casm

macro-circuit-assembler

Expand a macro-circuit into standard Bristol format

Running

The circuit assembler is located in casm.js and accepts two parameters like follows.

node casm.js </path/to/macro.casm> <path/to/output-circuit.txt>

For example, to assemble the 8-bit AND circuit, run:

node casm.js example/and8.casm output.txt

You can also run the assembler inside your node application:

const casm = require('casm');
console.log(casm.parseAndAssemble('path/to/macro.casm'));

Custom workflows are supported by using lower level functions. For example, to assemble a macro description that is currently in memory as text or as a circuit object:

const macroText = '...';

const inputCircuitObject = casm.parse(macroText);
const assembledCircuitObject = casm.assemble(inputCircuitObject, 'working/dir');
const assembledCircuitText = casm.stringify(assembledCircuitObject);

// if the macroText referes to other files (either macro or circuit)
// for example 'circuit/some/circuit.txt', the assembler will look for these
// circuit under 'working/dir', for example 'working/dir/circuit/some/circuit.txt'
// unless the nested file path is absolute.
// working directory defaults to the current working directory if it is not provided.

Capabilities

Syntax

Macro format extends the bristol fashion.

The file must start with the following header:

<number of gates> <number of wires>
<number of inputs> <size of each input> ...
<number of outputs> <size of each output> ...

Following this header, every line defines a gate, which itself can be another circuit, macro, or plain gate.

<number of input wires> <number of output wires> <input wire 1> ... <output wire 1> ... <gate type>

For example

3 12
8 1
1 2
4 1 0 1 2 3 8 ../circuits/and4.txt
4 1 4 5 6 7 9 /home/casm/circuits/and4.casm
2 1 8 9 10 AND
1 1 10 11 INV

Plain gate can have type AND, XOR, or INV, while nested circuits and macros can be defined by using their file path as type, which must end with either .txt or .casm respectively.

Relative paths are resolved relative to the directory in which the macro is stored. Absolute paths are also allowed.

Directives

Macro format provides the following directives, which can be used wherever wire numbers are appropriate:

[start:end]  // wires numbered start to end
[start:end:increment]  // incremental numbered wires
[start|>multiplicity]  // multiple wires from a starting id

For example [10|>5] represents 10 11 12 13 14 and [2:10:2] gives 2 4 6 8 10. Using a negative increment is also legal. For example [end:start:-1] reverses a range of inputs.

Line comments are supported and marked by hashes "#".

Applications

Boolean circuit definitions are useful in multi-party computation applications such as JIGG and SCALE-MAMBA.