OS_LAB/getcwd.c

#define __LIBRARY__
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <fcntl.h>

#include <linux/kernel.h>
#include <linux/sched.h>
#include <asm/segment.h>
#include <sys/stat.h>

#define BUF_MAX  128
#define	DIRBUF  8192
#define NAME_MAX  14

struct dirent {                            /* Ŀ¼<C4BF><C2BC>ṹ<EFBFBD><E1B9B9> */
	long           d_ino;                  /* i<>ڵ<EFBFBD> */
	off_t          d_off;                  /* λ<><CEBB> */
	unsigned short d_reclen;               /* <20>ļ<EFBFBD><C4BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> */
	char           d_name[NAME_MAX + 1];   /* <20>ļ<EFBFBD><C4BC><EFBFBD> */
};

typedef struct
{
	int	dd_fd;			/* <20>ļ<EFBFBD><C4BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> */
	int	dd_loc;			/* <20><><EFBFBD><EFBFBD>ƫ<EFBFBD><C6AB> */
	int	dd_size;		/* <20><>Ч<EFBFBD><D0A7><EFBFBD>ݴ<EFBFBD>С */
	char* dd_buf;		/* -> directory block */
}	DIR;			    /* Ŀ¼<C4BF><C2BC> */

struct direct {
	ino_t d_ino;
	char d_name[NAME_MAX];
};

static struct dirent result;

_syscall3(int, read, int, fildes, char*, buf, off_t, count)
_syscall2(int, fstat, int, fildes, struct stat*, stat_buf)
_syscall2(int, stat, const char*, filename, struct stat*, stat_buf)
_syscall1(int, chdir, const char*, filename)

struct dirent* readdir(DIR* dir)              /* <20><><EFBFBD>ز<EFBFBD><D8B2><EFBFBD>dirĿ¼<C4BF><C2BC><EFBFBD><EFBFBD><EFBFBD>¸<EFBFBD>Ŀ¼<C4BF><C2BC><EFBFBD><EFBFBD><EFBFBD> */
{                                             /* <20><>ȡ<EFBFBD><C8A1>Ŀ¼<C4BF><C2BC>Ϣ<EFBFBD><CFA2><EFBFBD><EFBFBD><EFBFBD>ptrָ<72><D6B8><EFBFBD>Ŀ¼<C4BF>ṹ<EFBFBD><E1B9B9><EFBFBD>У<EFBFBD>ֻ<EFBFBD><D6BB>i<EFBFBD>ڵ<EFBFBD><DAB5>Ŀ¼<C4BF><C2BC> */
	struct direct* ptr;                       /* <20><>ȡ<EFBFBD><C8A1>ǰĿ¼<C4BF><C2BC>ͬʱ<CDAC><CAB1>ȡ<EFBFBD><C8A1><EFBFBD>¸<EFBFBD>Ŀ¼<C4BF><C2BC><EFBFBD><EFBFBD>Ϣ<EFBFBD><CFA2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>result<6C><74> */
											  /* <20><><EFBFBD><EFBFBD>ĩβ<C4A9><CEB2><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>NULL */
	if (!dir) {
		errno = EBADF;
		return NULL;
	}
	if (!dir->dd_buf)
		if (!(dir->dd_buf = malloc(DIRBUF)))
			return NULL;
		else
			dir->dd_size = dir->dd_loc = 0;
	while (1) {
		if (dir->dd_size <= dir->dd_loc) {
			dir->dd_loc = 0;
			dir->dd_size = read(dir->dd_fd, dir->dd_buf, DIRBUF);
		}
		if (dir->dd_size <= 0)
			return NULL;
		ptr = (struct direct*)(dir->dd_loc + dir->dd_buf);
		dir->dd_loc += sizeof(*ptr);
		if (!ptr->d_ino)
			continue;
		result.d_ino = ptr->d_ino;
		strncpy(result.d_name, ptr->d_name, NAME_MAX);
		result.d_name[NAME_MAX] = 0;
		result.d_reclen = strlen(result.d_name);
		return &result;
	}
}

int closedir(DIR* dir)        /* <20>رղ<D8B1><D5B2><EFBFBD>dir<69><72>ָ<EFBFBD><D6B8><EFBFBD>Ŀ¼<C4BF><C2BC> */
{
	int fd;

	if (!dir) {
		errno = EBADF;
		return -1;
	}
	fd = dir->dd_fd;
	free(dir->dd_buf);
	free(dir);
	return close(fd);
}

