accounts/abi: Abi binding support for nested arrays, fixes #15648, including nested array unpack fix (#15676)

* accounts/abi/bind: support for multi-dim arrays

Also:
- reduce usage of regexes a bit.
- fix minor Java syntax problems

Fixes #15648

* accounts/abi/bind: Add some more documentation

* accounts/abi/bind: Improve code readability

* accounts/abi: bugfix for unpacking nested arrays

The code previously assumed the arrays/slices were always 1 level
deep. While the packing supports nested arrays (!!!).

The current code for unpacking doesn't return the "consumed" length, so
this fix had to work around that by calculating it (i.e. packing and
 getting resulting length) after the unpacking of the array element.
It's far from ideal, but unpacking behaviour is fixed now.

* accounts/abi: Fix unpacking of nested arrays

Removed the temporary workaround of packing to calculate size, which was
incorrect for slice-like types anyway.
Full size of nested arrays is used now.

* accounts/abi: deeply nested array unpack test

Test unpacking of an array nested more than one level.

* accounts/abi: Add deeply nested array pack test

Same as the deep nested array unpack test, but the other way around.

* accounts/abi/bind: deeply nested arrays bind test

Test the usage of bindings that were generated
for methods with multi-dimensional (and not
just a single extra dimension, like foo[2][3])
array arguments and returns.

edit: trigger rebuild, CI failed to fetch linter module.

* accounts/abi/bind: improve array binding

wrapArray uses a regex now, and arrayBindingJava is improved.

* accounts/abi: Improve naming of element size func

The full step size for unpacking an array
 is now retrieved with "getFullElemSize".

* accounts/abi: support nested nested array args

Previously, the code only considered the outer-size of the array,
ignoring the size of the contents. This was fine for most types,
but nested arrays are packed directly into it, and count towards
the total size. This resulted in arguments following a nested
array to replicate some of the binary contents of the array.

The fix: for arrays, calculate their complete contents size:
 count the arg.Type.Elem.Size when Elem is an Array, and
 repeat when their child is an array too, etc.
The count is the number of 32 byte elements, similar to how it
 previously counted, but nested.

* accounts/abi: Test deep nested arr multi-arguments

Arguments with a deeply nested array should not cause the next arguments
to be read from the wrong position.

accounts/abi/argument.go

@@ -169,6 +169,21 @@ func (arguments Arguments) unpackAtomic(v interface{}, marshalledValues []interf
 	return set(elem, reflectValue, arguments.NonIndexed()[0])
 }
 
+// Computes the full size of an array;
+// i.e. counting nested arrays, which count towards size for unpacking.
+func getArraySize(arr *Type) int {
+	size := arr.Size
+	// Arrays can be nested, with each element being the same size
+	arr = arr.Elem
+	for arr.T == ArrayTy {
+		// Keep multiplying by elem.Size while the elem is an array.
+		size *= arr.Size
+		arr = arr.Elem
+	}
+	// Now we have the full array size, including its children.
+	return size
+}
+
 // UnpackValues can be used to unpack ABI-encoded hexdata according to the ABI-specification,
 // without supplying a struct to unpack into. Instead, this method returns a list containing the
 // values. An atomic argument will be a list with one element.
@@ -181,9 +196,14 @@ func (arguments Arguments) UnpackValues(data []byte) ([]interface{}, error) {
 			// If we have a static array, like [3]uint256, these are coded as
 			// just like uint256,uint256,uint256.
 			// This means that we need to add two 'virtual' arguments when
-			// we count the index from now on
-
-			virtualArgs += arg.Type.Size - 1
+			// we count the index from now on.
+			//
+			// Array values nested multiple levels deep are also encoded inline:
+			// [2][3]uint256: uint256,uint256,uint256,uint256,uint256,uint256
+			//
+			// Calculate the full array size to get the correct offset for the next argument.
+			// Decrement it by 1, as the normal index increment is still applied.
+			virtualArgs += getArraySize(&arg.Type) - 1
 		}
 		if err != nil {
 			return nil, err

accounts/abi/bind/bind.go

@@ -164,118 +164,147 @@ var bindType = map[Lang]func(kind abi.Type) string{
 	LangJava: bindTypeJava,
 }
 
