C/C++源代码静态检测系统的设计和实现

为了检测出C/C++源代码程序中常见的运行时错误,设计了一个静态检测系统。该系统通过词法分析、语法分析、语义分析来获取程序的语法树。然后系统的检测程序将会分析语法树的每一个结点,判断结点中的属性信息是否存在错误。创新点在于语法树数据结构和检测程序的设计。通过检测程序对结点的属性值的分析,能够检测出C/C++源代码程序中出现的数组越界、指针错误、字符串函数错误,内存泄露等问题。     

源代码自动分析系统中词法分析模块的分析与设计

编译器技术是计算机科学技术理论与实践结合的最好典范,词法分析技术为编译器前端的词法分析需求提供保障。词法分析是编译的第一步,其功能是读入输入的字符串后产生记号序列,以供语法分析使用。本文以编译程序的语法分析模块为对象进行分析与设计,为编译程序的实施提供基础。     

一种格式化字符串脆弱性动态检测技术

为了提高计算机软件的安全性,对C程序中的格式化字符串脆弱性的原理、特征进行了分析,在分析的基础上提出了一种动态检测技术.利用此检测技术实现的一种格式化字符串脆弱性检测工具能较准确地检测到C目标程序中的格式化字符串脆弱性.分析结果对编写更安全的C程序具有参考价值,检测技术具有实用价值.     

词法分析及其C语言实现

介绍了编译过程的第一阶段——词法分析的功能和输出,词法分析器的实现模式及词法出错的处理,并在此基础上依据C语言的范式给出了设计C语言程序的词法分析器的基本思路和需要考虑的问题。     

在列表框中实现精确字符串搜索

PowerBuilder为列表框(ListBox)提供了一个Findltem()函数,使用它可进行字符串的搜索。但是该函数并不严格要求字符串的匹配。只要在列表框中有以提供的字符串开头的字符串,它就认为已经匹配从而给出返回值。在某些情况下(例如,对所要查找的单词的拼写情况并不清楚时),该函数比较有用;但对于需要精确搜索字符串场合(例如,需要查找一个人名),这个函数就显得力不从心了。那么,在列表框中能不能实现精确字符串搜索呢?答案是肯定的。下面举一个例子来加以说明。     

高清手持式显微镜嵌入式Web服务器设计

搭建一个高效的嵌入式Web服务器,实现高清手持式显微镜网络化,让用户可通过客户端对其进行远程访问。搭建过程中不仅要依靠主控芯片TMS320DM368与网卡芯片DM9161BEP为主要硬件支持,而且软件方面也选择了性能高、可移植以及源码开放的Boa服务器为主体,配合扩展CGI程序以满足动态网页需求,最终完成该嵌入式Web服务器的搭建工作,实现了用户在客户端,通过网络对所拍摄视频画面进行访问、监看与控制的目标。     

计算字符串相似度的矩阵算法

用2个字符串滑动比较时匹配的字符数和2字符串滑动比较的重叠率定义了相似度的衡量指标,在确定一个字符串比另一个字符串少的情况下,设计了一种算法,试验结果表明该算法实现了在字符串匹配矩阵中确定插入空格的位置使相似度指标达到最大值,并且算法的计算次数也明显地减少。该算法可以用于信息的模糊检索。     

词法分析原理在网管软件中的应用

词法分析是程序编译的第一个阶段，是识别源程序中单词的过程。文章介绍了在通信网管软件中．应用词法分析的原理来识别脚本文件中的关键字的一种实现方式。     

双语法规则程序依赖性分析

为了提高传统程序依赖性分析的应用范围和灵活性,提出一种新的程序分析方法。该方法分为不完整性分析和完整性分析两部分。在gcc3.2和Linux内核2.4.20-8的编译环境下,利用不同的词法和语法分析模块对程序结构、数据依赖和控制信息进行提取,加快了程序分析的速度,并有效降低了程序数据流依赖分析和控制流依赖分析中算法的复杂度。最后用具体的程序实现证明了该算法的可行性。     

源码重构优化WCET

为了明确重构能否优化程序的WCET,分析了WCET估计的基本原理,进而明确了WCET优化的基本原则.以其为依据,从传统重构方法中甄选出七种用于WCET优化.实验结果表明,源码重构可以优化WCET,但其优化效果受到目标处理器的配置、程序的控制结构、编译器的优化级别等多方面的影响.相对于传统基于编译器的性能优化技术,源码重构更适合于实时程序开发的早期编码阶段.合理应用源码重构将有助于及时修复时效缺陷、确保软件的时效安全.     

从FPGA自举加载DSP程序的实现方法

提出在FPGA与DSP组成系统硬件平台的情况下，将FPGA的ROM作为DSP的外部存储器，从FPGA自举加载DSP程序。经过实践验证，该方法准确可靠，与传统的单独使用EEPROM或者FLASH作为DSP外部程序存储器的方法相比，具有充分利用系统资源、实现简单等优点。在给出了DSP自举加载原理的基础上，详细介绍了硬件及软件设计方案，并给出了关键程序的代码。     

一种EAS扫频信号源的设计与实现

电子商品防盗系统的不断优化与升级对扫频信号源的性能和特色提出了更高的要求。在硬件模块升级的同时,提出了一种频率可锁定的扫频信号源的的设计方案并成功实现。首先分析了正弦波的合成原理,并对系统使用芯片进行简要介绍;然后对系统的硬件设计方案展开论述,包括电源、时钟、JTAG调试端口以及接口设计,并给出了电路图;最后,详细介绍系统软件设计,并给出了程序流程图与详细代码。测试结果表明:设计输出的正弦波频率精确度高,幅度稳定,相位噪声较小,尤其是其所具有的锁频功能,更有利于标签的正确检测和识别。     

