468 lines
19 KiB
Markdown
468 lines
19 KiB
Markdown
![]() |
# yauzl
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[![Build Status](https://travis-ci.org/thejoshwolfe/yauzl.svg?branch=master)](https://travis-ci.org/thejoshwolfe/yauzl)
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[![Coverage Status](https://img.shields.io/coveralls/thejoshwolfe/yauzl.svg)](https://coveralls.io/r/thejoshwolfe/yauzl)
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yet another unzip library for node. For zipping, see
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[yazl](https://github.com/thejoshwolfe/yazl).
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Design principles:
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* Follow the spec.
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Don't scan for local file headers.
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Read the central directory for file metadata.
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(see [No Streaming Unzip API](#no-streaming-unzip-api)).
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* Don't block the JavaScript thread.
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Use and provide async APIs.
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* Keep memory usage under control.
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Don't attempt to buffer entire files in RAM at once.
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* Never crash (if used properly).
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Don't let malformed zip files bring down client applications who are trying to catch errors.
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* Catch unsafe filenames entries.
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A zip file entry throws an error if its file name starts with `"/"` or `/[A-Za-z]:\//`
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or if it contains `".."` path segments or `"\\"` (per the spec).
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## Usage
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```js
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var yauzl = require("yauzl");
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var fs = require("fs");
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var path = require("path");
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var mkdirp = require("mkdirp"); // or similar
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yauzl.open("path/to/file.zip", {lazyEntries: true}, function(err, zipfile) {
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if (err) throw err;
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zipfile.readEntry();
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zipfile.on("entry", function(entry) {
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if (/\/$/.test(entry.fileName)) {
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// directory file names end with '/'
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mkdirp(entry.fileName, function(err) {
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if (err) throw err;
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zipfile.readEntry();
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});
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} else {
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// file entry
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zipfile.openReadStream(entry, function(err, readStream) {
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if (err) throw err;
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// ensure parent directory exists
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mkdirp(path.dirname(entry.fileName), function(err) {
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if (err) throw err;
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readStream.pipe(fs.createWriteStream(entry.fileName));
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readStream.on("end", function() {
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zipfile.readEntry();
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});
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});
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});
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}
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});
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});
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```
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## API
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The default for every optional `callback` parameter is:
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```js
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function defaultCallback(err) {
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if (err) throw err;
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}
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```
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### open(path, [options], [callback])
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Calls `fs.open(path, "r")` and gives the `fd`, `options`, and `callback` to `fromFd()` below.
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`options` may be omitted or `null`. The defaults are `{autoClose: true, lazyEntries: false}`.
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`autoClose` is effectively equivalent to:
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```js
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zipfile.once("end", function() {
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zipfile.close();
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});
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```
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`lazyEntries` indicates that entries should be read only when `readEntry()` is called.
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If `lazyEntries` is `false`, `entry` events will be emitted as fast as possible to allow `pipe()`ing
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file data from all entries in parallel.
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This is not recommended, as it can lead to out of control memory usage for zip files with many entries.
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See [issue #22](https://github.com/thejoshwolfe/yauzl/issues/22).
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If `lazyEntries` is `true`, an `entry` or `end` event will be emitted in response to each call to `readEntry()`.
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This allows processing of one entry at a time, and will keep memory usage under control for zip files with many entries.
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### fromFd(fd, [options], [callback])
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Reads from the fd, which is presumed to be an open .zip file.
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Note that random access is required by the zip file specification,
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so the fd cannot be an open socket or any other fd that does not support random access.
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The `callback` is given the arguments `(err, zipfile)`.
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An `err` is provided if the End of Central Directory Record Signature cannot be found in the file,
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which indicates that the fd is not a zip file.
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`zipfile` is an instance of `ZipFile`.
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`options` may be omitted or `null`. The defaults are `{autoClose: false, lazyEntries: false}`.
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See `open()` for the meaning of the options.
