某储备粮的“学习笔记” - Sum Up

Software Architecture - CS 446 Midterm Outline

2012-06-22T10:46:34+08:00

Software Design Process ModelsDesign as search. Design spaces. Design state, goal structure, generative design operations, early quantitative evaluations, control of design process. Basic models of design (transformational, plan/architecture driven). Relationship to other life-cycle activities.Terms Module: a collection of classes Subsystem: a collection of classes with an interface Design window: the time, which design decision have to be made Service: the operation in common purpose, offered by a subsystem Different Views Analysis focus on the problem domain Analyst, end user, customer Design focus on the solution domain designer, implementer Goals Designer Specify interface of subsystems Usability Reusability Implementer implementer Extender User Major Design Goals Behavioural Model Concurrency Resource Handling Software Control Structural Model Hardware/Software mapping Data Management Use Case Model Boundary Conditions (边缘情况) Non Functional Requirements Feasibility (可行性) A lot of others.Most of them involves trade off between each otherDecomposition High cohesion Low coupling Architecture/Design RepresentationWhat should be represented (structure, behaviour)? Informal representations of design, examples of design notations. Formal representation of design. Domain specific architecture descriptions. Role of standards, reference architectures. Design documentation.Terms Subsystem decomposition: identify subsystems, service, and their association in between Architectural style: pattern for a subsystem decomposition Software architecture: instance of a style. composed of components and connectors Components: encapsulated subsystem, provides services Connectors: Facilitate communication within software. Simple procedure calls or shared data accesses - Conceptual Arch Concrete Arch Evolution Degradation Drift: add things to conceptual Erosion: conflict to conceptual Recover: determining from implementation Architectural Style Vocab of design elements Set of config rules Semantic interpretation Benefits Design/Code reuse Visualization Interoperability (WTH is this word…) Style-specific analyses Style Examples Main program and subroutines Object-Oriented Style Layered Style Virtual Machine Layers Closed/Open Layering 3/4-Tier Client/Server Peer-to-Peer Batch Sequential Pipes and Filters Repository Implicit Invocation Publish-Subscribe Event-Based MVC Interpreter Sservice-Oriented Arch (SOA) Architectural ModelArch Views and ViewpointsDifferent views should be consistent between each other. Logical View UML component diagram Physical View Deployment View UML deployment diagram Concurrency/Process View Behavioral View UML collaboration diagram Metamodel意会了, 但是不知道怎么总结…主要用来保证view之间的consistencyDesign Goals Reduce Complexity Scalability Adaptability Heterogeneity Portability Dependability Reliability Availability Robustness Fault-tolerant Detail design activities Identify modules Data Flow Analysis (DFA) Identify control structure Instantiation of modules Management of base processes Decide on overall control structure Centralized/Decentralized control Address boundary control conditions Address persistent data management Address hardware/software mapping Implement concurrency Define access control ...继续ing...Design Plans/ArchitectureReview of small/medium scale plans (data structures, programming language structures, concurrency). Plans/architectures for common types of software systems (translators, embedded, real-time, user interface)....未开始...

CS 341 Algorithm 复习小记

2011-12-16T00:27:48+08:00

Master TheoremT(n) = a * T(n / b) + f(n) x = log_b(a) T(n) = θ(n^x) if f(n) = O(n^(x-ε)) θ(n^x * lg(n)) if f(n) = θ(n^x) θ(f(n)) if f(n) = Ω(n^(x+ε)) and a * f(n/b) <= c * f(n) Greedy At each step, make the "best" next choice. Never backtrack or change past choices. Never look ahead to see if this choice has negative consequences. Greedy Proof, Type 1 Describe a greedy local choice strategy Setup the configurations of the greedy solution G and the optimal solution O Argue that O can become G by replacing each entry in OFor each replacement, show it is possible, because it consist the compatibilty and optimality The last two step involves induction In basecase, focusing on how the first greedy choice can be used in an optimal solution During induction,assume the first k choices in an optimal solution are made by the greedy algorithm, show that the k+1 choice can be made by the greedy algorithm as well Greedy Proof, Type 2 Describe a greedy local choice strategy Setup the configurations of the greedy solution G and the optimal solution O Find out the difference between O and G Try to reorder O to G and consists the optimality Dynamic ProgrammingDynamic Programming calculates a solution based on the result of a previous calculation. It saves the previous result so that no duplicate calculation needed. Dynamic Programming Design Recipe Find out the subproblem give a score evaluation function give a recursive difinition State how an array can be used to evaluate the scores dimension evaluation order basecase final result How to recover the solution GraphRepresentations of Graphs Pointers vertices have pointers to adjacent vertices Cannot determine whether an edge exists directly Adjacency matrix A matrix M, M[i, j] = 1 iff exists edge from i to j waste a lot of space Adjacency lists Link-list like representation 继续ing...

