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q-io.js
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q-io.js
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/**
* Q Promise IO streams for Node
* @module
*/
var FS = require("fs"); // node
var SYS = require("sys"); // node
var Q = require("q"); // q package
/*whatsupdoc*/
/**
* Wraps a Node readable stream, providing an API similar
* to a Narwhal synchronous `io` stream except returning
* Q promises for long latency operations.
* @param stream any Node readable stream
* @returns {Promise * Reader} a promise for
* the text stream reader.
* @constructor
*/
exports.Reader = function (_stream, charset) {
var self = Object.create(exports.Reader.prototype);
if (charset && _stream.setEncoding) // TODO complain about inconsistency
_stream.setEncoding(charset);
var begin = Q.defer();
var end = Q.defer();
// prevent indefinite buffering; resume on demand
//_stream.pause();
_stream.on("error", function (reason) {
begin.reject(reason);
});
var chunks = [];
var receiver;
_stream.on("end", function () {
begin.resolve(self);
end.resolve()
});
_stream.on("data", function (chunk) {
begin.resolve(self);
if (receiver)
receiver(chunk);
else
chunks.push(chunk);
});
function slurp() {
if (charset) {
var result = chunks.join("");
chunks = [];
return result;
} else {
consolidate(chunks);
return chunks.shift();
}
}
/***
* Reads all of the remaining data from the stream.
* @returns {Promise * String} a promise for a String
* containing the entirety the remaining stream.
*/
self.read = function () {
receiver = undefined;
//_stream.resume();
var deferred = Q.defer();
Q.when(end.promise, function () {
deferred.resolve(slurp());
});
return deferred.promise;
};
/***
* Reads and writes all of the remaining data from the
* stream in chunks.
* @param {Function(Promise * String)} write a function
* to be called on each chunk of input from this stream.
* @returns {Promise * Undefined} a promise that will
* be resolved when the input is depleted.
*/
self.forEach = function (write) {
//_stream.resume();
if (chunks && chunks.length)
write(slurp());
receiver = write;
return Q.when(end.promise, function () {
receiver = undefined;
});
};
return begin.promise;
};
/**
* Wraps a Node writable stream, providing an API similar to
* Narwhal's synchronous `io` streams, except returning and
* accepting promises for long-latency operations.
*
* @param stream any Node writable stream
* @returns {Promise * Writer} a promise for the
* text writer.
*/
exports.Writer = function (_stream, charset) {
var self = Object.create(exports.Writer.prototype);
if (charset && _stream.setEncoding) // TODO complain about inconsistency
_stream.setEncoding(charset);
var begin = Q.defer();
var end = Q.defer();
var drained = Q.defer();
_stream.on("error", function (reason) {
begin.reject(reason);
});
_stream.on("drain", function () {
begin.resolve(self);
drained.resolve();
drained = Q.defer();
});
_stream.on("end", function () {
begin.resolve(self);
end.resolve()
});
/***
* Writes content to the stream.
* @param {String} content
* @returns {Promise * Undefined} a promise that will
* be resolved when the buffer is empty, meaning
* that all of the content has been sent.
*/
self.write = function (content) {
if (!_stream.writeable && !_stream.writable)
return Q.reject("Stream not writable");
if (!_stream.write(content)) {
return drained;
}
};
/***
* Waits for all data to flush on the stream.
*
* @returns {Promise * Undefined} a promise that will
* be resolved when the buffer is empty
*/
self.flush = function () {
return drained;
};
/***
* Closes the stream, waiting for the internal buffer
* to flush.
*
* @returns {Promise * Undefined} a promise that will
* be resolved when the stream has finished writing,
* flushing, and closed.
*/
self.close = function () {
_stream.end();
return end;
};
/***
* Terminates writing on a stream, closing before
* the internal buffer drains.
*
* @returns {Promise * Undefined} a promise that will
* be resolved when the stream has finished closing.
*/
self.destroy = function () {
_stream.destroy();
return end;
};
return self; // todo returns the begin.promise
};
exports.consolidate = consolidate;
function consolidate(buffers) {
var length = 0;
var at;
var i;
var ii = buffers.length;
var buffer;
var result;
for (i = 0; i < ii; i++) {
buffer = buffers[i];
length += buffer.length;
}
result = new Buffer(length);
at = 0;
for (i = 0; i < ii; i++) {
buffer = buffers[i];
buffer.copy(result, at, 0);
at += buffer.length;
}
buffers.splice(0, ii, result);
}