Big Integer Package for Zig

A neither feature complete nor bug free (at least it's very unlikely) big integer package written in Zig.

Memory for integers is always dynamically allocated and must be freed using deinit.

Integer De-/ Serialization

Integers from Strings

To create a new integer from a string one can use the fromStringAlloc function.

consti=tryBigInt.fromStringAlloc("0xaabbccdd",0,allocator);deferi.deinit(std.testing.allocator);

The first argument is a string representing an integer. Currently, only binary (0b), octal (0o) and hexadecimal (0x) are supported. The second argument is the base. Use 0 if the base should be derived from the string. The third argument is an allocator used to allocate the memory required to store the integer in memory.

Integers to Strings

To serialize a BigInt into a string, use the formatAlloc method.

conststr=tryi.formatAlloc(16,allocator);deferallocator.free(str);

The first argument is the base that should be used to format the integer string and the second argument is an allocator used to allocated the memory required for the string.

Arithmetic Operations

Addition

vari1=tryBigInt.fromStringAlloc("-0xd7b3f9b6be6d0ba69561e026d1a71713f000da0eebcdf648d2f3651614f37f04bf",0,allocator);deferi1.deinit(allocator);vari2=tryBigInt.fromStringAlloc("0xd5612187a8fd23f35e21b1f7d63e224244c37658d6e020657c494a59d52e69b1355ee2b3ec44397b67",0,allocator);deferi2.deinit(allocator);// "0xd5612187a8fd23f2866db84117d1169baf619632053909518c48704ae9607368626b7d9dd750ba76a8"consti3=tryi1.add(i2,std.testing.allocator);deferi3.deinit(allocator);

Subtraction

vari1=tryBigInt.fromStringAlloc("0xc9f2c9cd04674edea3fffffff",0,allocator);deferi1.deinit(allocator);vari2=tryBigInt.fromStringAlloc("0xab54a98ceb1f0ad2",0,allocator);deferi2.deinit(allocator);// "0xc9f2c9ccf9b20445d54e0f52d"consti3=tryi1.sub(i2,std.testing.allocator);deferi3.deinit(allocator);

Multiplication

vari1=tryBigInt.fromStringAlloc("0xd7b3f9b6be6d0ba69561e026d1a71713f000da0eebcdf648d2f3651614f37f04bf",0,allocator);deferi1.deinit(allocator);vari2=tryBigInt.fromStringAlloc("0xd7b3f9b6be6d0ba69561e026d1a71713f000da0eebcdf648d2f3651614f37f04bf",0,allocator);deferi2.deinit(allocator);// "0xb5bfcbf81cfe76f38b3bf893a9c64ec5e31c53f13bfd68c9dcdf25ce3dd5f99ac8b58dd6b4b1a3c0c687c26e1bf4ded1cbee18ee138e28d61a2920f9f3e04f988681"consti3=tryi1.mul(i2,std.testing.allocator);deferi3.deinit(allocator);

Division

Division with Remainder

Compared to most other methods divrem will return a tuple consisting of the result of the division and the remainder.

vari1=tryBigInt.fromStringAlloc("0x9f4f2726179a224501d762422c946590d9bb54a98ceb1f0ad2",0,allocator);deferi1.deinit(allocator);vari2=tryBigInt.fromStringAlloc("0x9f4f2726179a224501d762422c946590d90fffffffffffffff",0,allocator);deferi2.deinit(allocator);constres,constrem=tryi1.divrem(i2,std.testing.allocator);deferres.deinit(allocator);// "0x1"deferrem.deinit(allocator);// "0xab54a98ceb1f0ad3"

Remainder

To calculate only the remainder use the remainder method.

vari1=tryBigInt.fromStringAlloc("0x9f4f2726179a224501d762422c946590d9bb54a98ceb1f0ad2",0,allocator);deferi1.deinit(allocator);vari2=tryBigInt.fromStringAlloc("0x9f4f2726179a224501d762422c946590d90fffffffffffffff",0,allocator);deferi2.deinit(allocator);constrem=tryi1.remainder(i2,std.testing.allocator);deferrem.deinit(allocator);// "0xab54a98ceb1f0ad3"

Modulo

To calculate n mod m where m is the module use the mod method.

varn=tryBigInt.fromStringAlloc("-0xab54a98ceb1f0ad2",0,allocator);defern.deinit(allocator);varm=tryBigInt.fromStringAlloc("0xc9f2c9cd04674edea3fffffff",0,allocator);deferm.deinit(allocator);consta=tryn.mod(m,std.testing.allocator);defera.deinit(allocator);// "0xc9f2c9ccf9b20445d54e0f52d"

Multiplicative Inverse

One can calculate the multiplicative inverse d of a value e where e * d = 1 (mod m) using the mulinv method.

It is important to note that this method will only succeed if e and m do not share a common divisor, i.e. the method will always succeed if one chooses a prime for m.

vare=tryBigInt.fromStringAlloc("0x13cb6d5a698890d16746620b38ad51b169dfde8cd89c474c14a98248f794bcba",0,allocator);defere.deinit(allocator);varm=tryBigInt.fromStringAlloc("0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffefffffc2f",0,allocator);deferm.deinit(allocator);constd=trye.mulinv(m,std.testing.allocator);deferd.deinit(allocator);// "0xf38c3f1da477ede38da56515070d2a6d2d0ff4ae146125caf3115b1e8ded63f"// e * d = 1 (mod m)