Skip to content

Commit

Permalink
fs: align fs.ReadStream buffer pool writes to 8-byte boundary
Browse files Browse the repository at this point in the history
Prevents alignment issues when creating a typed array from a buffer.

Fixes: #24817

PR-URL: #24838
Reviewed-By: Ben Noordhuis <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
  • Loading branch information
trxcllnt authored and targos committed May 4, 2019
1 parent a278814 commit a0353fd
Show file tree
Hide file tree
Showing 2 changed files with 19 additions and 5 deletions.
23 changes: 18 additions & 5 deletions lib/internal/fs/streams.js
Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,10 @@ function checkPosition(pos, name) {
}
}

function roundUpToMultipleOf8(n) {
return (n + 7) & ~7; // Align to 8 byte boundary.
}

function ReadStream(path, options) {
if (!(this instanceof ReadStream))
return new ReadStream(path, options);
Expand Down Expand Up @@ -172,10 +176,18 @@ ReadStream.prototype._read = function(n) {
// Now that we know how much data we have actually read, re-wind the
// 'used' field if we can, and otherwise allow the remainder of our
// reservation to be used as a new pool later.
if (start + toRead === thisPool.used && thisPool === pool)
thisPool.used += bytesRead - toRead;
else if (toRead - bytesRead > kMinPoolSpace)
poolFragments.push(thisPool.slice(start + bytesRead, start + toRead));
if (start + toRead === thisPool.used && thisPool === pool) {
const newUsed = thisPool.used + bytesRead - toRead;
thisPool.used = roundUpToMultipleOf8(newUsed);
} else {
// Round down to the next lowest multiple of 8 to ensure the new pool
// fragment start and end positions are aligned to an 8 byte boundary.
const alignedEnd = (start + toRead) & ~7;
const alignedStart = roundUpToMultipleOf8(start + bytesRead);
if (alignedEnd - alignedStart >= kMinPoolSpace) {
poolFragments.push(thisPool.slice(alignedStart, alignedEnd));
}
}

if (bytesRead > 0) {
this.bytesRead += bytesRead;
Expand All @@ -189,7 +201,8 @@ ReadStream.prototype._read = function(n) {
// Move the pool positions, and internal position for reading.
if (this.pos !== undefined)
this.pos += toRead;
pool.used += toRead;

pool.used = roundUpToMultipleOf8(pool.used + toRead);
};

ReadStream.prototype._destroy = function(err, cb) {
Expand Down
1 change: 1 addition & 0 deletions test/parallel/test-fs-read-stream.js
Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@ const rangeFile = fixtures.path('x.txt');

file.on('data', function(data) {
assert.ok(data instanceof Buffer);
assert.ok(data.byteOffset % 8 === 0);
assert.ok(!paused);
file.length += data.length;

Expand Down

0 comments on commit a0353fd

Please sign in to comment.