OS161 Memory Management

2011-11-20T13:08:45+08:00

这次Assignment除了Physical Memory Management, 其他几个部分都相互关联. 所以在设计完成前几部分的时候, 最好将所有需要解决的问题都搞明白, 然后统一设计Address Space的结构.TLB Management和TLB有关的, 需要解决的问题有这么几个: Context Switch的时候, 如果不是两个不同的thread, 则不需要flush TLB 当TLB被占满的时候, 要替换最老的TLB entry TLB内保存read-only信息然后一个一个说… 只要检查上一次flush TLB时候的thread, 和现在的是不是同一个thread即可这部分这次Assignment已经把code写好大半了…`你需要做的就是把tlb_get_rr_victim return回来的那个entry替换掉理解MIPS TLB的每个flag bits的用处, 然后把read-only flag放在对应的位置.当程序试图写入一个read-only的memory时候, vm_fault拿到的faulttype是VM_FAULT_READONLY.Don't PANIC!!! TLB基本就这么多= =||`没啥东西…On-Demand LoadingThis is the fun part…哈哈哈这部分, 需要, 灰常严谨的逻辑和计算…`还要对page loading的步骤非常清晰. 任何一点对内存地址或者file offset的计算错误, 或者理解错误, 都会mess up.所以, 咱们重新来列一遍从程序开始运行, 到page loading结束的整个过程: runprogram/execv拿到一个progname (ELF file's path), 并call load_elf. load_elf不立刻load到physical memory,而是把ELF中的每一个segment所对应的virtual address定义好, 并且保存load这个segment所需要的所有信息.(这些信息如何/以什么样的形式保存, 需要在动手之前就先明确!) 当系统碰到一个TLB Miss时, 会有两种情况: 这个page还没有被load到physical memory, 说明这个page是第一次被访问, 找到这个page所对应的segment的信息计算load这个page所需要的所有相关数据从physical memory steal一个page的内存将这个page的数据从file load到physical memory中(提示: PADDR_TO_KVADDR is useful) 将这个physical memory保存成这个segment vaddr对应的paddr 将这对vaddr和paddr存入TLB 反之, 直接将已知的一对vaddr和paddr存入TLB即可本身, 整个过程还是很straight forward的. 可有一些special case需要handle… 有的segment不是从一个page的顶头开始的有的segment跨越多个page 有的data segment的filesize是0, 但memsize需要填零 …好像还有别的, = =想不起来了, 大家写的时候发现了, 告诉我下, 哈哈最容易出错的部分还是计算, filesize, memsize, file offset, memory offset, 等各种数据…大家加油 Address Space多写两句和as有关的很多人在刚开始写这个assignment的时候, 最先纠结的就是, as的结构要不要改...这是个好问题, 但答案是: 不一定要改as, 但肯定需要+东西.在解释为什么之前, 咱们先来看看dumb_vm的as里, 每个东西都是干嘛用的.struct addrspace { #if OPT_DUMBVM vaddr_t as_vbase1; paddr_t as_pbase1; size_t as_npages1; vaddr_t as_vbase2; paddr_t as_pbase2; size_t as_npages2; paddr_t as_stackpbase; #else /* Put stuff here for your VM system */ #endif }; dumb_vm里只保存两个segment/region的内存信息 vbase是每个reg在virtual address上开始的位置 pbase是每个reg在physical address上开始的位置 npages是每一个reg一共占用了多少个virtual page/physical frame stackpbase顾名思义, stack在physical address上的底是哪里然后咱们再研究下, 可能需要记录哪些信息. (并不一定全部都需要记录, 有些可以相互计算)为了计算写入TLB的值, 需要每个reg在virtual & physical address的开始位置每个reg有多少个page/frame 每个reg的permission flags 为了On-Demand Loading, 需要当前app对应的ELF file是什么每个reg里的每个page/frame是否被load过每个reg里的每个page/frame的vaddr和paddr开始位置每个reg里的每个page/frame所对应在ELF-FILE中的program header information (例如: file offset) stack已经占用了多少个page 对比一下上下两个列表, 我们缺点什么呢?原来的as没有记录reg的permissions, 没有记录page/frame是不是被load过了, 没有分别记录每个page/frame的vaddr+paddr(当然, 可以通过seg的数据进行计算), 也没有每个reg对应的ELF信息...stack也是固定大小所以原本的as是100%缺少东西的, 但这些额外的东西, 具体应该保存到哪里就自由发挥了.补充1: OS161里假设了一个ELF程序只包括两个segment. 虽然实际可能不止2个, 但现阶段, 只支持2个也没问题.更新1: 叫seg不太确切, 还是叫region好了. 另补充了一些需要记录的内容.Physical Memory Management在dumbvm里, Physical Memory的分配机制非常简单. 在first和last之间, 一页一页的把内存分配出去, first逐次往后移动, 直到first = last, 就没有memory可用了. 也不回收, 不重复使用.要想改变优化这个机制, 首先需要增加一个能够tracking所有可用Physical Frame使用状态的table. 在进行malloc或者free某个frame的时候, 在table中记录下来这个frame的状态. 这样, 如果存在free过的page, 这些page就可以优先被malloc, 从而重复利用已经free了的内存.整体流程: 系统启动进入vm_bootstrap 取得现在可用的Physical Memory的地址范围通过地址范围计算出有多少个可用的frame 建立保存Physical Frame Status的table 完成其他vm_bootstrap所需要做的工作再次取得可用的Physical Memory的地址范围, 这就是真正可用的内存范围停用原本的Physical Memory管理机制, 并接管所有alloc_kpages和free_kpages的操作 vm系统启动完成除此之外, 还需要修改allocation和free时候的操作, 让alloc能够通过某种algorithm来重复使用已经被free的内存位置. (用什么样的Algorithm就看各位了, 实在不行做liner search也是方法之一, 嘿嘿)个别要点: 建立的table可能比最后实际需要的大, 但并无大碍. (因为table本身占用了一部分内存) alloc_kpages的时候, 有可能需要一次alloc超过一页的frame.如果你使用的algorithm不方便在被free的内存中找出多个连续的frame, 那尽管把从未用过的连续frame分配出去吧. 其他的待补充... Instrumentation实在没什么好写的, 把declaration和initialization放对地方就好了.

