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diff --git a/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol
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+++ b/packages/contracts/src/2.0.0/protocol/AssetProxy/ERC721Proxy.sol
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+/*
+
+ Copyright 2018 ZeroEx Intl.
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+
+*/
+
+pragma solidity ^0.4.24;
+pragma experimental ABIEncoderV2;
+
+import "../../utils/LibBytes/LibBytes.sol";
+import "./MixinAuthorizable.sol";
+
+contract ERC721Proxy is
+ MixinAuthorizable
+{
+ // Id of this proxy.
+ bytes4 constant PROXY_ID = bytes4(keccak256("ERC721Token(address,uint256,bytes)"));
+
+ function ()
+ external
+ {
+ assembly {
+ // The first 4 bytes of calldata holds the function selector
+ let selector := and(calldataload(0), 0xffffffff00000000000000000000000000000000000000000000000000000000)
+
+ // `transferFrom` will be called with the following parameters:
+ // assetData Encoded byte array.
+ // from Address to transfer asset from.
+ // to Address to transfer asset to.
+ // amount Amount of asset to transfer.
+ // bytes4(keccak256("transferFrom(bytes,address,address,uint256)")) = 0xa85e59e4
+ if eq(selector, 0xa85e59e400000000000000000000000000000000000000000000000000000000) {
+
+ // To lookup a value in a mapping, we load from the storage location keccak256(k, p),
+ // where k is the key left padded to 32 bytes and p is the storage slot
+ let start := mload(64)
+ mstore(start, and(caller, 0xffffffffffffffffffffffffffffffffffffffff))
+ mstore(add(start, 32), authorized_slot)
+
+ // Revert if authorized[msg.sender] == false
+ if iszero(sload(keccak256(start, 64))) {
+ // Revert with `Error("SENDER_NOT_AUTHORIZED")`
+ mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+ mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+ mstore(64, 0x0000001553454e4445525f4e4f545f415554484f52495a454400000000000000)
+ mstore(96, 0)
+ revert(0, 100)
+ }
+
+ // `transferFrom`.
+ // The function is marked `external`, so no abi decodeding is done for
+ // us. Instead, we expect the `calldata` memory to contain the
+ // following:
+ //
+ // | Area | Offset | Length | Contents |
+ // |----------|--------|---------|-------------------------------------|
+ // | Header | 0 | 4 | function selector |
+ // | Params | | 4 * 32 | function parameters: |
+ // | | 4 | | 1. offset to assetData (*) |
+ // | | 36 | | 2. from |
+ // | | 68 | | 3. to |
+ // | | 100 | | 4. amount |
+ // | Data | | | assetData: |
+ // | | 132 | 32 | assetData Length |
+ // | | 164 | ** | assetData Contents |
+ //
+ // (*): offset is computed from start of function parameters, so offset
+ // by an additional 4 bytes in the calldata.
+ //
+ // WARNING: The ABIv2 specification allows additional padding between
+ // the Params and Data section. This will result in a larger
+ // offset to assetData.
+
+ // Asset data itself is encoded as follows:
+ //
+ // | Area | Offset | Length | Contents |
+ // |----------|--------|---------|-------------------------------------|
+ // | Header | 0 | 4 | function selector |
+ // | Params | | 3 * 32 | function parameters: |
+ // | | 4 | 12 + 20 | 1. token address |
+ // | | 36 | | 2. tokenId |
+ // | | 68 | | 3. offset to receiverData (*) |
+ // | Data | | | receiverData: |
+ // | | 100 | 32 | receiverData Length |
+ // | | 132 | ** | receiverData Contents |
+
+ // We construct calldata for the `token.safeTransferFrom` ABI.
+ // The layout of this calldata is in the table below.
+ //
+ // | Area | Offset | Length | Contents |
+ // |----------|--------|---------|-------------------------------------|
+ // | Header | 0 | 4 | function selector |
+ // | Params | | 4 * 32 | function parameters: |
+ // | | 4 | | 1. from |
+ // | | 36 | | 2. to |
+ // | | 68 | | 3. tokenId |
+ // | | 100 | | 4. offset to receiverData (*) |
+ // | Data | | | receiverData: |
+ // | | 132 | 32 | receiverData Length |
+ // | | 164 | ** | receiverData Contents |
+
+ // There exists only 1 of each token.
