/usr/lib/nodejs/schlock/lib/schlock.js is in node-schlock 0.2.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 | // schlock.js
//
// Cheaply-made in-process lock broker
//
// Copyright 2012, StatusNet Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
var SchlockDoc = function(name, log) {
var readers = 0,
writers = 0,
readQueue = [],
writeQueue = [];
var runLater = function(runme) {
process.nextTick(function() {
runme(null);
});
};
var runNext = function() {
var writer,
reader;
// XXX: assert(writers === 0);
if (writeQueue.length > 0) {
if (readers === 0) {
if (log) log.info("Running queued writer for " + name);
writer = writeQueue.shift();
writers++;
runLater(writer);
}
} else if (readQueue.length > 0) {
if (log) log.info("Running " + readQueue.length + " queued reader(s) for " + name);
while (readQueue.length > 0) {
reader = readQueue.shift();
readers++;
runLater(reader);
}
}
};
this.idle = function() {
return (readers === 0 &&
writers === 0 &&
readQueue.length === 0 &&
writeQueue.length === 0);
};
this.readLock = function(callback) {
if (log) log.info("Read lock request for " + name);
if (writers > 0 || writeQueue.length > 0) {
if (log) log.info("Queueing reader for " + name);
readQueue.push(callback);
} else {
if (log) log.info("Running reader immediately for " + name);
readers++;
runLater(callback);
}
};
this.writeLock = function(callback) {
if (log) log.info("Write lock request for " + name);
if (writers > 0 || readers > 0 || writeQueue.length > 0) {
if (log) log.info("Queueing writer for " + name);
writeQueue.push(callback);
} else {
if (log) log.info("Running writer immediately for " + name);
writers++;
runLater(callback);
}
};
this.readUnlock = function(callback) {
if (log) log.info("Read unlock request for " + name);
if (readers > 0) {
if (log) log.info("Decrementing readers for " + name);
readers--;
}
runLater(callback);
runNext();
};
this.writeUnlock = function(callback) {
if (log) log.info("Write unlock request for " + name);
if (writers > 0) {
if (log) log.info("Decrementing writers for " + name);
writers--;
}
runLater(callback);
runNext();
};
};
var Schlock = function(logParent) {
var that = this,
docs = {},
log = (logParent) ? logParent.child({component: "schlock"}) : null;
var getDoc = function(name) {
if (log) log.info("Getting lock record for " + name);
if (!docs.hasOwnProperty(name)) {
if (log) log.info("New lock record for " + name);
docs[name] = new SchlockDoc(name, log);
}
return docs[name];
};
var rmDoc = function(name) {
if (log) log.info("Removing lock record for " + name);
delete docs[name];
};
this.readLock = function(name, callback) {
var sd = getDoc(name);
sd.readLock(callback);
};
this.writeLock = function(name, callback) {
var sd = getDoc(name);
sd.writeLock(callback);
};
this.readUnlock = function(name, callback) {
var sd = getDoc(name);
sd.readUnlock(callback);
if (sd.idle()) {
if (log) log.info("Lock record idle for " + name);
rmDoc(name);
}
};
this.writeUnlock = function(name, callback) {
var sd = getDoc(name);
sd.writeUnlock(callback);
if (sd.idle()) {
if (log) log.info("Lock record idle for " + name);
rmDoc(name);
}
};
};
module.exports = Schlock;
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