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Viewing changes to tools/sfio/sfread.c

  • Committer: Bazaar Package Importer
  • Author(s): Stephen M Moraco
  • Date: 2002-02-05 18:52:12 UTC
  • Revision ID: james.westby@ubuntu.com-20020205185212-8i04c70te00rc40y
Tags: upstream-1.7.16
Import upstream version 1.7.16

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tools/sfio/sfread.c
 
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#include        "sfhdr.h"
 
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/*      Read n bytes from a stream into a buffer
 
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**
 
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**      Written by Kiem-Phong Vo.
 
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*/
 
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#if __STD_C
 
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ssize_t sfread(reg Sfio_t* f, Void_t* buf, reg size_t n)
 
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#else
 
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ssize_t sfread(f,buf,n)
 
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reg Sfio_t*     f;      /* read from this stream.       */
 
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Void_t*         buf;    /* buffer to read into          */
 
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reg size_t      n;      /* number of bytes to be read.  */
 
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#endif
 
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{
 
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        reg uchar       *s, *begs;
 
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        reg ssize_t     r;
 
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        reg int         local, justseek;
 
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        SFMTXSTART(f, (ssize_t)(-1));
 
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        GETLOCAL(f,local);
 
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        justseek = f->bits&SF_JUSTSEEK; f->bits &= ~SF_JUSTSEEK;
 
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        if(!buf)
 
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                SFMTXRETURN(f, (ssize_t)(-1) );
 
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        /* release peek lock */
 
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        if(f->mode&SF_PEEK)
 
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        {       if(!(f->mode&SF_READ) )
 
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                        SFMTXRETURN(f, (ssize_t)(-1));
 
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                if(f->mode&SF_GETR)
 
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                {       if(((uchar*)buf + f->val) != f->next &&
 
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                           (!f->rsrv || f->rsrv->data != (uchar*)buf) )
 
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                                SFMTXRETURN(f, (ssize_t)(-1));
 
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                        f->mode &= ~SF_PEEK;
 
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                        SFMTXRETURN(f, 0);
 
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                }
 
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                else
 
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                {       if((uchar*)buf != f->next)
 
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                                SFMTXRETURN(f, (ssize_t)(-1));
 
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                        f->mode &= ~SF_PEEK;
 
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                        if(f->mode&SF_PKRD)
 
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                        {       /* actually read the data now */
 
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                                f->mode &= ~SF_PKRD;
 
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                                if(n > 0)
 
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                                        n = (r = read(f->file,f->data,n)) < 0 ? 0 : r;
 
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                                f->endb = f->data+n;
 
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                                f->here += n;
 
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                        }
 
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                        f->next += n;
 
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                        f->endr = f->endb;
 
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                        SFMTXRETURN(f, n);
 
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                }
 
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        }
 
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        s = begs = (uchar*)buf;
 
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        for(;; f->mode &= ~SF_LOCK)
 
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        {       /* check stream mode */
 
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                if(SFMODE(f,local) != SF_READ && _sfmode(f,SF_READ,local) < 0)
 
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                {       n = s > begs ? s-begs : (size_t)(-1);
 
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                        SFMTXRETURN(f, (ssize_t)n);
 
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                }
 
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                SFLOCK(f,local);
 
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                if((r = f->endb - f->next) > 0) /* has buffered data */
 
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                {       if(r > (ssize_t)n)
 
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                                r = (ssize_t)n;
 
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                        if(s != f->next)
 
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                                memcpy(s, f->next, r);
 
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                        f->next += r;
 
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                        s += r;
 
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                        n -= r;
 
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                }
 
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                if(n <= 0)      /* all done */
 
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                        break;
 
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                if(!(f->flags&SF_STRING) && !(f->bits&SF_MMAP) )
 
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                {       f->next = f->endb = f->data;
 
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                        /* exact IO is desirable for these cases */
 
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                        if(SFDIRECT(f,n) ||
 
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                           ((f->flags&SF_SHARE) && f->extent < 0) )
 
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                                r = (ssize_t)n;
 
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                        else if(justseek && n <= f->iosz && f->iosz <= f->size)
 
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                                r = f->iosz;    /* limit buffering */
 
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                        else    r = f->size;    /* full buffering */
 
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                        /* if read almost full size, then just do it direct */
 
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                        if(r > (ssize_t)n && (r - r/8) <= (ssize_t)n)
 
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                                r = (ssize_t)n;
 
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                        /* read directly to user's buffer */
 
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                        if(r == (ssize_t)n && (r = SFRD(f,s,r,f->disc)) >= 0)
 
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                        {       s += r;
 
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                                n -= r;
 
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                                if(r == 0 || n == 0) /* eof or eob */ 
 
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                                        break;
 
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                        }
 
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                        else    goto do_filbuf;
 
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                }
 
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                else
 
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                { do_filbuf:
 
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                        if(justseek)
 
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                                f->bits |= SF_JUSTSEEK;
 
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                        if(SFFILBUF(f,-1) <= 0)
 
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                                break;
 
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                }
 
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        }
 
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        SFOPEN(f,local);
 
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        r = s-begs;
 
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        SFMTXRETURN(f, r);
 
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}