## NAME

DwString -- String class

## SYNOPSIS

    class DW_EXPORT DwString {

    public:

        static const size_t npos;
        DwString();
        DwString(const DwString& aStr, size_t aPos=0, size_t aLen=npos);
        DwString(const char* aBuf, size_t aLen);
        DwString(const char* aCstr);
        DwString(size_t aLen, char aChar);
        DwString(char* aBuf, size_t aSize, size_t aStart, size_t aLen);
        virtual ~DwString();
        DwString& operator = (const DwString& aStr);
        DwString& operator = (const char* aCstr);
        DwString& operator = (char aChar);
        size_t size() const;
        size_t length() const;
        size_t max_size() const;
        void resize(size_t aLen, char aChar);
        void resize(size_t aLen);
        size_t capacity() const;
        void reserve(size_t aSize);
        void clear();
        DwBool empty() const;
        const char& operator [] (size_t aPos) const;
        char& operator [] (size_t aPos);
        const char& at(size_t aPos) const;
        char& at(size_t aPos);
        DwString& operator += (const DwString& aStr);
        DwString& operator += (const char* aCstr);
        DwString& operator += (char aChar);
        DwString& append(const DwString& aStr);
        DwString& append(const DwString& aStr, size_t aPos, size_t aLen);
        DwString& append(const char* aBuf, size_t aLen);
        DwString& append(const char* aCstr);
        DwString& append(size_t aLen, char aChar);
        DwString& assign(const DwString& aStr);
        DwString& assign(const DwString& aStr, size_t aPos, size_t aLen);
        DwString& assign(const char* aBuf, size_t aLen);
        DwString& assign(const char* aCstr);
        DwString& assign(size_t aLen, char aChar);
        DwString& insert(size_t aPos1, const DwString& aStr);
        DwString& insert(size_t aPos1, const DwString& aStr, size_t aPos2,
            size_t aLen2);
        DwString& insert(size_t aPos1, const char* aBuf, size_t aLen2);
        DwString& insert(size_t aPos1, const char* aCstr);
        DwString& insert(size_t aPos1, size_t aLen2, char aChar);
        DwString& erase(size_t aPos=0, size_t aLen=npos);
        DwString& replace(size_t aPos1, size_t aLen1, const DwString& aStr);
        DwString& replace(size_t aPos1, size_t aLen1, const DwString& aStr,
            size_t aPos2, size_t aLen2);
        DwString& replace(size_t aPos1, size_t aLen1, const char* aBuf,
            size_t aLen2);
        DwString& replace(size_t aPos1, size_t aLen1, const char* aCstr);
        DwString& replace(size_t aPos1, size_t aLen1, size_t aLen2, char aChar);
        size_t copy(char* aBuf, size_t aLen, size_t aPos=0) const;
        void swap(DwString& aStr);
        const char* c_str() const;
        const char* data() const;
        size_t find(const DwString& aStr, size_t aPos=0) const;
        size_t find(const char* aBuf, size_t aPos, size_t aLen) const;
        size_t find(const char* aCstr, size_t aPos=0) const;
        size_t find(char aChar, size_t aPos=0) const;
        size_t rfind(const DwString& aStr, size_t aPos=npos) const;
        size_t rfind(const char* aBuf, size_t aPos, size_t aLen) const;
        size_t rfind(const char* aCstr, size_t aPos=npos) const;
        size_t rfind(char aChar, size_t aPos=npos) const;
        size_t find_first_of(const DwString& aStr, size_t aPos=0) const;
        size_t find_first_of(const char* aBuf, size_t aPos, size_t aLen) const;
        size_t find_first_of(const char* aCstr, size_t aPos=0) const;
        size_t find_last_of(const DwString& aStr, size_t aPos=npos) const;
        size_t find_last_of(const char* aBuf, size_t aPos, size_t aLen) const;
        size_t find_last_of(const char* aCstr, size_t aPos=npos) const;
        size_t find_first_not_of(const DwString& aStr, size_t aPos=0) const;
        size_t find_first_not_of(const char* aBuf, size_t aPos, size_t aLen) const;
        size_t find_first_not_of(const char* aCstr, size_t aPos=0) const;
        size_t find_last_not_of(const DwString& aStr, size_t aPos=npos) const;
        size_t find_last_not_of(const char* aBuf, size_t aPos, size_t aLen) const;
        size_t find_last_not_of(const char* aCstr, size_t aPos=npos) const;
        DwString substr(size_t aPos=0, size_t aLen=npos) const;
        int compare(const DwString& aStr) const;
        int compare(size_t aPos1, size_t aLen1, const DwString& aStr) const;
        int compare(size_t aPos1, size_t aLen1, const DwString& aStr,
            size_t aPos2, size_t aLen2) const;
        int compare(const char* aCstr) const;
        int compare(size_t aPos1, size_t aLen1, const char* aBuf,
            size_t aLen2=npos) const;
        virtual const char* ClassName() const;
        int ObjectId() const;
        void ConvertToLowerCase();
        void ConvertToUpperCase();
        void Trim();
        void WriteTo(ostream& aStrm) const;
        int RefCount() const;
        void TakeBuffer(char* aBuf, size_t aSize, size_t aStart, size_t aLen);
        void ReleaseBuffer(char** aBuf, size_t* aSize, size_t* aStart, size_t* aLen);
        void CopyTo(DwString* aStr) const;

