- •Thinking in C++ 2nd edition Volume 2: Standard Libraries & Advanced Topics
- •Preface
- •What’s new in the second edition
- •What’s in Volume 2 of this book
- •How to get Volume 2
- •Prerequisites
- •Learning C++
- •Goals
- •Chapters
- •Exercises
- •Exercise solutions
- •Source code
- •Language standards
- •Language support
- •The book’s CD ROM
- •Seminars, CD Roms & consulting
- •Errors
- •Acknowledgements
- •Library overview
- •1: Strings
- •What’s in a string
- •Creating and initializing C++ strings
- •Initialization limitations
- •Operating on strings
- •Appending, inserting and concatenating strings
- •Replacing string characters
- •Concatenation using non-member overloaded operators
- •Searching in strings
- •Finding in reverse
- •Finding first/last of a set
- •Removing characters from strings
- •Stripping HTML tags
- •Comparing strings
- •Using iterators
- •Iterating in reverse
- •Strings and character traits
- •A string application
- •Summary
- •Exercises
- •2: Iostreams
- •Why iostreams?
- •True wrapping
- •Iostreams to the rescue
- •Sneak preview of operator overloading
- •Inserters and extractors
- •Manipulators
- •Common usage
- •Line-oriented input
- •Overloaded versions of get( )
- •Reading raw bytes
- •Error handling
- •File iostreams
- •Open modes
- •Iostream buffering
- •Seeking in iostreams
- •Creating read/write files
- •User-allocated storage
- •Output strstreams
- •Automatic storage allocation
- •Proving movement
- •A better way
- •Output stream formatting
- •Internal formatting data
- •Format fields
- •Width, fill and precision
- •An exhaustive example
- •Formatting manipulators
- •Manipulators with arguments
- •Creating manipulators
- •Effectors
- •Iostream examples
- •Code generation
- •Maintaining class library source
- •Detecting compiler errors
- •A simple datalogger
- •Generating test data
- •Verifying & viewing the data
- •Counting editor
- •Breaking up big files
- •Summary
- •Exercises
- •3: Templates in depth
- •Nontype template arguments
- •Typedefing a typename
- •Using typename instead of class
- •Function templates
- •A string conversion system
- •A memory allocation system
- •Type induction in function templates
- •Taking the address of a generated function template
- •Local classes in templates
- •Applying a function to an STL sequence
- •Template-templates
- •Member function templates
- •Why virtual member template functions are disallowed
- •Nested template classes
- •Template specializations
- •A practical example
- •Pointer specialization
- •Partial ordering of function templates
- •Design & efficiency
- •Preventing template bloat
- •Explicit instantiation
- •Explicit specification of template functions
- •Controlling template instantiation
- •Template programming idioms
- •Summary
- •Containers and iterators
- •STL reference documentation
- •The Standard Template Library
- •The basic concepts
- •Containers of strings
- •Inheriting from STL containers
- •A plethora of iterators
- •Iterators in reversible containers
- •Iterator categories
- •Input: read-only, one pass
- •Output: write-only, one pass
- •Forward: multiple read/write
- •Bidirectional: operator--
- •Random-access: like a pointer
- •Is this really important?
- •Predefined iterators
- •IO stream iterators
- •Manipulating raw storage
- •Basic sequences: vector, list & deque
- •Basic sequence operations
- •vector
- •Cost of overflowing allocated storage
- •Inserting and erasing elements
- •deque
- •Converting between sequences
- •Cost of overflowing allocated storage
- •Checked random-access
- •list
- •Special list operations
- •list vs. set
- •Swapping all basic sequences
- •Robustness of lists
- •Performance comparison
- •A completely reusable tokenizer
- •stack
- •queue
- •Priority queues
- •Holding bits
- •bitset<n>
- •vector<bool>
- •Associative containers
- •Generators and fillers for associative containers
- •The magic of maps
- •A command-line argument tool
- •Multimaps and duplicate keys
- •Multisets
- •Combining STL containers
- •Creating your own containers
- •Summary
- •Exercises
- •5: STL Algorithms
- •Function objects
- •Classification of function objects
- •Automatic creation of function objects
- •Binders
- •Function pointer adapters
- •SGI extensions
- •A catalog of STL algorithms
- •Support tools for example creation
- •Filling & generating
- •Example
- •Counting
- •Example
- •Manipulating sequences
- •Example
- •Searching & replacing
- •Example
- •Comparing ranges
- •Example
- •Removing elements
- •Example
- •Sorting and operations on sorted ranges
- •Sorting
- •Example
- •Locating elements in sorted ranges
- •Example
- •Merging sorted ranges
- •Example
- •Set operations on sorted ranges
- •Example
- •Heap operations
- •Applying an operation to each element in a range
- •Examples
- •Numeric algorithms
- •Example
- •General utilities
- •Creating your own STL-style algorithms
- •Summary
- •Exercises
- •Perspective
- •Duplicate subobjects
- •Ambiguous upcasting
- •virtual base classes
- •The "most derived" class and virtual base initialization
- •"Tying off" virtual bases with a default constructor
- •Overhead
- •Upcasting
- •Persistence
- •MI-based persistence
- •Improved persistence
- •Avoiding MI
- •Mixin types
- •Repairing an interface
- •Summary
- •Exercises
- •7: Exception handling
- •Error handling in C
- •Throwing an exception
- •Catching an exception
- •The try block
- •Exception handlers
- •Termination vs. resumption
- •The exception specification
- •Better exception specifications?
