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i INTRODUCTION C Richard Heathfield Lawrence Kirby et al. A Division of Macmillan USA 201 West 103rd Street Indianapolis, Indiana 46290 C ii UNLEASHED C Unleashed EXECUTIVEEDITOR RosemarieGraham Copyright# 2000bySamsPublishing FontSILSophialPA93usedinChapter25iscopyrightedbytheSummerInstitute ACQUISITIONSEDITOR ofLinguistics,7500W.CampWisdomRoad,DallasTX75236,usedwith CarolAckerman permission. DEVELOPMENTEDITOR Allrightsreserved.Nopartofthisbookshallbereproduced,storedinaretrieval GusA.Miklos system,ortransmittedbyanymeans,electronic,mechanical,photocopying, recording,orotherwise,withoutwrittenpermissionfromthepublisher.Nopatent MANAGINGEDITOR liabilityisassumedwithrespecttotheuseoftheinformationcontainedherein. MattPurcell Althougheveryprecautionhasbeentakeninthepreparationofthisbook,the publisherandauthorsassumenoresponsibilityforerrorsoromissions.Neitheris SENIOREDITOR anyliabilityassumedfordamagesresultingfromtheuseoftheinformation KarenA.Walsh containedherein. COPYEDITOR InternationalStandardBookNumber:0-672-31896-2 KimCofer LibraryofCongressCatalogCardNumber:99-068209 INDEXER PrintedintheUnitedStatesofAmerica DianeBrenner FirstPrinting:July2000 PROOFREADERS 02 01 00 4 3 2 1 JuliCook CandiceHightower Trademarks MattWynalda Alltermsmentionedinthisbookthatareknowntobetrademarksorservice TECHNICALEDITORS markshavebeenappropriatelycapitalized.SamsPublishingcannotattesttothe SteveKrattiger accuracyofthisinformation.Useofaterminthisbookshouldnotberegardedas PeterSeebach affectingthevalidityofanytrademarkorservicemark. VinayPai ThispublicationwasproducedusingtheAdvent3B2PublishingSystem. SOFTWAREDEVELOPMENT Warning and Disclaimer SPECIALIST Everyefforthasbeenmadetomakethisbookascompleteandasaccurateas WilliamC.ElandJr. possible,butnowarrantyorfitnessisimplied.Theinformationprovidedisonan INTERIORDESIGN ‘‘asis’’basis.Theauthorsandthepublishershallhaveneitherliabilityor GaryAdair responsibilitytoanypersonorentitywithrespecttoanylossordamagesarising fromtheinformationcontainedinthisbookorfromtheuseoftheCDor COVERDESIGN programsaccompanyingit. ArenHowell COPYWRITER EricBorgert 3B2DESIGN MichelleMitchell DanielaRaderstorf 3B2LAYOUTTECHNICIANS SusanGeiselman BradLenser iii INTRODUCTION Contents at a Glance PART I The C Language Revisited 1 1 C ProgrammerUnleashed! 3 2 Holy Wars:ProgrammingStandards—Causes andCures 21 3 Optimization 75 4 Dealing withDates 113 5 Playing withBitsandBytes 131 6 OfflineData StorageandRetrieval 161 7 When ThingsGoWrong:Code-Mending 203 8 Managing Memory 259 9 Simulations andControllers 299 10 Recursion 315 PART II Data Organization 341 11 SimpleAbstract DataStructures 343 12 Binary SearchTrees 455 13 Rapid SortingTechniques 507 14 Tries 571 15 Sparse Matrix 591 16 WorkingwithGraphs 641 PART III Advanced Topics 709 17 Matrix Arithmetic 711 18 DigitalSignalProcessing 759 19 Expression ParsingandEvaluation 839 20 MakingSoftwareTools 911 21 Genetic Algorithms 977 22 Cross-Platform Development:CommunicationsProgramming 1001 23 WritingCommonGateway Interface(CGI)Applicationsin C 1053 24 Arbitrary PrecisionArithmetic 1087 C iv UNLEASHED 25 NaturalLanguageProcessing 1139 26 Encryption 1171 27 EmbeddedSystems 1209 28 ParallelProcessing 1225 29 Lookingto theFuture:C99 1243 PART IV Part IV Appendixes 1259 A GNU GeneralPublicLicense 1261 B SelectedBibliography 1269 Index 1273 v CONTENTS Contents PART I The C Language Revisited 1 1 C Programmer Unleashed! 3 WhoShouldRead ThisBook? ...................................... 5 WhatKnowledge IsAssumed? ...................................... 6 Howto GettheMost fromThisBook................................ 8 WhyAnother BookAbout C?....................................... 9 WhyANSI C?.................................................... 10 WhatPlatformsDoes ThisBookCover?............................. 11 About theSource Codein ThisBook ............................... 11 Code Quality ..................................................... 12 HowThisBook IsOrganized....................................... 12 CopyrightIssues .................................................. 14 On theCD........................................................ 15 The CProgrammingCommunity ................................... 15 Summary......................................................... 19 2 Holy Wars: Programming Standards—Causes and Cures 21 Bracing Styles .................................................... 23 1TBS ......................................................... 23 Allman........................................................ 23 Whitesmith.................................................... 24 GNU.......................................................... 24 Use ofWhitespace ................................................ 26 Indentation .................................................... 26 TabsandMainframeCompilers.................................. 27 WhitespaceAround Tokens ..................................... 27 CosmeticCode Fixes........................................... 28 Structured Programming ........................................... 29 goto.......................................................... 29 break......................................................... 30 continue...................................................... 30 while(1)...................................................... 31 return........................................................ 