util.c

Android 一些工具

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <ctype.h>
#include <errno.h>

#include <sys/stat.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>

/* for ANDROID_SOCKET_* */
#include <cutils/sockets.h>

#include <private/android_filesystem_config.h>

#include "init.h"

static int log_fd = -1;
/* Inital log level before init.rc is parsed and this this is reset. */
static int log_level = LOG_DEFAULT_LEVEL;


void log_set_level(int level) {
    log_level = level;
}

void log_init(void)
{
    static const char *name = "/dev/__kmsg__";
    if (mknod(name, S_IFCHR | 0600, (1 << 8) | 11) == 0) {
        log_fd = open(name, O_WRONLY);
        fcntl(log_fd, F_SETFD, FD_CLOEXEC);
        unlink(name);
    }
}

#define LOG_BUF_MAX 512

void log_write(int level, const char *fmt, ...)
{
    char buf[LOG_BUF_MAX];
    va_list ap;
    
    if (level > log_level) return;
    if (log_fd < 0) return;
    
    va_start(ap, fmt);
    vsnprintf(buf, LOG_BUF_MAX, fmt, ap);
    buf[LOG_BUF_MAX - 1] = 0;
    va_end(ap);
    write(log_fd, buf, strlen(buf));
}

/*
 * android_name_to_id - returns the integer uid/gid associated with the given
 * name, or -1U on error.
 */
static unsigned int android_name_to_id(const char *name)
{
    struct android_id_info *info = android_ids;
    unsigned int n;

    for (n = 0; n < android_id_count; n++) {
        if (!strcmp(info[n].name, name))
            return info[n].aid;
    }

    return -1U;
}

/*
 * decode_uid - decodes and returns the given string, which can be either the
 * numeric or name representation, into the integer uid or gid. Returns -1U on
 * error.
 */
unsigned int decode_uid(const char *s)
{
    unsigned int v;

    if (!s || *s == '\0')
        return -1U;
    if (isalpha(s[0]))
        return android_name_to_id(s);

    errno = 0;
    v = (unsigned int) strtoul(s, 0, 0);
    if (errno)
        return -1U;
    return v;
}

/*
 * create_socket - creates a Unix domain socket in ANDROID_SOCKET_DIR
 * ("/dev/socket") as dictated in init.rc. This socket is inherited by the
 * daemon. We communicate the file descriptor's value via the environment
 * variable ANDROID_SOCKET_ENV_PREFIX<name> ("ANDROID_SOCKET_foo").
 */
int create_socket(const char *name, int type, mode_t perm, uid_t uid, gid_t gid)
{
    struct sockaddr_un addr;
    int fd, ret;

    fd = socket(PF_UNIX, type, 0);
    if (fd < 0) {
        ERROR("Failed to open socket '%s': %s\n", name, strerror(errno));
        return -1;
    }

    memset(&addr, 0 , sizeof(addr));
    addr.sun_family = AF_UNIX;
    snprintf(addr.sun_path, sizeof(addr.sun_path), ANDROID_SOCKET_DIR"/%s",
             name);

    ret = unlink(addr.sun_path);
    if (ret != 0 && errno != ENOENT) {
        ERROR("Failed to unlink old socket '%s': %s\n", name, strerror(errno));
        goto out_close;
    }

    ret = bind(fd, (struct sockaddr *) &addr, sizeof (addr));
    if (ret) {
        ERROR("Failed to bind socket '%s': %s\n", name, strerror(errno));
        goto out_unlink;
    }

    chown(addr.sun_path, uid, gid);
    chmod(addr.sun_path, perm);

    INFO("Created socket '%s' with mode '%o', user '%d', group '%d'\n",
         addr.sun_path, perm, uid, gid);

    return fd;

out_unlink:
    unlink(addr.sun_path);
out_close:
    close(fd);
    return -1;
}

/* reads a file, making sure it is terminated with \n \0 */
void *read_file(const char *fn, unsigned *_sz)
{
    char *data;
    int sz;
    int fd;

    data = 0;
    fd = open(fn, O_RDONLY);
    if(fd < 0) return 0;

    sz = lseek(fd, 0, SEEK_END);
    if(sz < 0) goto oops;

    if(lseek(fd, 0, SEEK_SET) != 0) goto oops;

    data = (char*) malloc(sz + 2);
    if(data == 0) goto oops;

    if(read(fd, data, sz) != sz) goto oops;
    close(fd);
    data[sz] = '\n';
    data[sz+1] = 0;
    if(_sz) *_sz = sz;
    return data;

oops:
    close(fd);
    if(data != 0) free(data);
    return 0;
}

void list_init(struct listnode *node)
{
    node->next = node;
    node->prev = node;
}

void list_add_tail(struct listnode *head, struct listnode *item)
{
    item->next = head;
    item->prev = head->prev;
    head->prev->next = item;
    head->prev = item;
}

void list_remove(struct listnode *item)
{
    item->next->prev = item->prev;
    item->prev->next = item->next;
}