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Annotation of researchv10no/cmd/cfront/libC/iostream/README, revision 1.1

1.1     ! root        1: 
        !             2: 5/9/89: Have filebuf::sync() reset last_seek.  This will have the
        !             3:         effect that if somebody else moves the file pointer
        !             4:         after a sync() but before a seek(), the filebuf will behave
        !             5:        sensibly.
        !             6: 
        !             7: 5/9/89: Fix define of "hardfail".
        !             8: 
        !             9: 5/5/89: Lots of stuff to improve buffering. New function 
        !            10:        
        !            11:        ostream::osfx()
        !            12:                Perform "suffix" actions before returning from
        !            13:                inserters.  This is called by all predefined
        !            14:                inserters.  It isn't called by the binary output functions.
        !            15:                And should be called by user inserters
        !            16:                after any direct manipulation of the streambuf.
        !            17: 
        !            18:        There are two new format flags:
        !            19: 
        !            20:                unitbuf: when set a flush is performed by osfx() ;
        !            21:                stdio: when set stdout and stderr are flushed by osfx() ;
        !            22: 
        !            23:        cerr is now unitbuf'ed rather than unbuffered.
        !            24: 
        !            25:        sync_with_stdio makes cout, cerr unit buffered rather than
        !            26:        unbuffered.
        !            27: 
        !            28:        cin and cout now get the arrays they use dynamically. (Previously
        !            29:        they were statically allocated.)  This change is prompted
        !            30:        by people who complained about wasting 2K when they didn't
        !            31:        use cin or cout.
        !            32: 
        !            33: 5/5/89: Add check in streambuf* insertor so that it sets failbit when
        !            34:        given the null pointer.  (Right now it just core dumps).
        !            35: 
        !            36: 5/5/89: Change ios::clear to have an int argument
        !            37: 
        !            38: cycle 16
        !            39: 
        !            40: 5/4/89: Change all open_mode arguments to ints.
        !            41: 
        !            42: 5/3/89: Fix ws manipulator so that it will flushed tied ostream
        !            43:        when required.
        !            44: 
        !            45: 5/2/89: More cleanup of open_mode arguments.  Add defaults for
        !            46:        ifstream::open and ofstream::open.  Change all
        !            47:        defaults to filebuf::openprot
        !            48: 
        !            49: cycle 15
        !            50: 
        !            51: 4/28/89. Add default open_mode arguments to ifstream and ofstream
        !            52:         constructors.
        !            53: 
        !            54: cycle 14?
        !            55: 
        !            56: 4/18/89.  Fix bug is filebuf::seekoff that also caused problems
        !            57:          for tellg and tellp.  
        !            58: 
        !            59: 4/13/89.  Change cstreams.c so it doesn't refer to skip (which is
        !            60:        a stream compatibility function.
        !            61: 
        !            62: ------------------------------------------------
        !            63: Cycle 13
        !            64: 
        !            65: Change typedef in strstream.c to avoid use of size_t.  (This is
        !            66: because of header file compatibility problems.)
        !            67: 
        !            68: Change exit(10) to abort() in oldformat.c.
        !            69: 
        !            70: Cycle 12
        !            71: 
        !            72: Put in include of <iostream.h> in strstream.h
        !            73: 
        !            74: Change istream::get() so that it really gets expanded inline.
        !            75: Previous definition was being outlined.
        !            76: 
        !            77: Reorder declarations so that ipfx comes before any operator>>. Not
        !            78: just before the ones that have inline code refering to it. The old
        !            79: ordering was resulting in a failure to expand ipfx where it should
        !            80: have been.
        !            81: 
        !            82: Move declaration of ios_user_union higher in stream.c in order to
        !            83: eliminate a new warning message.
        !            84: 
        !            85: Change values of O_CREAT O_TRUNC O_EXCL in cases where headers don't
        !            86: define them (the only known such system is V9)
        !            87: 
        !            88: Fix ostream::out_waiting.  It was just returning non-zero when there was stuff
        !            89: accumulated but not consumed.  It was supposed to return the number
        !            90: (at least according to the man page.)