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### fromBuffer(buffer, [options], [callback])
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Like `fromFd()`, but reads from a RAM buffer instead of an open file.
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`buffer` is a `Buffer`.
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`callback` is effectively passed directly to `fromFd()`.
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If a `ZipFile` is acquired from this method,
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it will never emit the `close` event,
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and calling `close()` is not necessary.
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`options` may be omitted or `null`. The defaults are `{lazyEntries: false}`.
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See `open()` for the meaning of the options.
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The `autoClose` option is ignored for this method.
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### fromRandomAccessReader(reader, totalSize, [options], [callback])
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This method of creating a zip file allows clients to implement their own back-end file system.
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For example, a client might translate read calls into network requests.
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The `reader` parameter must be of a type that is a subclass of
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[RandomAccessReader](#class-randomaccessreader) that implements the required methods.
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The `totalSize` is a Number and indicates the total file size of the zip file.
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`options` may be omitted or `null`. The defaults are `{autoClose: true, lazyEntries: false}`.
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See `open()` for the meaning of the options.
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### dosDateTimeToDate(date, time)
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Converts MS-DOS `date` and `time` data into a JavaScript `Date` object.
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Each parameter is a `Number` treated as an unsigned 16-bit integer.
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Note that this format does not support timezones,
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so the returned object will use the local timezone.
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### Class: ZipFile
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The constructor for the class is not part of the public API.
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Use `open()`, `fromFd()`, `fromBuffer()`, or `fromRandomAccessReader()` instead.
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#### Event: "entry"
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Callback gets `(entry)`, which is an `Entry`.
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See `open()` and `readEntry()` for when this event is emitted.
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#### Event: "end"
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Emitted after the last `entry` event has been emitted.
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See `open()` and `readEntry()` for more info on when this event is emitted.
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#### Event: "close"
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Emitted after the fd is actually closed.
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This is after calling `close()` (or after the `end` event when `autoClose` is `true`),
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and after all stream pipelines created from `openReadStream()` have finished reading data from the fd.
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If this `ZipFile` was acquired from `fromRandomAccessReader()`,
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the "fd" in the previous paragraph refers to the `RandomAccessReader` implemented by the client.
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If this `ZipFile` was acquired from `fromBuffer()`, this event is never emitted.
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#### Event: "error"
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Emitted in the case of errors with reading the zip file.
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(Note that other errors can be emitted from the streams created from `openReadStream()` as well.)
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After this event has been emitted, no further `entry`, `end`, or `error` events will be emitted,
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but the `close` event may still be emitted.
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#### readEntry()
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Causes this `ZipFile` to emit an `entry` or `end` event (or an `error` event).
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This method must only be called when this `ZipFile` was created with the `lazyEntries` option set to `true` (see `open()`).
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When this `ZipFile` was created with the `lazyEntries` option set to `true`,
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`entry` and `end` events are only ever emitted in response to this method call.
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The event that is emitted in response to this method will not be emitted until after this method has returned,
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so it is safe to call this method before attaching event listeners.
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After calling this method, calling this method again before the response event has been emitted will cause undefined behavior.
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Calling this method after the `end` event has been emitted will cause undefined behavior.
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Calling this method after calling `close()` will cause undefined behavior.
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#### openReadStream(entry, callback)
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`entry` must be an `Entry` object from this `ZipFile`.
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`callback` gets `(err, readStream)`, where `readStream` is a `Readable Stream`.
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If the entry is compressed (with a supported compression method),
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the read stream provides the decompressed data.
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If this zipfile is already closed (see `close()`), the `callback` will receive an `err`.
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It's possible for the `readStream` it to emit errors for several reasons.
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For example, if zlib cannot decompress the data, the zlib error will be emitted from the `readStream`.
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Two more error cases are if the decompressed data has too many or too few actual bytes
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compared to the reported byte count from the entry's `uncompressedSize` field.
