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| #include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/errno.h>
ssize_t read_ex(int fd, void *buf, size_t nbyte){
size_t read_remain = nbyte;
unsigned char *read_start = (unsigned char*)buf;
ssize_t read_num = -1;
ssize_t total_num = 0;
while(read_remain) {
read_num = read(fd, read_start, read_remain);
if(-1 == read_num){
return -1;
}
else if(0 == read_num){
break;
}
else{
read_remain -= read_num;
read_start += read_num;
total_num += read_num;
}
}
return total_num;
}
ssize_t write_ex(int fd, const void *buf, size_t nbyte){
size_t write_remain = nbyte;
unsigned char *write_start = (unsigned char*)buf;
ssize_t write_num = -1;
ssize_t total_num = 0;
while(write_remain) {
write_num = write(fd, write_start, write_remain);
if(-1 == write_num){
return -1;
}
else{
write_remain -= write_num;
write_start += write_num;
total_num += write_num;
}
}
return total_num;
}
int my_cp(const char *from, const char *to)
{
int fd1 = -1, fd2 = -1;
int rev = -1;
unsigned char *buffer = NULL, *buffer_zero = NULL;
long pagesize = 0;
long long blocks, blksize, size;
int read_num, write_num, write_remain, have_holes = 0;
struct stat st;
fd1 = open(from, O_RDONLY);
if(-1 == fd1){
perror("open file1 faild");
goto err;
}
if(fstat(fd1, &st) !=0) {
perror("fstat: ");
goto err;
}
else{
#ifdef _SC_PAGESIZE
pagesize = sysconf(_SC_PAGESIZE);
if (pagesize < 0) {
if (errno != 0) {
if (errno == EINVAL) {
fputs(" (not supported)\n", stdout);
pagesize = st.st_blksize;
}
else {
perror("sysconf error");
goto err;
}
} else {
fputs(" (no limit)\n", stdout);
pagesize = st.st_blksize;
}
}
printf("pagesize: %ld\n", pagesize);
#else
pagesize = st.st_blksize;
#endif
blocks = st.st_blocks;
blksize = st.st_blksize;
size = st.st_size;
printf("st.st_blocks: %lld\n", blocks);
printf("st.st_blksize: %lld\n", blksize);
printf("st.st_size: %lld\n", size);
if(S_ISREG(st.st_mode) && (size / pagesize + (size%pagesize?1:0)) * pagesize > 512 * blocks) {
have_holes = 1;
printf("%s is a sparse-block file!\n", from);
} else{
have_holes = 0;
printf("%s is not a sparse-block file!\n", from);
}
}
buffer = malloc(pagesize);
buffer_zero = malloc(pagesize);
if(buffer == NULL || buffer_zero == NULL) {
perror ("malloc fail");
goto err;
}
memset(buffer, '\0', pagesize);
memset(buffer_zero, '\0', pagesize);
fd2 = open(to, O_WRONLY | O_CREAT | O_TRUNC, S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH);
if (-1 == fd2) {
perror ("open file2 faild");
goto err;
}
while((read_num = read_ex(fd1, buffer, pagesize)) > 0) {
if(have_holes && !memcmp(buffer_zero, buffer, read_num)){
if(-1 == lseek(fd2, read_num, SEEK_CUR)){
perror("lseek file2 fail");
goto err;
}
}
else{
write_num = write_ex(fd2, buffer, read_num);
if (-1 == write_num){
perror( "write file2 error");
goto err;
}
}
}
if(-1 == read_num){
perror("read file1 error");
goto err;
}
rev = 0;
err:
if(buffer) free(buffer);
if(buffer_zero) free(buffer_zero);
close(fd1);
close(fd2);
return rev;
}
int main(int argc, char *argv[])
{
if(argc < 3) {
printf("Usage: %s file1 file2\n", argv[0]);
return -1;
}
my_cp(argv[1], argv[2]);
return 0;
}
|