- •Catching any exception
- •Rethrowing an exception
- •Uncaught exceptions
- •Function-level try blocks
- •Cleaning up
- •Constructors
- •Making everything an object
- •Exception matching
- •Standard exceptions
- •Programming with exceptions
- •When to avoid exceptions
- •Not for asynchronous events
- •Not for ordinary error conditions
- •Not for flow-of-control
- •You’re not forced to use exceptions
- •New exceptions, old code
- •Typical uses of exceptions
- •Always use exception specifications
- •Start with standard exceptions
- •Nest your own exceptions
- •Use exception hierarchies
- •Multiple inheritance
- •Catch by reference, not by value
- •Throw exceptions in constructors
- •Don’t cause exceptions in destructors
- •Avoid naked pointers
- •Overhead
- •Summary
- •Exercises
- •8: Run-time type identification
- •The “Shape” example
- •What is RTTI?
- •Two syntaxes for RTTI
- •Syntax specifics
- •Producing the proper type name
- •Nonpolymorphic types
- •Casting to intermediate levels
- •void pointers
- •Using RTTI with templates
- •References
- •Exceptions
- •Multiple inheritance
- •Sensible uses for RTTI
- •Revisiting the trash recycler
- •Mechanism & overhead of RTTI
- •Creating your own RTTI
- •Explicit cast syntax
- •Summary
- •Exercises
- •9: Building stable systems
- •Shared objects & reference counting
- •Reference-counted class hierarchies
- •Finding memory leaks
- •An extended canonical form
- •Exercises
- •10: Design patterns
- •The pattern concept
- •The singleton
- •Variations on singleton
- •Classifying patterns
- •Features, idioms, patterns
- •Basic complexity hiding
- •Factories: encapsulating object creation
- •Polymorphic factories
- •Abstract factories
- •Virtual constructors
- •Destructor operation
- •Callbacks
- •Observer
- •The “interface” idiom
- •The “inner class” idiom
- •The observer example
- •Multiple dispatching
- •Visitor, a type of multiple dispatching
- •Efficiency
- •Flyweight
- •The composite
- •Evolving a design: the trash recycler
- •Improving the design
- •“Make more objects”
- •A pattern for prototyping creation
- •Trash subclasses
- •Parsing Trash from an external file
- •Recycling with prototyping
- •Abstracting usage
- •Applying double dispatching
- •Implementing the double dispatch
- •Applying the visitor pattern
- •More coupling?
- •RTTI considered harmful?
- •Summary
- •Exercises
- •11: Tools & topics
- •The code extractor
- •Debugging
- •Trace macros
- •Trace file
- •Abstract base class for debugging
- •Tracking new/delete & malloc/free
- •CGI programming in C++
- •Encoding data for CGI
- •The CGI parser
- •Testing the CGI parser
- •Using POST
- •Handling mailing lists
- •Maintaining your list
- •Mailing to your list
- •A general information-extraction CGI program
- •Parsing the data files
- •Summary
- •Exercises
- •General C++
- •My own list of books
- •Depth & dark corners
- •Design Patterns
- •Index
9:Building stable systems
Shared objects & reference counting
Reference-counted class hierarchies
Finding memory leaks
1.For array bounds checking, use the Array template in C16:Array3.cpp of Volume 1 for all arrays. You can turn off the checking and increase efficiency when you’re ready to ship. (This doesn’t deal with the case of taking a pointer to an array, though
– perhaps that could be templatized somehow as well).
2.Use the C10:MemCheck (wrong chapter number) to guarantee that dynamic memory is released properly.
3.Check for non-virtual destructors in base classes.
423
The canonical object & singlyrooted hierarchies
An extended canonical form
Design by contract Integrated unit testing Dynamic aggregation
[[ This may actually be the “builder” design pattern in some form ]]
The examples we’ve seen so far are illustrative, but fairly simple. It’s useful to see an example that has more complexity so you can see that the STL will work in all situations.