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yauzl notices this false information and emits an error from the `readStream`
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after some number of bytes have already been piped through the stream.
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Because of this check, clients can always trust the `uncompressedSize` field in `Entry` objects.
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Guarding against [zip bomb](http://en.wikipedia.org/wiki/Zip_bomb) attacks can be accomplished by
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doing some heuristic checks on the size metadata and then watching out for the above errors.
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Such heuristics are outside the scope of this library,
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but enforcing the `uncompressedSize` is implemented here as a security feature.
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It is possible to destroy the `readStream` before it has piped all of its data.
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To do this, call `readStream.destroy()`.
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You must `unpipe()` the `readStream` from any destination before calling `readStream.destroy()`.
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If this zipfile was created using `fromRandomAccessReader()`, the `RandomAccessReader` implementation
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must provide readable streams that implement a `.destroy()` method (see `randomAccessReader._readStreamForRange()`)
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in order for calls to `readStream.destroy()` to work in this context.
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#### close()
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Causes all future calls to `openReadStream()` to fail,
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and closes the fd after all streams created by `openReadStream()` have emitted their `end` events.
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If the `autoClose` option is set to `true` (see `open()`),
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this function will be called automatically effectively in response to this object's `end` event.
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If the `lazyEntries` option is set to `false` (see `open()`) and this object's `end` event has not been emitted yet,
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this function causes undefined behavior.
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If the `lazyEntries` option is set to `true`,
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you can call this function instead of calling `readEntry()` to abort reading the entries of a zipfile.
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It is safe to call this function multiple times; after the first call, successive calls have no effect.
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This includes situations where the `autoClose` option effectively calls this function for you.
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#### isOpen
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`Boolean`. `true` until `close()` is called; then it's `false`.
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#### entryCount
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`Number`. Total number of central directory records.
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#### comment
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`String`. Always decoded with `CP437` per the spec.
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### Class: Entry
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Objects of this class represent Central Directory Records.
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Refer to the zipfile specification for more details about these fields.
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These fields are of type `Number`:
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* `versionMadeBy`
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* `versionNeededToExtract`
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* `generalPurposeBitFlag`
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* `compressionMethod`
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* `lastModFileTime` (MS-DOS format, see `getLastModDateTime`)
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* `lastModFileDate` (MS-DOS format, see `getLastModDateTime`)
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* `crc32`
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* `compressedSize`
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* `uncompressedSize`
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* `fileNameLength` (bytes)
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* `extraFieldLength` (bytes)
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* `fileCommentLength` (bytes)
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* `internalFileAttributes`
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* `externalFileAttributes`
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* `relativeOffsetOfLocalHeader`
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#### fileName
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`String`.
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Following the spec, the bytes for the file name are decoded with
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`UTF-8` if `generalPurposeBitFlag & 0x800`, otherwise with `CP437`.
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If `fileName` would contain unsafe characters, such as an absolute path or
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a relative directory, yauzl emits an error instead of an entry.
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#### extraFields
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`Array` with each entry in the form `{id: id, data: data}`,
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where `id` is a `Number` and `data` is a `Buffer`.
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This library looks for and reads the ZIP64 Extended Information Extra Field (0x0001)
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in order to support ZIP64 format zip files.
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None of the other fields are considered significant by this library.
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#### comment
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`String` decoded with the same charset as used for `fileName`.
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#### getLastModDate()
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Effectively implemented as:
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```js
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return dosDateTimeToDate(this.lastModFileDate, this.lastModFileTime);
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```
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### Class: RandomAccessReader
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This class is meant to be subclassed by clients and instantiated for the `fromRandomAccessReader()` function.
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An example implementation can be found in `test/test.js`.
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#### randomAccessReader._readStreamForRange(start, end)
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Subclasses *must* implement this method.
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`start` and `end` are Numbers and indicate byte offsets from the start of the file.
