This is Info file iostream.info, produced by Makeinfo-1.55 from the input file ./iostream.texi. START-INFO-DIR-ENTRY * iostream: (iostream). The C++ input/output facility. END-INFO-DIR-ENTRY This file describes libio, the GNU library for C++ iostreams and C stdio. libio includes software developed by the University of California, Berkeley. Copyright (C) 1993 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions. File: iostream.info, Node: Formatting, Next: Stdiobuf, Prev: Overflow, Up: Streambuf C-style formatting for `streambuf' objects ========================================== The GNU `streambuf' class supports `printf'-like formatting and scanning. - Method: int streambuf::vform (const char *FORMAT, ...) Similar to `fprintf(FILE, FORMAT, ...)'. The FORMAT is a `printf'-style format control string, which is used to format the (variable number of) arguments, printing the result on the `this' streambuf. The result is the number of characters printed. - Method: int streambuf::vform (const char *FORMAT, va_list ARGS) Similar to `vfprintf(FILE, FORMAT, ARGS)'. The FORMAT is a `printf'-style format control string, which is used to format the argument list ARGS, printing the result on the `this' streambuf. The result is the number of characters printed. - Method: int streambuf::scan (const char *FORMAT, ...) Similar to `fscanf(FILE, FORMAT, ...)'. The FORMAT is a `scanf'-style format control string, which is used to read the (variable number of) arguments from the `this' streambuf. The result is the number of items assigned, or `EOF' in case of input failure before any conversion. - Method: int streambuf::vscan (const char *FORMAT, va_list ARGS) Like `streambuf::scan', but takes a single `va_list' argument. File: iostream.info, Node: Stdiobuf, Next: Procbuf, Prev: Formatting, Up: Streambuf Wrappers for C `stdio' ====================== A "stdiobuf" is a `streambuf' object that points to a `FILE' object (as defined by `stdio.h'). All `streambuf' operations on the `stdiobuf' are forwarded to the `FILE'. Thus the `stdiobuf' object provides a wrapper around a `FILE', allowing use of `streambuf' operations on a `FILE'. This can be useful when mixing C code with C++ code. The pre-defined streams `cin', `cout', and `cerr' are normally implemented as `stdiobuf' objects that point to respectively `stdin', `stdout', and `stderr'. This is convenient, but it does cost some extra overhead. If you set things up to use the implementation of `stdio' provided with this library, then `cin', `cout', and `cerr' will be set up to to use `stdiobuf' objects, since you get their benefits for free. *Note C Input and Output: Stdio. File: iostream.info, Node: Procbuf, Next: Backing Up, Prev: Stdiobuf, Up: Streambuf Reading/writing from/to a pipe ============================== The "procbuf" class is a GNU extension. It is derived from `streambuf'. A `procbuf' can be "closed" (in which case it does nothing), or "open" (in which case it allows communicating through a pipe with some other program). - Constructor: procbuf::procbuf () Creates a `procbuf' in a "closed" state. - Method: procbuf* procbuf::open (const char *COMMAND, int MODE) Uses the shell (`/bin/sh') to run a program specified by COMMAND. If MODE is `ios::in', standard output from the program is sent to a pipe; you can read from the pipe by reading from the `procbuf'. (This is similar to `popen(COMMAND, "r")'.) If MODE is `ios::out', output written written to the `procbuf' is written to a pipe; the program is set up to read its standard input from (the other end of) the pipe. (This is similar to `popen(COMMAND, "w")'.) The `procbuf' must start out in the "closed" state. Returns `*this' on success, and `NULL' on failure. - Constructor: procbuf::procbuf (const char *COMMAND, int MODE) Calls `procbuf::open (COMMAND, MODE)'. - Method: procbuf* procbuf::close () Waits for the program to finish executing, and then cleans up the resources used. Returns `*this' on success, and `NULL' on failure. - Destructor: procbuf::~procbuf () Calls `procbuf::close'. File: iostream.info, Node: Backing Up, Next: Indirectbuf, Prev: Procbuf, Up: Streambuf Backing up ========== The GNU iostream library allows you to ask a `streambuf' to remember the current position. This allows you to