/*********************************************************************** * * * This software is part of the ast package * * Copyright (c) 1985-2009 AT&T Intellectual Property * * and is licensed under the * * Common Public License, Version 1.0 * * by AT&T Intellectual Property * * * * A copy of the License is available at * * http://www.opensource.org/licenses/cpl1.0.txt * * (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9) * * * * Information and Software Systems Research * * AT&T Research * * Florham Park NJ * * * * Glenn Fowler <gsf@research.att.com> * * David Korn <dgk@research.att.com> * * Phong Vo <kpv@research.att.com> * * * ***********************************************************************/ #include "sfdchdr.h" /* Discipline to treat a contiguous segment of a stream as a stream ** in its own right. The hard part in all this is to allow multiple ** segments of the stream to be used as substreams at the same time. ** ** Written by David G. Korn and Kiem-Phong Vo (03/18/1998) */ typedef struct _subfile_s { Sfdisc_t disc; /* sfio discipline */ Sfio_t* parent; /* parent stream */ Sfoff_t offset; /* starting offset */ Sfoff_t extent; /* size wanted */ Sfoff_t here; /* current seek location */ } Subfile_t; #if __STD_C static ssize_t streamio(Sfio_t* f, Void_t* buf, size_t n, Sfdisc_t* disc, int type) #else static ssize_t streamio(f, buf, n, disc, type) Sfio_t* f; Void_t* buf; size_t n; Sfdisc_t* disc; int type; #endif { reg Subfile_t *su; reg Sfoff_t here, parent; reg ssize_t io; su = (Subfile_t*)disc; /* read just what we need */ if(su->extent >= 0 && (ssize_t)n > (io = (ssize_t)(su->extent - su->here)) ) n = io; if(n <= 0) return n; /* save current location in parent stream */ parent = sfsk(f,(Sfoff_t)0,SEEK_CUR,disc); /* read data */ here = su->here + su->offset; if(sfsk(f,here,SEEK_SET,disc) != here) io = 0; else { if(type == SF_WRITE) io = sfwr(f,buf,n,disc); else io = sfrd(f,buf,n,disc); if(io > 0) su->here += io; } /* restore parent current position */ sfsk(f,parent,SEEK_SET,disc); return io; } #if __STD_C static ssize_t streamwrite(Sfio_t* f, const Void_t* buf, size_t n, Sfdisc_t* disc) #else static ssize_t streamwrite(f, buf, n, disc) Sfio_t* f; Void_t* buf; size_t n; Sfdisc_t* disc; #endif { return streamio(f,(Void_t*)buf,n,disc,SF_WRITE); } #if __STD_C static ssize_t streamread(Sfio_t* f, Void_t* buf, size_t n, Sfdisc_t* disc) #else static ssize_t streamread(f, buf, n, disc) Sfio_t* f; Void_t* buf; size_t n; Sfdisc_t* disc; #endif { return streamio(f,buf,n,disc,SF_READ); } #if __STD_C static Sfoff_t streamseek(Sfio_t* f, Sfoff_t pos, int type, Sfdisc_t* disc) #else static Sfoff_t streamseek(f, pos, type, disc) Sfio_t* f; Sfoff_t pos; int type; Sfdisc_t* disc; #endif { reg Subfile_t* su; reg Sfoff_t here, parent; su = (Subfile_t*)disc; switch(type) { case SEEK_SET: here = 0; break; case SEEK_CUR: here = su->here; break; case SEEK_END: if(su->extent >= 0) here = su->extent; else { parent = sfsk(f,(Sfoff_t)0,SEEK_CUR,disc); if((here = sfsk(f,(Sfoff_t)0,SEEK_END,disc)) < 0) return -1; else here -= su->offset; sfsk(f,parent,SEEK_SET,disc); } break; default: return -1; } pos += here; if(pos < 0 || (su->extent >= 0 && pos >= su->extent)) return -1; return (su->here = pos); } #if __STD_C static int streamexcept(Sfio_t* f, int type, Void_t* data, Sfdisc_t* disc) #else static int streamexcept(f, type, data, disc) Sfio_t* f; int type; Void_t* data; Sfdisc_t* disc; #endif { if(type == SF_FINAL || type == SF_DPOP) free(disc); return 0; } #if __STD_C Sfio_t* sfdcsubstream(Sfio_t* f, Sfio_t* parent, Sfoff_t offset, Sfoff_t extent) #else Sfio_t* sfdcsubstream(f, parent, offset, extent) Sfio_t* f; /* stream */ Sfio_t* parent; /* parent stream */ Sfoff_t offset; /* offset in f */ Sfoff_t extent; /* desired size */ #endif { reg Sfio_t* sp; reg Subfile_t* su; reg Sfoff_t here; /* establish that we can seek to offset */ if((here = sfseek(parent,(Sfoff_t)0,SEEK_CUR)) < 0 || sfseek(parent,offset,SEEK_SET) < 0) return 0; else sfseek(parent,here,SEEK_SET); sfpurge(parent); if (!(sp = f) && !(sp = sfnew(NIL(Sfio_t*), NIL(Void_t*), (size_t)SF_UNBOUND, dup(sffileno(parent)), parent->flags))) return 0; if(!(su = (Subfile_t*)malloc(sizeof(Subfile_t)))) { if(sp != f) sfclose(sp); return 0; } memset(su, 0, sizeof(*su)); su->disc.readf = streamread; su->disc.writef = streamwrite; su->disc.seekf = streamseek; su->disc.exceptf = streamexcept; su->parent = parent; su->offset = offset; su->extent = extent; if(sfdisc(sp, (Sfdisc_t*)su) != (Sfdisc_t*)su) { free(su); if(sp != f) sfclose(sp); return 0; } return sp; }