    protected:

        DwStringRep* mRep;
        size_t  mStart;
        size_t  mLength;
        void _copy();
        void _replace(size_t aPos1, size_t aLen1, const char* aBuf, size_t aLen2);
        void _replace(size_t aPos1, size_t aLen1, size_t aLen2, char aChar);
        friend void mem_free(char*);

    public:

        virtual void PrintDebugInfo(ostream& aStrm) const;
        virtual void CheckInvariants() const;
    };

## DESCRIPTION

`DwString` is the workhorse of the MIME++ library. Creating, parsing, or otherwise manipulating MIME messages is basically a matter of manipulating strings. `DwString` provides all the basic functionality required of a string object, including copying, comparing, concatenating, and so on.

`DwString` is similar to the `string` class that is part of the proposed ANSI standard C++ library. Some of the member functions present in the ANSI `string` are not present in `DwString`: mostly these are the functions that deal with iterators. `DwString` also includes some member functions and class utility functions that are not a part of the ANSI `string` class. These non-ANSI functions are easy to distinguish: they all begin with upper-case letters, and all ANSI functions begin with lower-case letters. The library classes themselves use only the ANSI `string` functions. At some point in the future, MIME++ will probably allow the option to substitute the ANSI `string` class for `DwString`.

`DwString` makes extensive use of copy-on-write, even when extracting substrings. It is this feature that distiguishes `DwString` from most other string classes. `DwString` also handles binary data, which can contain embedded NUL characters.

## Public Member Functions

DwString()
DwString(const DwString& aStr, size_t aPos=0, size_t aLen=npos)
DwString(const char* aBuf, size_t aLen)
DwString(const char* aCstr)
DwString(size_t aLen, char aChar)
DwString(char* aBuf, size_t aSize, size_t aStart, size_t aLen)

The first constructor is the default constructor, which sets the `DwString` object's contents to be empty.

The second constructor is the copy constructor, which copies at most `aLen` characters beginning at position `aPos` from `aStr` to the new `DwString` object. It will not copy more characters than what are available in `aStr`. `aPos` must be less than or equal to `aStr.size()`.

The third constructor copies `aLen` characters from the buffer `aBuf` into the new `DwString` object. `aBuf` need not be NUL-terminated and may contain NUL characters.

The fourth constructor copies the contents of the NUL-terminated string `aCstr` into the new `DwString` object.

The fifth constructor sets the contents of the new `DwString` object to be the character `aChar` repeated `aLen` times.

The sixth constructor is an advanced constructor that sets the contents of the new `DwString` object to the `aLen` characters starting at offset `aStart` in the buffer `aBuf`. `aSize` is the allocated size of `aBuf`. This constructor is provided for efficiency in setting a new `DwString`'s contents from a large buffer. It is efficient because no copying takes place. Instead, `aBuf` becomes the buffer used internally by the `DwString` object, which takes responsibility for deleting the buffer. Because `DwString` will free the buffer using `delete []`, the buffer should have been allocated using `new`. See also: TakeBuffer(), and ReleaseBuffer().

DwString& operator = (const DwString& aStr)
DwString& operator = (const char* aCstr)
DwString& operator = (char aChar)

Assigns the contents of the operand to this string. `aCstr` must point to a NUL-terminated array of characters (a C string). Returns `*this`.

size_t size() const

Returns the number of characters in this string's contents. This member function is identical to `length()`

size_t length() const

Returns the number of characters in this string's contents. This member function is identical to `size()`

size_t max_size() const

Returns the maximum length that this string can ever attain.

void resize(size_t aLen, char aChar)
void resize(size_t aLen)

Changes the length of this string. If the string shortened, the final characters are truncated. If the string is expanded, the added characters will be NULs or the character specified by `aChar`.

size_t capacity() const

Returns the size of the internal buffer used for this string, which will always be greater than or equal to the length of the string.

void reserve(size_t aSize)

If `aSize` is greater than the current capacity of this string, this member function will increase the capacity to be at least `aSize`.

void clear()

Sets this string's contents to be empty.

