--- name: "eoibuf" section: "3bobcat" platform: "linux" package: "libbobcat-dev" version: "6.07.01-2" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/eoibuf" --- # eoibuf(3bobcat) std::streambuf class offering an eoi manipulator ## NAME FBB::EoiBuf - std::streambuf class offering an eoi manipulator ## SYNOPSIS **#include \**\ Linking option: *-lbobcat* ## DESCRIPTION The class *EoiBuf* inherits from *Eoi* and may therefore be used as a base class of classes specializing *std::streambuf*. It also provides a configurable character buffer for storing characters received from their devices. Often, when deriving classes from *std::streambuf* the derived classes must implement storage to and retrieval from a character buffer. By deriving from *EoiBuf* buffer-handling is automatically provided: it contains a (resizable) character buffer, and offers a *setp* member as well as a *setg* member that can be used to specify the index rage of the buffer from which extractions receive characters. Also, when overriding its base class’s *eoi\_* member it can be used to signal the end of input inserted into *std::ostream* classes using *EoiBuf* objects as *std::streambuf* objects. ## NAMESPACE **FBB**\ All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace **FBB**. ## INHERITS FROM *FBB::Eoi* (and thus from: *std::streambuf*) ## PROTECTED CONSTRUCTOR Analogously to *std::streambuf* only protected constructors are available. - o **EoiBuf()**:\ The default constructor initializes an empty buffer. - - o **EoiBuf(size\_t size)**:\ This initializes an empty buffer of a predefined size of *size* characters . Note that there’s no inherent limit to the size of the internal buffer: its size can always be enlarged or reduced. Copy and move constructors (and assignment operators) are not available. ## PROTECTED MEMBER FUNCTIONS All members of *std:streambuf* and *Eoi* are available, as **FBB::EoiBuf** inherits from these classes. - o **std::string &buffer()**:\ A reference to the internal buffer is returned; - - o **size\_t bufSize() const**:\ The length (size) of the internal buffer is returned; - - o **void resize(size\_t size)**:\ The size of the internal buffer is changed to *size* characters; - - o **void setg(unsigned next, unsigned beyond)**:\ The *streambuf::eback* member returns the address of the internal buffer’s first character, *streambuf::gptr* returns the address of the internal buffer’s *next* character, *streambuf::egptr* returns the the address of the internal buffer’s *beyond* character; - - o **void setp()**:\ The *streambuf::pbase* and *pptr* members return the address of the internal buffer’s first character, *streambuf::epptr* returns the address immediately beyond the internal buffer’s last character; - - o **unsigned char \*ucharPtr()**:\ The address of the first character of the internal buffer is returned as a pointer to an unsigned character; - - o **unsigned char const \*ucharPtr() const**:\ Same as the previous member, but this time the address of the first character of the internal buffer is returned as a pointer to an immutable unsigned character. ## PROTECTED STATIC MEMBER FUNCTIONS The following two static members are provided as convenient functions for derived classes to convert the address of the first character of *std::string* objects to pointers to unsigned characters: - o **unsigned char \*ucharPtr(std::string &str)**:\ The address of the first character of *str* is returned as a pointer to an unsigned character; - o **unsigned char const \*ucharPtr(std::string const &str) const**:\ Same as the previous member, but this time the address of the first character of *str* is returned as a pointer to an immutable unsigned character. ## EXAMPLE The following two functions are defined in the (internally used only) class *FBB::OSymCryptBase*, which is the base class of [**osymcryptstreambuf**(3bobcat)](/osymcryptstreambuf/3bobcat.md). - o *evpUpdate* updates the ongoing encryption or decryption, e.g., using the openssl function *EVP\_EncryptUpdate*, using *ucharPtr* to access characters currently in *EoiBuf’s* buffer: - ``` #include "osymcryptbase.ih" void OSymCryptBase::evpUpdate() { size_t inBufRead = pptr() - pbase(); // # read chars checkOutBufSize(inBufRead); int nOutputChars; if (not ((*d_evpUpdate)( // en/decrypt the bytes in d_inBuf ctx(), uOutBuf(), &nOutputChars, ucharPtr(), inBufRead )) ) throw Exception{} << "EVP_{En,De}cryptUpdate failed"; d_outStream.write(outBuf(), nOutputChars); // write the processed // chars to d_outSteam setp(); } ``` - - o *eoi\_* overrides *FBB::Eoi::eoi\_()* function, preventing new information from being inserted into the *FBB::OSymCryptBase* object (and thus from being inserted into its *FBB::OSymCryptStreambuf* derived class): - ``` #include "osymcryptbase.ih" void OSymCryptBase::eoi_() { if (d_eoi) return; evpUpdate(); // process available chars in the input d_eoi = true; resize(0); // clear the input buffer evpUpdate(); // update an empty buffer } ``` ## FILES *bobcat/eoibuf* - defines the class interface ## SEE ALSO [**bobcat**(7)](/bobcat/7.md), [**eoi**(3bobcat)](/eoi/3bobcat.md) ## BUGS None Reported. ## BOBCAT PROJECT FILES - o *https://fbb-git.gitlab.io/bobcat/*: gitlab project page; Debian Bobcat project files: - o *libbobcat6*: debian package containing the shared library, changelog and copyright note; - o *libbobcat-dev*: debian package containing the static library, headers, manual pages, and developer info; ## BOBCAT Bobcat is an acronym of \`Brokken’s Own Base Classes And Templates’. ## COPYRIGHT This is free software, distributed under the terms of the GNU General Public License (GPL). ## AUTHOR Frank B. Brokken (**f.b.brokken@rug.nl**).