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Create writeLength function in LibBytes

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This commit is contained in:
Amir Bandeali 2019-09-01 18:32:52 -07:00
parent d131c39e46
commit 9a3a302754
3 changed files with 102 additions and 8 deletions
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14
contracts/utils/contracts/src/LibBytes.sol
View File

@ -616,4 +616,18 @@ library LibBytes {
sourceLen
);
}
/// @dev Writes a new length to a byte array.
/// Decreasing length will lead to removing the corresponding lower order bytes from the byte array.
/// Increasing length may lead to appending adjacent in-memory bytes to the end of the byte array.
/// @param b Bytes array to write new length to.
/// @param length New length of byte array.
function writeLength(bytes memory b, uint256 length)
internal
pure
{
assembly {
mstore(b, length)
}
}
}

22
contracts/utils/contracts/test/TestLibBytes.sol
View File

@ -303,4 +303,26 @@ contract TestLibBytes {
result = LibBytes.sliceDestructive(b, from, to);
return (result, b);
}
/// @dev Returns a byte array with an updated length.
/// @dev Writes a new length to a byte array.
/// Decreasing length will lead to removing the corresponding lower order bytes from the byte array.
/// Increasing length may lead to appending adjacent in-memory bytes to the end of the byte array.
/// @param b Bytes array to write new length to.
/// @param length New length of byte array.
/// @param extraBytes Bytes that are appended to end of b in memory.
function publicWriteLength(
bytes memory b,
uint256 length,
bytes memory extraBytes
)
public
pure
returns (bytes memory)
{
uint256 bEnd = b.contentAddress() + b.length;
LibBytes.memCopy(bEnd, extraBytes.contentAddress(), extraBytes.length);
b.writeLength(length);
return b;
}
}