+// Helper function for the binding generators.
+// It reads the unmatched characters after the inner type-match,
+//  (since the inner type is a prefix of the total type declaration),
+//  looks for valid arrays (possibly a dynamic one) wrapping the inner type,
+//  and returns the sizes of these arrays.
+//
+// Returned array sizes are in the same order as solidity signatures; inner array size first.
+// Array sizes may also be "", indicating a dynamic array.
+func wrapArray(stringKind string, innerLen int, innerMapping string) (string, []string) {
+	remainder := stringKind[innerLen:]
+	//find all the sizes
+	matches := regexp.MustCompile(`\[(\d*)\]`).FindAllStringSubmatch(remainder, -1)
+	parts := make([]string, 0, len(matches))
+	for _, match := range matches {
+		//get group 1 from the regex match
+		parts = append(parts, match[1])
+	}
+	return innerMapping, parts
+}
+
+// Translates the array sizes to a Go-lang declaration of a (nested) array of the inner type.
+// Simply returns the inner type if arraySizes is empty.
+func arrayBindingGo(inner string, arraySizes []string) string {
+	out := ""
+	//prepend all array sizes, from outer (end arraySizes) to inner (start arraySizes)
+	for i := len(arraySizes) - 1; i >= 0; i-- {
+		out += "[" + arraySizes[i] + "]"
+	}
+	out += inner
+	return out
+}
+
 // bindTypeGo converts a Solidity type to a Go one. Since there is no clear mapping
 // from all Solidity types to Go ones (e.g. uint17), those that cannot be exactly
 // mapped will use an upscaled type (e.g. *big.Int).
 func bindTypeGo(kind abi.Type) string {
 	stringKind := kind.String()
+	innerLen, innerMapping := bindUnnestedTypeGo(stringKind)
+	return arrayBindingGo(wrapArray(stringKind, innerLen, innerMapping))
+}
+
+// The inner function of bindTypeGo, this finds the inner type of stringKind.
+// (Or just the type itself if it is not an array or slice)
+// The length of the matched part is returned, with the the translated type.
+func bindUnnestedTypeGo(stringKind string) (int, string) {
 
 	switch {
 	case strings.HasPrefix(stringKind, "address"):
-		parts := regexp.MustCompile(`address(\[[0-9]*\])?`).FindStringSubmatch(stringKind)
-		if len(parts) != 2 {
-			return stringKind
-		}
-		return fmt.Sprintf("%scommon.Address", parts[1])
+		return len("address"), "common.Address"
 
 	case strings.HasPrefix(stringKind, "bytes"):
-		parts := regexp.MustCompile(`bytes([0-9]*)(\[[0-9]*\])?`).FindStringSubmatch(stringKind)
-		if len(parts) != 3 {
-			return stringKind
-		}
-		return fmt.Sprintf("%s[%s]byte", parts[2], parts[1])
+		parts := regexp.MustCompile(`bytes([0-9]*)`).FindStringSubmatch(stringKind)
+		return len(parts[0]), fmt.Sprintf("[%s]byte", parts[1])
 
 	case strings.HasPrefix(stringKind, "int") || strings.HasPrefix(stringKind, "uint"):
-		parts := regexp.MustCompile(`(u)?int([0-9]*)(\[[0-9]*\])?`).FindStringSubmatch(stringKind)
-		if len(parts) != 4 {
-			return stringKind
-		}
+		parts := regexp.MustCompile(`(u)?int([0-9]*)`).FindStringSubmatch(stringKind)
 		switch parts[2] {
 		case "8", "16", "32", "64":
-			return fmt.Sprintf("%s%sint%s", parts[3], parts[1], parts[2])
+			return len(parts[0]), fmt.Sprintf("%sint%s", parts[1], parts[2])
 		}
-		return fmt.Sprintf("%s*big.Int", parts[3])
+		return len(parts[0]), "*big.Int"
 
