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 | } |