OS161 System Calls Implementation Notes

2011-10-31T12:38:37+08:00

这篇文章的目的是记录CS350 Assignment2中, 我编写各种System Calls时所采用的思路. 实际coding的时候, 同一种System Call的实现方式很可能不止一种, 但殊途同归.注1: 文章顺序和实际coding顺序并不一定一致, 请参考Assignment中的Strategy部分.注2: 如果没有仔细读过code和Assignment...这里很有些东西你可能读的似懂非懂.欢迎在评论中提问...General Tips 别管写什么function, 第一步永远是检查parameter是否有效!!!(比如, pointer是不是NULL, string是不是空, etc) 不要放过任何一个warning...需要explicit cast的时候, 千万不要偷懒. function一般使用parameter中的pointer进行value return, 正常的return用来return errno. 开始coding之前, 除了读Assignment, 读code, 还要好好读Assignment Hint! 解答了很多FAQ 注意在header file里用#ifndef, 保证header不会出现重复include kmalloc了的东西...在destroy的时候一定要kfree. 不然A3里, 你会发现各种memory leak(Create某些data structure的中间, 如果出现error, 则需要首先free已经allocated的内存, 然后返回error) 善用spl解决mutex问题. 当然, 首先你要明白什么样的操作需要mutex! 我会边写这个Note边添加Tips...Part 1, Play with the files and console在OS161中, 所有应用程序在打开, 关闭, 读取, 写入一个文件的时候, 都是通过一个file descriptor [ID]来标识某一个文件的. 需要注意的是, file descriptor [ID]和vnode是完全两个东西.每个thread都有单独一套file descriptors [ID], 但两个thread的两个不同的file descriptor [ID]如果标识的是同一个文件, 则共用一个vnode.(这里所说的file descriptors实际上只是一个int, 是代表一个file descriptor的ID, 而实际上file descriptor要保存很多内容. 后边继续)简单来说, 我们需要给每一个thread都增加一个, 记录所有opened file的机制. 我们暂称之为file table.file table可以就是个简单的array, 但为了让file table的operation和thread以及syscall相互独立, 减少重复code并减少bug机会, 我强烈建议大家把file table相关的所有operations都写成独立的functions, 放在单独的文件里.file table & file descriptorfile table其实很简单, 一个array外加一个size_t记录array的长度, 就ok了. (这里说的所有array都是struct array, OS161中自带的kernel array lib)file descriptor中需要记录以下几个东西, vnode pointer permission flags the current offset in file probably need something else, depends on your implementation. (like a reference counter, etc.) 然后就是操作file table的各种function, 比如 create file table destroy file table duplicate file table (is one of the most important part of execv fork, but not nessesary for now) add/get/delete a file descriptor may need extra functions or helpers for convenience 至此基本没有难点 (就类似写个小"class").之后要把file table添加到thread里, 并且在thread_fork中进行initialization.Stdin & Stdout 也是FILE!!!这是Assignment在"Implementing file system calls"中特别提到的一点.在建立一个新的process时候, 不止要initialization一个file table, 而且还要把table的0, 1, 2分别设置成standard input, standard output和standard error, 不然printf就不work哦, 哈哈哈.注: OS161中stdout和stderr是一样的.知道了怎么Open, Close就简单了open步骤 1. 创建file descriptor 2. vfs_open打开文件 (获取vnode) 3. 往file descriptor中存需要的数据 4. 