[[ Add a factory method that takes a vector of string]]
The class that will be created as the example will be reasonably complex: it’s a bicycle which can have a choice of parts. In addition, you can change the parts during the lifetime of a Bicycle object; this includes the ability to add new parts or to upgrade from standard-quality parts to “fancy” parts. The BicyclePart class is a base class with many different types, and the Bicycle class contains a vector<BicyclePart*> to hold the various combination of parts that may be attached to a Bicycle:
//: C09:Bicycle.h
// Complex class involving dynamic aggregation #ifndef BICYCLE_H
#define BICYCLE_H #include <vector> #include <string> #include <iostream> #include <typeinfo>
class LeakChecker { int count;
public:
LeakChecker() : count(0) {}
Chapter 16: Design Patterns |
424 |
void print() {
std::cout << count << std::endl;
}
~LeakChecker() { print(); }
void operator++(int) { count++; } void operator--(int) { count--; }
};
class BicyclePart { static LeakChecker lc;
public:
BicyclePart() { lc++; }
virtual BicyclePart* clone() = 0; virtual ~BicyclePart() { lc--; } friend std::ostream&
operator<<(std::ostream& os, BicyclePart* bp) { return os << typeid(*bp).name();
}
friend class Bicycle;
};
enum BPart {
Frame, Wheel, Seat, HandleBar, Sprocket, Deraileur,
};
template<BPart id>
class Part : public BicyclePart { public:
BicyclePart* clone() { return new Part<id>; }
};
class Bicycle { public:
typedef std::vector<BicyclePart*> VBP; Bicycle();
Bicycle(const Bicycle& old);
Bicycle& operator=(const Bicycle& old);
//[Other operators as needed go here:]
//[...]
//[...]
~Bicycle() { purge(); }
//So you can change parts on a bike (but be
//careful: you must clean up any objects you
Chapter 16: Design Patterns |
425 |
// remove from the bicycle!)
VBP& bikeParts() { return parts; } friend std::ostream&
operator<<(std::ostream& os, Bicycle* b); static void print(std::vector<Bicycle*>& vb,
std::ostream& os = std::cout); private:
static int counter; int id;
VBP parts; void purge();
};
//Both the Bicycle and the generator should
//provide more variety than this. But this gives
//you the idea.
struct BicycleGenerator { Bicycle* operator()() {
return new Bicycle;
}
};
#endif // BICYCLE_H ///:~
The operator<< for ostream and Bicycle moves through and calls the operator<< for each BicyclePart, and that prints out the class name of the part so you can see what a Bicycle contains. The BicyclePart::clone( ) member function is necessary in the copy-constructor of Bicycle, since it just has a vector<BicyclePart*> and wouldn’t otherwise know how to copy the BicycleParts correctly. The cloning process, of course, will be more involved when there are data members in a BicyclePart.
BicyclePart::partcount is used to keep track of the number of parts created and destroyed (so you can detect memory leaks). It is incremented every time a new BicyclePart is created and decremented when one is destroyed; also, when partcount goes to zero this is reported and if it goes below zero there will be an assert( ) failure.
If you want to change BicycleParts on a Bicycle, you just call Bicycle::bikeParts( ) to get the vector<BicyclePart*> which you can then modify. But whenever you remove a part from a Bicycle, you must call delete for that pointer, otherwise it won’t get cleaned up.
Here’s the implementation:
//: C09:Bicycle.cpp {O} // Bicycle implementation #include "Bicycle.h" #include <map>
#include <algorithm> #include <cassert>
Chapter 16: Design Patterns |
426 |
using namespace std;
// Static member definitions: LeakChecker BicyclePart::lc; int Bicycle::counter = 0;
Bicycle::Bicycle() : id(counter++) { BicyclePart *bp[] = {
new Part<Frame>,
new Part<Wheel>, new Part<Wheel>, new Part<Seat>, new Part<HandleBar>,
new Part<Sprocket>, new Part<Deraileur>,
};
const int bplen = sizeof bp / sizeof *bp; parts = VBP(bp, bp + bplen);
}
Bicycle::Bicycle(const Bicycle& old)
: parts(old.parts.begin(), old.parts.end()) { for(int i = 0; i < parts.size(); i++)
parts[i] = parts[i]->clone();
}
Bicycle& Bicycle::operator=(const Bicycle& old) { purge(); // Remove old lvalues parts.resize(old.parts.size()); copy(old.parts.begin(),
old.parts.end(), parts.begin()); for(int i = 0; i < parts.size(); i++)
parts[i] = parts[i]->clone(); return *this;
}
void Bicycle::purge() { for(VBP::iterator it = parts.begin();
it != parts.end(); it++) { delete *it;
*it = 0; // Prevent multiple deletes
}
}
ostream& operator<<(ostream& os, Bicycle* b) { copy(b->parts.begin(), b->parts.end(),
ostream_iterator<BicyclePart*>(os, "\n"));
Chapter 16: Design Patterns |
427 |