FlapJackApps/libdivecomputer
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Fix the ringbuffer start address.

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Currently the profile ringbuffer starts at the base address 0x4000, but
I believe the real start is one 0x20 byte page earlier, at 0x3FE0. I
have two reasons for this:

1. To locate the start of a dive, we always have to substract one page
from the pointers in the logbook ringbuffer. With the new base address,
they would point directly to the start of the dive, which makes a lot
more sense.

2. When comparing the divetime as stored in the header with the one
obtained by counting the number of samples, they always match except for
dives that span the ringbuffer wrap point. If those extra 0x20 bytes are
included, the counts do match again.

Unfortunately, this change breaks the assumption that the ringbuffer is
aligned to packet boundaries. As a workaround, we define a virtual
ringbuffer that is slightly larger than the actual ringbuffer, but
properly aligned. Data outside the real ringbuffer is downloaded and
then immediately dropped.
This commit is contained in:
Jef Driesen 2015-03-21 10:29:40 +01:00
parent ad6ec1e7f5
commit 9ae985a499
1 changed files with 32 additions and 17 deletions
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49
src/cressi_edy.c
View File

@ -47,7 +47,7 @@
#define BASE 0x4000
#define RB_PROFILE_BEGIN 0x4000
#define RB_PROFILE_BEGIN 0x3FE0
#define RB_PROFILE_END 0x7F80
#define RB_LOGBOOK_OFFSET 0x7F80
@ -436,11 +436,6 @@ cressi_edy_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, v
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);
@ -481,6 +476,13 @@ cressi_edy_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, v
unsigned int available = 0;
unsigned int offset = total;
// Align the ringbuffer to packet boundaries. This results in a
// virtual ringbuffer that is slightly larger than the actual
// ringbuffer. Data outside the real ringbuffer is downloaded
// and then immediately dropped.
unsigned int rb_profile_begin = ifloor(RB_PROFILE_BEGIN, SZ_PACKET);
unsigned int rb_profile_end = iceil(RB_PROFILE_END, SZ_PACKET);
// Align the initial memory address to the next packet boundary, and
// calculate the amount of padding bytes, so we can easily skip
// them later.
@ -498,34 +500,47 @@ cressi_edy_device_foreach (dc_device_t *abstract, dc_dive_callback_t callback, v
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)
address = RB_PROFILE_END;
if (address == rb_profile_begin)
address = rb_profile_end;
address -= SZ_PACKET;
offset -= SZ_PACKET;
// Read the memory page.
rc = cressi_edy_device_read (abstract, address, buffer + offset, SZ_PACKET);
unsigned char packet[SZ_PACKET];
rc = cressi_edy_device_read (abstract, address, packet, sizeof(packet));
if (rc != DC_STATUS_SUCCESS) {
ERROR (abstract->context, "Failed to read the memory page.");
free(buffer);
return rc;
}
// At the head and tail of the ringbuffer, the packet can
// contain extra data, originating from the larger virtual
// ringbuffer. This data must be removed from the packet.
unsigned int head = 0;
unsigned int tail = 0;
unsigned int len = SZ_PACKET;
if (address < RB_PROFILE_BEGIN) {
head = RB_PROFILE_BEGIN - address;
}
if (address + SZ_PACKET > RB_PROFILE_END) {
tail = (address + SZ_PACKET) - RB_PROFILE_END;
}
len -= head + tail;
offset -= len;
// Copy the data packet to the buffer.
memcpy(buffer + offset, packet + head, len);
// Update and emit a progress event.
progress.current += SZ_PACKET;
progress.current += len;
device_event_emit (abstract, DC_EVENT_PROGRESS, &progress);
nbytes += SZ_PACKET - skip;
nbytes += len - skip;
skip = 0;
}