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`end` is exclusive, so `_readStreamForRange(0x1000, 0x2000)` would indicate to read `0x1000` bytes.
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`end - start` will always be at least `1`.
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This method should return a readable stream which will be `pipe()`ed into another stream.
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It is expected that the readable stream will provide data in several chunks if necessary.
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If the readable stream provides too many or too few bytes, an error will be emitted.
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Any errors emitted on the readable stream will be handled and re-emitted on the client-visible stream
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(returned from `zipfile.openReadStream()`) or provided as the `err` argument to the appropriate callback
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(for example, for `fromRandomAccessReader()`).
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The returned stream *must* implement a method `.destroy()`
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if you call `readStream.destroy()` on streams you get from `openReadStream()`.
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If you never call `readStream.destroy()`, then streams returned from this method do not need to implement a method `.destroy()`.
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`.destroy()` should abort any streaming that is in progress and clean up any associated resources.
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`.destroy()` will only be called after the stream has been `unpipe()`d from its destination.
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Note that the stream returned from this method might not be the same object that is provided by `openReadStream()`.
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The stream returned from this method might be `pipe()`d through one or more filter streams (for example, a zlib inflate stream).
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#### randomAccessReader.read(buffer, offset, length, position, callback)
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Subclasses may implement this method.
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The default implementation uses `createReadStream()` to fill the `buffer`.
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This method should behave like `fs.read()`.
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#### randomAccessReader.close(callback)
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Subclasses may implement this method.
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The default implementation is effectively `setImmediate(callback);`.
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`callback` takes parameters `(err)`.
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This method is called once the all streams returned from `_readStreamForRange()` have ended,
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and no more `_readStreamForRange()` or `read()` requests will be issued to this object.
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## How to Avoid Crashing
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When a malformed zipfile is encountered, the default behavior is to crash (throw an exception).
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If you want to handle errors more gracefully than this,
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be sure to do the following:
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* Provide `callback` parameters where they are allowed, and check the `err` parameter.
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* Attach a listener for the `error` event on any `ZipFile` object you get from `open()`, `fromFd()`, `fromBuffer()`, or `fromRandomAccessReader()`.
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* Attach a listener for the `error` event on any stream you get from `openReadStream()`.
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## Limitations
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### No Streaming Unzip API
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Due to the design of the .zip file format, it's impossible to interpret a .zip file from start to finish
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(such as from a readable stream) without sacrificing correctness.
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The Central Directory, which is the authority on the contents of the .zip file, is at the end of a .zip file, not the beginning.
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A streaming API would need to either buffer the entire .zip file to get to the Central Directory before interpreting anything
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(defeating the purpose of a streaming interface), or rely on the Local File Headers which are interspersed through the .zip file.
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However, the Local File Headers are explicitly denounced in the spec as being unreliable copies of the Central Directory,
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so trusting them would be a violation of the spec.
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Any library that offers a streaming unzip API must make one of the above two compromises,
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which makes the library either dishonest or nonconformant (usually the latter).
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This library insists on correctness and adherence to the spec, and so does not offer a streaming API.
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### Limitted ZIP64 Support
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For ZIP64, only zip files smaller than `8PiB` are supported,
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not the full `16EiB` range that a 64-bit integer should be able to index.
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This is due to the JavaScript Number type being an IEEE 754 double precision float.
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The Node.js `fs` module probably has this same limitation.
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### ZIP64 Extensible Data Sector Is Ignored
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The spec does not allow zip file creators to put arbitrary data here,
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but rather reserves its use for PKWARE and mentions something about Z390.
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This doesn't seem useful to expose in this library, so it is ignored.
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### No Multi-Disk Archive Support
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This library does not support multi-disk zip files.
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The multi-disk fields in the zipfile spec were intended for a zip file to span multiple floppy disks,
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which probably never happens now.
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If the "number of this disk" field in the End of Central Directory Record is not `0`,
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the `open()`, `fromFd()`, `fromBuffer()`, or `fromRandomAccessReader()` `callback` will receive an `err`.
