Extend and rephrase the VCD output module, to support mixed signal data,
support higher channel counts, and address other minor issues.
Increase the number of VCD identifiers which can get generated. Bump the
limit from 94 to 18346 channels. Prefer single letter names for backwards
compatibility for the first channels. Use two or three letter identifiers
as needed for higher channel counts.
Add support for analog channels, and carefully organize a queue such
that timestamps and their data only get written after input data for
_all_ channels was received from the session feed. Provide IEEE754
double precision values for maximum compatibility with other VCD aware
software, although sigrok internally passes analog data with single
precision. This makes potential later adjustment transparent to external
software.
Factor out and rephrase code while we are here. This implementation
avoids glib calls where they'd hurt performance. A local pool reduces
malloc() pressure to increase throughput. String manipulation is tuned
for simplicity and reduced cost. Special code paths were added to tune
the use cases where mixed signals are not involved (immediate write to
the output text, bypassing the output module's local queue).
An srzip input implementation detail still makes the VCD output consume
lots of memory during merge sort of channels' data. See bug #1566.
Other nits got addressed in bypassing: Adjust data types. Separate the
gathering of detail information and the construction of the VCD header
text to simplify review and future maintenance. Skip VCD identifiers for
disabled channels. Emit a final timestamp to flush the last sample, and
communicate the total capture length.
Update comments. Update the copyright for recent non-trivial changes.
The previous implementation inspected the input stream's samplerate, and
simply used the next 1kHz/1MHz/1GHz timescale for VCD export. Re-import
of the exported file might suffer from rather high an overhead, where
users might have to downsample the input stream. Also exported data
might use an "odd" timescale which doesn't represent the input stream's
timing well.
Rephrase the samplerate to VCD timescale conversion such that the lowest
frequency is used which satisfies the file format's constraints as well
as provides high enough a resolution to communicate the input stream's
timing with minimal loss. Do limit this scaling support to at most three
orders above the input samplerate, to most appropriately cope with odd
rates.
As a byproduct the rephrased implementation transparently supports rates
above 1GHz. Input streams with no samplerate now result in 1s timescale
instead of the 1ms timescale of the previous implementation.
The 'period' member of the VCD output module's context is supposed to
hold frequencies that correspond to the timescale used during export.
An 'int' (in combination with VCD's 1/10/100 constraint) thus would
result in a 1GHz limit, use uint64_t instead to support higher rates.
The previous implementation only emitted data for the first enabled
channels, and "saw no changes" after emission of the initial value for
channels on positions that followed a disabled channel.
Assume that the received data from the session bus communicates the bits
of enabled channels in a packed representation. Skip the mapping of
output bit indices to sigrok channel numbers.
This fixes the remaining part of bug #519.
Tested by inspecting in gtkwave the result of command:
$ sigrok-cli -d demo -C D1,D3,D6 -c samplerate=2M --samples 2500 -O vcd -o trace.vcd
When we find that all input sources (device drivers, and input modules)
provide a dense bit field, all of the mapping logic can get removed
here. This commit just quickly disables the logic.
Identifiers for channels in the VCD header section could be "sparse"
when sigrok channels were disabled. Make sure to not assign names to
disabled channels. This will e.g. assign !, ", and # to channels D1, D3,
and D6, when D0, D2, D4-D5, and D7 are disabled.
This addresses part of bug #519.
Since Autoconf places some important feature flags only into the
configuration header, it is necessary to include it globally to
guarantee a consistent build.
Move the include flags for files in the source tree from
configure.ac to Makefile.am where they belong. Also use
AM_CPPFLAGS instead of CFLAGS/CXXFLAGS to make sure the
files in the build/source tree are always picked up first.
Also, remove the include/libsigrok sub-directory from the
search path, thereby making the <libsigrok/> prefix mandatory
when building libsigrok itself. This matches the convention
already imposed on users of the library.
Gerhard Sittig
Martin Ling
Uwe Hermann
Soeren Apel
Daniel Elstner
Joel Holdsworth
Bert Vermeulen