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1 /* ========================================================================
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2 * Copyright 1988-2007 University of Washington
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3 *
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4 * Licensed under the Apache License, Version 2.0 (the "License");
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5 * you may not use this file except in compliance with the License.
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6 * You may obtain a copy of the License at
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7 *
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8 * http://www.apache.org/licenses/LICENSE-2.0
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9 *
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10 *
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11 * ========================================================================
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12 */
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13
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14 /*
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15 * Program: File descriptor string routines
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16 *
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17 * Author: Mark Crispin
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18 * Networks and Distributed Computing
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19 * Computing & Communications
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20 * University of Washington
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21 * Administration Building, AG-44
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22 * Seattle, WA 98195
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23 * Internet: MRC@CAC.Washington.EDU
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24 *
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25 * Date: 15 April 1997
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26 * Last Edited: 4 April 2007
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27 */
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28
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29 #include "mail.h"
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30 #include "osdep.h"
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31 #include "misc.h"
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32 #include "fdstring.h"
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33
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34 /* String driver for fd stringstructs */
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35
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36 static void fd_string_init (STRING *s,void *data,unsigned long size);
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37 static char fd_string_next (STRING *s);
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38 static void fd_string_setpos (STRING *s,unsigned long i);
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39
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40 STRINGDRIVER fd_string = {
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41 fd_string_init, /* initialize string structure */
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42 fd_string_next, /* get next byte in string structure */
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43 fd_string_setpos /* set position in string structure */
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44 };
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45
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46
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47 /* Initialize string structure for fd stringstruct
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48 * Accepts: string structure
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49 * pointer to string
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50 * size of string
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51 */
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52
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53 static void fd_string_init (STRING *s,void *data,unsigned long size)
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54 {
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55 FDDATA *d = (FDDATA *) data;
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56 /* note fd */
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57 s->data = (void *) (unsigned long) d->fd;
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58 s->data1 = d->pos; /* note file offset */
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59 s->size = size; /* note size */
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60 s->curpos = s->chunk = d->chunk;
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61 s->chunksize = (unsigned long) d->chunksize;
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62 s->offset = 0; /* initial position */
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63 /* and size of data */
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64 s->cursize = min (s->chunksize,size);
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65 /* move to that position in the file */
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66 lseek (d->fd,d->pos,L_SET);
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67 read (d->fd,s->chunk,(size_t) s->cursize);
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68 }
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69
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70 /* Get next character from fd stringstruct
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71 * Accepts: string structure
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72 * Returns: character, string structure chunk refreshed
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73 */
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74
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75 static char fd_string_next (STRING *s)
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76 {
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77 char c = *s->curpos++; /* get next byte */
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78 SETPOS (s,GETPOS (s)); /* move to next chunk */
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79 return c; /* return the byte */
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80 }
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81
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82
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83 /* Set string pointer position for fd stringstruct
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84 * Accepts: string structure
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85 * new position
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86 */
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87
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88 static void fd_string_setpos (STRING *s,unsigned long i)
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89 {
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90 if (i > s->size) i = s->size; /* don't permit setting beyond EOF */
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91 s->offset = i; /* set new offset */
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92 s->curpos = s->chunk; /* reset position */
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93 /* set size of data */
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94 if (s->cursize = min (s->chunksize,SIZE (s))) {
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95 /* move to that position in the file */
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96 lseek ((long) s->data,s->data1 + s->offset,L_SET);
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97 read ((long) s->data,s->curpos,(size_t) s->cursize);
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98 }
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99 }
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