--- name: "ifdbuf" section: "3bobcat" platform: "linux" package: "libbobcat-dev" version: "6.07.01-2" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/ifdbuf" --- # ifdbuf(3bobcat) Input stream buffer initialized by a file descriptor ## NAME FBB::IFdBuf - Input stream buffer initialized by a file descriptor ## SYNOPSIS **#include \** (when using **FBB::IFdBuf**\ **#include \** (when using **FBB::IFdBufS** Linking option: *-lbobcat* ## DESCRIPTION **FBB::IFdBuf** objects may be used as a *std::streambuf* of *std::istream* objects to allow extractions from a file descriptor. **FBB::IFdBufS** objects operate like **FBB::IFdBuf** objects but use **FBB::Selector** objects to check whether information on the object’s file descriptor is available before reading information from the file descriptor. File descriptors are not defined within the context of **C++**, but they can be used on operating systems that support the concept. Realize that using file descriptors introduces operating system dependencies. ## NAMESPACE **FBB**\ All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace **FBB**. ## INHERITS FROM **std::streambuf** ## ENUMERATION The public enumeration *Mode* defined in the class *FBB::IFdStreamBuf* has the following values: - o **CLOSE\_FD**, indicating that the file descriptor used by the object must be closed; - o **KEEP\_FD** (the default) indicating that the file descriptor used by the object must not be closed. ## CONSTRUCTORS - o **IFdBuf()**:\ This constructor initializes the streambuf, without associating it to a file descriptor, and without using buffering. The member *reset* can be used subsequently to associate the object with a file descriptor and optionally a buffer size. When the object is destroyed or if the mode-less overloaded version of the *reset* member is called, the file descriptor is not closed. - - o **IFdBuf(Mode mode)**:\ This constructor initializes the streambuf, without associating it to a file descriptor, and without using buffering. The member *reset* can be used subsequently to associate the object with a file descriptor and optionally a buffer size. When the object is destroyed or if the mode-less overloaded version of the member *reset* is called, the *Mode* argument determines whether the file descriptor will be closed or will remain open. - - o **IFdBuf(int fd, size\_t n = 1)**:\ This constructor initializes the streambuf, associating it to file descriptor *fd*, and an optional unget buffer size (by default having size 1). When the object is destroyed or if the mode-less overloaded version of the member *reset* is called, the file descriptor is not closed. - - o **IFdBuf(int fd, Mode mode, size\_t n = 1)**:\ This constructor initializes the streambuf, associating it to file descriptor *fd*, and an optional unget buffer size (by default having size 1). When the object is destroyed or if the mode-less overloaded version of the *reset* member is called, the *Mode* argument determines whether the file descriptor will be closed or will remain open. - - o **IFdBufS constructors**:\ Use **IFdBufS** constructors corresponding to **IFdBuf** constructors to construct the corresponding **IFdBufS** objects. Copy and move constructors (and assignment operators) are not available. ## MEMBER FUNCTIONS All members of *std::streambuf* are available, as *FBB::IFdBuf(S)* inherits from this class. - o **void close()**:\ The file descriptor used by the *IFdBuf(S)* is closed, irrespective of the *Mode* that was specified when the *IFdBuf(S)* object was constructed. Following *close* the *IFdBuf(S)* object can no longer be used until one of its *reset* members has been called. - - o **int fd() const**:\ The file descriptor used by the *IFdBuf(S)* object is returned. If the *OFdBuf* is not associated with a file descriptor -1 is returned. - - o **void reset(int fd, size\_t n = 1)**:\ The streambuf is (re)initialized, using file descriptor *fd*, and an optional unget buffer size (by default having size 1). When called repeatedly, the *Mode* specification used whem the object was constructed determines whether the file descriptor will be closed or will remain open. - - o **void reset(int fd, Mode mode, size\_t n = 1)**:\ The streambuf is (re)initialized, using file descriptor *fd*, a file descriptor closing parameter and an optional unget buffer size (by default having size 1). Depending on the *Mode* argument the object’s currently used file descriptor will be closed or will remain open when the *IFdBuf(S)* object is destroyed. ## EXAMPLE ``` #include #include #include #include using namespace std; using namespace FBB; int main(int argc, char **argv) { // define a streambuf of 20 or argv[1] characters IFdBuf buf{ STDIN_FILENO, argc == 1 ? 20 : stoul(argv[1]) }; istream in{ &buf }; cout << in.rdbuf(); } ``` ## FILES *bobcat/ifdbuf* - defines the **FBB::IFdBuf** class interface\ *bobcat/ifdbufs* - defines the **FBB::IFdBufS** class interface ## SEE ALSO [**bobcat**(7)](/bobcat/7.md), [**ifdstream**(3bobcat)](/ifdstream/3bobcat.md), [**ofdbuf**(3bobcat)](/ofdbuf/3bobcat.md), **std::streambuf** ## BUGS The member *xsgetn(char \*dest, std::streamsize n)* sets *istream::good()* to *false* when fewer bytes than *n* were read using *istream::read()*. Also see *xsgetn*’s description. Note that by default the provided file descriptors remain open. The complementary class [**ofdbuf**(3bobcat)](/ofdbuf/3bobcat.md) by default *closes* the file descriptor. ## 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**).