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Align all read operations to packet boundaries.

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Packets have a fixed size of 0x80 bytes, while a single page is only
0x20 bytes long. Thus each read operation always returns 4 pages at
once. Now, if the end-of-profile pointer is not nicely aligned on a
packet boundary, then the download algorithm won't arrive exactly at the
start address of the ringbuffer, because the ringbuffer is properly
aligned. The consequence is that we won't even notice we reached the
ringbuffer boundary and happily continue reading outside the ringbuffer.
Oops!

This is fixed by aligning the end-of-profile pointer, which guarantees
that all read operations are now nicely aligned to packet boundaries.
This commit is contained in:
Jef Driesen 2015-03-19 21:57:34 +01:00
parent c4233c091d
commit ad6ec1e7f5
1 changed files with 88 additions and 16 deletions
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104
src/cressi_edy.c
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@ -77,6 +77,19 @@ static const dc_device_vtable_t cressi_edy_device_vtable = {
cressi_edy_device_close /* close */
};
static unsigned int
ifloor (unsigned int x, unsigned int n)
{
// Round down to next lower multiple.
return (x / n) * n;
}
static unsigned int
iceil (unsigned int x, unsigned int n)
{
// Round up to next higher multiple.
return ((x + n - 1) / n) * n;
}
static dc_status_t
cressi_edy_packet (cressi_edy_device_t *device, const unsigned char command[], unsigned int csize, unsigned char answer[], unsigned int asize, int trailer)
@ -387,10 +400,6 @@ cressi_edy_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, v
return rc;
}
// Update and emit a progress event.
progress.current += SZ_PACKET;
device_event_emit (abstract, DC_EVENT_PROGRESS, &progress);
// Get the logbook pointers.
unsigned int last = config[0x7C];
unsigned int first = config[0x7D];
@ -412,16 +421,13 @@ cressi_edy_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, v
return DC_STATUS_DATAFORMAT;
}
// Memory buffer for the profile data.
unsigned char buffer[RB_PROFILE_END - RB_PROFILE_BEGIN] = {0};
unsigned int available = 0;
unsigned int offset = RB_PROFILE_END - RB_PROFILE_BEGIN;
unsigned int previous = eop;
unsigned int address = previous;
// The logbook ringbuffer can store at most 60 dives, even if the profile
// data could store more (e.g. many small dives). But it's also possible
// that the profile ringbuffer is filled faster than the logbook ringbuffer
// (e.g. many large dives). We detect this by checking the total length.
unsigned int total = 0;
unsigned int idx = last;
unsigned int previous = eop;
for (unsigned int i = 0; i < count; ++i) {
// Get the pointer to the profile data.
unsigned int current = array_uint16_le (config + 2 * idx) * SZ_PAGE + BASE;
@ -438,6 +444,68 @@ cressi_edy_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, v
// Get the profile length.
unsigned int length = ringbuffer_distance (current, previous, 1, RB_PROFILE_BEGIN, RB_PROFILE_END);
// Check for a ringbuffer overflow.
if (total + length > RB_PROFILE_END - RB_PROFILE_BEGIN) {
count = i;
break;
}
total += length;
previous = current;
if (idx == RB_LOGBOOK_BEGIN)
idx = RB_LOGBOOK_END;
idx--;
}
// Because dives are not necessary aligned to packet boundaries, and
// we always do aligned reads, there can be padding bytes present on
// both sides of the memory buffer. These extra bytes need to be
// included in the total length.
total += (previous - ifloor(previous, SZ_PACKET)) +
(iceil(eop, SZ_PACKET) - eop);
// Update and emit a progress event.
progress.current += SZ_PACKET;
progress.maximum = SZ_PACKET + total;
device_event_emit (abstract, DC_EVENT_PROGRESS, &progress);
// Memory buffer for the profile data.
unsigned char *buffer = (unsigned char *) malloc (total);
if (buffer == NULL) {
ERROR (abstract->context, "Failed to allocate memory.");
return DC_STATUS_NOMEMORY;
}
unsigned int available = 0;
unsigned int offset = total;
// Align the initial memory address to the next packet boundary, and
// calculate the amount of padding bytes, so we can easily skip
// them later.
unsigned int address = iceil(eop, SZ_PACKET);
unsigned int skip = address - eop;
idx = last;
previous = eop;
for (unsigned int i = 0; i < count; ++i) {
// Get the pointer to the profile data.
unsigned int current = array_uint16_le (config + 2 * idx) * SZ_PAGE + BASE;
if (current < RB_PROFILE_BEGIN || current >= RB_PROFILE_END) {
ERROR (abstract->context, "Invalid ringbuffer pointer detected.");
free(buffer);
return DC_STATUS_DATAFORMAT;
}
// Position the pointer at the start of the header.
if (current == RB_PROFILE_BEGIN)
current = RB_PROFILE_END;
current -= SZ_PAGE;
// Get the profile length.
unsigned int length = ringbuffer_distance (current, previous, 1, RB_PROFILE_BEGIN, RB_PROFILE_END);
unsigned nbytes = available;
while (nbytes < length) {
if (address == RB_PROFILE_BEGIN)
@ -449,6 +517,7 @@ cressi_edy_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, v
rc = cressi_edy_device_read (abstract, address, buffer + offset, SZ_PACKET);
if (rc != DC_STATUS_SUCCESS) {
ERROR (abstract->context, "Failed to read the memory page.");
free(buffer);
return rc;
}
@ -456,7 +525,8 @@ cressi_edy_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, v
progress.current += SZ_PACKET;
device_event_emit (abstract, DC_EVENT_PROGRESS, &progress);
nbytes += SZ_PACKET;
nbytes += SZ_PACKET - skip;
skip = 0;
}
available = nbytes - length;
@ -465,15 +535,17 @@ cressi_edy_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, v
unsigned char *p = buffer + offset + available;
if (memcmp (p, device->fingerprint, sizeof (device->fingerprint)) == 0)
return DC_STATUS_SUCCESS;
break;
if (callback && !callback (p, length, p, sizeof (device->fingerprint), userdata))
return DC_STATUS_SUCCESS;
break;
if (idx == RB_LOGBOOK_BEGIN)
idx = RB_LOGBOOK_END;
idx--;
}
free(buffer);
return DC_STATUS_SUCCESS;
}