ashmem-host.c revision dd7bc3319deb2b77c5d07a51b7d6cd7e11b5beb0 
1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17/*
18 * Implementation of the user-space ashmem API for the simulator, which lacks
19 * an ashmem-enabled kernel. See ashmem-dev.c for the real ashmem-based version.
20 */
21
22#include <unistd.h>
23#include <string.h>
24#include <stdlib.h>
25#include <sys/types.h>
26#include <sys/stat.h>
27#include <fcntl.h>
28#include <stdio.h>
29#include <errno.h>
30#include <time.h>
31#include <limits.h>
32
33#include <cutils/ashmem.h>
34
35int ashmem_create_region(const char *ignored, size_t size)
36{
37	static const char txt[] = "abcdefghijklmnopqrstuvwxyz"
38				  "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
39	char name[64];
40	unsigned int retries = 0;
41	pid_t pid = getpid();
42	int fd;
43
44	srand(time(NULL) + pid);
45
46retry:
47	/* not beautiful, its just wolf-like loop unrolling */
48	snprintf(name, sizeof(name), "/tmp/android-ashmem-%d-%c%c%c%c%c%c%c%c",
49		pid,
50		txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
51		txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
52		txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
53		txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
54		txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
55		txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
56		txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
57		txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))]);
58
59	/* open O_EXCL & O_CREAT: we are either the sole owner or we fail */
60	fd = open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
61	if (fd == -1) {
62		/* unlikely, but if we failed because `name' exists, retry */
63		if (errno == EEXIST && ++retries < 6)
64			goto retry;
65		return -1;
66	}
67
68	/* truncate the file to `len' bytes */
69	if (ftruncate(fd, size) == -1)
70		goto error;
71
72	if (unlink(name) == -1)
73		goto error;
74
75	return fd;
76error:
77	close(fd);
78	return -1;
79}
80
81int ashmem_set_prot_region(int fd, int prot)
82{
83	return 0;
84}
85
86int ashmem_pin_region(int fd, size_t offset, size_t len)
87{
88	return ASHMEM_NOT_PURGED;
89}
90
91int ashmem_unpin_region(int fd, size_t offset, size_t len)
92{
93	return ASHMEM_IS_UNPINNED;
94}
95