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Resolved edge case in Memcpy where where send would eventually turn "negative" and wrap around.

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This commit is contained in:
Greg Hysen
2018-05-31 16:49:10 -07:00
parent 249a1e6d8d
commit 05f1e9e3b8
2 changed files with 139 additions and 129 deletions
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28
packages/contracts/src/contracts/current/utils/LibMem/LibMem.sol
View File

@@ -19,7 +19,7 @@
pragma solidity ^0.4.24;
contract LibMem {
function getMemAddress(bytes memory input)
internal
pure
@@ -30,7 +30,7 @@ contract LibMem {
}
return address_;
}
/// @dev Copies `length` bytes from memory location `source` to `dest`.
/// @param dest memory address to copy bytes to
/// @param source memory address to copy bytes from
@@ -58,7 +58,7 @@ contract LibMem {
if (source == dest) {
return;
}
// For large copies we copy whole words at a time. The final
// word is aligned to the end of the range (instead of after the
// previous) to handle partial words. So a copy will look like this:
@@ -76,6 +76,9 @@ contract LibMem {
//
if (source > dest) {
assembly {
// Record the total number of full words to copy
let nwords := div(length, 32)
// We subtract 32 from `send` and `dend` because it
// is easier to compare with in the loop, and these
// are also the addresses we need for copying the
@@ -83,44 +86,47 @@ contract LibMem {
length := sub(length, 32)
let send := add(source, length)
let dend := add(dest, length)
// Remember the last 32 bytes of source
// This needs to be done here and not after the loop
// because we may have overwritten the last bytes in
// source already due to overlap.
let last := mload(send)
// Copy whole words front to back
for {} lt(source, send) {} {
for {let i := 0} lt(i, nwords) {i := add(i, 1)} {
mstore(dest, mload(source))
source := add(source, 32)
dest := add(dest, 32)
}
// Write the last 32 bytes
mstore(dend, last)
}
} else {
assembly {
// Record the total number of full words to copy
let nwords := div(length, 32)
// We subtract 32 from `send` and `dend` because those
// are the starting points when copying a word at the end.
length := sub(length, 32)
let send := add(source, length)
let dend := add(dest, length)
// Remember the first 32 bytes of source
// This needs to be done here and not after the loop
// because we may have overwritten the first bytes in
// source already due to overlap.
let first := mload(source)
// Copy whole words back to front
for {} lt(source, send) {} {
for {let i := 0} lt(i, nwords) {i := add(i, 1)} {
mstore(dend, mload(send))
send := sub(send, 32)
dend := sub(dend, 32)
}
// Write the first 32 bytes
mstore(dest, first)
}

240
packages/contracts/test/libraries/lib_mem.ts
View File

@@ -11,13 +11,11 @@ const expect = chai.expect;
// BUG: Ideally we would use Buffer.from(memory).toString('hex')
// https://github.com/Microsoft/TypeScript/issues/23155
const toHex = (buf: Uint8Array): string =>
buf.reduce((a, v) => a + ('00' + v.toString(16)).slice(-2), '0x');
const toHex = (buf: Uint8Array): string => buf.reduce((a, v) => a + ('00' + v.toString(16)).slice(-2), '0x');
const fromHex = (str: string): Uint8Array =>
Uint8Array.from(Buffer.from(str.slice(2), 'hex'));
const fromHex = (str: string): Uint8Array => Uint8Array.from(Buffer.from(str.slice(2), 'hex'));
describe('LibMem', () => {
describe.only('LibMem', () => {
let owner: string;
let testLibMem: TestLibMemContract;
@@ -30,10 +28,9 @@ describe('LibMem', () => {
});
describe('memcpy', () => {
// Create memory 0x000102...FF
const memSize = 256;
const memory = (new Uint8Array(memSize)).map((_, i) => i);
const memory = new Uint8Array(memSize).map((_, i) => i);
const memHex = toHex(memory);
// Reference implementation to test against
