Revision of push-bit.c

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1 file changed, 87 insertions

push-bit.c(arquivo criado)

		@@ -0,0 +1,87 @@
1	+
2	+	#include <stdio.h>
3	+	#include <stdint.h>
4	+
5	+	uint64_t *bits = (uint64_t[64]) { 0 };
6	+	uint64_t top = 0;
7	+
8	+	/* gcc push-bit.c -O3 && objdump -D a.out \| less
9	+	0000000000001240 <get_bit>:
10	+	1240: 48 8b 05 f1 2d 00 00 mov 0x2df1(%rip),%rax # 4038 <bits>
11	+	1247: 48 89 fa mov %rdi,%rdx
12	+	124a: 48 c1 ea 06 shr $0x6,%rdx
13	+	124e: 48 8b 04 d0 mov (%rax,%rdx,8),%rax
14	+	1252: 48 0f a3 f8 bt %rdi,%rax
15	+	1256: 0f 92 c0 setb %al
16	+	1259: 0f b6 c0 movzbl %al,%eax
17	+	125c: c3 ret
18	+	125d: 0f 1f 00 nopl (%rax)
19	+	*/
20	+
21	+	uint64_t
22	+	get_bit (uint64_t const addr) {
23	+	uint64_t const shift = addr & (uint64_t) 0b111111;
24	+	uint64_t const index = addr >> 6;
25	+
26	+	return (bits[index] >> shift) & 1;
27	+	}
28	+
29	+	/* gcc push-bit.c -O3 && objdump -D a.out \| less
30	+	0000000000001260 <set_bit>:
31	+	1260: 48 8b 05 d1 2d 00 00 mov 0x2dd1(%rip),%rax # 4038 <bits>
32	+	1267: 48 89 fa mov %rdi,%rdx
33	+	126a: 48 89 f9 mov %rdi,%rcx
34	+	126d: 83 e6 01 and $0x1,%esi
35	+	1270: 48 c1 ea 06 shr $0x6,%rdx
36	+	1274: 48 d3 e6 shl %cl,%rsi
37	+	1277: 48 8d 14 d0 lea (%rax,%rdx,8),%rdx
38	+	127b: 48 c7 c0 fe ff ff ff mov $0xfffffffffffffffe,%rax
39	+	1282: 48 d3 c0 rol %cl,%rax
40	+	1285: 48 23 02 and (%rdx),%rax
41	+	1288: 48 09 f0 or %rsi,%rax
42	+	128b: 48 89 02 mov %rax,(%rdx)
43	+	128e: c3 ret
44	+	128f: 90 nop
45	+	*/
46	+
47	+	void
48	+	set_bit (uint64_t const addr, uint64_t const value) {
49	+	uint64_t const shift = addr & (uint64_t) 0b111111;
50	+	uint64_t const index = addr >> 6;
51	+
52	+	bits[index] &= ~((uint64_t) 1 << shift); // clear
53	+	bits[index] \|= ((value & 1) << shift); // set
54	+	}
55	+
56	+	void
57	+	push_bit (uint64_t const value) {
58	+	set_bit(top, value);
59	+	top++;
60	+	}
61	+
62	+	void
63	+	print_bits (void) {
64	+	printf(":: ");
65	+	for (uint64_t i = 0; i < top; i++) {
66	+	putchar(get_bit(i) ? '1' : '0');
67	+	if (i > 0 && (i + 1) % 4 == 0) {
68	+	putchar('.');
69	+	}
70	+	}
71	+	putchar('\n');
72	+	}
73	+
74	+	int
75	+	main (int argc, char const **argv) {
76	+	printf("[%s, Press Ctrl+D or Ctrl+C to Quit]\n", argv[0]);
77	+	printf("[Type 0 or 1 to push a bit, Type P to print stack]\n");
78	+	while (!feof(stdin)) {
79	+	int const c = getchar();
80	+	switch (c) {
81	+	break; case '0': push_bit(0);
82	+	break; case '1': push_bit(1);
83	+	break; case 'p': print_bits();
84	+	}
85	+	}
86	+	return 0;
87	+	}

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