Code summarization aims to facilitate code com-prehension by automatically generating brief and informative summaries for source code. In software development, different projects often exhibit distinct characteristics. However, existing research frequently overlooks such project-specific knowledge, which may result in sub-optimal summarization performance. In this paper, we propose Precos, a retrieval-based method that leverages the historical examples within the project (i.e., internal corpus) for generating better code summaries. First we construct the internal corpus as a datastore, and extend the datastore by retrieving the most relevant examples for the current project from a large-scale external corpus based on the internal corpus. Then during generation, we retrieve the nearest neighbors from the datastore at each decoding step to interpolate the vanilla target-token distribution. For the retrieved neighbors, we introduce a novel locality-aware distance calibration mechanism, which calibrates the retrieval distance based on the locality of the nearest neighbors, thereby providing more accurate predictions. Experimental results demonstrate that Precos achieves a substantial improvement of up to 8.5 BLEU scores compared to the model before project-specific enhancement, and can generate better code summaries than other comparison methods while maintaining satisfactory results in additional storage, time overhead, and prediction speed11Our source code is available at https://github.com/ztw33/Precos.

Injection vulnerabilities are among the most serious and dangerous security defects, as they can be exploited by attackers to inject malicious inputs and carry out cybercrimes. Timely fixing of injection vulnerabilities is crucial. However, manual repairs of injection vulnerabilities often require specialized knowledge and are prone to errors, posing a challenge and a heavy burden on developers. In recent years, Automated Program Repair (APR) techniques have shown promising momentum in automatically fixing general defects. Yet, there has been no research on how APR techniques perform in repairing injection vulnerabilities. Therefore, in this paper, we conduct an empirical study. We first construct a benchmark for injection vulnerability repair and evaluate several representative state-of-the-art APR approaches on this benchmark. The results show that existing APR tools do not adequately support the repair of injection vulnerabilities. To investigate the underlying reasons, we compare the characteristics of patches for injection vulnerabilities and general defects, and explore whether the plastic surgery hypothesis widely used in APR still holds for injection vulnerabilities. The results reveal that fixing injection vulnerabilities is more complex than fixing general defects due to significant differences in the characteristics of their patches. Additionally, the support for the plastic surgery hypothesis is much lower in the context of injection vulnerability repair. We also analyzed developers' intentions when fixing injection vulnerabilities. Finally, we summarize the implications and point out potential research directions for injection vulnerability repair.

Code completion is an important feature in Integrated Development Environments (IDEs). These years, researchers have been making efforts for intelligent code completion. However, existing work on intelligent code completion either only considered production code, or did not distinguish between production code and test code. It is unclear how effective existing completion models are for test code completion, nor whether we can further improve it. In this work, we focus on the completion of test code. We first find through experiments that completion models for production code are suboptimal for test code completion. Then we analyze the specific characteristics of test code, and observe that test code has inter- and intra-project similarities, and a strong relationship with its focal class and other production classes depending on the focal class (i.e., focal-related code). By incorporating test code from other projects to fine-tune existing models, we leverage the inter-project similarity of test code to improve the completion of tokens specific to test code. By introducing a local component and constructing existing test code as well as the focal-related code in the project as references, we enhance existing code completion models with the intra-project similarity and the focal-related code of test code. Experiments show that each characteristic of test code we exploit can bring substantial improvement to test code completion and our integrated framework outperforms other baseline frameworks. Compared to the base completion model, on token-level completion, our optimal model for test code completion relatively improves all-token and identifier completion accuracy by 7.68% and 19.96%, respectively; on line-level completion, it relatively improves edit-distance similarity and exact-match metrics by 8.89% and 22.82%, respectively. Moreover, we perform error analysis and point out potential directions for future work.

Code summarization aims to generate short functional descriptions for source code to facilitate code comprehension. While Information Retrieval (IR) approaches that leverage similar code snippets and corresponding summaries have led the early research, Deep Learning (DL) approaches that use neural models to capture statistical properties between code and summaries are now mainstream. Although some preliminary studies suggest that IR approaches are more effective in some cases, it is currently unclear how effective the existing approaches can be in general, where and why IR/DL approaches perform better, and whether the integration of IR and DL can achieve better performance. Consequently, there is an urgent need for a comprehensive study of the IR and DL code summarization approaches to provide guidance for future development in this area. This article presents the first large-scale empirical study of 18 IR, DL, and hybrid code summarization approaches on five benchmark datasets. We extensively compare different types of approaches using automatic metrics, we conduct quantitative and qualitative analyses of where and why IR and DL approaches perform better, respectively, and we also study hybrid approaches for assessing the effectiveness of integrating IR and DL. The study shows that the performance of IR approaches should not be underestimated, that while DL models perform better in predicting tokens from method signatures and capturing structural similarities in code, simple IR approaches tend to perform better in the presence of code with high similarity or long reference summaries, and that existing hybrid approaches do not perform as well as individual approaches in their respective areas of strength. Based on our findings, we discuss future research directions for better code summarization.