@@ -60,131 +57,138 @@ describe('LibMem', () => {
test([[0, 0, 0, 'copies zero bytes with overlap']]);
describe('copies forward', () => test([
[128, 0, 0, 'zero bytes'],
[128, 0, 1, 'one byte'],
[128, 0, 11, 'eleven bytes'],
[128, 0, 31, 'thirty-one bytes'],
[128, 0, 32, 'one word'],
[128, 0, 64, 'two words'],
[128, 0, 96, 'three words'],
[128, 0, 33, 'one word and one byte'],
[128, 0, 72, 'two words and eight bytes'],
[128, 0, 100, 'three words and four bytes'],
]));
describe('copies forward', () =>
test([
[128, 0, 0, 'zero bytes'],
[128, 0, 1, 'one byte'],
[128, 0, 11, 'eleven bytes'],
[128, 0, 31, 'thirty-one bytes'],
[128, 0, 32, 'one word'],
[128, 0, 64, 'two words'],
[128, 0, 96, 'three words'],
[128, 0, 33, 'one word and one byte'],
[128, 0, 72, 'two words and eight bytes'],
[128, 0, 100, 'three words and four bytes'],
]));
describe('copies forward within one word', () => test([
[16, 0, 0, 'zero bytes'],
[16, 0, 1, 'one byte'],
[16, 0, 11, 'eleven bytes'],
[16, 0, 16, 'sixteen bytes'],
]));
describe('copies forward within one word', () =>
test([
[16, 0, 0, 'zero bytes'],
[16, 0, 1, 'one byte'],
[16, 0, 11, 'eleven bytes'],
[16, 0, 16, 'sixteen bytes'],
]));
describe('copies forward with one byte overlap', () => test([
[0, 0, 1, 'one byte'],
[10, 0, 11, 'eleven bytes'],
[30, 0, 31, 'thirty-one bytes'],
[31, 0, 32, 'one word'],
[32, 0, 33, 'one word and one byte'],
[71, 0, 72, 'two words and eight bytes'],
[99, 0, 100, 'three words and four bytes'],
]));
describe('copies forward with one byte overlap', () =>
test([
[0, 0, 1, 'one byte'],
[10, 0, 11, 'eleven bytes'],
[30, 0, 31, 'thirty-one bytes'],
[31, 0, 32, 'one word'],
[32, 0, 33, 'one word and one byte'],
[71, 0, 72, 'two words and eight bytes'],
[99, 0, 100, 'three words and four bytes'],
]));
describe('copies forward with thirty-one bytes overlap', () => test([
[0, 0, 31, 'thirty-one bytes'],
[1, 0, 32, 'one word'],
[2, 0, 33, 'one word and one byte'],
[41, 0, 72, 'two words and eight bytes'],
[69, 0, 100, 'three words and four bytes'],
]));
describe('copies forward with thirty-one bytes overlap', () =>
test([
[0, 0, 31, 'thirty-one bytes'],
[1, 0, 32, 'one word'],
[2, 0, 33, 'one word and one byte'],
[41, 0, 72, 'two words and eight bytes'],
[69, 0, 100, 'three words and four bytes'],
]));
describe('copies forward with one word overlap', () => test([
[0, 0, 32, 'one word'],
[1, 0, 33, 'one word and one byte'],
[41, 0, 72, 'two words and eight bytes'],
[69, 0, 100, 'three words and four bytes'],
]));
describe('copies forward with one word overlap', () =>
test([
[0, 0, 32, 'one word'],
[1, 0, 33, 'one word and one byte'],
[41, 0, 72, 'two words and eight bytes'],
[69, 0, 100, 'three words and four bytes'],
]));
describe('copies forward with one word and one byte overlap', () => test([
[0, 0, 33, 'one word and one byte'],
[40, 0, 72, 'two words and eight bytes'],
[68, 0, 100, 'three words and four bytes'],
]));
describe('copies forward with one word and one byte overlap', () =>
test([
[0, 0, 33, 'one word and one byte'],
[40, 0, 72, 'two words and eight bytes'],
[68, 0, 100, 'three words and four bytes'],
]));
describe('copies forward with two words overlap', () => test([
[0, 0, 64, 'two words'],
[8, 0, 72, 'two words and eight bytes'],
[36, 0, 100, 'three words and four bytes'],
]));
describe('copies forward with two words overlap', () =>
test([
[0, 0, 64, 'two words'],
[8, 0, 72, 'two words and eight bytes'],
[36, 0, 100, 'three words and four bytes'],
]));
describe('copies forward within one word and one byte overlap', () => test([
[0, 0, 1, 'one byte'],
[10, 0, 11, 'eleven bytes'],
[15, 0, 16, 'sixteen bytes'],
]));
describe('copies forward within one word and one byte overlap', () =>