DwBool empty() const

Returns a true value if and only if the contents of this string are empty.

const char& operator [] (size_t aPos) const
char& operator [] (size_t aPos)

Returns `DwString::at(aPos) const` or `DwString::at(aPos)`. Note that the non-const version always assumes that the contents will be modified and therefore always copies a shared internal buffer before it returns.

const char& at(size_t aPos) const
char& at(size_t aPos)

Returns the character at position `aPos` in the string's contents. The non-const version returns an lvalue that may be assigned to. Note that the non-const version always assumes that the contents will be modified and therefore always copies a shared internal buffer before it returns.

DwString& operator += (const DwString& aStr)
DwString& operator += (const char* aCstr)
DwString& operator += (char aChar)

Appends the contents of the operand to this string. `aCstr` must point to a NUL-terminated array of characters (a C string). Returns `*this`.

DwString& append(const DwString& aStr)
DwString& append(const DwString& aStr, size_t aPos, size_t aLen)
DwString& append(const char* aBuf, size_t aLen)
DwString& append(const char* aCstr)
DwString& append(size_t aLen, char aChar)

Appends characters to (the end of) this string. Returns `*this`.

The first version appends all of the characters from `aStr`.

The second version appends at most `aLen` characters from `aStr` beginning at position `aPos`. `aPos` must be less than or equal to `aStr.size()`. The function will not append more characters than what are available in `aStr`.

The third version appends `aLen` characters from `aBuf`, which is not assumed to be NUL-terminated and can contain embedded NULs.

The fourth version appends characters from the NUL-terminated string `aCstr`.

The fifth version appends `aChar` repeated `aLen` times.

DwString& assign(const DwString& aStr)
DwString& assign(const DwString& aStr, size_t aPos, size_t aLen)
DwString& assign(const char* aBuf, size_t aLen)
DwString& assign(const char* aCstr)
DwString& assign(size_t aLen, char aChar)

Assigns characters to this string. Returns `*this`.

The first version assigns all of the characters from `aStr`.

The second version assigns at most `aLen` characters from `aStr` beginning at position `aPos`. `aPos` must be less than or equal to `aStr.size()`. The function will not assign more characters than what are available in `aStr`.

The third version assigns `aLen` characters from `aBuf`, which is not assumed to be NUL-terminated and can contain embedded NULs.

The fourth version assigns characters from the NUL-terminated string `aCstr`.

The fifth version assigns `aChar` repeated `aLen` times.

DwString& insert(size_t aPos1, const DwString& aStr)
DwString& insert(size_t aPos1, const DwString& aStr, size_t aPos2, size_t aLen2)
DwString& insert(size_t aPos1, const char* aBuf, size_t aLen2)
DwString& insert(size_t aPos1, const char* aCstr)
DwString& insert(size_t aPos1, size_t aLen2, char aChar)

Inserts characters into this string beginning at position `aPos1`. Returns `*this`.

The first version inserts all of the characters from `aStr`.

The second version inserts at most `aLen2` characters from `aStr` beginning at position `aPos2`. `aPos1` must be less than or equal to `aStr.size()`. The function will not assign more characters than what are available in `aStr`.

The third version inserts `aLen2` characters from `aBuf`, which is not assumed to be NUL-terminated and can contain embedded NULs.

The fourth version inserts characters from the NUL-terminated string `aCstr`.

The fifth version inserts `aChar` repeated `aLen2` times.

DwString& erase(size_t aPos=0, size_t aLen=npos)

Erases (removes) at most `aLen` characters beginning at position `aPos` from this string. The function will not erase more characters than what are available. Returns `*this`.

DwString& replace(size_t aPos1, size_t aLen1, const DwString& aStr)
DwString& replace(size_t aPos1, size_t aLen1, const DwString& aStr, size_t aPos2, size_t aLen2)
DwString& replace(size_t aPos1, size_t aLen1, const char* aBuf, size_t aLen2)
DwString& replace(size_t aPos1, size_t aLen1, const char* aCstr)
DwString& replace(size_t aPos1, size_t aLen1, size_t aLen2, char aChar)

Removes `aLen1` characters beginning at position `aPos1` and inserts other characters. Returns `*this`.

The first version inserts all of the characters from `aStr`.

