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fix: lock source to ensure no double reads happen #4

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fix: lock source to ensure no double reads happen #4

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17 changes: 13 additions & 4 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@

var fs = require('fs');
var Decoder = require('pull-utf8-decoder')
var Lock = require('lock')
/**
# pull-file

Expand All @@ -25,6 +26,7 @@ module.exports = function(filename, opts) {

var ended, closeNext, busy;
var _buffer = new Buffer(bufferSize)
var lock = Lock()
var live = opts && !!opts.live
var liveCb, closeCb
var watcher
Expand Down Expand Up @@ -78,10 +80,12 @@ module.exports = function(filename, opts) {
return cb(err);
}

if(count === buffer.length) {
if(count === toRead && count === buffer.length) {
cb(null, buffer);
} else if(count === 0 && live) {
liveCb = cb; closeNext = true
} else if (count === 0) {
cb(ended = true)
} else {
closeNext = true;
cb(null, buffer.slice(0, count));
Expand Down Expand Up @@ -161,11 +165,16 @@ module.exports = function(filename, opts) {
readNext(cb);
};

var lockedSource = function (end, cb) {
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the locking causes the abort only to be propagated after the previous read is done. I would appreciate some input on how to best solve this.

what happens if a termination signal skips the lock?

something like:

var lockedSource = function (end, cb) {
  if (end) return source(end, cb)
  lock('source', function (release) {
    source(null, release(cb))
  })
}

lock('source', function (release) {
source(end, release(cb))
})
}

//read directly to text
if(opts && opts.encoding)
return Decoder(opts.encoding)(source)
return Decoder(opts.encoding)(lockedSource)

return source
return lockedSource

};

3 changes: 2 additions & 1 deletion package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@
},
"homepage": "https://github.com/DamonOehlman/pull-file",
"dependencies": {
"lock": "^0.1.3",
"pull-utf8-decoder": "^1.0.2"
}
}
}
35 changes: 35 additions & 0 deletions test/largefile.js
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Original file line number Diff line number Diff line change
Expand Up @@ -43,8 +43,43 @@ test('large file as ascii strings', function(t) {
);
});

test('large file fast reads', function(t) {
var big = crypto.pseudoRandomBytes(10*1024*1024)
fs.writeFileSync(tmpfile, big)

var read = file(tmpfile, {bufferSize: 1024 * 1024})
var items = []

read(null, checkRead)
read(null, checkRead)
read(null, checkRead)
read(null, checkRead)
read(null, checkRead)

setTimeout(function () {
read(null, checkRead)
read(null, checkRead)
read(null, checkRead)
read(null, checkRead)
read(null, checkRead)
read(null, function (err, data) {
t.equal(err, true)
t.equal(data, undefined)
next()
})
}, 10)

function checkRead (err, data) {
t.equal(data.length, 1024 * 1024)
items.push(data)
next()
}

var i = 0
function next () {
if (++i === 11) {
t.equal(hash(big), hash(Buffer.concat(items)))
t.end()
}
}
})