go back to this position later, after reading further. You can back up arbitrary amounts, even on unbuffered files or multiple buffers' worth, as long as you tell the library in advance. This unbounded backup is very useful for scanning and parsing applications. This example shows a typical scenario: // Read either "dog", "hound", or "hounddog". // If "dog" is found, return 1. // If "hound" is found, return 2. // If "hounddog" is found, return 3. // If none of these are found, return -1. int my_scan(streambuf* sb) { streammarker fence(sb); char buffer[20]; // Try reading "hounddog": if (sb->sgetn(buffer, 8) == 8 && strncmp(buffer, "hounddog", 8) == 0) return 3; // No, no "hounddog": Back up to 'fence' sb->seekmark(fence); // // ... and try reading "dog": if (sb->sgetn(buffer, 3) == 3 && strncmp(buffer, "dog", 3) == 0) return 1; // No, no "dog" either: Back up to 'fence' sb->seekmark(fence); // // ... and try reading "hound": if (sb->sgetn(buffer, 5) == 5 && strncmp(buffer, "hound", 5) == 0) return 2; // No, no "hound" either: Back up and signal failure. sb->seekmark(fence); // Backup to 'fence' return -1; } - Constructor: streammarker::streammarker (streambuf* SBUF) Create a `streammarker' associated with SBUF that remembers the current position of the get pointer. - Method: int streammarker::delta (streammarker& MARK2) Return the difference between the get positions corresponding to `*this' and MARK2 (which must point into the same `streambuffer' as `this'). - Method: int streammarker::delta () Return the position relative to the streambuffer's current get position. - Method: int streambuf::seekmark (streammarker& MARK) Move the get pointer to where it (logically) was when MARK was constructed. File: iostream.info, Node: Indirectbuf, Prev: Backing Up, Up: Streambuf Forwarding I/O activity ======================= An "indirectbuf" is one that forwards all of its I/O requests to another streambuf. An `indirectbuf' can be used to implement Common Lisp synonym-streams and two-way-streams: class synonymbuf : public indirectbuf { Symbol *sym; synonymbuf(Symbol *s) { sym = s; } virtual streambuf *lookup_stream(int mode) { return coerce_to_streambuf(lookup_value(sym)); } }; File: iostream.info, Node: Stdio, Next: Index, Prev: Streambuf, Up: Top C Input and Output ****************** `libio' is distributed with a complete implementation of the ANSI C `stdio' facility. It is implemented using `streambuf' objects. *Note Wrappers for C `stdio': Stdiobuf. The `stdio' package is intended as a replacement for the whatever `stdio' is in your C library. Since `stdio' works best when you build `libc' to contain it, and that may be inconvenient, it is not installed by default. Extensions beyond ANSI: * A stdio `FILE' is identical to a streambuf. Hence there is no need to worry about synchronizing C and C++ input/output--they are by definition always synchronized. * If you create a new streambuf sub-class (in C++), you can use it as a `FILE' from C. Thus the system is extensible using the standard `streambuf' protocol. * You can arbitrarily mix reading and writing, without having to seek in between. * Unbounded `ungetc()' buffer. File: iostream.info, Node: Index, Prev: Stdio, Up: Top Index ***** * Menu: * (: States. * (: States. * << on ostream: Operators. * >> on istream: Operators. * iostream destructor: Iostream. * badbit: States. * beg: Output Position. * cerr: Operators. * cin: Operators. * class fstreambase: Files. * class fstream: Files. * class ifstream: Files. * class istrstream: Strings. * class ostream: Files. * class ostrstream: Strings. * class strstreambase: Strings. * class strstreambuf: Strings. * class strstream: Strings. * cout: Operators. * cur: Output Position. * dec: Manipulators. * destructor for iostream: Iostream. * end: Output Position. * endl: Manipulators. * ends: Manipulators. * eofbit: States. * failbit: States. * flush: Ostream Housekeeping. * flush: Manipulators. * fstream: Files. * fstreambase: Files. * fstreambase::close: Files. * get area: Areas. * goodbit: States. * hex: Manipulators. * ifstream: Files and Strings. * ifstream: Files. * ifstream::ifstream: Files. * ifstream::ifstream: Files. * ifstream::ifstream: Files. * ifstream::open: Files. * ios::app: Files. * ios::ate: