feat(write): low level write method

README.md

@@ -254,10 +254,11 @@ smb2Client.createWriteStream('path\\to\\the\\file', function(err, readStream) {
 ### Low-level API
 
 ```javascript
-smb2Client.open('path\\to\\the\\file', function(err, fd) {
+smb2Client.open('path\\to\\the\\file', 'r', function(err, fd) {
   if (err) throw err;
 
   smb2Client.read(
+    fd, // file descriptor
     Buffer.alloc(10), // buffer where to store the data
     0, // offset in the buffer
     10, // number of bytes to read
@@ -270,6 +271,24 @@ smb2Client.open('path\\to\\the\\file', function(err, fd) {
     }
   );
 });
+
+smb2Client.open('path\\to\\the\\file', 'w', function(err, fd) {
+  if (err) throw err;
+
+  smb2Client.write(
+    fd, // file descriptor
+    Buffer.from('foo bar\n'), // data to write to the file
+    0, // offset in the buffer
+    10, // number of bytes to write
+    0, // offset in the file
+    function(err, bytesWritten, buffer) {
+      smb2Client.close(fd, function() {});
+
+      if (err) throw cb(err);
+      console.log(bytesWritten);
+    }
+  );
+});
 ```
 
 > This API is modeled after Node's `fs` module.

lib/api/createWriteStream.js

 var Writable = require('stream').Writable;
 
 var BigInt = require('../tools/bigint');
+var constants = require('../structures/constants');
 var parseFlags = require('../tools/parse-flags');
 var request = require('../tools/smb2-forge').request;
 
-// Where does it come from?!
-var maxPacketSize = 0x00010000 - 0x71;
-
 module.exports = function createWriteStream(path, options, cb) {
   if (typeof options === 'function') {
     cb = options;
@@ -31,7 +29,7 @@ module.exports = function createWriteStream(path, options, cb) {
       var close = request.bind(undefined, 'close', file, connection);
 
       function write(buffer, i, cb) {
-        var j = i + maxPacketSize;
+        var j = i + constants.MAX_WRITE_LENGTH;
         var chunk = buffer.slice(i, j);
         request(
           'write',

lib/api/write.js

+var assert = require('assert');
+
+var BigInt = require('../tools/bigint');
+var request = require('../tools/smb2-forge').request;
+var MAX_WRITE_LENGTH = require('../structures/constants').MAX_WRITE_LENGTH;
+
+module.exports = function write(file, buffer, offset, length, start, cb) {
+  assert(Buffer.isBuffer(buffer));
+  if (offset == null) {
+    offset = 0;
+  } else {
+    assert.strictEqual(typeof offset, 'number');
+    assert(offset > 0);
+    assert(offset < buffer.length);
+  }
+  if (length == null) {
+    length = buffer.length - offset;
+  } else {
+    assert.strictEqual(typeof length, 'number');
+    assert(length > 0);
+    length = Math.min(length, buffer.length - offset);
+  }
+  assert.strictEqual(typeof start, 'number');
+
+  var connection = this;
+  var pos = start;
+  var chunkLength;
+
+  function onWrite(err) {
+    if (err != null) {
+      return cb(err, pos - start, buffer);
+    }
+
+    length -= chunkLength;
+    offset += chunkLength;
+    pos += chunkLength;
+
+    writeChunk();
+  }
+  function writeChunk() {
+    if (length <= 0) {
+      cb(null, pos - start, buffer);
+    }
+
+    chunkLength = Math.min(MAX_WRITE_LENGTH, length);
+    request(
+      'write',
+      {
+        Buffer: buffer.slice(offset, offset + chunkLength),
+        FileId: file.FileId,
+        Offset: new BigInt(8, pos).toBuffer(),
+      },
+      connection,
+      onWrite
+    );
+  }
+
+  process.nextTick(writeChunk);
+};

lib/api/writeFile.js

 var SMB2Forge = require('../tools/smb2-forge');
 var SMB2Request = SMB2Forge.request;
 var BigInt = require('../tools/bigint');
+var constants = require('../structures/constants');
 var parseFlags = require('../tools/parse-flags');
 
 /*
@@ -84,7 +85,7 @@ module.exports = function writeFile(filename, data, options, cb) {
     var offset = new BigInt(8);
     var stop = false;
     var nbRemainingPackets = 0;
-    var maxPacketSize = new BigInt(8, 0x00010000 - 0x71);
+    var maxPacketSize = new BigInt(8, constants.MAX_WRITE_LENGTH);
     // callback manager
     function callback() {
       return function(err) {

lib/smb2.js

@@ -126,4 +126,13 @@ proto.read = autoPromise(require('./api/read'), function(bytesRead, buffer) {
     buffer: buffer,
   };
 });
+proto.write = autoPromise(require('./api/write'), function(
+  bytesWritten,
+  buffer
+) {
+  return {
+    bytesWritten: bytesWritten,
+    buffer: buffer,
+  };
+});
 proto.close = autoPromise(require('./api/close'));

lib/structures/constants.js

@@ -10,6 +10,7 @@ module.exports = {
   FILE_OVERWRITE: 0x00000004,
   FILE_OVERWRITE_IF: 0x00000005,
 
-  // Where does it come from?!
+  // Where do they come from?!
   MAX_READ_LENGTH: 0x00010000,
+  MAX_WRITE_LENGTH: 0x00010000 - 0x71,
 };

test/index.js

@@ -29,6 +29,22 @@ const tests = {
   unlink: function(client) {
     return client.unlink(file);
   },
+  'open new file and write': asyncFn(function*(client) {
+    const fd = yield client.open(file, 'w');
+    try {
+      try {
+        t.same(yield client.write(fd, data, undefined, undefined, 0), {
+          bytesWritten: data.length,
+          buffer: data,
+        });
+      } finally {
+        yield client.close(fd);
+      }
+      t.same(yield client.readFile(file), data);
+    } finally {
+      yield client.unlink(file);
+    }
+  }),
   rmdir: function(client) {
     return client.rmdir(dir);
   },
@@ -40,7 +56,6 @@ asyncFn(function*() {
   );
   options.autoCloseTimeout = 0;
   const client = new Smb2(options);
-
   try {
     let result;
     for (const name of Object.keys(tests)) {