137 lines
3.1 KiB
Plaintext
137 lines
3.1 KiB
Plaintext
_GETTING A HANDLE ON VIRTUAL MEMORY_
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by Walter Bright
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[LISTING ONE]
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/* Compile with: ZTC wc -ml */
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/* (Use large model so strcmp() can handle far pointers.) */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <ctype.h>
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#include <handle.h>
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struct tree
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{
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char __handle *word;
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int count;
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struct tree __handle *left;
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struct tree __handle *right;
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};
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int readword(char *w, int nbytes)
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{
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int c;
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do {
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c = getchar();
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if (c == EOF)
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return 0;
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}
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while (!isalpha(c));
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do {
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if (nbytes > 1)
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{
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*w++ = c;
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nbytes--;
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}
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c = getchar();
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}
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while (isalnum(c));
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*w = 0;
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return 1;
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}
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void tree_insert(struct tree __handle * __handle *pt, char *w)
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{
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int cmp;
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struct tree __handle *p;
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while ((p = *pt) != NULL)
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{
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if ((cmp = strcmp(w,p->word)) == 0)
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goto gotit;
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pt = (cmp < 0) ? &p->left : &p->right;
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}
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p = (struct tree __handle *) handle_calloc(sizeof(struct tree));
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if (!p || (p->word = handle_strdup(w)) == NULL)
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{
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printf("Out of memory\n");
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exit(EXIT_FAILURE);
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}
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*pt = p;
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gotit:
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p->count++;
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}
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tree_print(struct tree __handle *p)
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{
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while (p)
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{
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tree_print(p->left);
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printf("%5d %s\n",p->count,(char far *)p->word);
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p = p->right;
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}
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}
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tree_free(struct tree __handle *p)
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{
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struct tree __handle *pn;
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while (p)
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{
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handle_free(p->word);
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tree_free(p->left);
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pn = p->right;
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handle_free(p);
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p = pn;
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}
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}
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main()
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{
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struct tree __handle *root = NULL;
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char word[32];
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while (readword(word,sizeof(word)))
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tree_insert(&root, word);
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tree_print(root);
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tree_free(root);
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return EXIT_SUCCESS;
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}
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[Figure 1: Typical pointer types used in most PC implementations of C]
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void *p; /* pointer type is default for the memory model */
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char far *pc; /* far (segment and offset pair) pointer */
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int near *p; /* near (offset only, segment is assumed) */
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[Figure 2: Converting pointers from handle to far]
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R 65,T 5
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int __handle *h;
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struct A __handle *h2;
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int far *f;
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int i;
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extern void func(int far *pi);
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f = h;
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*h = i;
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h[3] = *f;
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i = *(h + 6);
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h2->b = i;
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func(h);
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h = (int far *) h;
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[Figure 3: Example showing that the optimizer is handle aware]
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struct { int a,b; } __handle *h;
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h->a = 1;
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h->b = 2;
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/* Converted code */
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struct { int a,b; } __handle *h, far *p;
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p = h;
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p->a = 1;
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p->b = 2;
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