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zlib: be strict about what strategies are accepted #10934

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zlib: be strict about what strategies are accepted #10934

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26 changes: 10 additions & 16 deletions lib/zlib.js
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Original file line number Diff line number Diff line change
Expand Up @@ -277,6 +277,12 @@ function isValidFlushFlag(flag) {
flag === constants.Z_BLOCK;
}

const strategies = [constants.Z_FILTERED,
constants.Z_HUFFMAN_ONLY,
constants.Z_RLE,
constants.Z_FIXED,
constants.Z_DEFAULT_STRATEGY];

// the Zlib class they all inherit from
// This thing manages the queue of requests, and returns
// true or false if there is anything in the queue when
Expand Down Expand Up @@ -326,15 +332,8 @@ function Zlib(opts, mode) {
}
}

if (opts.strategy) {
if (opts.strategy != constants.Z_FILTERED &&
opts.strategy != constants.Z_HUFFMAN_ONLY &&
opts.strategy != constants.Z_RLE &&
opts.strategy != constants.Z_FIXED &&
opts.strategy != constants.Z_DEFAULT_STRATEGY) {
throw new Error('Invalid strategy: ' + opts.strategy);
}
}
if (opts.strategy && !(strategies.includes(opts.strategy)))
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@lpinca lpinca Jan 21, 2017 •
edited
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Nit: why !(strategies.includes(opts.strategy)) instead of just !strategies.includes(opts.strategy)?

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Happy to remove it if it's bothersome, but the reason I (sometimes) use the parentheses like that are:

  • clarity of intention
  • helps out people who may not know operator precedence
  • force of habit from !(foo instanceof Buffer) being the correct way to do things because !foo instanceof Buffer means checking that !foo is an instance of Buffer which is not at all the same as foo not an instances of Buffer....

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No problem, keep it the way it is.

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A range check may be faster than includes ...e.g.

if (opts.strategy >= constants.Z_DEFAULT_STRATEGY &&
   opt.strategy <= constants.Z_FIXED) { ... }

A bit more work to maintain if these values ever change but it avoids the linear scan of the array that includes() requires.

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Given the overhead of actually compressing and/or decompressing, I suspect such a change for performance purposes in the constructor would be something that would be impossible to measure in any real-world scenario. Counter-examples more than welcome. Barring that, I would prefer the code be clear and not be dependent on unspoken assumptions about constants defined externally.

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works for me

throw new Error('Invalid strategy: ' + opts.strategy);

if (opts.dictionary) {
if (!(opts.dictionary instanceof Buffer)) {
Expand Down Expand Up @@ -378,7 +377,7 @@ function Zlib(opts, mode) {
this.once('end', this.close);

Object.defineProperty(this, '_closed', {
get: () => { return !this._handle; },
get: () => !this._handle,
configurable: true,
enumerable: true
});
Expand All @@ -391,13 +390,8 @@ Zlib.prototype.params = function(level, strategy, callback) {
level > constants.Z_MAX_LEVEL) {
throw new RangeError('Invalid compression level: ' + level);
}
if (strategy != constants.Z_FILTERED &&
strategy != constants.Z_HUFFMAN_ONLY &&
strategy != constants.Z_RLE &&
strategy != constants.Z_FIXED &&
strategy != constants.Z_DEFAULT_STRATEGY) {
if (!(strategies.includes(strategy)))
throw new TypeError('Invalid strategy: ' + strategy);
}

if (this._level !== level || this._strategy !== strategy) {
var self = this;
Expand Down
6 changes: 6 additions & 0 deletions test/parallel/test-zlib-deflate-constructors.js
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Expand Up @@ -86,6 +86,12 @@ assert.doesNotThrow(
() => { new zlib.Deflate({ strategy: zlib.constants.Z_DEFAULT_STRATEGY}); }
);

// Throws if opt.strategy is the wrong type.
assert.throws(
() => { new zlib.Deflate({strategy: '' + zlib.constants.Z_RLE }); },
/^Error: Invalid strategy: 3$/
);

// Throws if opts.strategy is invalid
assert.throws(
() => { new zlib.Deflate({strategy: 'this is a bogus strategy'}); },
Expand Down