a7p 1.2.4

A7P ballistic profile format — encode/decode, validation, and field constraints.

a7p

A7P ballistic profile format for Dart — encode/decode, MD5-hash-prefixed wire format, field validation, and field constraints (raw wire scale vs. UI display precision).

Format

A .a7p file is [32-byte MD5 hex string][protobuf-encoded Payload bytes] — the hash is stored as ASCII hex text, not raw binary. See lib/src/a7p_file.dart.

Regenerating the protobuf bindings

Requires protoc (the Protocol Buffers compiler) and the Dart plugin — once per machine:

# Linux
sudo apt-get install -y protobuf-compiler
# macOS
brew install protobuf

dart pub global activate protoc_plugin

Then, after editing ../proto/profedit.proto (the canonical copy lives at the a7p repo root, shared with the py/js packages — this only works when dart/ is checked out inside an a7p tree):

dart run bin/generate_proto.dart

Regenerating the embedded validation schema

A7pValidator validates against ../schema/a7p.schema.json (also shared with py/js), embedded as a Dart string constant in lib/src/generated/a7p_schema.g.dart — see that file's header and README.md at the a7p repo root ("--dart" section) for why. After editing the schema:

python scripts/compile.py --dart   # from the a7p repo root

Dimensions

To obtain values from an .a7p profile in the desired units, you need to divide them by the multiplier. For the reverse operation, you need to perform the inverse operation and convert to an integer. A7pFieldConstraints (lib/src/a7p_field_constraints.dart) is the source of truth for these — toRaw/fromRaw do this conversion for you.

key	unit	multiplier	desc
scHeight	mm	1	sight height in mm
rTwist	inch	100	positive twist value
cZeroTemperature	C	1	temperature at cMuzzleVelocity
cMuzzleVelocity	mps	10	muzzle velocity at cZeroTemperature
cTCoeff	%/15C	1000	temperature sensitivity
cZeroDistanceIdx	<int>	1	index of zero distance from distances table
cZeroAirTemperature	C	1	air temperature at zero
cZeroAirPressure	hPa	10	air pressure at zero
cZeroAirHumidity	%	1	air humidity at zero
cZeroPTemperature	C	1	powder temperature at zero
cZeroWPitch	deg	1	zeroing look angle
bDiameter	inch	1000	bullet diameter
bWeight	grain	10	bullet weight
bLength	inch	1000	bullet length
twistDir	RIGHT|LEFT		twist direction
bcType	G1|G7|CUSTOM		g-func type
distances	m	100	distances table in m
zeroX	<int>	1000	zeroing h-clicks for specific device
zeroY	<int>	1000	zeroing v-clicks for specific device
coefRows[].bcCd (G1/G7)		10000	bc coefficient for mv
coefRows[].mv (G1/G7)	mps	10	mv for bc provided
coefRows[].bcCd (CUSTOM)		10000	drag coefficient (Cd)
coefRows[].mv (CUSTOM)	mach	10000	speed in mach

Testing

dart pub get
dart analyze
dart test

Formatting

dart format lib test bin

License

LGPL-3.0 — see LICENSE.