github.com/ccccaoqing/test@v0.0.0-20220510085219-3985d23445c0/src/libbio/bgetc.c (about)

     1  /*
     2  http://code.google.com/p/inferno-os/source/browse/libbio/bgetc.c
     3  
     4  	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
     5  	Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com).  All rights reserved.
     6  
     7  Permission is hereby granted, free of charge, to any person obtaining a copy
     8  of this software and associated documentation files (the "Software"), to deal
     9  in the Software without restriction, including without limitation the rights
    10  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    11  copies of the Software, and to permit persons to whom the Software is
    12  furnished to do so, subject to the following conditions:
    13  
    14  The above copyright notice and this permission notice shall be included in
    15  all copies or substantial portions of the Software.
    16  
    17  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    18  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    19  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    20  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    21  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    22  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    23  THE SOFTWARE.
    24  */
    25  
    26  #include	<u.h>
    27  #include	<libc.h>
    28  #include	<bio.h>
    29  
    30  int
    31  Bgetc(Biobuf *bp)
    32  {
    33  	int i;
    34  
    35  loop:
    36  	i = bp->icount;
    37  	if(i != 0) {
    38  		bp->icount = i+1;
    39  		return bp->ebuf[i];
    40  	}
    41  	if(bp->state != Bractive) {
    42  		if(bp->state == Bracteof)
    43  			bp->state = Bractive;
    44  		return Beof;
    45  	}
    46  	/*
    47  	 * get next buffer, try to keep Bungetsize
    48  	 * characters pre-catenated from the previous
    49  	 * buffer to allow that many ungets.
    50  	 */
    51  	memmove(bp->bbuf-Bungetsize, bp->ebuf-Bungetsize, Bungetsize);
    52  	i = (int)read(bp->fid, bp->bbuf, (size_t)bp->bsize);
    53  	bp->gbuf = bp->bbuf;
    54  	if(i <= 0) {
    55  		bp->state = Bracteof;
    56  		if(i < 0)
    57  			bp->state = Binactive;
    58  		return Beof;
    59  	}
    60  	if(i < bp->bsize) {
    61  		memmove(bp->ebuf-i-Bungetsize, bp->bbuf-Bungetsize, (size_t)(i+Bungetsize));
    62  		bp->gbuf = bp->ebuf-i;
    63  	}
    64  	bp->icount = -i;
    65  	bp->offset += i;
    66  	goto loop;
    67  }
    68  
    69  int
    70  Bgetle2(Biobuf *bp)
    71  {
    72  	int l, h;
    73  
    74  	l = Bgetc(bp);
    75  	h = Bgetc(bp);
    76  	return l|(h<<8);
    77  }
    78  
    79  int
    80  Bgetle4(Biobuf *bp)
    81  {
    82  	int l, h;
    83  
    84  	l = Bgetle2(bp);
    85  	h = Bgetle2(bp);
    86  	return (int)((uint32)l|((uint32)h<<16));
    87  }
    88  
    89  int
    90  Bungetc(Biobuf *bp)
    91  {
    92  
    93  	if(bp->state == Bracteof)
    94  		bp->state = Bractive;
    95  	if(bp->state != Bractive)
    96  		return Beof;
    97  	bp->icount--;
    98  	return 1;
    99  }