test([[0, 0, 1, 'one byte'], [10, 0, 11, 'eleven bytes'], [15, 0, 16, 'sixteen bytes']]));
describe('copies backward', () => test([
[0, 128, 0, 'zero bytes'],
[0, 128, 1, 'one byte'],
[0, 128, 11, 'eleven bytes'],
[0, 128, 31, 'thirty-one bytes'],
[0, 128, 32, 'one word'],
[0, 128, 64, 'two words'],
[0, 128, 96, 'three words'],
[0, 128, 33, 'one word and one byte'],
[0, 128, 72, 'two words and eight bytes'],
[0, 128, 100, 'three words and four bytes'],
]));
describe('copies backward', () =>
test([
[0, 128, 0, 'zero bytes'],
[0, 128, 1, 'one byte'],
[0, 128, 11, 'eleven bytes'],
[0, 128, 31, 'thirty-one bytes'],
[0, 128, 32, 'one word'],
[0, 128, 64, 'two words'],
[0, 128, 96, 'three words'],
[0, 128, 33, 'one word and one byte'],
[0, 128, 72, 'two words and eight bytes'],
[0, 128, 100, 'three words and four bytes'],
]));
describe('copies backward within one word', () => test([
[0, 16, 0, 'zero bytes'],
[0, 16, 1, 'one byte'],
[0, 16, 11, 'eleven bytes'],
[0, 16, 16, 'sixteen bytes'],
]));
describe('copies backward within one word', () =>
test([
[0, 16, 0, 'zero bytes'],
[0, 16, 1, 'one byte'],
[0, 16, 11, 'eleven bytes'],
[0, 16, 16, 'sixteen bytes'],
]));
describe('copies backward with one byte overlap', () => test([
[0, 0, 1, 'one byte'],
[0, 10, 11, 'eleven bytes'],
[0, 30, 31, 'thirty-one bytes'],
[0, 31, 32, 'one word'],
[0, 32, 33, 'one word and one byte'],
[0, 71, 72, 'two words and eight bytes'],
[0, 99, 100, 'three words and four bytes'],
]));
describe('copies backward with one byte overlap', () =>
test([
[0, 0, 1, 'one byte'],
[0, 10, 11, 'eleven bytes'],
[0, 30, 31, 'thirty-one bytes'],
[0, 31, 32, 'one word'],
[0, 32, 33, 'one word and one byte'],
[0, 71, 72, 'two words and eight bytes'],
[0, 99, 100, 'three words and four bytes'],
]));
describe('copies backward with thirty-one bytes overlap', () => test([
[0, 0, 31, 'thirty-one bytes'],
[0, 1, 32, 'one word'],
[0, 2, 33, 'one word and one byte'],
[0, 41, 72, 'two words and eight bytes'],
[0, 69, 100, 'three words and four bytes'],
]));
describe('copies backward with thirty-one bytes overlap', () =>
test([
[0, 0, 31, 'thirty-one bytes'],
[0, 1, 32, 'one word'],
[0, 2, 33, 'one word and one byte'],
[0, 41, 72, 'two words and eight bytes'],
[0, 69, 100, 'three words and four bytes'],
]));
describe('copies backward with one word overlap', () => test([
[0, 0, 32, 'one word'],
[0, 1, 33, 'one word and one byte'],
[0, 41, 72, 'two words and eight bytes'],
[0, 69, 100, 'three words and four bytes'],
]));
describe('copies backward with one word overlap', () =>
test([
[0, 0, 32, 'one word'],
[0, 1, 33, 'one word and one byte'],
[0, 41, 72, 'two words and eight bytes'],
[0, 69, 100, 'three words and four bytes'],
]));
describe('copies backward with one word and one byte overlap', () => test([
[0, 0, 33, 'one word and one byte'],
[0, 40, 72, 'two words and eight bytes'],
[0, 68, 100, 'three words and four bytes'],
]));
describe('copies backward with one word and one byte overlap', () =>
test([
[0, 0, 33, 'one word and one byte'],
[0, 40, 72, 'two words and eight bytes'],
[0, 68, 100, 'three words and four bytes'],
]));
describe('copies backward with two words overlap', () => test([
[0, 0, 64, 'two words'],
[0, 8, 72, 'two words and eight bytes'],
[0, 36, 100, 'three words and four bytes'],
]));
describe('copies forward within one word and one byte overlap', () => test([
[0, 0, 1, 'one byte'],
[0, 10, 11, 'eleven bytes'],
[0, 15, 16, 'sixteen bytes'],
]));
describe('copies backward with two words overlap', () =>
test([
[0, 0, 64, 'two words'],
[0, 8, 72, 'two words and eight bytes'],
[0, 36, 100, 'three words and four bytes'],
]));
describe('copies forward within one word and one byte overlap', () =>
test([[0, 0, 1, 'one byte'], [0, 10, 11, 'eleven bytes'], [0, 15, 16, 'sixteen bytes']]));
});
});