74
contracts/utils/test/lib_bytes.ts
View File

@ -668,7 +668,7 @@ describe('LibBytes', () => {
describe('writeBytesWithLength', () => {
it('should successfully write short, nested array of bytes when it takes up the whole array', async () => {
const testBytesOffset = new BigNumber(0);
const emptyByteArray = ethUtil.bufferToHex(new Buffer(shortTestBytesAsBuffer.byteLength));
const emptyByteArray = ethUtil.bufferToHex(ethUtil.toBuffer(shortTestBytesAsBuffer.byteLength));
const bytesWritten = await libBytes.publicWriteBytesWithLength.callAsync(
emptyByteArray,
testBytesOffset,
@ -683,7 +683,7 @@ describe('LibBytes', () => {
const prefixDataAsBuffer = ethUtil.toBuffer(prefixData);
const prefixOffset = new BigNumber(0);
const emptyByteArray = ethUtil.bufferToHex(
new Buffer(prefixDataAsBuffer.byteLength + shortTestBytesAsBuffer.byteLength),
ethUtil.toBuffer(prefixDataAsBuffer.byteLength + shortTestBytesAsBuffer.byteLength),
);
let bytesWritten = await libBytes.publicWriteBytesWithLength.callAsync(
emptyByteArray,
@ -703,7 +703,7 @@ describe('LibBytes', () => {
});
it('should successfully write a nested array of bytes - one word in length - when it takes up the whole array', async () => {
const testBytesOffset = new BigNumber(0);
const emptyByteArray = ethUtil.bufferToHex(new Buffer(wordOfTestBytesAsBuffer.byteLength));
const emptyByteArray = ethUtil.bufferToHex(ethUtil.toBuffer(wordOfTestBytesAsBuffer.byteLength));
const bytesWritten = await libBytes.publicWriteBytesWithLength.callAsync(
emptyByteArray,
testBytesOffset,
@ -718,7 +718,7 @@ describe('LibBytes', () => {
const prefixDataAsBuffer = ethUtil.toBuffer(prefixData);
const prefixOffset = new BigNumber(0);
const emptyByteArray = ethUtil.bufferToHex(
new Buffer(prefixDataAsBuffer.byteLength + wordOfTestBytesAsBuffer.byteLength),
ethUtil.toBuffer(prefixDataAsBuffer.byteLength + wordOfTestBytesAsBuffer.byteLength),
);
let bytesWritten = await libBytes.publicWriteBytesWithLength.callAsync(
emptyByteArray,
@ -738,7 +738,7 @@ describe('LibBytes', () => {
});
it('should successfully write a long, nested bytes when it takes up the whole array', async () => {
const testBytesOffset = new BigNumber(0);
const emptyByteArray = ethUtil.bufferToHex(new Buffer(longTestBytesAsBuffer.byteLength));
const emptyByteArray = ethUtil.bufferToHex(ethUtil.toBuffer(longTestBytesAsBuffer.byteLength));
const bytesWritten = await libBytes.publicWriteBytesWithLength.callAsync(
emptyByteArray,
testBytesOffset,
@ -753,7 +753,7 @@ describe('LibBytes', () => {
const prefixDataAsBuffer = ethUtil.toBuffer(prefixData);
const prefixOffset = new BigNumber(0);
const emptyByteArray = ethUtil.bufferToHex(
new Buffer(prefixDataAsBuffer.byteLength + longTestBytesAsBuffer.byteLength),
ethUtil.toBuffer(prefixDataAsBuffer.byteLength + longTestBytesAsBuffer.byteLength),
);
let bytesWritten = await libBytes.publicWriteBytesWithLength.callAsync(
emptyByteArray,
@ -769,7 +769,7 @@ describe('LibBytes', () => {
});
it('should fail if the byte array is too short to hold the length of a nested byte array', async () => {
const offset = new BigNumber(0);
const emptyByteArray = ethUtil.bufferToHex(new Buffer(1));
const emptyByteArray = ethUtil.bufferToHex(ethUtil.toBuffer(1));
const inputLen = new BigNumber((longData.length - 2) / 2);
const expectedError = new LibBytesRevertErrors.InvalidByteOperationError(
LibBytesRevertErrors.InvalidByteOperationErrorCodes.LengthGreaterThanOrEqualsNestedBytesLengthRequired,
@ -781,7 +781,7 @@ describe('LibBytes', () => {
).to.revertWith(expectedError);
});
it('should fail if the length between the offset and end of the byte array is too short to hold the length of a nested byte array', async () => {
const emptyByteArray = ethUtil.bufferToHex(new Buffer(shortTestBytesAsBuffer.byteLength));
const emptyByteArray = ethUtil.bufferToHex(ethUtil.toBuffer(shortTestBytesAsBuffer.byteLength));
const badOffset = new BigNumber(ethUtil.toBuffer(shortTestBytesAsBuffer).byteLength);
const inputLen = new BigNumber((shortData.length - 2) / 2);
const expectedError = new LibBytesRevertErrors.InvalidByteOperationError(
@ -1074,5 +1074,63 @@ describe('LibBytes', () => {
expect(result).to.eq(byteArrayLongerThan32Bytes);
});
});
describe('writeLength', () => {
it('should return a null byte array if length is set to 0', async () => {
const result = await libBytes.publicWriteLength.callAsync(
byteArrayLongerThan32Bytes,
constants.ZERO_AMOUNT,
constants.NULL_BYTES,
);
expect(result).to.eq(constants.NULL_BYTES);
});
it('should return the same byte array if length is unchanged', async () => {
const byteLen = (byteArrayLongerThan32Bytes.length - 2) / 2;
const result = await libBytes.publicWriteLength.callAsync(
byteArrayLongerThan32Bytes,
new BigNumber(byteLen),
constants.NULL_BYTES,
);
expect(result).to.eq(byteArrayLongerThan32Bytes);
});
it('should shave off lower order bytes if new length is less than original', async () => {
const byteLen = (byteArrayLongerThan32Bytes.length - 2) / 2;
const newLen = new BigNumber(byteLen).dividedToIntegerBy(2);
const result = await libBytes.publicWriteLength.callAsync(
byteArrayLongerThan32Bytes,
newLen,
constants.NULL_BYTES,
);
expect(result).to.eq(
byteArrayLongerThan32Bytes.slice(
0,
newLen
.multipliedBy(2)
.plus(2)
.toNumber(),
),
);
});
it("should right pad with 0's if new length is greater than original and no extra bytes are appended", async () => {
const byteLen = (byteArrayLongerThan32Bytes.length - 2) / 2;
const newLen = new BigNumber(byteLen).multipliedBy(2);
const result = await libBytes.publicWriteLength.callAsync(
byteArrayLongerThan32Bytes,
newLen,
constants.NULL_BYTES,
);
expect(result).to.eq(`${byteArrayLongerThan32Bytes}${'0'.repeat(byteArrayLongerThan32Bytes.length - 2)}`);
});
it('should right pad with extra bytes if specified', async () => {
const byteLen = (byteArrayLongerThan32Bytes.length - 2) / 2;
const newLen = new BigNumber(byteLen).multipliedBy(2);
const result = await libBytes.publicWriteLength.callAsync(
byteArrayLongerThan32Bytes,
newLen,
byteArrayLongerThan32Bytes,
);
expect(result).to.eq(`${byteArrayLongerThan32Bytes}${byteArrayLongerThan32Bytes.slice(2)}`);
});
});
});
// tslint:disable:max-file-line-count