Managing secure communications with multilevel security andrestricted character set translation

It has been shown that a source file can be translated using a restricted character set. US Naval message traffic is transmitted with a restricted character set, and the files are optionally compressed. Both character translation and data compression can be used as add-on data encryption. Various schemes of restricted character set translation have been investigated and their implementations on computers are discussed. Translation algorithms that use a restricted character set have been implemented with multilevel security access control using the master key scheme and have been incorporated in a data compression program for military applications. Although the key management scheme discussed is perfectly feasible, it is by no means the single or best possibility. The method used here allows only for the availability of different keys for different links and hosts, but does not differentiate the different functions or activities for which the keys are used. The functions stressed in this study are data compression and character translation     

Joint Source and Channel Coding using Punctured Ring Convolutional Coded CPM

In this paper, a novel trellis source encoding scheme based on punctured ring convolutional codes is presented. Joint source and channel coding (JSCC) using trellis coded continuous phase modulation (CPM) with punctured convolutional codes over rings is investigated. The channels considered are the additive white gaussian noise (AWGN) channel and the Rayleigh fading channel. Optimal soft decoding for the proposed JSCC scheme is studied. The soft decoder is based on the a posteriori probability (APP) algorithm for trellis coded CPM with punctured ring convolutional codes. It is shown that these systems with soft decoding outperform the same systems with hard decoding especially when the systems operate at low to medium signal-to-noise ratio (SNR). Furthermore, adaptive JSCC approaches based on the proposed source coding scheme are investigated. Compared with JSCC schemes with fixed source coding rates, the proposed adaptive approaches can achieve much better performance in the high SNR region. The novelties of this work are the development of a trellis source encoding method based on punctured ring convolutional codes, the use of a soft decoder, the APP algorithm for the combined systems and the adaptive approaches to the JSCC problem.     

Two-dimensional dot codes for product identification

In automated manufacturing the two-dimensional representation of product identification numbers by means of square dot codes offers a number of advantages over the use of bar codes. In this paper a method is described for the encoding of product identification numbers into square matrices of round dots on a contrasting background. It consists of an optimal source coding scheme for the encoding of identification numbers into channel message words, and a channel coding scheme offering error-detection and error-correction for random bit errors (dot corruptions). For the channel coding scheme, a special class of error-correcting codes is introduced, called {em square-cyclic codes.} It is shown how to transform quasi-cyclic and (shortened) cyclic codes into square-cyclic codes.     

Low-complexity iterative joint source-channel decoding for variable-length encoded Markov sources

In this paper, we present a novel packetized bit-level decoding algorithm for variable-length encoded Markov sources, which calculates reliability information for the decoded bits in the form of a posteriori probabilities (APPs). An interesting feature of the proposed approach is that symbol-based source statistics in the form of the transition probabilities of the Markov source are exploited as a priori information on a bit-level trellis. This method is especially well-suited for long input blocks, since in contrast to other symbol-based APP decoding approaches, the number of trellis states does not depend on the packet length. When additionally the variable-length encoded source data is protected by channel codes, an iterative source-channel decoding scheme can be obtained in the same way as for serially concatenated codes. Furthermore, based on an analysis of the iterative decoder via extrinsic information transfer charts, it can be shown that by using reversible variable-length codes with a free distance of two, in combination with rate-1 channel codes and residual source redundancy, a reliable transmission is possible even for highly corrupted channels. This justifies a new source-channel encoding technique where explicit redundancy for error protection is only added in the source encoder.     

Lossy Distributed Source Coding Using LDPC Codes

In this paper, we propose a practical scheme for lossy distributed source coding with side information available at the decoder. Our proposed scheme is based on sending parity bits using LDPC codes. We provide the design procedure for the LDPC code that guarantees performance close to the Wyner-Ziv limit for long LDPC codes. Using simulation results, we show that the proposed method performs close to the theoretical limit for even short length codes.     

LDPC-Coded Cooperation with Receive Multi-Antenna and Unknown CSI in the Destination

This paper studies a coded cooperation scheme with receive multi-antenna in the destination. A kind of simple-encoding irregular systematic low-density-parity-check (LDPC) codes is applied to the scheme. For Rayleigh block fading channels, in the unknown channel state information scenario, space-based adaptive least-mean square (LMS) transversal filters are adopted in the destination to realize receive diversity gain. The filtered signals from the source and relay are decoded by a joint “Min-Sum” iterative decoding algorithm. This algorithm agrees with the bilayer Tanner graph that can be used to fully characterize two distinct irregular systematic LDPC codes employed by the source and relay. Simulation results verify the effectiveness of the space-based adaptive LMS transversal filters in the coded cooperation scheme. Meanwhile, theoretical analysis and numerical simulation show that the proposed coded cooperation scheme can well combine cooperation diversity, multi-receive diversity and channel coding gains, and clearly outperforms the coded non-cooperation one under the same conditions.     

Joint source and channel coding using turbo codes over rings

Turbo codes are a practical solution for achieving large coding gains. We present a new turbo coding scheme where the component codes are convolutional codes (CCs) over the ring of integers modulo M, with M being the alphabet size of the source encoder. The a priori knowledge of the source statistics is used during the iterative decoding procedure for improved decoder performance. As an example of application, we examine differential pulse code modulation (DPCM) encoded image transmission