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https://issues.apache.org/jira/browse/THRIFT-2933?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14275615#comment-14275615
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Dan Heller commented on THRIFT-2933:
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[~codesf] thanks for explaining. Sure, I can do it that way. I'll take a
crack at it now.
> v0.9.2: doubles encoded in node with compact protocol cannot be decoded by
> python
> ---------------------------------------------------------------------------------
>
> Key: THRIFT-2933
> URL: https://issues.apache.org/jira/browse/THRIFT-2933
> Project: Thrift
> Issue Type: Bug
> Components: Node.js - Library
> Affects Versions: 0.9.2
> Reporter: Dan Heller
> Attachments: little-endian.patch, thrift-double.tgz
>
>
> I've noticed that with Thrift v0.9.2, using the Compact protocol, I can't
> encode doubles in node and decode them in python. It looks like in python,
> we're decoding little-endian for compact and big-endian for binary, and in
> node, writing big-endian in all cases (therefore, Binary works fine). I've
> attached a test program to show this behavior. I have not found the thrift
> binary spec, so I'm not sure which side is wrong.
> {code}
> [~/thrift-double]$ thrift --version
> Thrift version 0.9.2
> [~/thrift-double]$ grep -i thrift package.json
> "thrift": "0.9.2"
> "compile": "thrift --gen js:node --gen py test.thrift"
> [~/thrift-double]$ pip show thrift
> ---
> Name: thrift
> Version: 0.9.2
> Location: /Library/Python/2.7/site-packages
> Requires:
> [~/thrift-double]$ npm run compile
> > [email protected] compile /Users/dh/thrift-double
> > thrift --gen js:node --gen py test.thrift
> [~/thrift-double]$ node test.js binary | python test.py binary
> Trying to send { intField: 100, doubleField: 99.88 }
> Reading with binary protocol.
> Got test object: TestType(intField=100, doubleField=99.88)
> [~/thrift-double]$ node test.js compact | python test.py compact
> Trying to send { intField: 100, doubleField: 99.88 }
> Reading with compact protocol.
> Got test object: TestType(intField=100, doubleField=-2.24248483894553e-38)
> [~/thrift-double]$
> {code}
> I notice the following snippets.
> * TBinaryProtocol.py: network format (big-endian)
> {code}
> def readDouble(self):
> buff = self.trans.readAll(8)
> val, = unpack('!d', buff)
> return val
> {code}
> * TCompactProtocol.py: little-endian
> {code}
> def readDouble(self):
> buff = self.trans.readAll(8)
> val, = unpack('<d', buff)
> return val
> {code}
> * binary.js: my best IEEE floating point days are behind me but this looks
> big-endian. In any case it's used for both compact and binary.
> {code}
> exports.writeDouble = function(buff, v) {
> var m, e, c;
> buff[0] = (v < 0 ? 0x80 : 0x00);
> v = Math.abs(v);
> if (v !== v) {
> // NaN, use QNaN IEEE format
> m = 2251799813685248;
> e = 2047;
> } else if (v === Infinity) {
> m = 0;
> e = 2047;
> } else {
> e = Math.floor(Math.log(v) / Math.LN2);
> c = Math.pow(2, -e);
> if (v * c < 1) {
> e--;
> c *= 2;
> }
> if (e + 1023 >= 2047)
> {
> // Overflow
> m = 0;
> e = 2047;
> }
> else if (e + 1023 >= 1)
> {
> // Normalized - term order matters, as Math.pow(2, 52-e) and
> v*Math.pow(2, 52) can overflow
> m = (v*c-1) * POW_52;
> e += 1023;
> }
> else
> {
> // Denormalized - also catches the '0' case, somewhat by chance
> m = (v * POW_1022) * POW_52;
> e = 0;
> }
> }
> buff[1] = (e << 4) & 0xf0;
> buff[0] |= (e >> 4) & 0x7f;
> buff[7] = m & 0xff;
> m = Math.floor(m / POW_8);
> buff[6] = m & 0xff;
> m = Math.floor(m / POW_8);
> buff[5] = m & 0xff;
> m = Math.floor(m / POW_8);
> buff[4] = m & 0xff;
> m >>= 8;
> buff[3] = m & 0xff;
> m >>= 8;
> buff[2] = m & 0xff;
> m >>= 8;
> buff[1] |= m & 0x0f;
> return buff;
> };
> {code}
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