The second version inserts at most `aLen2` characters from `aStr` beginning at position `aPos2`. `aPos1` must be less than or equal to `aStr.size()`. The function will not assign more characters than what are available in `aStr`.

The third version inserts `aLen2` characters from `aBuf`, which is not assumed to be NUL-terminated and can contain embedded NULs.

The fourth version inserts characters from the NUL-terminated string `aCstr`.

The fifth version inserts `aChar` repeated `aLen2` times.

size_t copy(char* aBuf, size_t aLen, size_t aPos=0) const

Copies at most `aLen` characters beginning at position `aPos` from this string to the buffer pointed to by `aBuf`. Returns the number of characters copied.

void swap(DwString& aStr)

Swaps the contents of this string and `aStr`.

const char* c_str() const

const char* data() const

These member functions permit access to the internal buffer used by the `DwString` object. `c_str()` returns a NUL-terminated string suitable for use in C library functions. `data()` returns a pointer to the internal buffer, which may not be NUL-terminated.

`c_str()` may copy the internal buffer in order to place the terminating NUL. This is not a violation of the const declaration: it is a logical const, not a bit-representation const. It could have the side effect of invalidating a pointer previously returned by `c_str()` or `data()`.

The characters in the returned string should not be modified, and should be considered invalid after any call to a non-const member function or another call to `c_str()`.

size_t find(const DwString& aStr, size_t aPos=0) const
size_t find(const char* aBuf, size_t aPos, size_t aLen) const
size_t find(const char* aCstr, size_t aPos=0) const
size_t find(char aChar, size_t aPos=0) const

Performs a forward search for a sequence of characters in the `DwString` object. The return value is the position of the sequence in the string if found, or `DwString::npos` if not found.

The first version searches beginning at position `aPos` for the sequence of characters in `aStr`.

The second version searches beginning at position `aPos` for the sequence of `aLen` characters in `aBuf`, which need not be NUL-terminated and can contain embedded NULs.

The third version searches beginning at position `aPos` for the sequence of characters in the NUL-terminated string `aCstr`.

The fourth version searches beginning at position `aPos` for the character `aChar`.

size_t rfind(const DwString& aStr, size_t aPos=npos) const
size_t rfind(const char* aBuf, size_t aPos, size_t aLen) const
size_t rfind(const char* aCstr, size_t aPos=npos) const
size_t rfind(char aChar, size_t aPos=npos) const

Performs a reverse search for a sequence of characters in the `DwString` object. The return value is the position of the sequence in the string if found, or `DwString::npos` if not found.

The first version searches beginning at position `aPos` for the sequence of characters in `aStr`.

The second version searches beginning at position `aPos` for the sequence of `aLen` characters in `aBuf`, which need not be NUL-terminated and can contain embedded NULs.

The third version searches beginning at position `aPos` for the sequence of characters in the NUL-terminated string `aCstr`.

The fourth version searches beginning at position `aPos` for the character `aChar`.

size_t find_first_of(const DwString& aStr, size_t aPos=0) const
size_t find_first_of(const char* aBuf, size_t aPos, size_t aLen) const
size_t find_first_of(const char* aCstr, size_t aPos=0) const

Performs a forward search beginning at position `aPos` for the first occurrence of any character from a specified set of characters. The return value is the position of the character if found, or `DwString::npos` if not found.

The first version searches for any character in the string `aStr`.

The second version searches for any of the `aLen` characters in `aBuf`.

The third version searches for any character in the NUL-terminated string `aCstr`.

size_t find_last_of(const DwString& aStr, size_t aPos=npos) const
size_t find_last_of(const char* aBuf, size_t aPos, size_t aLen) const
size_t find_last_of(const char* aCstr, size_t aPos=npos) const

Performs a reverse search beginning at position `aPos` for the first occurrence of any character from a specified set of characters. If `aPos` is greater than or equal to the number of characters in the string, then the search starts at the end of the string. The return value is the position of the character if found, or `DwString::npos` if not found.

The first version searches for any character in the string `aStr`.

The second version searches for any of the `aLen` characters in `aBuf`.

The third version searches for any character in the NUL-terminated string `aCstr`.

size_t find_first_not_of(const DwString& aStr, size_t aPos=0) const
size_t find_first_not_of(const char* aBuf, size_t aPos, size_t aLen) const
size_t find_first_not_of(const char* aCstr, size_t aPos=0) const

Performs a forward search beginning at position `aPos` for the first occurrence of any character not in a specified set of characters. The return value is the position of the character if found, or `DwString::npos` if not found.

The first version searches for any character not in the string `aStr`.

