR_PRIV int text_cleanup(struct sr_output *o)
+{
+	struct context *ctx;
+
+	if (!o)
+		return SR_ERR_ARG;
+
+	ctx = o->internal;
+
+	g_free(ctx->header);
+	g_free(ctx->linebuf);
+	g_free(ctx->linevalues);
+
+	if (ctx->prevsample)
+		g_free(ctx->prevsample);
+
+	g_slist_free(ctx->probenames);
+
+	g_free(ctx);
+
+	o->internal = NULL;
+
+	return SR_OK;
+}
+
 SR_PRIV int event(struct sr_output *o, int event_type, uint8_t **data_out,
 		  uint64_t *length_out)
 {
@@ -195,8 +220,6 @@ SR_PRIV int event(struct sr_output *o, int event_type, uint8_t **data_out,
 		flush_linebufs(ctx, outbuf);
 		*data_out = outbuf;
 		*length_out = strlen((const char *)outbuf);
-		g_free(o->internal);
-		o->internal = NULL;
 		break;
 	default:
 		*data_out = NULL;

output/text/text.h

@@ -48,6 +48,7 @@ struct context {
 
 SR_PRIV void flush_linebufs(struct context *ctx, uint8_t *outbuf);
 SR_PRIV int init(struct sr_output *o, int default_spl, enum outputmode mode);
+SR_PRIV int text_cleanup(struct sr_output *o);
 SR_PRIV int event(struct sr_output *o, int event_type, uint8_t **data_out,
 		  uint64_t *length_out);