blobToSharesV0

foundry.toml

@@ -2,3 +2,4 @@
 solc_version = "0.8.22"
 via_ir = true
 gas_reports = ["*"]
+fs_permissions = [{ access = "read", path = "./"}]

src/lib/commitment/Commitment.sol

@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.22;
+
+import {Namespace, isReservedNamespace} from "../tree/Types.sol";
+import "openzeppelin-contracts/contracts/utils/math/Math.sol";
+import "forge-std/console.sol";
+
+// Turn little-endian into big-endian
+// Source: https://ethereum.stackexchange.com/a/83627
+function reverse(uint32 input) pure returns (uint32 v) {
+    v = input;
+
+    // swap bytes
+    v = ((v & 0xFF00FF00) >> 8) |
+        ((v & 0x00FF00FF) << 8);
+
+    // swap 2-byte long pairs
+    v = (v >> 16) | (v << 16);
+}
+
+function div_ceil(uint256 x, uint256 y) pure returns (uint256 z) {
+    z = x / y + (x % y == 0 ? 0 : 1);
+}
+
+function num_shares(uint256 blobSize) pure returns (uint256) {
+    return div_ceil((Math.max(blobSize, 478) - 478), 482) + 1;
+}
+
+function copyNamespace(bytes memory share, bytes29 namespaceBytes) pure {
+    for (uint256 i = 0; i < namespaceBytes.length; i++) {
+        share[i] = namespaceBytes[i];
+    }
+}
+
+function writeInfoByteV0(bytes memory share, bool startingSequence) pure {
+    share[29] = bytes1(startingSequence ? 1 : 0);
+}
+
+function writeSequenceLength(bytes memory share, uint32 sequenceLength) pure {
+    // Removed the "reverse", because it didn't work- apparently it's already big-endian?
+    //bytes4 sequenceLengthBigEndianBytes = bytes4(abi.encodePacked(reverse(sequenceLength)));
+    bytes4 sequenceLengthBigEndianBytes = bytes4(abi.encodePacked(sequenceLength));
+    share[30] = sequenceLengthBigEndianBytes[0];
+    share[31] = sequenceLengthBigEndianBytes[1];
+    share[32] = sequenceLengthBigEndianBytes[2];
+    share[33] = sequenceLengthBigEndianBytes[3];
+}
+
+function copyBytes(bytes memory buffer, uint32 cursor, bytes memory data, uint32 length) pure returns (uint32) {
+
+    uint256 start = buffer.length - length;
+    for (uint256 i = start; i < buffer.length; i++) {
+        if (cursor < data.length) {
+            buffer[i] = data[cursor];
+            cursor++;
+        }
+        else {
+            buffer[i] = 0;
+        }
+    }
+    return cursor;
+}
+
+function bytesToHexString(bytes memory buffer) pure returns (string memory) {
+
+    // Fixed buffer size for hexadecimal convertion
+    bytes memory converted = new bytes(buffer.length * 2);
+
+    bytes memory _base = "0123456789abcdef";
+
+    for (uint256 i = 0; i < buffer.length; i++) {
+        converted[i * 2] = _base[uint8(buffer[i]) / _base.length];
+        converted[i * 2 + 1] = _base[uint8(buffer[i]) % _base.length];
+    }
+
+    return string(abi.encodePacked(converted));
+}
+
+// Share Version 0
+function bytesToSharesV0(bytes memory blobData, Namespace memory namespace) pure returns (bytes[] memory shares, bool err) {
+    if (namespace.version != 0) {
+        return (new bytes[](0), true);
+    }
+    if (isReservedNamespace(namespace)) {
+        return (new bytes[](0), true);
+    }
+    // Allocate memory for the shares
+    uint256 numShares = num_shares(blobData.length); 
+    bytes[] memory _shares = new bytes[](numShares);
+    for (uint256 i = 0; i < _shares.length; i++) {
+        _shares[i] = new bytes(512);
+    }
+    // Get the namespace bytes
+    bytes29 namespaceBytes = namespace.toBytes();
+
+    // The first share is special, because it has startingSequence set to true and the 4-byte sequence length
+    copyNamespace(_shares[0], namespaceBytes);
+    writeInfoByteV0(_shares[0], true);
+    writeSequenceLength(_shares[0], uint32(blobData.length));
+    uint32 cursor = 0;
+    cursor = copyBytes(_shares[0], cursor, blobData, uint32(478)); //only 478 bytes, because 4 bytes are used for the sequence length
+
+    if (shares.length != 1) {
+        // The remaining shares are all the same
+        for (uint256 i = 1; i < _shares.length; i++) {
+            // Copy the namespace
+            copyNamespace(_shares[i], namespaceBytes);
+            // Write the info byte
+            writeInfoByteV0(_shares[i], false);
+            // Copy the data
+            cursor = copyBytes(_shares[i], cursor, blobData, uint32(482)); // copy the full 482 bytes
+        }
+    }
+
+    shares = _shares;
+    err = false;
+}

