From b3d2c603ddec9758fb36706bbde46ce23ca9f0ed Mon Sep 17 00:00:00 2001
From: John Van Ostrand <john@vanostrand.com>
Date: Wed, 31 May 2017 19:24:47 -0400
Subject: [PATCH] Retry read operations on failure

[Jef Driesen: Modified to retry only for non-fatal errors.]
---
 src/cochran_commander.c | 34 +++++++++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/src/cochran_commander.c b/src/cochran_commander.c
index e0c991f..2854c78 100644
--- a/src/cochran_commander.c
+++ b/src/cochran_commander.c
@@ -32,6 +32,8 @@
 
 #define C_ARRAY_SIZE(array) (sizeof (array) / sizeof *(array))
 
+#define MAXRETRIES 2
+
 #define COCHRAN_MODEL_COMMANDER_AIR_NITROX 0
 #define COCHRAN_MODEL_EMC_14 1
 #define COCHRAN_MODEL_EMC_16 2
@@ -435,6 +437,31 @@ cochran_commander_read (cochran_commander_device_t *device, dc_event_progress_t
 	return DC_STATUS_SUCCESS;
 }
 
+static unsigned int
+cochran_commander_read_retry (cochran_commander_device_t *device, dc_event_progress_t *progress, unsigned int address, unsigned char data[], unsigned int size)
+{
+	// Save the state of the progress events.
+	unsigned int saved = progress->current;
+
+	unsigned int nretries = 0;
+	dc_status_t rc = DC_STATUS_SUCCESS;
+	while ((rc = cochran_commander_read (device, progress, address, data, size)) != DC_STATUS_SUCCESS) {
+		// Automatically discard a corrupted packet,
+		// and request a new one.
+		if (rc != DC_STATUS_PROTOCOL && rc != DC_STATUS_TIMEOUT)
+			return rc;
+
+		// Abort if the maximum number of retries is reached.
+		if (nretries++ >= MAXRETRIES)
+			return rc;
+
+		// Restore the state of the progress events.
+		progress->current = saved;
+	}
+
+	return rc;
+}
+
 
 /*
  *  For corrupt dives the end-of-samples pointer is 0xFFFFFFFF
@@ -890,7 +917,7 @@ cochran_commander_device_foreach (dc_device_t *abstract, dc_dive_callback_t call
 				sample_end_address = cochran_commander_guess_sample_end_address(device, &data, i);
 
 			if (sample_start_address <= sample_end_address) {
-				rc = cochran_commander_read (device, &progress, sample_start_address, dive + device->layout->rb_logbook_entry_size, sample_size);
+				rc = cochran_commander_read_retry (device, &progress, sample_start_address, dive + device->layout->rb_logbook_entry_size, sample_size);
 				if (rc != DC_STATUS_SUCCESS) {
 					ERROR (abstract->context, "Failed to read the sample data.");
 					status = rc;
@@ -901,14 +928,15 @@ cochran_commander_device_foreach (dc_device_t *abstract, dc_dive_callback_t call
 				// It wrapped the buffer, copy two sections
 				unsigned int size = device->layout->rb_profile_end - sample_start_address;
 
-				rc = cochran_commander_read (device, &progress, sample_start_address, dive + device->layout->rb_logbook_entry_size, size);
+				rc = cochran_commander_read_retry (device, &progress, sample_start_address, dive + device->layout->rb_logbook_entry_size, size);
 				if (rc != DC_STATUS_SUCCESS) {
 					ERROR (abstract->context, "Failed to read the sample data.");
 					status = rc;
 					free(dive);
 					goto error;
 				}
-				rc = cochran_commander_read (device, &progress, device->layout->rb_profile_begin, dive + device->layout->rb_logbook_entry_size + size, sample_end_address - device->layout->rb_profile_begin);
+
+				rc = cochran_commander_read_retry (device, &progress, device->layout->rb_profile_begin, dive + device->layout->rb_logbook_entry_size + size, sample_end_address - device->layout->rb_profile_begin);
 				if (rc != DC_STATUS_SUCCESS) {
 					ERROR (abstract->context, "Failed to read the sample data.");
 					status = rc;