把file descriptor加到file table中, 并取得ID 5. return ID给user program如何用vfs_open打开文件, 请参考runprogram.cRead和Write差在细节有file descriptor就有vnode...如何用VOP_READ配合vnode和uio读文件, 请参看loadelf.c注意offset怎么算!!!!!考验你读code读够不够细致的时候到了...好好读vnode.h(的comment)吧.Write和Read差在uio的配置, 和用VOP_WRITE.请细读uio.h(的comment)= =...都是comment有用, code看不懂影响不是很大.Part 2, Get the process organizedfork, getpid, waitpid, _exit...注: 按我的理解, OS161所有的thread都是process, 只不过有parent和child之分.这部分中, PID的管理逻辑是关键, 主要解决几个问题. 如何让一个process wait在一个PID上, 并在exit的时候wake up所有在当前PID waiting的process 如何防止deadlock (P1 wait on P2, and P2 wait on P1) 如何保存exitcode. 并明确, 何时可以安全的删除这个exitcode的记录如何重复使用已经空闲的PID 除此之外, fork还要考虑其他问题, 后边再说. Table解决一切问题...和file descriptor类似, PID也需要构建一个table. 区别在于, process table必须是global的! 也就是说, 整个系统只有一个process table.然后考虑, 我们需要为每个PID/process保存哪些信息, 才能解决上边列举的几个问题.process table相关的function (仅供参考), create process table (use in thread_bootstrap) destroy process table (use in thread_shutdown) assign and save a PID for new process (use in thread_fork) mark a PID as inactive and save the exitcode (use when _exit is called) you may also want to add other things here. Like the actual implementation of waitpid, wakeup waitings, release a exited PID or any other PID related functions. But its all depends on your implementation decision. Wait&Wakeup的钥匙 - A magical memory address第一个Assignment写完, 对于thread_sleep和thread_wakeup应该都很熟悉了.两个function都consume一个pointer作为钥匙. 只要sleep的thread和wakeup的thread用的是同一个钥匙, 睡着的所有thread就能被唤醒.这在implement waitpid和_exit的时候是很实用的.fork意味着, 一模一样这估计是这次Assignment中最难的部分.fork的作用是生成一个和当前thread完全一样的thread. 说具体点就是, CPU的每个register值一模一样 address space中的memory一模一样打开的file一模一样 (duplicate a file table) 其他一个thread中可能包含的部分只有PID不一样!!! fork system call要点: consume一个东西, trapframe. 这里保存着user program进入privilege mode之前, 所有register的数据. 用memcpy把trapframe复制一份给新thread用调用thread_fork的时候, 用复制的trapframe和md_forkentry作为parameter. thread_fork要点: thread_fork要想办法知道, 是不是被fork system call调用的如果是, 需要复制address space 如果是, 需要duplicate file table. 否则, 创建新的 md_forkentry要点: trapframe要复制到kernel stack上 (太简单了以至于有时候想不到用) fork里复制的trapframe要free掉在trapframe里设置return value, (pc貌似也要increment...回忆不起来当时increment的原因了) address space需要activate Follow这些要点, 应该可以比较顺利的搞定fork. 但我仍推荐先把fork和md_forkentry的工作原理搞明白, 再开始.(如果写完了还没明白, 为什么要把md_forkentry pass给thread_fork, 那你绝对是奇葩)到这里, A2中最难的部分过去了...runprogram和execv, 我不确定有没有时间在下周一之前总结出来.这两个大同小异, runprogram写好, execv只是稍微多点东西.exception handling是打酱油...大家加油