        !            91: 
        !            92: -----------------------------------------------------
        !            93: Cycle 11
        !            94: 
        !            95: Change cstreams.c for change to way explicit placement works.
        !            96: 
        !            97: Implement bidirectional strstream. 
        !            98: 
        !            99: ----------------------------------------------------
        !           100: Cycle 9 
        !           101: 
        !           102: Fix bug in void* inserter.  (Showbase should have been set
        !           103: but wasn't)
        !           104: 
        !           105: 
        !           106: --------------------------------------------------
        !           107: Cycle 8
        !           108: 
        !           109: streambuf::snextc was not incrementing the get pointer before
        !           110: it called underflow.  This had no effect because the streambuf
        !           111: classes assume that when underflow is called there
        !           112: was nothing in the buffer.  The man page said that although this
        !           113: was "normally the case" but doesn't guarantee it.  I wrote a new
        !           114: streambuf class that checked for the condition and it failed.
        !           115: I've fixed snextc.  
        !           116: 
        !           117: ---------------------------------------------------
        !           118: Cycle 7  
        !           119: 
        !           120: Fix bug in setstate.  
        !           121: 
        !           122: Change return type of filebuf::close to filebuf*
        !           123: 
        !           124: Add noreplace to open_mode 
        !           125: 
        !           126: Fixed bug in adjustment of floating fields
        !           127: 
        !           128: -----------------------------------------------------
        !           129: 
        !           130: Cycle 6.1 
        !           131: 
        !           132: Interpretation of justification fields was screwed up.
        !           133: 
        !           134: Fix for whitespace eating of character extractor of cycle 6  was
        !           135: incomplete. (It might read characters when the stream was
        !           136: in error status).
        !           137: 
        !           138: -----------------------------------------------------
        !           139: Cycle 6
        !           140: 
        !           141: Make streambuf::xsgetn and streambuf::xsputn virtuals
        !           142: 
        !           143: ios::operator int changed to ios::operator void* in order to allow
        !           144: detection of "cin << 5" without requiring any extractor or inserter
        !           145: to be declared in class iostream.
        !           146: 
        !           147: sync is moved from ios to istream,  the corresponding action on
        !           148: ostreams is flushing.
        !           149: 
        !           150: Reorder declarations in iostream.h to avoid forward enum tag
        !           151: declarations.
        !           152: 
        !           153: Fixes to single character extractors to make sure they skip
        !           154: whitespace when required.
        !           155: 
        !           156: Massive simplification of format control stuff
        !           157: 
        !           158:        struct fmtinfo goes away as do pushing and popping of it.
        !           159: 
        !           160:        several format state variables are consolodated into
        !           161:        a single flag field and new flags are added to control
        !           162:        more stuff.  Remaining state variables are fill, precision and
        !           163:        width.  New statevariable "flags".
