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var grpc = require('bindings')('grpc.node');
var common = require('./common');
var Duplex = require('stream').Duplex;
var util = require('util');
util.inherits(GrpcClientStream, Duplex);
/**
* Class for representing a gRPC client side stream as a Node stream. Extends
* from stream.Duplex.
* @constructor
* @param {grpc.Call} call Call object to proxy
* @param {object} options Stream options
*/
function GrpcClientStream(call, options) {
Duplex.call(this, options);
var self = this;
// Indicates that we can start reading and have not received a null read
var can_read = false;
// Indicates that a read is currently pending
var reading = false;
// Indicates that we can call startWrite
var can_write = false;
// Indicates that a write is currently pending
var writing = false;
this._call = call;
/**
* Callback to handle receiving a READ event. Pushes the data from that event
* onto the read queue and starts reading again if applicable.
* @param {grpc.Event} event The READ event object
*/
function readCallback(event) {
var data = event.data;
if (self.push(data)) {
if (data == null) {
// Disable starting to read after null read was received
can_read = false;
reading = false;
} else {
call.startRead(readCallback);
}
} else {
// Indicate that reading can be resumed by calling startReading
reading = false;
}
};
/**
* Initiate a read, which continues until self.push returns false (indicating
* that reading should be paused) or data is null (indicating that there is no
* more data to read).
*/
function startReading() {
call.startRead(readCallback);
}
// TODO(mlumish): possibly change queue implementation due to shift slowness
var write_queue = [];
/**
* Write the next chunk of data in the write queue if there is one. Otherwise
* indicate that there is no pending write. When the write succeeds, this
* function is called again.
*/
function writeNext() {
if (write_queue.length > 0) {
writing = true;
var next = write_queue.shift();
var writeCallback = function(event) {
next.callback();
writeNext();
};
call.startWrite(next.chunk, writeCallback, 0);
} else {
writing = false;
}
}
call.startInvoke(function(event) {
can_read = true;
can_write = true;
startReading();
writeNext();
}, function(event) {
self.emit('metadata', event.data);
}, function(event) {
self.emit('status', event.data);
}, 0);
this.on('finish', function() {
call.writesDone(function() {});
});
/**
* Indicate that reads should start, and start them if the INVOKE_ACCEPTED
* event has been received.
*/
this._enableRead = function() {
if (!reading) {
reading = true;
if (can_read) {
startReading();
}
}
};
/**
* Push the chunk onto the write queue, and write from the write queue if
* there is not a pending write
* @param {Buffer} chunk The chunk of data to write
* @param {function(Error=)} callback The callback to call when the write
* completes
*/
this._tryWrite = function(chunk, callback) {
write_queue.push({chunk: chunk, callback: callback});
if (can_write && !writing) {
writeNext();
}
};
}
/**
* Start reading. This is an implementation of a method needed for implementing
* stream.Readable.
* @param {number} size Ignored
*/
GrpcClientStream.prototype._read = function(size) {
this._enableRead();
};
/**
* Attempt to write the given chunk. Calls the callback when done. This is an
* implementation of a method needed for implementing stream.Writable.
* @param {Buffer} chunk The chunk to write
* @param {string} encoding Ignored
* @param {function(Error=)} callback Ignored
*/
GrpcClientStream.prototype._write = function(chunk, encoding, callback) {
this._tryWrite(chunk, callback);
};
/**
* Make a request on the channel to the given method with the given arguments
* @param {grpc.Channel} channel The channel on which to make the request
* @param {string} method The method to request
* @param {array=} metadata Array of metadata key/value pairs to add to the call
* @param {(number|Date)=} deadline The deadline for processing this request.
* Defaults to infinite future.
* @return {stream=} The stream of responses
*/
function makeRequest(channel,
method,
metadata,
deadline) {
if (deadline === undefined) {
deadline = Infinity;
}
var call = new grpc.Call(channel, method, deadline);
if (metadata) {
call.addMetadata(metadata);
}
return new GrpcClientStream(call);
}
/**
* See documentation for makeRequest above
*/
exports.makeRequest = makeRequest;
/**
* Represents a client side gRPC channel associated with a single host.
*/
exports.Channel = grpc.Channel;
/**
* Status name to code number mapping
*/
exports.status = grpc.status;
/**
* Call error name to code number mapping
*/
exports.callError = grpc.callError;
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