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By extension the following zip file fields are ignored by this library and not provided to clients:
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* Disk where central directory starts
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* Number of central directory records on this disk
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* Disk number where file starts
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### No Encryption Support
|
||
|
|
||
|
Currently, the presence of encryption is not even checked,
|
||
|
and encrypted zip files will cause undefined behavior.
|
||
|
|
||
|
### Local File Headers Are Ignored
|
||
|
|
||
|
Many unzip libraries mistakenly read the Local File Header data in zip files.
|
||
|
This data is officially defined to be redundant with the Central Directory information,
|
||
|
and is not to be trusted.
|
||
|
Aside from checking the signature, yauzl ignores the content of the Local File Header.
|
||
|
|
||
|
### No CRC-32 Checking
|
||
|
|
||
|
This library provides the `crc32` field of `Entry` objects read from the Central Directory.
|
||
|
However, this field is not used for anything in this library.
|
||
|
|
||
|
### versionNeededToExtract Is Ignored
|
||
|
|
||
|
The field `versionNeededToExtract` is ignored,
|
||
|
because this library doesn't support the complete zip file spec at any version,
|
||
|
|
||
|
### No Support For Obscure Compression Methods
|
||
|
|
||
|
Regarding the `compressionMethod` field of `Entry` objects,
|
||
|
only method `0` (stored with no compression)
|
||
|
and method `8` (deflated) are supported.
|
||
|
Any of the other 15 official methods will cause the `openReadStream()` `callback` to receive an `err`.
|
||
|
|
||
|
### Data Descriptors Are Ignored
|
||
|
|
||
|
There may or may not be Data Descriptor sections in a zip file.
|
||
|
This library provides no support for finding or interpreting them.
|
||
|
|
||
|
### Archive Extra Data Record Is Ignored
|
||
|
|
||
|
There may or may not be an Archive Extra Data Record section in a zip file.
|
||
|
This library provides no support for finding or interpreting it.
|
||
|
|
||
|
### No Language Encoding Flag Support
|
||
|
|
||
|
Zip files officially support charset encodings other than CP437 and UTF-8,
|
||
|
but the zip file spec does not specify how it works.
|
||
|
This library makes no attempt to interpret the Language Encoding Flag.
|
||
|
|
||
|
## Change History
|
||
|
|
||
|
* 2.4.1
|
||
|
* Fix error handling.
|
||
|
* 2.4.0
|
||
|
* Add ZIP64 support. [issue #6](https://github.com/thejoshwolfe/yazl/issues/6)
|
||
|
* Add `lazyEntries` option. [issue #22](https://github.com/thejoshwolfe/yazl/issues/22)
|
||
|
* Add `readStream.destroy()` method. [issue #26](https://github.com/thejoshwolfe/yazl/issues/26)
|
||
|
* Add `fromRandomAccessReader()`. [issue #14](https://github.com/thejoshwolfe/yazl/issues/14)
|
||
|
* Add `examples/unzip.js`.
|
||
|
* 2.3.1
|
||
|
* Documentation updates.
|
||
|
* 2.3.0
|
||
|
* Check that `uncompressedSize` is correct, or else emit an error. [issue #13](https://github.com/thejoshwolfe/yazl/issues/13)
|
||
|
* 2.2.1
|
||
|
* Update dependencies.
|
||
|
* 2.2.0
|
||
|
* Update dependencies.
|
||
|
* 2.1.0
|
||
|
* Remove dependency on `iconv`.
|
||
|
* 2.0.3
|
||
|
* Fix crash when trying to read a 0-byte file.
|
||
|
* 2.0.2
|
||
|
* Fix event behavior after errors.
|
||
|
* 2.0.1
|
||
|
* Fix bug with using `iconv`.
|
||
|
* 2.0.0
|
||
|
* Initial release.
|