Neural code intelligence models are cutting-edge automated code understanding technologies that have achieved remarkable performance in various software engineering tasks. However, the lack of deep learning models’ interpretability hinders the application of deep learning based code intelligence models in real-world scenarios, particularly in security-critical domains. Previous studies use program simplification to understand neural code intelligence models, but they have overlooked the fact that the most significant difference between source code and natural language is the code’s structural semantics.

Automated GUI testing through the reuse of existing tests has recently gained prominence in research. Cross-platform migration of GUI tests between different platform versions of an application offers a promising opportunity for test reuse. Widget mapping, identifying similarities between source and target application widgets and connecting semantically analogous pairs, is central to these approaches. Vision-based widget mapping approaches are supposed to provide platform-agnostic solutions more suitable for cross-platform migration, considering that different platform versions frequently display strong resemblances in the appearance of their semantically similar widgets. However, the efficacy of vision-based widget mapping for cross-platform migration remains limited and the reasons remain unclear. In this paper, we present the first comprehensive investigation of vision-based widget mapping for cross-platform GUI test migration. We devote considerable effort to constructing a dataset consisting of 6,730 bi-directional mapped widget pairs across the iOS and Android platforms, and categorize the mapped widgets into eight classifications to thoroughly assess the capabilities of various approaches. We implement 89 configurations, derived from five distinct vision-based widget mapping methodologies, and evaluate their performance utilizing our dataset. Our findings reveal valuable insights that can be employed to advance vision-based widget mapping techniques: (1) The current approach exhibits potential for improvement, as certain configurations demonstrate superior performance in comparison to existing methods; (2) Some features can adversely impact the mapping, requiring more consideration; (3) A substantial proportion of mapped widgets display varying inconsistent contents in their appearance, which require more sophisticated vision algorithms.

Large Language Models (LLMs) have demonstrated remarkable performance in code completion. However, due to the lack of domain-specific knowledge, they may not be optimal in completing code that requires intensive domain knowledge for example completing the library names. Although there are several works that have confirmed the effectiveness of fine-tuning techniques to adapt language models for code completion in specific domains. They are limited by the need for constant fine-tuning of the model when the project is in constant iteration. To address this limitation, in this paper, we propose$k$NM-LM, a retrieval-augmented language model (R-LM), that integrates domain knowledge into language models without fine-tuning. Different from previous techniques, our approach is able to automatically adapt to different language models and domains. Specifically, it utilizes the in-domain code to build the retrieval-based database decoupled from LM, and then combines it with LM through Bayesian inference to complete the code. The extensive experiments on the completion of intra-project and intra-scenario have confirmed that$k$NM-LM brings about appreciable enhancements when compared to CodeGPT and UnixCoder. A deep analysis of our tool including the responding speed, storage usage, specific type code completion, and API invocation completion has confirmed that$k$NM-LM provides satisfactory performance, which renders it highly appropriate for domain adaptive code completion. Furthermore, our approach operates without the requirement for direct access to the language model's parameters. As a result, it can seamlessly integrate with black-box code completion models, making it easy to integrate our approach as a plugin to further enhance the performance of these models.

In distributed data stores, performance fluctuations generally occur across servers, especially when the servers are deployed in a cloud environment. Hence, the replica selected for a reading request will directly affect the response latency. However, replica selection is challenging in latency-critical data stores (e.g., key-value stores). Such data stores generally deal with small size data, and clients have to select replicas independently. Even the state-of-the-art algorithm of replica selection (C3) still has considerable room for improving the latency. According to our experiments, compared with C3, using the ideal replica selection (Oracle) reduces the 99th latency by about 34-60 percent. In this article, we propose NetRS to address the fundamental factors that prevent replica selection algorithms from being effective. NetRS is a framework that enables in-network replica selection for distributed data stores. It exploits emerging network devices, including programmable switches and network accelerators, to select replicas for requests. NetRS supports diverse algorithms of replica selection and is suited to the network topology of modern data centers. According to our extensive evaluations, compared with the conventional scheme of clients selecting replicas for requests, NetRS reduces the mean latency by up to 50.3 percent, and the 99th latency by up to 56.3 percent. Moreover, NetRS could effectively cut the response latency even when unexpected events (e.g., workload changes, network device failures), and network congestion occur.