The second version searches for any character not among the `aLen` characters in `aBuf`.

The third version searches for any character not in the NUL-terminated string `aCstr`.

size_t find_last_not_of(const DwString& aStr, size_t aPos=npos) const
size_t find_last_not_of(const char* aBuf, size_t aPos, size_t aLen) const
size_t find_last_not_of(const char* aCstr, size_t aPos=npos) const

Performs a reverse search beginning at position `aPos` for the first occurrence of any character not in a specified set of characters. If `aPos` is greater than or equal to the number of characters in the string, then the search starts at the end of the string. The return value is the position of the character if found, or `DwString::npos` if not found.

The first version searches for any character not in the string `aStr`.

The second version searches for any character not among the `aLen` characters in `aBuf`.

The third version searches for any character not in the NUL-terminated string `aCstr`.

DwString substr(size_t aPos=0, size_t aLen=npos) const

Returns a string that contains at most `aLen` characters from the `DwString` object beginning at position `aPos`. The returned substring will not contain more characters than what are available in the superstring `DwString` object.

int compare(const DwString& aStr) const
int compare(size_t aPos1, size_t aLen1, const DwString& aStr) const
int compare(size_t aPos1, size_t aLen1, const DwString& aStr, size_t aPos2, size_t aLen2) const
int compare(const char* aCstr) const
int compare(size_t aPos1, size_t aLen1, const char* aBuf, size_t aLen2=npos) const

These member functions compare a sequence of characters to this `DwString` object, or a segment of this `DwString` object. They return -1, 0, or 1, depending on whether this `DwString` object is less than, equal to, or greater than the compared sequence of characters, respectively.

The first version compares `aStr` to this string.

The second version compares `aStr` to the segment of this string of length `aLen` beginning at position `aPos`.

The third version compares the {tt aLen2} characters beginning at position `aPos2` in `aStr` with the `aLen1` characters beginning at position `aPos1` in this `DwString` object.

The fourth version compares the NUL-terminated string `aCstr` to this `DwString`.

The fifth version compares the `aLen2` characters in `aBuf` with this `DwString`.

virtual const char* ClassName() const

This virtual function returns the name of the class as a NUL-terminated char string.

int ObjectId() const

Returns the unique object id for this `DwString`.

void ConvertToLowerCase()
void ConvertToUpperCase()

Converts this `DwString` object's characters to all lower case or all upper case.

void Trim()

Removes all white space from the beginning and the end of this `DwString` object. White space characters include ASCII HT, LF, and SPACE.

void WriteTo(ostream& aStrm) const

Writes the contents of this `DwString` object to the stream `aStrm`.

int RefCount() const

This advanced member function returns the number of references to the internal buffer used by the `DwString` object.

void TakeBuffer(char* aBuf, size_t aSize, size_t aStart, size_t aLen)

This advanced member function sets the contents of the `DwString` object to the `aLen` characters starting at offset `aStart` in the buffer `aBuf`. `aSize` is the allocated size of `aBuf`. This member function is provided for efficiency in setting a `DwString`'s contents from a large buffer. It is efficient because no copying takes place. Instead, `aBuf` becomes the buffer used internally by the `DwString` object, which takes responsibility for deleting the buffer. Because DwString will free the buffer using `delete []`, the buffer should have been allocated using `new`. See also: ReleaseBuffer().

void ReleaseBuffer(char** aBuf, size_t* aSize, size_t* aStart, size_t* aLen)

This advanced member function is the symmetric opposite of `TakeBuffer()`, to the extent that such an opposite is possible. It provides a way to ``export'' the buffer used internally by the `DwString` object. Note, however, that because of the copy-on-modify feature of `DwString`, the `DwString` object may not have sole ownership of its internal buffer. When that is case, `ReleaseBuffer()` will return a copy of the buffer. You can check to see if the internal buffer is shared by calling `RefCount()`. On return from this member function, the `DwString` object will have valid, but empty, contents. It is recommended that you use this function only on rare occasions where you need to export efficiently a large buffer.

void CopyTo(DwString* aStr) const

This advanced member function copies this `DwString` object to `aStr`. This member function is different from the assignment operator, because it physically copies the buffer instead of just duplicating a reference to it.

virtual void PrintDebugInfo(ostream& aStrm) const

Prints debugging information about the object to `aStrm`.

This member function is available only in the debug version of the library.

virtual void CheckInvariants() const

Aborts if one of the invariants of the object fails. Use this member function to track down bugs.

This member function is available only in the debug version of the library.

## Public Data Members

static const size_t npos

`npos` is assigned the value (size_t)-1.