-	case strings.HasPrefix(stringKind, "bool") || strings.HasPrefix(stringKind, "string"):
-		parts := regexp.MustCompile(`([a-z]+)(\[[0-9]*\])?`).FindStringSubmatch(stringKind)
-		if len(parts) != 3 {
-			return stringKind
-		}
-		return fmt.Sprintf("%s%s", parts[2], parts[1])
+	case strings.HasPrefix(stringKind, "bool"):
+		return len("bool"), "bool"
+
+	case strings.HasPrefix(stringKind, "string"):
+		return len("string"), "string"
 
 	default:
-		return stringKind
+		return len(stringKind), stringKind
 	}
 }
 
+// Translates the array sizes to a Java declaration of a (nested) array of the inner type.
+// Simply returns the inner type if arraySizes is empty.
+func arrayBindingJava(inner string, arraySizes []string) string {
+	// Java array type declarations do not include the length.
+	return inner + strings.Repeat("[]", len(arraySizes))
+}
+
 // bindTypeJava converts a Solidity type to a Java one. Since there is no clear mapping
 // from all Solidity types to Java ones (e.g. uint17), those that cannot be exactly
 // mapped will use an upscaled type (e.g. BigDecimal).
 func bindTypeJava(kind abi.Type) string {
 	stringKind := kind.String()
+	innerLen, innerMapping := bindUnnestedTypeJava(stringKind)
+	return arrayBindingJava(wrapArray(stringKind, innerLen, innerMapping))
+}
+
+// The inner function of bindTypeJava, this finds the inner type of stringKind.
+// (Or just the type itself if it is not an array or slice)
+// The length of the matched part is returned, with the the translated type.
+func bindUnnestedTypeJava(stringKind string) (int, string) {
 
 	switch {
 	case strings.HasPrefix(stringKind, "address"):
 		parts := regexp.MustCompile(`address(\[[0-9]*\])?`).FindStringSubmatch(stringKind)
 		if len(parts) != 2 {
-			return stringKind
+			return len(stringKind), stringKind
 		}
 		if parts[1] == "" {
-			return fmt.Sprintf("Address")
+			return len("address"), "Address"
 		}
-		return fmt.Sprintf("Addresses")
+		return len(parts[0]), "Addresses"
 
 	case strings.HasPrefix(stringKind, "bytes"):
-		parts := regexp.MustCompile(`bytes([0-9]*)(\[[0-9]*\])?`).FindStringSubmatch(stringKind)
-		if len(parts) != 3 {
-			return stringKind
-		}
-		if parts[2] != "" {
-			return "byte[][]"
+		parts := regexp.MustCompile(`bytes([0-9]*)`).FindStringSubmatch(stringKind)
+		if len(parts) != 2 {
+			return len(stringKind), stringKind
 		}
-		return "byte[]"
+		return len(parts[0]), "byte[]"
 
 	case strings.HasPrefix(stringKind, "int") || strings.HasPrefix(stringKind, "uint"):
-		parts := regexp.MustCompile(`(u)?int([0-9]*)(\[[0-9]*\])?`).FindStringSubmatch(stringKind)
-		if len(parts) != 4 {
-			return stringKind
-		}
-		switch parts[2] {
-		case "8", "16", "32", "64":
-			if parts[1] == "" {
-				if parts[3] == "" {
-					return fmt.Sprintf("int%s", parts[2])
-				}
-				return fmt.Sprintf("int%s[]", parts[2])
-			}
+		//Note that uint and int (without digits) are also matched,
+		// these are size 256, and will translate to BigInt (the default).
+		parts := regexp.MustCompile(`(u)?int([0-9]*)`).FindStringSubmatch(stringKind)
+		if len(parts) != 3 {
+			return len(stringKind), stringKind
 		}
-		if parts[3] == "" {
-			return fmt.Sprintf("BigInt")
+
+		namedSize := map[string]string{
+			"8":  "byte",
+			"16": "short",
+			"32": "int",
+			"64": "long",
+		}[parts[2]]
+
+		//default to BigInt
+		if namedSize == "" {
+			namedSize = "BigInt"
 		}
-		return fmt.Sprintf("BigInts")
+		return len(parts[0]), namedSize
 
 	case strings.HasPrefix(stringKind, "bool"):
-		parts := regexp.MustCompile(`bool(\[[0-9]*\])?`).FindStringSubmatch(stringKind)
-		if len(parts) != 2 {
-			return stringKind
-		}
-		if parts[1] == "" {
-			return fmt.Sprintf("bool")
-		}
-		return fmt.Sprintf("bool[]")
+		return len("bool"), "boolean"
 
 	case strings.HasPrefix(stringKind, "string"):
-		parts := regexp.MustCompile(`string(\[[0-9]*\])?`).FindStringSubmatch(stringKind)
-		if len(parts) != 2 {
-			return stringKind
-		}
-		if parts[1] == "" {
-			return fmt.Sprintf("String")
-		}
-		return fmt.Sprintf("String[]")
+		return len("string"), "String"
 
