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zlib: expose amount of data read for engines
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Added bytesRead property to Zlib engines

Fixes: #8874
PR-URL: #13088
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
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AlexanderOMara authored and addaleax committed May 31, 2017
1 parent d0b1b52 commit e710036
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11 changes: 11 additions & 0 deletions doc/api/zlib.md
Original file line number Diff line number Diff line change
Expand Up @@ -386,6 +386,17 @@ added: v0.5.8
Not exported by the `zlib` module. It is documented here because it is the base
class of the compressor/decompressor classes.

### zlib.bytesRead
<!-- YAML
added: REPLACEME
-->

* {number}

The `zlib.bytesRead` property specifies the number of bytes read by the engine
before the bytes are processed (compressed or decompressed, as appropriate for
the derived class).

### zlib.flush([kind], callback)
<!-- YAML
added: v0.5.8
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4 changes: 4 additions & 0 deletions lib/zlib.js
Original file line number Diff line number Diff line change
Expand Up @@ -175,6 +175,8 @@ class Zlib extends Transform {
opts = opts || {};
super(opts);

this.bytesRead = 0;

this._opts = opts;
this._chunkSize = opts.chunkSize || constants.Z_DEFAULT_CHUNK;

Expand Down Expand Up @@ -429,6 +431,8 @@ class Zlib extends Transform {
var have = availOutBefore - availOutAfter;
assert(have >= 0, 'have should not go down');

self.bytesRead += availInBefore - availInAfter;

if (have > 0) {
var out = self._buffer.slice(self._offset, self._offset + have);
self._offset += have;
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93 changes: 93 additions & 0 deletions test/parallel/test-zlib-bytes-read.js
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@@ -0,0 +1,93 @@
'use strict';
const common = require('../common');
const assert = require('assert');
const zlib = require('zlib');

const expectStr = 'abcdefghijklmnopqrstuvwxyz'.repeat(2);
const expectBuf = Buffer.from(expectStr);

function createWriter(target, buffer) {
const writer = { size: 0 };
const write = () => {
target.write(Buffer.from([buffer[writer.size++]]), () => {
if (writer.size < buffer.length) {
target.flush(write);
} else {
target.end();
}
});
};
write();
return writer;
}

for (const method of [
['createGzip', 'createGunzip', false],
['createGzip', 'createUnzip', false],
['createDeflate', 'createInflate', true],
['createDeflateRaw', 'createInflateRaw', true]
]) {
let compWriter;
let compData = new Buffer(0);

const comp = zlib[method[0]]();
comp.on('data', function(d) {
compData = Buffer.concat([compData, d]);
assert.strictEqual(this.bytesRead, compWriter.size,
`Should get write size on ${method[0]} data.`);
});
comp.on('end', common.mustCall(function() {
assert.strictEqual(this.bytesRead, compWriter.size,
`Should get write size on ${method[0]} end.`);
assert.strictEqual(this.bytesRead, expectStr.length,
`Should get data size on ${method[0]} end.`);

{
let decompWriter;
let decompData = new Buffer(0);

const decomp = zlib[method[1]]();
decomp.on('data', function(d) {
decompData = Buffer.concat([decompData, d]);
assert.strictEqual(this.bytesRead, decompWriter.size,
`Should get write size on ${method[0]}/` +
`${method[1]} data.`);
});
decomp.on('end', common.mustCall(function() {
assert.strictEqual(this.bytesRead, compData.length,
`Should get compressed size on ${method[0]}/` +
`${method[1]} end.`);
assert.strictEqual(decompData.toString(), expectStr,
`Should get original string on ${method[0]}/` +
`${method[1]} end.`);
}));
decompWriter = createWriter(decomp, compData);
}

// Some methods should allow extra data after the compressed data
if (method[2]) {
const compDataExtra = Buffer.concat([compData, new Buffer('extra')]);

let decompWriter;
let decompData = new Buffer(0);

const decomp = zlib[method[1]]();
decomp.on('data', function(d) {
decompData = Buffer.concat([decompData, d]);
assert.strictEqual(this.bytesRead, decompWriter.size,
`Should get write size on ${method[0]}/` +
`${method[1]} data.`);
});
decomp.on('end', common.mustCall(function() {
assert.strictEqual(this.bytesRead, compData.length,
`Should get compressed size on ${method[0]}/` +
`${method[1]} end.`);
assert.strictEqual(decompData.toString(), expectStr,
`Should get original string on ${method[0]}/` +
`${method[1]} end.`);
}));
decompWriter = createWriter(decomp, compDataExtra);
}
}));
compWriter = createWriter(comp, expectBuf);
}

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