        !           164: 
        !           165:        Flags declared in an enum within ios:
        !           166: 
        !           167:        enum            { skipws=01,    
        !           168:                                        /* skip whitespace on input */
        !           169:                          left=02,  right=04, internal=010,
        !           170:                                        /* padding location */
        !           171:                          dec=020, oct=040, hex=0100, 
        !           172:                                        /* conversion base */
        !           173:                          showbase=0200, showpoint=0400, uppercase=01000,
        !           174:                          showpos=02000, 
        !           175:                                        /* modifiers */
        !           176:                          scientific=04000, fixed=010000
        !           177:                                        /* floating point notation */                                             } ;
        !           178:        
        !           179:        Functions to manipulate the flag field
        !           180:                s.flags()       return current flag
        !           181:                s.flags(b)      sets flags to b 
        !           182:                s.setf(b)       turns on bits marked in f in flags
        !           183:                s.setf(b,f)     assigns b to "field" specified by f
        !           184:                                (i.e. bits that are on in f)
        !           185: 
        !           186:         static ios int members for convienent reference to fields
        !           187:                 ios::basefield = hex|dec|oct ;
        !           188:                 ios::adjustfield = left|right|internal ;
        !           189:                 ios::floatfield = scientific|fixed ;
        !           190: 
        !           191: New manipulators
        !           192: 
        !           193:        s << setfill(f)         sets fill state variable
        !           194:        s << setprecision(p)    sets precision state variable
        !           195:        s << setiosflags(b)     does s.setf(b)
        !           196:        s << resetiosflags(b)   does s.setf(0,b)
        !           197: 
        !           198: New user setable state variables
        !           199: 
        !           200:        flags are a long user code may use unassigned bits
        !           201:        s.iword(x)              returns a long& 
        !           202:        s.pword(s)              returns a void*& (sharing space with s.iword(x)
        !           203:        
        !           204: 
        !           205:        ios::bitalloc()         returns a previously unallocated bit
        !           206:        ios::xalloc()           returns a previously unused index
        !           207:        
        !           208: ---------------------------------------------
        !           209: Cycle 5
        !           210: 
        !           211: Eliminated a lot of warnings about assigning longs to ints and
        !           212: the like.
        !           213: 
        !           214: Put in some overflow detection on integer input (it is still very
        !           215: incomplete). 
        !           216: 
        !           217: Change sync_with_stdio into a static member function
        !           218: 
        !           219: Add enum_mode, nocreate.  Causes failure of an open if file does not
        !           220: previously exist. 
        !           221: 
        !           222: Changed popfmt to reset width to 0.  This is more consistent with the
        !           223: normal use.
        !           224: 
        !           225: Fixed some bugs in interaction of EOF eating whitespace and "ignore"
        !           226: 
        !           227: ------------------------------------------
        !           228: 
        !           229: Multiple Inheritance Version.  
        !           230: 
        !           231: Changes from previous version:
        !           232: 
        !           233: MI structure in classes.  Mainly this is a lot of trivial changes.
        !           234: But one substantive change arises.  Because ios is now inherited
        !           235: as a virtual base class, a constructor with no arguments must
        !           236: be used.  Therefore ios::init(streambuf*) is declared protected and
        !           237: must be used to initialize in derived classes.
        !           238: 
        !           239: -------------------------------------------
        !           240: 
        !           241: The latest version of the iostream package incorporates a large
        !           242: number of changes and bug fixes.  They are listed here in my
        !           243: estimation of their importance.
        !           244: 
        !           245: In principle, istream, ostream, and iostream are now distinct
        !           246: classes. istream only contains input operations and ostream only
        !           247: contains output operations.  iostream is the "join" of the two. There
        !           248: is a new class ios containing the common state information from which
        !           249: all these are derived.
        !           250: 
        !           251: This means, for example, that cin should't be passed to a function
        !           252: expecting an iostream.
        !           253: 
        !           254: In practice to do this would have required a good implementation of
        !           255: multiple inheritance with virtual base classes. To avoid relying on
        !           256: this feature of C++ all the stream classes are typedefed to ios.
        !           257: 
        !           258: As a consequence of this change several classes derived from
        !           259: "istream" and "ostream" have been added.  Namely ifstream, ofstream,
        !           260: istrstream and ostrstream.  These (rather than the bidrectional
        !           261: fstream and strstream) should be used when a stream for only input or
        !           262: only output is desired.
        !           263: 
        !           264: The kludge that used #defines and pointer variables to implement cin,
        !           265: cour, cerr and cdebug has been eliminated. The standard streams are
        !           266: now declared as extern variables in iostream.h. Their types are
        !           267: classes derived from iostream with an assignment operator. So that it
        !           268: is now permitted to assign streams to them.