关系模型概念整理 (Relational Model)

2011-10-19T08:49:01+08:00

Definition实在不知道怎么概括= =... Intention of a relation: relation definition and constrains Extention of a relation: the actual data, tuples Relation properties Set Theory Attributes has order (not necessary) Value are used to identify tuples Tuples dont have order Tuples cant have duplication Attribute value are atomic Degree: How many attributes in the schema Cardinality: How many tuples in an instance Constraints Let the DBMS to ensure the entry or modification on data are legal Give applications' bug no chance to ruin the data Three Constraint Level Tuple-level Domain restrictions (datatype) Attribute comparisons (好像是指check) Relation-level Special type of keys Superkey: 能uniquely identifies a tuple的一个or一组attribute Candidate key: Superkey的最小集, (最简单的一个or一组attribute) Primary key: 被选中, 用来identity tuples的Candidate key Database-level Referential integrity Foreign key: 其他relation中的primary key Referential integrity: 不允许出现和对应relation中的记录不符的情况 Inclusion dependencies: = =`不懂

数据库基础概念整理

2011-10-19T04:55:14+08:00

Definitions Database: is a large and persistent collection of pieces of information organized in a way that facilitate efficient retrieval and modification. DBMS: is a program that manages details related to storage and access for a database. Schema: is a description of the data interface to the database. Instance: is a database that conforms to a given schema. Transaction: is an application-specified atomic and durable unit of work. View: is a relation in the external schema whose instance is determined by the instances of the relations in the conceptual schema. Trigger: is a procedure executed by the database in response to a change to the database instance Three Level Schema Architecture External schema (view): visualized data Conceptual schema: logical structure Physical schema: file/storage devices Data Independence Application access the data through an abstract data model provided by the DBMS, rather than direct access Physical: applications cant touch the storage stucture Logical: applications cant change the data organization Four Transaction PropertiesNoSQL据说就是要break these properties= =`IDK why... Atomic: once the transaction happens, it happened. No intermediate stage! Consistency: transaction follows the database consitences Isolated: concurrent transactions wont effect each other Durable: transaction results permanently What DBMS do Remoce common code from applications Provide uniform access to data Guarantee data integrity manage concurrent access Protect against system failure Set access policies for data