+ // require(amount == 1, "INVALID_AMOUNT")
+ if sub(calldataload(100), 1) {
+ // Revert with `Error("INVALID_AMOUNT")`
+ mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+ mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+ mstore(64, 0x0000000e494e56414c49445f414d4f554e540000000000000000000000000000)
+ mstore(96, 0)
+ revert(0, 100)
+ }
+
+ // Require assetData to be at least 132 bytes
+ let offset := calldataload(4)
+ if lt(calldataload(add(offset, 4)), 132) {
+ // Revert with `Error("LENGTH_GREATER_THAN_131_REQUIRED")`
+ mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+ mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+ mstore(64, 0x000000204c454e4754485f475245415445525f5448414e5f3133315f52455155)
+ mstore(96, 0x4952454400000000000000000000000000000000000000000000000000000000)
+ revert(0, 100)
+ }
+
+ /////// Setup State ///////
+ // `cdStart` is the start of the calldata for
+ // `token.safeTransferFrom` (equal to free memory ptr).
+ let cdStart := mload(64)
+ // `dataAreaLength` is the total number of words
+ // needed to store `receiverData`
+ // As-per the ABI spec, this value is padded up to
+ // the nearest multiple of 32,
+ // and includes 32-bytes for length.
+ // It's calculated as folows:
+ // - Unpadded length in bytes = `mload(receiverData) + 32`
+ // - Add 31 to convert rounding down to rounding up.
+ // Combined with the previous and this is `63`.
+ // - Round down to nearest multiple of 32 by clearing
+ // bits 0x1F. This is done with `and` and a mask.
+
+ /////// Setup Header Area ///////
+ // This area holds the 4-byte `transferFromSelector`.
+ // Any trailing data in transferFromSelector will be
+ // overwritten in the next `mstore` call.
+ mstore(cdStart, 0xb88d4fde00000000000000000000000000000000000000000000000000000000)
+
+ /////// Setup Params Area ///////
+ // Each parameter is padded to 32-bytes.
+ // The entire Params Area is 128 bytes.
+ // Notes:
+ // 1. A 20-byte mask is applied to addresses
+ // to zero-out the unused bytes.
+ // 2. The offset to `receiverData` is the length
+ // of the Params Area (128 bytes).
+
+ let length := calldataload(add(offset, 136))
+ let token := calldataload(add(offset, 40))
+
+ // Round length up to multiple of 32
+ length := and(add(length, 31), 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFE0)
+
+ // Copy `from` and `to`
+ calldatacopy(add(cdStart, 4), 36, 64)
+
+ // TokenId
+ mstore(add(cdStart, 68), calldataload(add(offset, 72)))
+
+ // Offset to receiverData
+ mstore(add(cdStart, 100), 128)
+
+ // receiverData (including length)
+ calldatacopy(add(cdStart, 132), add(offset, 136), add(length, 32))
+
+ /////// Call `token.safeTransferFrom` using the calldata ///////
+ let success := call(
+ gas, // forward all gas
+ token, // call address of token contract
+ 0, // don't send any ETH
+ cdStart, // pointer to start of input
+ add(length, 164), // length of input
+ 0, // write output to null
+ 0 // output size is 0 bytes
+ )
+ if success {
+ return(0, 0)
+ }
+
+ // Revert with `Error("TRANSFER_FAILED")`
+ mstore(0, 0x08c379a000000000000000000000000000000000000000000000000000000000)
+ mstore(32, 0x0000002000000000000000000000000000000000000000000000000000000000)
+ mstore(64, 0x0000000f5452414e534645525f4641494c454400000000000000000000000000)
+ mstore(96, 0)
+ revert(0, 100)
+ }
+ }
+ }
+
+ /// @dev Gets the proxy id associated with the proxy address.
+ /// @return Proxy id.
+ function getProxyId()
+ external
+ pure
+ returns (bytes4)
+ {
+ return PROXY_ID;
+ }
+}