32 Initialization ...................................................... 35 MultipleDefinitionsonOne Line................................ 35 Initializationat Definition....................................... 36 C vi UNLEASHED StaticsandGlobals.................................................38 ProblemswithRe-use...........................................39 IdentifierNames...................................................40 Length.........................................................40 Intelligibility ...................................................41 ReservedNames................................................42 Prefixes:the‘‘TransylvanianHeresy’’.............................44 NamingVariables...............................................45 NamingConstants ..............................................46 NamingTypes..................................................46 NamingMacros ................................................47 NamingFunctions ..............................................47 WritingUseful Comments..........................................48 CommentLayoutStyles.........................................49 WhenNotto Comment..........................................51 CommentWhattheCode Does ..................................51 CommentComplexCode........................................52 CommentClosingBraces........................................52 Don’t‘‘CommentOut’’ Code....................................53 CommonErrorsandMisunderstandings..............................53 Thevoidmain Heresy...........................................54 NumberofArguments for main() ...............................56 IntegerMathVersusFloatingPointMath..........................57 SignalHandling ................................................58 PassingbyValue ...............................................58 ProblemswithUnions...........................................61 Thesizeof Operator............................................62 Thereturn Keyword ...........................................63 UnderstandingDeclarations, Definitions,andPrototypes...............63 Declarations....................................................63 Definitions.....................................................63 Prototypes......................................................64 TheImportanceofPortability.......................................64 OnesandTwosComplement.....................................65 DefiningUndefinedBehavior....................................65 SizesofIntegerTypes...........................................69 StructurePadding...............................................70 Macros ...........................................................71 CVersusC++.....................................................72 Summary .........................................................73 vii CONTENTS 3 Optimization 75 The AppealofOptimizationandSomeAncient History............... 76 TimeWell Spent............................................... 76 CIs AlreadyaVeryFastLanguage.............................. 77 The ImportanceofMeasurements................................ 78 ThinkingAbout Performance....................................... 78 ASense ofPerspective ......................................... 78 O-Notation .................................................... 81 Profiling.......................................................... 85 FlatProfiling................................................... 86 Graphing Profilers.............................................. 87 Other ProfilingMethods ........................................ 89 AlgorithmicStrategiesforOptimization ............................. 90 RealityCheck.................................................. 91 ImplementationStrategiesforOptimization,orMicro-Optimizations. 91 SomeAdditionalOptimizationStrategies........................ 103 Cooperative andParallelOptimizations............................. 104 SomeNewMeasurements...................................... 105 Client/Server andParallelism................................... 105 ImplicitParallelism............................................ 107 User InterfaceConsiderationsfor Time-ConsumingAlgorithms................................ 108 WhenNot toOptimize............................................ 110 Premature OptimizationIs theRootofAllEvil .................. 110 It isEasier toMakeaCorrect ProgramFastThan aFast ProgramCorrect............................................ 110 Don’tOptimizeAway Portability ............................... 111 LettheCompilerDo It ........................................ 111 Summary........................................................ 112 4 Dealing with Dates 113 Date andTime Functions ......................................... 114 BasicDate andTimeFunctions................................. 114 Breaking DatesandTimesinto UsefulQuantities................. 116 SimpleTime StringFormatting................................. 117 ComplexTime Formatting ..................................... 118 Reading andManipulatingDates andTimes ..................... 121 MeasuringExecution Time..................................... 123 The MillenniumBug:Date-RelatedProblems....................... 124 Useful BitsandPieces............................................ 126 Leap Years ................................................... 126 ISO 8601:DateFormatsandWeekNumbers .................... 127 Summary........................................................ 