 	default:
-		return stringKind
+		return len(stringKind), stringKind
 	}
 }
 
@@ -325,11 +354,13 @@ func namedTypeJava(javaKind string, solKind abi.Type) string {
 		return "String"
 	case "string[]":
 		return "Strings"
-	case "bool":
+	case "boolean":
 		return "Bool"
-	case "bool[]":
+	case "boolean[]":
 		return "Bools"
-	case "BigInt":
+	case "BigInt[]":
+		return "BigInts"
+	default:
 		parts := regexp.MustCompile(`(u)?int([0-9]*)(\[[0-9]*\])?`).FindStringSubmatch(solKind.String())
 		if len(parts) != 4 {
 			return javaKind
@@ -344,8 +375,6 @@ func namedTypeJava(javaKind string, solKind abi.Type) string {
 		default:
 			return javaKind
 		}
-	default:
-		return javaKind
 	}
 }
 

accounts/abi/pack_test.go

@@ -299,6 +299,11 @@ func TestPack(t *testing.T) {
 			[32]byte{1},
 			common.Hex2Bytes("0100000000000000000000000000000000000000000000000000000000000000"),
 		},
+		{
+			"uint32[2][3][4]",
+			[4][3][2]uint32{{{1, 2}, {3, 4}, {5, 6}}, {{7, 8}, {9, 10}, {11, 12}}, {{13, 14}, {15, 16}, {17, 18}}, {{19, 20}, {21, 22}, {23, 24}}},
+			common.Hex2Bytes("000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000003000000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000050000000000000000000000000000000000000000000000000000000000000006000000000000000000000000000000000000000000000000000000000000000700000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000009000000000000000000000000000000000000000000000000000000000000000a000000000000000000000000000000000000000000000000000000000000000b000000000000000000000000000000000000000000000000000000000000000c000000000000000000000000000000000000000000000000000000000000000d000000000000000000000000000000000000000000000000000000000000000e000000000000000000000000000000000000000000000000000000000000000f000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000110000000000000000000000000000000000000000000000000000000000000012000000000000000000000000000000000000000000000000000000000000001300000000000000000000000000000000000000000000000000000000000000140000000000000000000000000000000000000000000000000000000000000015000000000000000000000000000000000000000000000000000000000000001600000000000000000000000000000000000000000000000000000000000000170000000000000000000000000000000000000000000000000000000000000018"),
+		},
 		{
 			"address[]",
 			[]common.Address{{1}, {2}},

accounts/abi/unpack.go

@@ -93,6 +93,17 @@ func readFixedBytes(t Type, word []byte) (interface{}, error) {
 
 }
 
+func getFullElemSize(elem *Type) int {
+	//all other should be counted as 32 (slices have pointers to respective elements)
+	size := 32
+	//arrays wrap it, each element being the same size
+	for elem.T == ArrayTy {
+		size *= elem.Size
+		elem = elem.Elem
+	}
+	return size
+}
+
 // iteratively unpack elements
 func forEachUnpack(t Type, output []byte, start, size int) (interface{}, error) {
 	if size < 0 {
@@ -104,7 +115,6 @@ func forEachUnpack(t Type, output []byte, start, size int) (interface{}, error)
 
 	// this value will become our slice or our array, depending on the type
 	var refSlice reflect.Value
-	slice := output[start : start+size*32]
 
 	if t.T == SliceTy {
 		// declare our slice
@@ -116,15 +126,20 @@ func forEachUnpack(t Type, output []byte, start, size int) (interface{}, error)
 		return nil, fmt.Errorf("abi: invalid type in array/slice unpacking stage")
 	}
 
-	for i, j := start, 0; j*32 < len(slice); i, j = i+32, j+1 {
-		// this corrects the arrangement so that we get all the underlying array values
-		if t.Elem.T == ArrayTy && j != 0 {
-			i = start + t.Elem.Size*32*j
-		}
+	// Arrays have packed elements, resulting in longer unpack steps.
+	// Slices have just 32 bytes per element (pointing to the contents).
+	elemSize := 32
+	if t.T == ArrayTy {
+		elemSize = getFullElemSize(t.Elem)
+	}
+
+	for i, j := start, 0; j < size; i, j = i+elemSize, j+1 {
+
 		inter, err := toGoType(i, *t.Elem, output)
 		if err != nil {
 			return nil, err
 		}
+
 		// append the item to our reflect slice
 		refSlice.Index(j).Set(reflect.ValueOf(inter))
 	}