Files. * ios::bad: States. * ios::beg: Input Position. * ios::bin: Files. * ios::bitalloc: Extending. * ios::clear: States. * ios::cur: Input Position. * ios::dec: Format Control. * ios::end: Input Position. * ios::eof: States. * ios::fail: States. * ios::fill: Format Control. * ios::fill: Format Control. * ios::fixed: Format Control. * ios::flags: Format Control. * ios::flags: Format Control. * ios::good: States. * ios::hex: Format Control. * ios::in: Files. * ios::internal: Format Control. * ios::ios: Ios. * ios::iword: Extending. * ios::iword: Extending. * ios::left: Format Control. * ios::nocreate: Files. * ios::noreplace: Files. * ios::oct: Format Control. * ios::out: Files. * ios::precision: Format Control. * ios::precision: Format Control. * ios::pword: Extending. * ios::pword: Extending. * ios::rdbuf: Streambuf from Ios. * ios::rdstate: States. * ios::right: Format Control. * ios::scientific: Format Control. * ios::seekdir: Output Position. * ios::set: States. * ios::setf: Format Control. * ios::setf: Format Control. * ios::setstate: States. * ios::showbase: Format Control. * ios::showpoint: Format Control. * ios::showpos: Format Control. * ios::skipws: Format Control. * ios::stdio: Format Control. * ios::sync_with_stdio: Synchronization. * ios::tie: Synchronization. * ios::tie: Synchronization. * ios::trunc: Files. * ios::unitbuf: Format Control. * ios::unsetf: Format Control. * ios::uppercase: Format Control. * ios::width: Format Control. * ios::width: Format Control. * ios::xalloc: Extending. * ios::~ios: Ios. * iostream::iostream: Iostream. * iostream::iostream: Iostream. * istream::gcount: Istream Housekeeping. * istream::get: Char Input. * istream::get: Char Input. * istream::get: String Input. * istream::get: String Input. * istream::getline: String Input. * istream::gets: String Input. * istream::ignore: Istream Housekeeping. * istream::ipfx: Istream Housekeeping. * istream::isfx: Istream Housekeeping. * istream::istream: Istream. * istream::istream: Istream. * istream::peek: Char Input. * istream::putback: Istream Housekeeping. * istream::read: String Input. * istream::scan: String Input. * istream::seekg: Input Position. * istream::seekg: Input Position. * istream::tellg: Input Position. * istream::unget: Istream Housekeeping. * istream::vscan: String Input. * istrstream: Strings. * istrstream: Files and Strings. * istrstream::istrstream: Strings. * oct: Manipulators. * ofstream: Files and Strings. * ofstream::ofstream: Files. * ofstream::ofstream: Files. * ofstream::ofstream: Files. * ofstream::open: Files. * ofstream::~ofstream: Files. * ostream: Files. * ostream::form: Writing. * ostream::opfx: Ostream Housekeeping. * ostream::osfx: Ostream Housekeeping. * ostream::ostream: Ostream. * ostream::ostream: Ostream. * ostream::put: Writing. * ostream::seekp: Output Position. * ostream::seekp: Output Position. * ostream::tellp: Output Position. * ostream::vform: Writing. * ostream::write: Writing. * ostrstream: Strings. * ostrstream: Files and Strings. * ostrstream::freeze: Strings. * ostrstream::frozen: Strings. * ostrstream::ostrstream: Strings. * ostrstream::ostrstream: Strings. * ostrstream::pcount: Strings. * ostrstream::str: Strings. * procbuf::close: Procbuf. * procbuf::open: Procbuf. * procbuf::procbuf: Procbuf. * procbuf::procbuf: Procbuf. * procbuf::~procbuf: Procbuf. * put area: Areas. * setbase: Manipulators. * setfill: Manipulators. * setprecision: Format Control. * setprecision: Manipulators. * setting ios::precision: Format Control. * setting ios::width: Format Control. * setw: Format Control. * setw: Manipulators. * streambuf::eback: Areas. * streambuf::egptr: Areas. * streambuf::epptr: Areas. * streambuf::gptr: Areas. * streambuf::pbase: Areas. * streambuf::pbump: Areas. * streambuf::pptr: Areas. * streambuf::scan: Formatting. * streambuf::seekmark: Backing Up. * streambuf::setg: Areas. * streambuf::setp: Areas. * streambuf::vform: Formatting. * streambuf::vform: Formatting. * streambuf::vscan: Formatting. * streambuf:gbump: Areas. * streammarker::delta: Backing Up. * streammarker::delta: Backing Up. * streammarker::streammarker: Backing Up. * strstream: Strings. * strstreambase: Strings. * strstreambase::rdbuf: Strings. * strstreambuf: Strings. * ws: Manipulators.