44 lines
1.5 KiB
C++
44 lines
1.5 KiB
C++
/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2011, 2012.
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This file is part of the Sortix C Library.
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The Sortix C Library is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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The Sortix C Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
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stdio/ftello.cpp
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Returns the current offset of a FILE.
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*******************************************************************************/
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#include <sys/types.h>
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#include <errno.h>
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#include <stdio.h>
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extern "C" off_t ftello(FILE* fp)
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{
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if ( !fp->tell_func )
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return errno = EBADF, -1;
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off_t offset = fp->tell_func(fp->user);
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if ( offset < 0 )
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return -1;
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off_t readahead = fp->amount_input_buffered - fp->offset_input_buffer;
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off_t writebehind = fp->amount_output_buffered;
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off_t result = offset - readahead + writebehind;
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if ( result < 0 ) // Too much ungetc'ing.
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return 0;
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return result;
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}
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