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| /*
* Copyright (C) 2013 Yongbing Chen <yongbing.chen.wh@gmail.com>
*
* 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 <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#define CHECK_RESULT(x) \
do { \
if (x != 0){ \
printf("error %s\n", strerror(errno)); \
return -1; \
} \
}while (0);
#ifndef TEMP_FAILURE_RETRY
#define TEMP_FAILURE_RETRY(x) \
({ \
int _result; \
do _result = (int) (x); \
while (_result == -1 && errno == EINTR); \
_result; \
})
#endif
static int copy_file(const char *src_file, const char *dst_file)
{
int ret = -1;
FILE *fp1, *fp2;
fp1 = fopen(src_file,"r");
if(fp1 == NULL){
printf("open %s error %s\n",src_file, strerror(errno));
return ret;
}
fp2 = fopen(dst_file,"w");
if(fp2 == NULL){
printf("open %s error %s\n", dst_file, strerror(errno)); fclose(fp1);
return ret;
}
fseek(fp1, 0 , SEEK_END);
int file_size = ftell(fp1);
fseek(fp1, 0 , SEEK_SET);
if (file_size == 0){
fclose(fp1); fclose(fp2);
return 0;
}
char *buffer = (char*)malloc(file_size);
if (NULL == buffer){
printf("error %s\n", strerror(errno)); fclose(fp1); fclose(fp2);
return -1;
}
printf("copy len %d from %s to %s\n", file_size, src_file, dst_file);
ret = fread(buffer, file_size, 1, fp1);
if (ret != 1){
printf("ret %d, error %s\n",ret, strerror(errno));
goto error;
}
ret = fwrite(buffer, file_size, 1, fp2);
if (ret != 1){
printf("ret %d, error %s\n",ret, strerror(errno));
goto error;
}
ret = 0;
error:
fclose(fp1);
fclose(fp2);
free(buffer);
return ret;
}
static int update_config_to_tmp_file(const char* curr_file, const char* file_name)
{
int fd = open(file_name, O_CREAT | O_APPEND | O_RDWR, 0660);
if(fd > 0){
if(access(curr_file, F_OK) == 0)
CHECK_RESULT(copy_file(curr_file, file_name));
int test_data = rand();
printf("writing data %d to config file %s\n", test_data, file_name);
int data_write = TEMP_FAILURE_RETRY(write(fd, &test_data, sizeof(test_data)));
if (data_write < 0 || data_write != sizeof(test_data)){
printf("%s failed len:%d %s",__func__, data_write, strerror(errno));
return -1;
}
}
else
return -1;
close(fd);
return 0;
}
static int sync_conf_file(const char* file_name)
{
int ret = -1;
int fd = open(file_name, O_RDONLY);
if(fd > 0){
ret = fsync(fd);
}
close(fd);
return ret;
}
int atomic_update_config_file()
{
const char* file_name = "config";
const char* file_name_new = "config.new";
CHECK_RESULT(update_config_to_tmp_file(file_name, file_name_new));//open, write, close inside this operation.
CHECK_RESULT(sync_conf_file(file_name_new));//open, fsync, close to achive a sync.
CHECK_RESULT(rename(file_name_new, file_name));
return 0;
}
int main(int argc, char **argv)
{
int ret = atomic_update_config_file();
if (ret != 0){
printf("update config failed, keeping original one.\n");
}
return 0;
}
|