diplodocus.org Git - nmh/blob - docs/historical/mh-6.8.5/miscellany/less-177/ifile.c

   1 /*
   2  * An IFILE represents an input file.
   3  *
   4  * It is actually a pointer to an ifile structure,
   5  * but is opaque outside this module.
   6  * Ifile structures are kept in a linked list in the order they
   7  * appear on the command line.
   8  * Any new file which does not already appear in the list is
   9  * inserted after the current file.
  10  */
  11
  12 #include "less.h"
  13
  14 struct ifile {
  15         struct ifile *h_next;           /* Links for command line list */
  16         struct ifile *h_prev;
  17         int h_index;                    /* Index within command line list */
  18         char *h_filename;               /* Name of the file */
  19         struct scrpos h_scrpos;         /* Saved position within the file */
  20 };
  21
  22 /*
  23  * Convert an IFILE (external representation)
  24  * to a struct file (internal representation), and vice versa.
  25  */
  26 #define int_ifile(h)    ((struct ifile *)(h))
  27 #define ext_ifile(h)    ((IFILE)(h))
  28
  29 /*
  30  * Anchor for linked list.
  31  */
  32 static struct ifile anchor = { &anchor, &anchor, 0 };
  33 static int ifiles = 0;
  34
  35 /*
  36  * Allocate a new ifile structure and stick a filename in it.
  37  * It should go after "prev" in the list
  38  * (or at the beginning of the list if "prev" is NULL).
  39  * Return a pointer to the new ifile structure.
  40  */
  41         static struct ifile *
  42 new_ifile(filename, prev)
  43         char *filename;
  44         struct ifile *prev;
  45 {
  46         register struct ifile *p;
  47         register struct ifile *np;
  48
  49         /*
  50          * Allocate and initialize structure.
  51          */
  52         p = (struct ifile *) ecalloc(1, sizeof(struct ifile));
  53         p->h_filename = filename;
  54         p->h_scrpos.pos = NULL_POSITION;
  55
  56         /*
  57          * Link into list.
  58          */
  59         if (prev == NULL)
  60                 prev = &anchor;
  61         p->h_next = prev->h_next;
  62         p->h_prev = prev;
  63         prev->h_next->h_prev = p;
  64         prev->h_next = p;
  65
  66         /*
  67          * Calculate index for the new one,
  68          * and adjust the indexes for subsequent ifiles in the list.
  69          */
  70         p->h_index = prev->h_index + 1;
  71         for (np = p->h_next;  np != &anchor;  np = np->h_next)
  72                 np->h_index++;
  73
  74         ifiles++;
  75         return (p);
  76 }
  77
  78 /*
  79  * Get the ifile after a given one in the list.
  80  */
  81         public IFILE
  82 next_ifile(h)
  83         IFILE h;
  84 {
  85         register struct ifile *p;
  86
  87         p = (h == NULL_IFILE) ? &anchor : int_ifile(h);
  88         if (p->h_next == &anchor)
  89                 return (NULL_IFILE);
  90         return (ext_ifile(p->h_next));
  91 }
  92
  93 /*
  94  * Get the ifile before a given one in the list.
  95  */
  96         public IFILE
  97 prev_ifile(h)
  98         IFILE h;
  99 {
 100         register struct ifile *p;
 101
 102         p = (h == NULL_IFILE) ? &anchor : int_ifile(h);
 103         if (p->h_prev == &anchor)
 104                 return (NULL_IFILE);
 105         return (ext_ifile(p->h_prev));
 106 }
 107
 108 /*
 109  * Return the number of ifiles.
 110  */
 111         public int
 112 nifile()
 113 {
 114         return (ifiles);
 115 }
 116
 117 /*
 118  * Find an ifile structure, given a filename.
 119  */
 120         static struct ifile *
 121 find_ifile(filename)
 122         char *filename;
 123 {
 124         register struct ifile *p;
 125
 126         for (p = anchor.h_next;  p != &anchor;  p = p->h_next)
 127                 if (strcmp(filename, p->h_filename) == 0)
 128                         return (p);
 129         return (NULL);
 130 }
 131
 132 /*
 133  * Get the ifile associated with a filename.
 134  * If the filename has not been seen before,
 135  * insert the new ifile after "prev" in the list.
 136  */
 137         public IFILE
 138 get_ifile(filename, prev)
 139         char *filename;
 140         IFILE prev;
 141 {
 142         register struct ifile *p;
 143
 144         if ((p = find_ifile(filename)) == NULL)
 145                 p = new_ifile(save(filename), int_ifile(prev));
 146         return (ext_ifile(p));
 147 }
 148
 149 /*
 150  * Get the filename associated with a ifile.
 151  */
 152         public char *
 153 get_filename(ifile)
 154         IFILE ifile;
 155 {
 156         if (ifile == NULL)
 157                 return (NULL);
 158         return (int_ifile(ifile)->h_filename);
 159 }
 160
 161 /*
 162  * Get the index of the file associated with a ifile.
 163  */
 164         public int
 165 get_index(ifile)
 166         IFILE ifile;
 167 {
 168         return (int_ifile(ifile)->h_index);
 169 }
 170
 171 /*
 172  * Save the file position to be associated with a given file.
 173  */
 174         public void
 175 store_pos(ifile, scrpos)
 176         IFILE ifile;
 177         struct scrpos *scrpos;
 178 {
 179         int_ifile(ifile)->h_scrpos = *scrpos;
 180 }
 181
 182 /*
 183  * Recall the file position associated with a file.
 184  * If no position has been associated with the file, return NULL_POSITION.
 185  */
 186         public void
 187 get_pos(ifile, scrpos)
 188         IFILE ifile;
 189         struct scrpos *scrpos;
 190 {
 191         *scrpos = int_ifile(ifile)->h_scrpos;
 192 }