How to define and use complex structures in circuits？

[doubiliu]

I'm trying to build a batch processing circuit

type BatchEncryptionWrapper[T1, S1, T2, S2 emulated.FieldParams] struct {
	Account      []AccountConstraints[T1, S1, T2, S2] `gnark:",secret"`
	CommentsHash []frontend.Variable                  `gnark:",public"`
}

type AccountConstraints[T1, S1, T2, S2 emulated.FieldParams] struct {
	SmallR emulated.Element[S1]
	BigR   sw_emulated.AffinePoint[T1]
	Pub    sw_emulated.AffinePoint[T1]
	RPub   sw_emulated.AffinePoint[T1]

	PlainChunks  [32]frontend.Variable
	Iv           [12]frontend.Variable
	ChunkIndex   frontend.Variable
	CipherChunks [64]frontend.Variable

	SmallFi emulated.Element[S2]
	Fi      sw_emulated.AffinePoint[T2]
}

But when I am testing,I met this problem:

panic: when parsing variable Account_0_CipherChunks_48: missing assignment [recovered]
	panic: when parsing variable Account_0_CipherChunks_48: missing assignment

I referred to the sample and used the following code to test

	err = test.IsSolved(&circuit, assignment, ecc.BN254.ScalarField())
	assert := test.NewAssert(t)
	assert.NoError(err)

[doubiliu]

@ivokub

[doubiliu]

Can you post the full example which leads to the panic?

type TempTeststruct[T1, S1, T2, S2 emulated.FieldParams] struct {
	Account []InnerWrapper[T1, S1, T2, S2] `gnark:",secret"`
}

type InnerWrapper[T1, S1, T2, S2 emulated.FieldParams] struct {
	TexT [32]frontend.Variable
}

func (c *TempTeststruct[T1, S1, T2, S2]) Define(api frontend.API) error {
	return nil
}

func TestTemp(t *testing.T) {
	Accounts := make([]InnerWrapper[emulated.Secp256k1Fp, emulated.Secp256k1Fr, emulated.BLS12381Fp, emulated.BLS12381Fr], 10)

	for index := 0; index < 10; index++ {
		//data format
		Text := [32]frontend.Variable{}

		var Account InnerWrapper[emulated.Secp256k1Fp, emulated.Secp256k1Fr, emulated.BLS12381Fp, emulated.BLS12381Fr]
		Account.TexT = Text
	}
	assignment := &TempTeststruct[emulated.Secp256k1Fp, emulated.Secp256k1Fr, emulated.BLS12381Fp, emulated.BLS12381Fr]{
		Account: Accounts,
	}
	circuit := TempTeststruct[emulated.Secp256k1Fp, emulated.Secp256k1Fr, emulated.BLS12381Fp, emulated.BLS12381Fr]{
		Account: make([]InnerWrapper[emulated.Secp256k1Fp, emulated.Secp256k1Fr, emulated.BLS12381Fp, emulated.BLS12381Fr], 10),
	}
	_, err := frontend.Compile(ecc.BN254.ScalarField(), r1cs.NewBuilder, &circuit)
	assert := test.NewAssert(t)
	err = test.IsSolved(&circuit, assignment, ecc.BN254.ScalarField())
	assert.NoError(err)
	return
}

[doubiliu]

error:

=== RUN   TestTemp
10:40:44 INF compiling circuit
10:40:44 INF parsed circuit inputs nbPublic=0 nbSecret=320
10:40:44 INF building constraint builder nbConstraints=0
--- FAIL: TestTemp (0.01s)
panic: when parsing variable Account_0_TexT_0: missing assignment [recovered]
	panic: when parsing variable Account_0_TexT_0: missing assignment

[ivokub]

See the following working example below:

func TestTemp(t *testing.T) {
	Accounts := make([]InnerWrapper[emulated.Secp256k1Fp, emulated.Secp256k1Fr, emulated.BLS12381Fp, emulated.BLS12381Fr], 10)

	for index := 0; index < 10; index++ {
		//data format
		Text := [32]frontend.Variable{}
		for i := 0; i < 32; i++ {
			Text[i] = 0
		}

		Accounts[index].TexT = Text
	}
	assignment := &TempTeststruct[emulated.Secp256k1Fp, emulated.Secp256k1Fr, emulated.BLS12381Fp, emulated.BLS12381Fr]{
		Account: Accounts,
	}
	circuit := TempTeststruct[emulated.Secp256k1Fp, emulated.Secp256k1Fr, emulated.BLS12381Fp, emulated.BLS12381Fr]{
		Account: make([]InnerWrapper[emulated.Secp256k1Fp, emulated.Secp256k1Fr, emulated.BLS12381Fp, emulated.BLS12381Fr], 10),
	}
	_, err := frontend.Compile(ecc.BN254.ScalarField(), r1cs.NewBuilder, &circuit)
	assert := test.NewAssert(t)
	err = test.IsSolved(&circuit, assignment, ecc.BN254.ScalarField())
	assert.NoError(err)
	return
}

There were two issues - first when you initialized the array Text then you didn't assign values to the array items. Secondly - you created the Account variable but didn't assign it to Accounts[index].

I hope that using this example you can extend on rest of your implementation.

[doubiliu]

Can I use a 2D array as input?
E.g: PlainChunks [][]frontend.Variable gnark:",secret"

[ivokub]

You can, but keep in mind that all the slices need to be initialized a la:

chunks := make([][]frontend.Variable, n)
for i := range chunks {
    chunks[i] = make([]frontend.Variable, m)
}
circuit := &Circuit{PlainChunks: chunks}