SQL语法整理

2011-10-17T06:00:15+08:00

SELECTSELECT attribute-expression-list FROM relation-list [ WHERE condition ]; attribute-expression-list: [relation-name.]attribute [relation-name.]attribute [arithmatic computation] AS another name i.e., E.Salary - 40000 AS SalaryDiff CASE WHEN ... THEN ...ELSE ... END i.e., CASE WHEN E.Salary < 40000 THEN 0ELSE E.Salary - 40000 END relation-list: list of table names seperate by comma condition: arithmetic operation +, -, *, / comparisions =, <>, <, <=, >. >= logical connectives AND, OR, NOT attribute IN (Q) attribute NOT IN (Q) attribute op SOME (Q) attribute op ALL (Q) EXISTS (Q) NOT EXISTS (Q) IS [NOT] NULL NULLAND Table AND TRUE FALSE NULL TRUE TRUE FALSE NULL FALSE FALSE FALSE FALSE NULL NULL FALSE NULL OR Table OR TRUE FALSE NULL TRUE TRUE TRUE TRUE FALSE TRUE FALSE NULL NULL TRUE NULL NULL NOT Table NOT TRUE FALSE NULL FALSE TRUE NULL UNION INTERSECT EXCEPT(Q1 and Q2 must have same attribute-list)Q1 UNION Q2 => Together all the tuples in Q1 and Q2Q1 INTERSECT Q2 => Only tuples in both Q1 and Q2Q1 EXCEPT Q2 => Tuples only in Q1 but not in Q2ALL关键字: 允许重复UNION ALL will include twice of duplicate tuplesINTERSECT ALL will include all possible pairs of match tuples, duplication possibleEXCEPT ALL will include all "not in Q2" tuples, duplication possible[INNER]/OUTER JOIN Inner join把两个表连接在一起, 返回两个表中相匹配的记录, 是2和3的交集 Left outer join, 左侧表所有的记录都返回, 右侧匹配的记录返回, 没有匹配的返回Null Right outer join, 与Left outer join相反, 右侧的记录返回, 左侧返回匹配的记录, 没有匹配返回Null Full outer join, 2和3的并集 Cross join, 两个表的笛卡儿积, 返回所有可能的值, 不允许有连接条件 ORDER BYSELECT ... ... ORDER BY attribute [DESC/ASC], attribute [DESC/ASC], ...... Note: 如果没有指定Order, return的数据可能是任意顺序GROUP BY, HAVING, Aggregate expressions{count, sum, avg, min, max} => Aggregate expressionsOrder: Group => Having => Aggregate count(*): number of tuples count(E): number of tupple for which E is non-NULL count(distinct E): number of distinct non-NULL E values sum(E) sum(distinct E) avg(E) avg(distinct E) min(E) max(E) Note: 没有被group by指定的attribute不能出现在SELECT的attr-list中, 除非是aggregateINSERT INTOINSERT INTO relation-name [( attribute-list )] VALUE ( value-list ); DELETEDELETE FROM relation-name [ WHERE condition ]; UPDATEUPDATE relation-name SET attribute-assignment-list [ WHERE condition ]; attribute-assignment-list: pairs of assignment seperate by comma i.e., WorkDept = 'E01', Address = 'Waterloo' CREATE TABLECREATE TABLE relation-name ( attribute-name attribute-type [constraints-list], ... ) attribute-type: http://www.w3school.com.cn/sql/sql_datatypes.aspconstraints-list: (Constraints的格式在各种数据库中都不太一样, 就不列举了) NOT NULL PRIMARY KEY UNIQUE FOREIGN KEY Column or Tuple CHECK CREATE VIEWCREATE VIEW view-name AS ( SELECT ... ) 从View SELECT的方法和table一样CREATE TRIGGERCREATE TRIGGER trigger-name AFTER UPDATE OF attribute-list ON relation-name REFERENCING OLD as instance-name(o) NEW as instance-name(n) FOR EACH ROW ... 不同database语法不一