Summary Performance isolation is highly desirable in cloud platforms where the virtual disks of virtual machines are simply large files on the shared and networked storage servers. However, existing isolation techniques cannot deal with the implications of the file system used by the networked storage servers, such that underlying resource usage is unpredictable (eg, the delayed write‐back mechanism could postpone writes, and the journaling mechanism could amplify writes). The lack of visibility on underlying resource usage leads to the predicament of being unable to meet isolation goals. In this paper, we present a software‐defined file system (SDFS) that exploits the underlying file system to allocate resources at per‐image‐file granularity and provide tenants with guaranteed throughput. The SDFS comprises two components: control plane and data plane. At the control plane, we provide a set of system calls to document tenant performance requirements into the metadata of image files. At the data plane, we construct a file‐based scheduler to manage memory and disk resources according to the tenant performance requirements. The SDFS design does not require a modification to guest operating systems, hypervisors, or file server protocols. Through a prototype implementation, we demonstrate that the SDFS can meet isolation goals and increase resource utilization with negligible overhead.

In distributed key-value stores, performance fluctuations generally occur across servers, especially when the servers are deployed in a cloud environment. Hence, the replica selected for a request will directly affect the response latency. In the context of key-value stores, even the state-of-the-art algorithm of replica selection still has considerable room for improving the response latency. In this paper, we present the fundamental factors that prevent replica selection algorithms from being effective. We address these factors by proposing NetRS, a framework that enables in-network replica selection for key-value stores. NetRS exploits emerging network devices, including programmable switches and network accelerators, to select replicas for requests. NetRS supports diverse algorithms of replica selection and is suited to the network topology of modern data centers. Compared with the conventional scheme of clients selecting replicas for requests, NetRS could effectively cut the response latency according to our extensive evaluations. Specifically, NetRS reduces the average latency by up to 48.4%, and the 99th latency by up to 68.7%.

With the rapid growth of application migration, the anonymity in data center networks becomes important in breaking attack chains and guaranteeing user privacy. However, existing anonymity systems are designed for the Internet environment, which suffer from high computational and network resource consumption and deliver low performance, thus failing to be directly deployed in data centers. In order to address this problem, this paper proposes an efficient and easily deployed anonymity scheme for software defined networking-based data centers, called mimic channel (MIC). The main idea behind MIC is to conceal the communication participants by modifying the source/destination addresses, such as media access control (MAC) and Internet protocol (IP) address at switch nodes, so as to achieve anonymity. Compared with the traditional overlay-based approaches, our in-network scheme has shorter transmission paths and less intermediate operations, thus achieving higher performance with less overhead. We also propose a collision avoidance mechanism to ensure the correctness of routing, and three mechanisms to enhance the traffic-analysis resistance. To enhance the practicality, we further propose solutions to enable MIC co-existing with some MIC-incompatible systems, such as packet analysis systems, intrusion detection systems, and firewall systems. Our security analysis demonstrates that MIC ensures unlinkability and improves traffic-analysis resistance. Our experiments show that MIC has extremely low overhead compared with the base-line transmission control protocol (TCP) (or secure sockets layer (SSL)), e.g., less than 1% overhead in terms of throughput. Experiments on MIC-based distributed file system show the applicability and efficiency of MIC.

With the rapid growth of application migration, the anonymity in data center networks becomes important in breaking attack chains and guaranteeing user privacy. However, existing anonymity systems are designed for the Internet environment, which suffer from high computational and network resource consumption and deliver low performance, thus failing to be directly deployed in data centers. In order to address this problem, this paper proposes an efficient and easily deployed anonymity scheme for SDN-based data centers, called MIC. The main idea behind MIC is to conceal the communication participants by modifying the source/destination addresses (such as MAC, IP and port) at switch nodes, so as to achieve anonymity. Compared with the traditional overlay-based approaches, our in-network scheme has shorter transmission paths and less intermediate operations, thus achieving higher performance with less overhead. We also propose a collision avoidance mechanism to ensure the correctness of routing, and two mechanisms to enhance the traffic-analysis resistance. Our security analysis demonstrates that MIC ensures unlinkability and improves traffic-analysis resistance. Our experiments show that MIC has extremely low overhead compared with the base-line TCP (or SSL), e.g., less than 1% overhead in terms of throughput.

Continuously enriched distributed systems in data centers generate much network traffic in push-style one-to-many group mode, raising new requirements for multicast transport in terms of efficiency and robustness. Existing reliable multicast solutions, which suffer from low robustness and inefficiency in either host-side protocols or multicast routing, are not suitable for data centers. In order to address the problems of inefficiency and low robustness, we present a sender-initiated, efficient, congestion-aware and robust reliable multicast solution mainly for small groups in SDN-based data centers, called MCTCP. The main idea behind MCTCP is to manage the multicast groups in a centralized manner, and reactively schedule multicast flows to active and low-utilized links, by extending TCP as the host-side protocol and managing multicast groups in the SDN-controller. The multicast spanning trees are calculated and adjusted according to the network status to perform a better allocation of resources. Our experiments show that, MCTCP can dynamically bypass the congested and failing links, achieving high efficiency and robustness. As a result, MCTCP outperforms the state-of-the-art reliable multicast schemes. Moreover, MCTCP improves the performance of data replication in HDFS compared with the original and TCP-SMO based ones, e.g., achieves 101% and 50% improvements in terms of bandwidth, respectively.