scoutos / prex-0.9.0 / usr / lib / libc / stdio / ftell.c @ 03e9c04a
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| 1 | 03e9c04a | Brad Neuman | /*-
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| 2 | * Copyright (c) 1990, 1993
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| 3 | * The Regents of the University of California. All rights reserved.
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| 4 | *
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| 5 | * This code is derived from software contributed to Berkeley by
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| 6 | * Chris Torek.
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| 7 | *
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| 8 | * Redistribution and use in source and binary forms, with or without
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| 9 | * modification, are permitted provided that the following conditions
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| 10 | * are met:
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| 11 | * 1. Redistributions of source code must retain the above copyright
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| 12 | * notice, this list of conditions and the following disclaimer.
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| 13 | * 2. Redistributions in binary form must reproduce the above copyright
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| 14 | * notice, this list of conditions and the following disclaimer in the
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| 15 | * documentation and/or other materials provided with the distribution.
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| 16 | * 3. Neither the name of the University nor the names of its contributors
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| 17 | * may be used to endorse or promote products derived from this software
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| 18 | * without specific prior written permission.
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| 19 | *
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| 20 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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| 21 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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| 22 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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| 23 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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| 24 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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| 25 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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| 26 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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| 27 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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| 28 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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| 29 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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| 30 | * SUCH DAMAGE.
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| 31 | */
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| 32 | |||
| 33 | #include <stdio.h> |
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| 34 | #include <errno.h> |
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| 35 | #include "local.h" |
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| 36 | |||
| 37 | /*
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| 38 | * ftell: return current offset.
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| 39 | */
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| 40 | long
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| 41 | ftell(fp) |
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| 42 | FILE *fp; |
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| 43 | {
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| 44 | fpos_t pos; |
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| 45 | |||
| 46 | /*
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| 47 | * Find offset of underlying I/O object, then
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| 48 | * adjust for buffered bytes.
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| 49 | */
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| 50 | pos = __sseek(fp, (fpos_t)0, SEEK_CUR);
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| 51 | if (pos == -(fpos_t)1) |
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| 52 | return (pos);
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| 53 | |||
| 54 | if (fp->_flags & __SRD) {
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| 55 | /*
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| 56 | * Reading. Any unread characters (including
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| 57 | * those from ungetc) cause the position to be
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| 58 | * smaller than that in the underlying object.
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| 59 | */
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| 60 | pos -= fp->_r; |
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| 61 | if (HASUB(fp))
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| 62 | pos -= fp->_ur; |
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| 63 | } else if (fp->_flags & __SWR && fp->_p != NULL) { |
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| 64 | /*
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| 65 | * Writing. Any buffered characters cause the
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| 66 | * position to be greater than that in the
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| 67 | * underlying object.
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| 68 | */
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| 69 | pos += fp->_p - fp->_bf._base; |
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| 70 | } |
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| 71 | return (pos);
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| 72 | } |