Java现学现卖之Layout Managers

2011-06-24T12:29:35+08:00

Java里一共提供了8种Layout Manager BorderLayout BoxLayout CardLayout FlowLayout GridBagLayout GridLayout GroupLayout SpringLayout 这其中最后两种是专门为GUI Builder设计的, 并不是很适合手动写, 我就没花时间研究, 但应该是这几种Layout Manager中, 灵活性最大的两种.网上有人说GridBagLayout是手写UI时`功能最强大的Layout...可一般强大就是复杂的代名词, 我也把它跳过了= =`(好吧, 我确实比较懒, 但更主要是时间不够)先说说基础,给一个container设置Layout使用 .setLayout(LayoutManager) 这个方法.针对不同的Layout, 添加component时候, .add()有时可能需要额外的参数然后来说说我玩明白了的几种LayoutBorderLayout这是所有content pane的默认Layout. 它将整个界面划分为PAGE_START, PAGE_END, CENTER, LINE_START, LINE_END 五个部分. 可以分别理解为一个页面的header, footer, content, left-sidebar, right-sidebar..add() 的时候需要在后边增加一个额外的参数, 标识这个component该被添加到哪个区域.例: pane.add(button, BorderLayout.PAGE_END);BoxLayout这个Layout适用于单纯的将components纵向或横向直线排列. 在Constructor中, 用X_AXIS或者Y_AXIS标识排列方向.BoxLayout本身无视components的 preferredSize, 但如果设置了maximumSize那就另当别论了. 这点在设置自适应宽度或高度的components时候, 很有用处.BoxLayout还有两个很有用的排版小工具, 通过 .add这几个小东西, 可以很轻松的调整Layout中的空间 Box.createHorizontalGlue(); 水平的自动填充空间 Box.createRigidArea(new Dimension(width, height)); 创建一个占据多大空间的空白 Trick: RigidArea的width或者height可以为0, 而且可以添加到任意其他Layout中FlowLayout这是JPanel的默认Layout. 和Box类似, 也是把components直线排列. 区别在于, 它更智能(当然有时候太聪明不是好事儿). 可以很方便的设置 .setAlignment() 左/右对齐 .setComponentOrientation() 从左到右/从右到左 .setHgap() .setVgap() components之间的水平/垂直间距 GridLayout这个Layout就是画格子. 把一个矩形空间分成n * m的格子, 可以自适应大小, 同Flow可以设置间距.其实还是很好用的, 但在排版中比较awkward...因为很多时候并不需要像表格一样的空间.创建方法很简单, new GridLayout(col, row);CardLayout 啊哈哈哈...这个我的最爱啊`!这个Layout其实就像一摞卡片, 每次你只能看到最上边的一张卡. 你可以按顺序前后切换, 也可以要求显示特定的一张, 在这次做翻页的时候非常给力!.add() 的时候, 需要增加一个额外的String参数, 标识这个card的name, 在.show(c, name)的时候会用到切换Card可以用.first(c) .last(c) .previous(c) .next(c)参考资料: enter link description here

