Function findDocumentFree

graphdb.js:731–801

(self, pageindex, callback, ready)

}

function findDocumentFree(self, pageindex, callback, ready) {

	var offset = offsetPage(self, pageindex);
	var buf = U.createBufferSize(self.header.pagesize);

	Fs.read(self.fd, buf, 0, buf.length, offset, function() {

		// ==== DB:PAGE (20b)
		// type (1b)              = from: 0
		// index (1b)             = from: 1
		// documents (2b)         = from: 2
		// freeslots (1b)         = from: 4
		// parentindex (4b)       = from: 5

		var relid = buf.readUInt32LE(5);
		if (!relid) {
			if (!ready) {
				callback(null, 0);
				return;
			}
		}

		// First page is the last page saved in meta therefore is needed to perform recursive with "ready"
		if (!ready) {
			findDocumentFree(self, relid, callback, true);
			return;
		}

		var documents = buf.readUInt16LE(2);
		if (documents >= self.header.pagelimit) {
			// Finds in parent if exists
			if (relid)
				findDocumentFree(self, relid, callback, true);
			else
				callback(null, 0);
			return;
		}

		// Finds a free document slot
		var index = getDocumentIndex(self, pageindex) - 1;
		var buffer = U.createBufferSize(self.header.pagelimit * self.header.documentsize);

		Fs.read(self.fd, buffer, 0, buffer.length, offset + self.header.pagesize, function() {
			while (true) {
				index++;
				var data = buffer.slice(0, self.header.documentsize);
				if (!data.length)
					break;

				if (data[2] === STATE_REMOVED) {

					if (F.isKilled)
						return;

					updPageMeta(self, pageindex, function(err, buf) {
						buf.writeUInt16LE(documents + 1, 2);
						setImmediate(callback, null, index, pageindex);
					});