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author | 2020-11-16 00:10:28 +0100 | |
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committer | 2020-11-16 00:10:28 +0100 | |
commit | e06ec920f7a5d784e674c4c4b4e6d1da3dc7391d (patch) | |
tree | 55713f725f77b44ebfec86e4eec3ce33e71458ca /node_modules/fs-write-stream-atomic/index.js | |
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Diffstat (limited to 'node_modules/fs-write-stream-atomic/index.js')
-rw-r--r-- | node_modules/fs-write-stream-atomic/index.js | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/node_modules/fs-write-stream-atomic/index.js b/node_modules/fs-write-stream-atomic/index.js new file mode 100644 index 0000000..1690ff5 --- /dev/null +++ b/node_modules/fs-write-stream-atomic/index.js @@ -0,0 +1,176 @@ +var fs = require('graceful-fs') +var Writable = require('readable-stream').Writable +var util = require('util') +var MurmurHash3 = require('imurmurhash') +var iferr = require('iferr') +var crypto = require('crypto') + +function murmurhex () { + var hash = MurmurHash3('') + for (var ii = 0; ii < arguments.length; ++ii) { + hash.hash('' + arguments[ii]) + } + return hash.result() +} + +var invocations = 0 +function getTmpname (filename) { + return filename + '.' + murmurhex(__filename, process.pid, ++invocations) +} + +var setImmediate = global.setImmediate || setTimeout + +module.exports = WriteStreamAtomic + +// Requirements: +// 1. Write everything written to the stream to a temp file. +// 2. If there are no errors: +// a. moves the temp file into its final destination +// b. emits `finish` & `closed` ONLY after the file is +// fully flushed and renamed. +// 3. If there's an error, removes the temp file. + +util.inherits(WriteStreamAtomic, Writable) +function WriteStreamAtomic (path, options) { + if (!(this instanceof WriteStreamAtomic)) { + return new WriteStreamAtomic(path, options) + } + Writable.call(this, options) + + this.__isWin = options && options.hasOwnProperty('isWin') ? options.isWin : process.platform === 'win32' + + this.__atomicTarget = path + this.__atomicTmp = getTmpname(path) + + this.__atomicChown = options && options.chown + + this.__atomicClosed = false + + this.__atomicStream = fs.WriteStream(this.__atomicTmp, options) + + this.__atomicStream.once('open', handleOpen(this)) + this.__atomicStream.once('close', handleClose(this)) + this.__atomicStream.once('error', handleError(this)) +} + +// We have to suppress default finish emitting, because ordinarily it +// would happen as soon as `end` is called on us and all of the +// data has been written to our target stream. So we suppress +// finish from being emitted here, and only emit it after our +// target stream is closed and we've moved everything around. +WriteStreamAtomic.prototype.emit = function (event) { + if (event === 'finish') return this.__atomicStream.end() + return Writable.prototype.emit.apply(this, arguments) +} + +WriteStreamAtomic.prototype._write = function (buffer, encoding, cb) { + var flushed = this.__atomicStream.write(buffer, encoding) + if (flushed) return cb() + this.__atomicStream.once('drain', cb) +} + +function handleOpen (writeStream) { + return function (fd) { + writeStream.emit('open', fd) + } +} + +function handleClose (writeStream) { + return function () { + if (writeStream.__atomicClosed) return + writeStream.__atomicClosed = true + if (writeStream.__atomicChown) { + var uid = writeStream.__atomicChown.uid + var gid = writeStream.__atomicChown.gid + return fs.chown(writeStream.__atomicTmp, uid, gid, iferr(cleanup, moveIntoPlace)) + } else { + moveIntoPlace() + } + } + + function moveIntoPlace () { + fs.rename(writeStream.__atomicTmp, writeStream.__atomicTarget, iferr(trapWindowsEPERM, end)) + } + + function trapWindowsEPERM (err) { + if (writeStream.__isWin && + err.syscall && err.syscall === 'rename' && + err.code && err.code === 'EPERM' + ) { + checkFileHashes(err) + } else { + cleanup(err) + } + } + + function checkFileHashes (eperm) { + var inprocess = 2 + var tmpFileHash = crypto.createHash('sha512') + var targetFileHash = crypto.createHash('sha512') + + fs.createReadStream(writeStream.__atomicTmp) + .on('data', function (data, enc) { tmpFileHash.update(data, enc) }) + .on('error', fileHashError) + .on('end', fileHashComplete) + fs.createReadStream(writeStream.__atomicTarget) + .on('data', function (data, enc) { targetFileHash.update(data, enc) }) + .on('error', fileHashError) + .on('end', fileHashComplete) + + function fileHashError () { + if (inprocess === 0) return + inprocess = 0 + cleanup(eperm) + } + + function fileHashComplete () { + if (inprocess === 0) return + if (--inprocess) return + if (tmpFileHash.digest('hex') === targetFileHash.digest('hex')) { + return cleanup() + } else { + return cleanup(eperm) + } + } + } + + function cleanup (err) { + fs.unlink(writeStream.__atomicTmp, function () { + if (err) { + writeStream.emit('error', err) + writeStream.emit('close') + } else { + end() + } + }) + } + + function end () { + // We have to use our parent class directly because we suppress `finish` + // events fired via our own emit method. + Writable.prototype.emit.call(writeStream, 'finish') + + // Delay the close to provide the same temporal separation a physical + // file operation would have– that is, the close event is emitted only + // after the async close operation completes. + setImmediate(function () { + writeStream.emit('close') + }) + } +} + +function handleError (writeStream) { + return function (er) { + cleanupSync() + writeStream.emit('error', er) + writeStream.__atomicClosed = true + writeStream.emit('close') + } + function cleanupSync () { + try { + fs.unlinkSync(writeStream.__atomicTmp) + } finally { + return + } + } +} |