实现getcwd

stat.c1

@@ -0,0 +1,185 @@
+/*
+ *  linux/fs/stat.c
+ *
+ *  (C) 1991  Linus Torvalds
+ */
+
+#include <errno.h>
+#include <sys/stat.h>
+
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <asm/segment.h>
+#include <fcntl.h>
+
+static void cp_stat(struct m_inode * inode, struct stat * statbuf)
+{
+	struct stat tmp;
+	int i;
+
+	verify_area(statbuf,sizeof (* statbuf));
+	tmp.st_dev = inode->i_dev;
+	tmp.st_ino = inode->i_num;
+	tmp.st_mode = inode->i_mode;
+	tmp.st_nlink = inode->i_nlinks;
+	tmp.st_uid = inode->i_uid;
+	tmp.st_gid = inode->i_gid;
+	tmp.st_rdev = inode->i_zone[0];
+	tmp.st_size = inode->i_size;
+	tmp.st_atime = inode->i_atime;
+	tmp.st_mtime = inode->i_mtime;
+	tmp.st_ctime = inode->i_ctime;
+	for (i=0 ; i<sizeof (tmp) ; i++)
+		put_fs_byte(((char *) &tmp)[i],&((char *) statbuf)[i]);
+}
+
+static void new_cp_stat(struct m_inode * inode, struct stat * statbuf)
+{
+	struct stat tmp;
+	int i;
+
+	verify_area(statbuf,sizeof (* statbuf));
+	tmp.st_dev = inode->i_dev;
+	tmp.st_ino = inode->i_num;
+	tmp.st_mode = inode->i_mode;
+	tmp.st_nlink = inode->i_nlinks;
+	tmp.st_uid = inode->i_uid;
+	tmp.st_gid = inode->i_gid;
+	tmp.st_rdev = inode->i_zone[0];
+	tmp.st_size = inode->i_size;
+	tmp.st_atime = inode->i_atime;
+	tmp.st_mtime = inode->i_mtime;
+	tmp.st_ctime = inode->i_ctime;
+	for (i=0 ; i<sizeof (tmp) ; i++)
+		//put_fs_byte(((char *) &tmp)[i],&((char *) statbuf)[i]);
+		((char *)statbuf)[i]=((char *) &tmp)[i];
+}
+
+
+int sys_stat(char * filename, struct stat * statbuf)
+{
+	struct m_inode * inode;
+
+	if (!(inode=namei(filename)))
+		return -ENOENT;
+	cp_stat(inode,statbuf);
+	iput(inode);
+	return 0;
+}
+
+int my_stat(char * filename, struct stat * statbuf)
+{
+	struct m_inode * inode;
+
+	if (!(inode=namei(filename)))
+		return -ENOENT;
+	new_cp_stat(inode,statbuf);
+	iput(inode);
+	return 0;
+}
+
+int sys_lstat(char * filename, struct stat * statbuf)
+{
+	return sys_stat(filename, statbuf);
+}
+
+int sys_fstat(unsigned int fd, struct stat * statbuf)
+{
+	struct file * f;
+	struct m_inode * inode;
+
+	if (fd >= NR_OPEN || !(f=current->filp[fd]) || !(inode=f->f_inode))
+		return -EBADF;
+	cp_stat(inode,statbuf);
+	return 0;
+}
+
+int sys_readlink()
+{
+	return -ENOSYS;
+}
+
+char *sys_getcwd(char *buf,size_t size)
+{
+	char path[128], cwd[128], name[16], res[128]; 
+	int dirp; 
+	struct stat sb, sb_d, sb_1; 
+	dev_t dev; 
+	ino_t ino; 
+	int tmp = 0, i; 
+	memset(res, 0, sizeof(res)); 
+	while(1) 
+	{ 
+		//将当前目录的字符串"."存入buf中才能作为stat的参数传入使用
+		put_fs_byte('.', &buf[0]); 
+		put_fs_byte(0, &buf[1]); 
+
+		//获取当前目录的文件信息
+		my_stat(buf, &sb); 
+		dev = sb.st_dev; 
+		ino = sb.st_ino;
+
+		//获取父目录的对应的目录流和父目录的文件信息,将父目录".."字符串写入buf中
+		put_fs_byte('.', &buf[0]); 
+		put_fs_byte('.', &buf[1]); 
+		put_fs_byte(0, &buf[2]); 
+
+		//获取父目录的对应的目录流
+		dirp = sys_open(buf, O_RDONLY, 0); 
+		//获取父目录的文件信息
+		my_stat(buf, &sb_1); 
+
+		//判断当前目录是否与父目录相同，相同则找到当前路径
+		if(sb_1.st_dev == dev && sb_1.st_ino == ino)
+		{ 
+			break; 
+		}
+
+		//在父目录对应的目录流读取条目
+		//遍历父目录下对应的所有目录与之前获取的当前目录想匹配，匹配成功的目录项对当前目录所在的目录项，即可保存名字后继续向前寻找
+		while(my_read(dirp, name, 16) > 0 && name[0])
+		{ 
+			tmp = 0; 
+			memset(path, 0, sizeof(path)); 
+			path[0] = '.';path[1] = '.';path[2] = '/'; 
+			while(name[tmp+2])
+			{ 
+				path[tmp+3] = name[tmp+2]; 
+				tmp++; 
+			}
+			path[tmp+3] = 0; 
+			for(i=0;i<size;i++)
+				put_fs_byte(path[i], &buf[i]); 
+
+		    //获取当前父目录下的目录项文件信息
+			my_stat(buf, &sb_d); 
+			if(dev == sb_d.st_dev && ino == sb_d.st_ino)
+			{ 
+				//若匹配成功，则写入文件路径
+				memset(cwd, 0, sizeof(cwd)); 
+				strcat(cwd, "/"); 
+				strcat(cwd, name+2); 
+				strcat(cwd, res); 
+				strncpy(res, cwd, size); 
+				break; 
+			}
+		}
+		//关闭当前打开的父目录
+		sys_close(dirp); 
+
+		//将buf重新修改为父目录对应的字符串".."
+		put_fs_byte('.', &buf[0]); 
+		put_fs_byte('.', &buf[1]); 
+		put_fs_byte(0, &buf[2]); 
+
+		//改变当前目录到上一级，继续上述遍历寻找步骤直到父目录与当前目录相一致
+		sys_chdir(buf);
+	}
+	//将得到的路径写入buf中
+	for(i=0;i<size;i++) 
+		put_fs_byte(res[i], &buf[i]); 
+	sys_close(dirp); 
+	sys_chdir(buf); 
+	return buf;
+}