root / prex-0.9.0 / usr / lib / libc / stdio / ungetc.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 <stdlib.h> |
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35 | #include <string.h> |
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36 | #include "local.h" |
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37 | |||
38 | int
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39 | ungetc(c, fp) |
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40 | int c;
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41 | FILE *fp; |
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42 | { |
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43 | if (c == EOF) |
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44 | return (EOF); |
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45 | if (!__sdidinit)
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46 | __sinit(); |
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47 | if ((fp->_flags & __SRD) == 0) { |
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48 | /*
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49 | * Not already reading: no good unless reading-and-writing.
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50 | * Otherwise, flush any current write stuff.
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51 | */
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52 | if ((fp->_flags & __SRW) == 0) |
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53 | return (EOF); |
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54 | if (fp->_flags & __SWR) {
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55 | if (__sflush(fp))
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56 | return (EOF); |
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57 | fp->_flags &= ~__SWR; |
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58 | fp->_w = 0;
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59 | } |
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60 | fp->_flags |= __SRD; |
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61 | } |
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62 | c = (unsigned char)c; |
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63 | |||
64 | /*
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65 | * If we are in the middle of ungetc'ing, just continue.
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66 | */
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67 | if (HASUB(fp)) {
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68 | if (fp->_r >= fp->_ub._size)
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69 | return (EOF); |
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70 | *--fp->_p = c; |
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71 | fp->_r++; |
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72 | return (c);
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73 | } |
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74 | fp->_flags &= ~__SEOF; |
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75 | |||
76 | /*
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77 | * If we can handle this by simply backing up, do so,
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78 | * but never replace the original character.
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79 | * (This makes sscanf() work when scanning `const' data.)
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80 | */
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81 | if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && |
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82 | fp->_p[-1] == c) {
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83 | fp->_p--; |
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84 | fp->_r++; |
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85 | return (c);
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86 | } |
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87 | |||
88 | /*
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89 | * Create an ungetc buffer.
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90 | * we will use the `reserve' buffer.
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91 | */
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92 | fp->_ur = fp->_r; |
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93 | fp->_up = fp->_p; |
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94 | fp->_ub._base = fp->_ubuf; |
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95 | fp->_ub._size = sizeof(fp->_ubuf);
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96 | fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; |
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97 | fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; |
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98 | fp->_r = 1;
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99 | return (c);
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100 | } |