129 C viii UNLEASHED 5 Playing with Bits and Bytes 131 RepresentationofValuesin C......................................132 TheRepresentation ofIntegerValues...............................133 UsingUnsignedTypeforBitManipulation..........................135 BitShifting ......................................................136 OtherBitOperators...............................................137 BitArrays (BitMaps).............................................140 BitCounting .....................................................144 BitMirroring.....................................................148 Bit-Fields........................................................151 Lookingat Portability.............................................153 Summary ........................................................159 6 Offline Data Storage and Retrieval 161 GoalsandApplications............................................162 TextandBinaryFormats .......................................163 StructuralIssues...............................................164 FormatDesignIssues ..........................................165 BasicTechniques.................................................166 TextFiles.....................................................166 BinaryFiles...................................................176 GenericFormats..................................................187 Whitespace-orTab-Delimited Files..............................187 Comma-SeparatedValues(CSV) ................................191 .iniFiles.....................................................194 AdvancedTechniques.............................................196 UpdatingRecords..............................................197 Indexing......................................................198 RelatedTopics....................................................200 Summary ........................................................202 7 When Things Go Wrong: Code-Mending 203 DealingwithDiagnostics..........................................204 UseWarningsWisely ..........................................205 Top-downApproach ...........................................210 LintIsYourFriend ............................................210 DebuggingCommon Errors........................................212 Off-by-One Errors .............................................217 FencepostErrors...............................................217 InfiniteLoops.................................................218 AssignmentInsteadofComparison..............................219 BufferOverflow...............................................220 ArrayBounds Violation ........................................222 ix CONTENTS MissingArguments............................................ 223 Pointers ...................................................... 224 DebuggingSoftware.............................................. 229 CommercialDebuggers........................................ 229 TraceMacros................................................. 230 Planto SucceedbyExpectingto Fail............................... 241 Debug-onlyCode ............................................. 242 UsingAssertion Statements .................................... 243 Compile-timeAssertions....................................... 246 The DebuggingProcess........................................... 247 KnowingWhatIs MeanttoHappen............................. 247 WatchingItHappen ........................................... 247 IdentifyingWhereIt Breaks.................................... 248 TypesofBugs ................................................ 249 BohrBugs.................................................... 250 Heisenbugs................................................... 251 Mandelbugs................................................... 253 Schroedinbugs ................................................ 253 A Programmer’s Nightmare ....................................... 255 Summary........................................................ 257 8 Managing Memory 259 WhatIs MemoryManagement?.................................... 260 CommonMemoryUsageErrors................................... 260 UsingMemoryYouDidn’tAllocate............................. 261 gets() FunctionConsideredHarmful........................... 263 FailingtoStore theAddress.................................... 263 NotChecking ReturnValues ................................... 265 NotUsing aSparePointerfor realloc.......................... 265 UsingMemoryYouNoLonger Own............................ 267 RelyingontheOS toReclaimMemory ......................... 268 WhenaMemoryAllocation FunctionFails......................... 269 Break DowntheMemoryRequirement.......................... 270 Use LessMemory............................................. 270 Use aFixed LengthBuffer..................................... 272 Allocate anEmergencyReserve ................................ 273 UsingDisk Space............................................. 273 Whatto Dowhen calloc Succeeds................................ 274 Stayingin Control................................................ 275 MemoryTrackingHeaderFile.................................. 277 ImplementingtheMemoryTrackingLibrary..................... 282 Redesigning realloc.......................................... 285 Unredesigning realloc........................................ 286
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