DIR* opendir(const char* dirname)         /* <20>򿪲<EFBFBD><F2BFAAB2><EFBFBD>dirnameָ<65><D6B8><EFBFBD><EFBFBD>Ŀ¼<C4BF><C2BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>DIR<49><52>̬<EFBFBD><CCAC>Ŀ¼<C4BF><C2BC><EFBFBD><EFBFBD>ʧ<EFBFBD>ܷ<EFBFBD><DCB7><EFBFBD>NULL */
{
	int fd;
	struct stat stat_buf;
	DIR* ptr;

	if ((fd = open(dirname, O_RDONLY)) < 0)  /* ִ<><D6B4>ϵͳ<CFB5><CDB3><EFBFBD><EFBFBD>read<61><64><EFBFBD><EFBFBD>ȡ<EFBFBD>ļ<EFBFBD><C4BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD> */
		return NULL;
	if (fstat(fd, &stat_buf) < 0 ||          /* ִ<><D6B4>ϵͳ<CFB5><CDB3><EFBFBD><EFBFBD>fstat<61><74>ͨ<EFBFBD><CDA8><EFBFBD>ļ<EFBFBD><C4BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȡ<EFBFBD>ļ<EFBFBD>״̬<D7B4><CCAC>Ϣ<EFBFBD><CFA2><EFBFBD><EFBFBD><EFBFBD>뻺<EFBFBD><EBBBBA><EFBFBD><EFBFBD>stat_buf */
		!S_ISDIR(stat_buf.st_mode) ||
		!(ptr = malloc(sizeof(*ptr)))) {
		close(fd);
		return NULL;
	}
	memset(ptr, 0, sizeof(*ptr));
	ptr->dd_fd = fd;
	return ptr;
}

char* sys_getcwd(char* buf, size_t size) {
	char through_name[BUF_MAX], cwd[BUF_MAX];
	DIR* pre_fstream;
	struct dirent* through_stream;
	struct stat current_direct_state, through_state, pre_direct_state;
	dev_t current_direct_dev;
	ino_t current_direct_inum;

	while (1) {
		if (stat(".", &current_direct_state == 0)) {            /* <20><>ȡ<EFBFBD><C8A1>ǰĿ¼<C4BF><C2BC><EFBFBD>ļ<EFBFBD>״̬<D7B4><CCAC>Ϣ */
			current_direct_dev = current_direct_state.st_dev;
			current_direct_inum = current_direct_state.st_ino;
		}

		pre_fstream = opendir("..");                            /* <20><>ȡ<EFBFBD><C8A1>ǰĿ¼<C4BF>ĸ<EFBFBD>Ŀ¼<C4BF><C2BC><EFBFBD>ļ<EFBFBD><C4BC><EFBFBD> */
		stat("..", &pre_direct_state);                          /* <20><>ȡ<EFBFBD><C8A1>ǰĿ¼<C4BF>ĸ<EFBFBD>Ŀ¼<C4BF><C2BC><EFBFBD>ļ<EFBFBD><C4BC><EFBFBD>Ϣ */
		if (pre_direct_state.st_dev == current_direct_dev && pre_direct_state.st_ino == current_direct_inum)
			break;                                              /* <20><><EFBFBD><EFBFBD><EFBFBD>Ŀ¼<C4BF>͵<EFBFBD>ǰĿ¼<C4BF><C2BC>ͬ<EFBFBD><CDAC>˵<EFBFBD><CBB5><EFBFBD>Ѿ<EFBFBD><D1BE><EFBFBD><EFBFBD>˸<EFBFBD>Ŀ¼<C4BF><C2BC><EFBFBD><EFBFBD>ʱ<EFBFBD>˳<EFBFBD>ѭ<EFBFBD><D1AD> */

		while ((through_stream = readdir(pre_fstream)) != NULL) {           /* <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ¼<C4BF>µ<EFBFBD>Ŀ¼<C4BF><EFBFBD><EEA3AC><EFBFBD><EFBFBD>ƥ<EFBFBD><C6A5> */
			memcpy(through_name, through_stream->d_name, BUF_MAX);          /* <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ¼<C4BF><C2BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD>֣<EFBFBD><D6A3><EFBFBD><EFBFBD><EFBFBD>ʹ<EFBFBD><CAB9>stat<61><74><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȡ<EFBFBD><C8A1>״̬<D7B4><CCAC>Ϣ */
			stat(through_name, &through_state);                             /* <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŀ¼<C4BF><C2BC><EFBFBD>״̬<D7B4><CCAC>Ϣ<EFBFBD><CFA2><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ƥ<EFBFBD><C6A5> */

			if (current_direct_dev == through_state.st_dev && current_direct_inum == through_state.st_ino) {
				memset(cwd, 0, sizeof(cwd));                    /* ƥ<>䵽<EFBFBD>˵<EFBFBD>ǰĿ¼<C4BF><C2BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>׷<EFBFBD>ӵ<EFBFBD>cwd<77><64> */
				strcat(cwd, "/");
				strcat(cwd, through_stream->d_name);
				strcat(cwd, buf);                               /* buf<75><66>¼<EFBFBD><C2BC><EFBFBD><EFBFBD><EFBFBD><EFBFBD>һ<EFBFBD><D2BB>ѭ<EFBFBD><D1AD><EFBFBD><EFBFBD>cwd<77><64><EFBFBD><EFBFBD><EFBFBD><EFBFBD>׷<EFBFBD>Ӹ<EFBFBD><D3B8><EFBFBD>ǰѭ<C7B0><D1AD><EFBFBD><EFBFBD>cwd */
				strncpy(buf, cwd, BUF_MAX);                     /* <20><>cwd<77><64><EFBFBD><EFBFBD><EFBFBD><EFBFBD>buf */
				break;
			}
		}
		closedir(pre_fstream);
		chdir("..");											/* <20>ı䵱ǰĿ¼Ϊ<C2BC>丸Ŀ¼ */
	}
	return buf;
}