        !           269: 
        !           270: Because cfront now distinguishes int from char in overload resolution
        !           271: cout << 'a' now outputs the character 'a' rather than the decimal
        !           272: value.  This is an incompatibility with the old stream package, but
        !           273: is such a large improvement that I thought it was worth any
        !           274: conversion problems it might cause.   This made the manipulator
        !           275: "onec" redundant and it has been removed.
        !           276: 
        !           277: The name space has been cleaned up.  A lot of identifiers that were
        !           278: previously part of the global name space have been made local to a
        !           279: class. A table of the old and new names follows.  Probably the most
        !           280: important is the renaming of open_modes.
        !           281: 
        !           282:        old name                new name
        !           283:        --------                --------
        !           284: 
        !           285:        iocdebug                        // eliminated
        !           286:        iocerr                          // eliminated
        !           287:        iocin                           // eliminated
        !           288:        iocout                          // eliminated
        !           289:        
        !           290:        cdebug                  clog    // Renamed because of
        !           291:                                        // complaints about old name
        !           292: 
        !           293:        state_value             io_state
        !           294:                                        // Renamed because state_value
        !           295:                                        // was too unspecific
        !           296: 
        !           297:        _bad                    ios::badbit
        !           298:        _eof                    ios::eofbit
        !           299:        _fail                   ios::failbit
        !           300:        _good                   ios::goodbit
        !           301: 
        !           302:        append                  ios::app
        !           303:        atend                   ios::ate
        !           304:        input                   ios::in
        !           305:        output                  ios::out
        !           306: 
        !           307:        seek_beg                ios::beg
        !           308:        seek_cur                ios::cur
        !           309:        seek_end                ios::end
        !           310: 
        !           311: stream.h contains declarations of the names required for backward
        !           312: compatibility with the stream package.
        !           313: 
        !           314: The macros for declaring manipulator classes (IOMANIP and  IOMANIP2)
        !           315: have been replaced by a collection of macros that are more
        !           316: "template-like". Two argument manipulators are not implemented.
        !           317: (Users may follow the pattern in iomanip.h to implement them
        !           318: themselves.)
        !           319: 
        !           320: filebuf and fstream operations no longer clear errno.
        !           321: 
        !           322: The virtual declaration of streambuf::setbuf now only has two
        !           323: arguments. The three argument form exists in streambuf for
        !           324: compatibility with the stream package, but the "official"
        !           325: definition has only two arguments. Similarly the documented
        !           326: constructor is now streambuf(char*,int).
        !           327: 
        !           328: The members of fstream (ifstream and ofstream) that used to return an
        !           329: int as an error indication (namely open, attach, close) now return
        !           330: void.  Errors are indicated by setting failbit in the error state.
        !           331: There was some confusion here about whether an error was indicated by
        !           332: returning 0 or EOF.  Declaraing these functions to return void
        !           333: eliminates the possibility of confusion.
        !           334: 
        !           335: strstreambuf now allows setbuf in order to control sizes of
        !           336: allocation in dynamic mode. (When character strings are being
        !           337: automatically extended.)
        !           338: 
        !           339: More careful checks for whether flushes are required on streams that
        !           340: are tied to other streams. (E.g. flushes on cout when characters are
        !           341: extracted from cin.)
        !           342: 
        !           343: Tieing now works for insertion. E.g. cerr is tied to cout, so
        !           344: insertion into cerr causes cout to be flushed.
        !           345: 
        !           346: Redundant calls to allocate have been removed from streambuf::xsgetn
        !           347: and streambuf::xsputn.  (This means that the only calls to
        !           348: streambuf::allocate from streambuf member functions are from the
        !           349: virtuals that may be overriden in derived classes.)
        !           350: 
        !           351: open with ios::ate (the old atend) no longer implies ios::out (the
        !           352: old output).  ios::app does.  (ate is a perfectly sensible mode
        !           353: for input.)
        !           354: 
        !           355: eatwhite is defined for compatibility with stream package.

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