accounts/abi/unpack_test.go

@@ -189,6 +189,11 @@ var unpackTests = []unpackTest{
 		enc:  "00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
 		want: [2]uint32{1, 2},
 	},
+	{
+		def:  `[{"type": "uint32[2][3][4]"}]`,
+		enc:  "000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000003000000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000050000000000000000000000000000000000000000000000000000000000000006000000000000000000000000000000000000000000000000000000000000000700000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000009000000000000000000000000000000000000000000000000000000000000000a000000000000000000000000000000000000000000000000000000000000000b000000000000000000000000000000000000000000000000000000000000000c000000000000000000000000000000000000000000000000000000000000000d000000000000000000000000000000000000000000000000000000000000000e000000000000000000000000000000000000000000000000000000000000000f000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000110000000000000000000000000000000000000000000000000000000000000012000000000000000000000000000000000000000000000000000000000000001300000000000000000000000000000000000000000000000000000000000000140000000000000000000000000000000000000000000000000000000000000015000000000000000000000000000000000000000000000000000000000000001600000000000000000000000000000000000000000000000000000000000000170000000000000000000000000000000000000000000000000000000000000018",
+		want: [4][3][2]uint32{{{1, 2}, {3, 4}, {5, 6}}, {{7, 8}, {9, 10}, {11, 12}}, {{13, 14}, {15, 16}, {17, 18}}, {{19, 20}, {21, 22}, {23, 24}}},
+	},
 	{
 		def:  `[{"type": "uint64[]"}]`,
 		enc:  "0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002",
@@ -435,6 +440,46 @@ func TestMultiReturnWithArray(t *testing.T) {
 	}
 }
 
+func TestMultiReturnWithDeeplyNestedArray(t *testing.T) {
+	// Similar to TestMultiReturnWithArray, but with a special case in mind:
+	//  values of nested static arrays count towards the size as well, and any element following
+	//  after such nested array argument should be read with the correct offset,
+	//  so that it does not read content from the previous array argument.
+	const definition = `[{"name" : "multi", "outputs": [{"type": "uint64[3][2][4]"}, {"type": "uint64"}]}]`
+	abi, err := JSON(strings.NewReader(definition))
+	if err != nil {
+		t.Fatal(err)
+	}
+	buff := new(bytes.Buffer)
+	// construct the test array, each 3 char element is joined with 61 '0' chars,
+	// to from the ((3 + 61) * 0.5) = 32 byte elements in the array.
+	buff.Write(common.Hex2Bytes(strings.Join([]string{
+		"", //empty, to apply the 61-char separator to the first element as well.
+		"111", "112", "113", "121", "122", "123",
+		"211", "212", "213", "221", "222", "223",
+		"311", "312", "313", "321", "322", "323",
+		"411", "412", "413", "421", "422", "423",
+	}, "0000000000000000000000000000000000000000000000000000000000000")))
+	buff.Write(common.Hex2Bytes("0000000000000000000000000000000000000000000000000000000000009876"))
+
+	ret1, ret1Exp := new([4][2][3]uint64), [4][2][3]uint64{
+		{{0x111, 0x112, 0x113}, {0x121, 0x122, 0x123}},
+		{{0x211, 0x212, 0x213}, {0x221, 0x222, 0x223}},
+		{{0x311, 0x312, 0x313}, {0x321, 0x322, 0x323}},
+		{{0x411, 0x412, 0x413}, {0x421, 0x422, 0x423}},
+	}
+	ret2, ret2Exp := new(uint64), uint64(0x9876)
+	if err := abi.Unpack(&[]interface{}{ret1, ret2}, "multi", buff.Bytes()); err != nil {
+		t.Fatal(err)
+	}
+	if !reflect.DeepEqual(*ret1, ret1Exp) {
+		t.Error("array result", *ret1, "!= Expected", ret1Exp)
+	}
+	if *ret2 != ret2Exp {
+		t.Error("int result", *ret2, "!= Expected", ret2Exp)
+	}
+}
+
 func TestUnmarshal(t *testing.T) {
 	const definition = `[
 	{ "name" : "int", "constant" : false, "outputs": [ { "type": "uint256" } ] },