src/lib/commitment/test/Commitment.t.sol

@@ -0,0 +1,67 @@
+pragma solidity ^0.8.22;
+
+import "ds-test/test.sol";
+import "forge-std/Vm.sol";
+import "forge-std/console.sol";
+import {bytesToSharesV0, bytesToHexString} from "../Commitment.sol";
+import {toNamespace, Namespace} from "../../tree/Types.sol";
+
+contract CommitmentTest is DSTest {
+    Vm private constant vm = Vm(address(uint160(uint256(keccak256("hevm cheat code")))));
+
+    struct TestVector {
+        string data;
+        string namespace;
+        string shares;
+    }
+
+    function fromHexChar(uint8 c) public pure returns (uint8) {
+        if (bytes1(c) >= bytes1('0') && bytes1(c) <= bytes1('9')) {
+            return c - uint8(bytes1('0'));
+        }
+        if (bytes1(c) >= bytes1('a') && bytes1(c) <= bytes1('f')) {
+            return 10 + c - uint8(bytes1('a'));
+        }
+        if (bytes1(c) >= bytes1('A') && bytes1(c) <= bytes1('F')) {
+            return 10 + c - uint8(bytes1('A'));
+        }
+        revert("fail");
+    }
+
+    function fromHex(string memory s) public pure returns (bytes memory) {
+        bytes memory ss = bytes(s);
+        require(ss.length%2 == 0); // length must be even
+        bytes memory r = new bytes(ss.length/2);
+        for (uint i=0; i<ss.length/2; ++i) {
+            r[i] = bytes1(fromHexChar(uint8(ss[2*i])) * 16 + fromHexChar(uint8(ss[2*i+1])));
+        }
+        return r;
+    }
+
+    function compareStrings(string memory a, string memory b) public pure returns (bool) {
+        return (keccak256(abi.encodePacked((a))) == keccak256(abi.encodePacked((b))));
+    }
+
+    function testBytesToSharesV0() view external {
+
+        // test vectors were generated here: https://github.com/S1nus/share-test-vec-gen
+        string memory path = "./src/lib/commitment/test/testVectors.json";
+        string memory jsonData = vm.readFile(path);
+        bytes memory vecsData = vm.parseJson(jsonData);
+        TestVector[] memory vecs = abi.decode(vecsData, (TestVector[]));
+
+        for (uint i = 0; i < vecs.length; i++) {
+            bytes29 nsString = bytes29(fromHex(vecs[i].namespace));
+            Namespace memory ns = toNamespace(nsString);
+            bytes memory data = fromHex(vecs[i].data);
+            (bytes[] memory shares, bool err) = bytesToSharesV0(data, ns);
+            string memory out = "";
+            for (uint j = 0; j < shares.length; j++) {
+                out = string.concat(out, bytesToHexString(shares[j]));
+            }
+            // none of the test vectors should cause an error
+            assert(!err);
+            assert(compareStrings(out, vecs[i].shares));
+        }
+    }
+}