XLib初接触

2011-05-15T04:24:52+08:00

XLib是X Window编程的基础Library, 使用时首先需要在文件头中#include 在绘制图形界面之前, 第一步要连接到一个Display. 就好比画画之前先要找到一张桌子或者画板, 你不能举着一张纸直接就往上泼墨...// Open display Display* display; display = XOpenDisplay(""); if(!display){ printf("Cannot open display\n"); exit(-1); } 之后可以通过一些函数, 获取当前Display的各种信息. 如需要, 可以保存到variable里供后边绘图时候使用.int printScreenInfo(Display* display){ int screen_num; // 当前屏幕的编号 int screen_width; // 当前屏幕的宽度 int screen_height; // 当前屏幕的高度 Window root_window; // root窗口的编号 unsigned long white_pixel; // 白色像素的编号 unsigned long black_pixel; // 黑色像素的编号 screen_num = DefaultScreen(display); screen_width = DisplayWidth(display, screen_num); screen_height = DisplayHeight(display, screen_num); root_window = RootWindow(display, screen_num); white_pixel = WhitePixel(display, screen_num); black_pixel = BlackPixel(display, screen_num); printf("Screen Number: \t%d\n Width: \t%d\n Height: \t%d\n Root: \t%d\n White: \t%d\n Black: \t%d\n", screen_num, screen_width, screen_height, root_window, white_pixel, black_pixel); return 0; } 画板摆好以后, 就要在上边铺上一张用来画画的纸, 也就是一个窗口...// Define window properties Window window; int x, y; unsigned int width, height, border_width; width = 850; height = 470; x = y = 50; border_width = 0; // Define display constants int screen_num = DefaultScreen(display); unsigned long white_pixel = WhitePixel(display, screen_num); unsigned long black_pixel = BlackPixel(display, screen_num); // Create window window = XCreateSimpleWindow(display, RootWindow(display, screen_num), x, y, width, height, border_width, black_pixel, white_pixel); // Map win to display & Flush display XMapWindow(display, win); XFlush(display); 万事俱备只欠画画儿了`XLib的function都挺容易看懂的...int drawInterface(Display* display, Window window, unsigned long black_pixel, unsigned long white_pixel ){ // Define GCs for drawing GC foregc; foregc = XCreateGC (display, window, 0, 0); XSetBackground( display, foregc, black_pixel ); XSetForeground( display, foregc, white_pixel ); // Start Drawing XClearWindow(display, window); // Door XDrawRectangle(display, window, foregc, 1, 1, 630, 460); XFillRectangle(display, window, foregc, 66, 66, 480, 330); // Dashboard XDrawRectangle(display, window, foregc, 633, 1, 215, 460); XDrawRectangle(display, window, foregc, 650, 45, 185, 330); // Timer XDrawRectangle(display, window, foregc, 660, 60, 160, 65); // And More... // Flush display to show everything changed XFlush(display); } Event Handling的部分晚点再整理

Compiler各个步骤的含义

2011-04-19T06:15:49+08:00

Step1: String -> Scanning (DFA) -> Tokens Scanner又叫Lexical analyzer或Lexer.其目的在于, 将需要compile的源代码逐字读入compiler, 并将每一个符合"词汇命名规则(Lexical Syntax)"的字段转换成token存储.换句话说, 就是一遍读, 一遍看每一个单词的拼写对不对. 对的就转成token, 拼错了就输出error.作业中对应: A6 P4(某些语言的compiler在Scanning之后还包含Preprocessing, 因为不在241讨论范围内, 不做解释)Step2: Tokens -> Parsing(LL/LR) -> Intermediate Format (WLI)Parsing又叫Syntactic Analysis.其目的在于, 将token与token联系在一起, 并将他们的转换成符合一定规范的"中间格式", 一般是某种树状结构, 例如241中定义的WLI.在Parsing过程中, 如果遇到不符合某种语言的"语法规则(Grammar)"时, 则输出error. 如果语法正确, 则输出对应格式.简单说, 就是看的说的话是不是人话, 有没有缺个标点少个括号.如果不是人话那就说明你该重新学语法去了.作业中对应: A8 P4Step3: Intermediate Format -> Semantic Analysis(Context-Sensitive Analysis) ->Semantic Analysis的目的在于, 检查程序是否存在语义上的冲突. 或者说, 上下文是不是相符.比如在C中, 如果没有declare过变量int a;, 则a = 3;就不合法.再比如, 如果a declare为int, 则a = 'b';就不合法, 因为a不能为char.作业中对应: A9 A10(Optimization为代码优化, 241没有涉及, 知道即可)Step4: -> Code Generation -> Code Fragment将Intermediate Format转换为另一种格式, 比如MIPS或者二进制文件, 可与上一步同步进行.作业中对应: A9 A10, A3, A4Step5: Code Fragements -> Linking -> Executable File(Single File)将多个compile好的多个文件链接在一起, 生成一个可执行的二进制文件(或仅生成合并以后的单个文件, 但文件本身可能无法执行)作业中对应: A5 P1, P2附: 09FALL 第二题答案 Scanning Parsing Semantic Analysis Parsing Semantic Analysis Linking Semantic Analysis Parsing 1A@#SR%$# + foo x