Viper_VRTE/os/_posix.vp

from stdint import *
import posix
import memhub
import stdlib


# Maximum POSIX path length
define MAX_PATH_LEN = 4096

# Module-level global MBuddy pointer (initialized by the user in main)
_mbuddy: memhub.MemBuddy*


# =============================================================================
# File/Directory Attribute Query
# =============================================================================

def _stat(path: str) -> posix.Stat*:
    """Call stat and return a Stat struct pointer. Return None on failure.
    Note: the Stat struct is allocated via _mbuddy; the caller must free it."""
    if _mbuddy is None:
        return None
    # 不能在栈上构造后返回其地址：栈对象随本帧失效（栈地址逃逸）。
    # 按本函数契约改为 _mbuddy 堆分配，由调用方 free。
    st: posix.Stat* = _mbuddy.alloc(posix.Stat.__sizeof__())
    if st is None:
        return None
    result: INT = posix.stat(path, st)
    if result != 0:
        _mbuddy.free(st)
        return None
    return st


def exists(path: str) -> bool:
    """Check whether the file/directory exists"""
    result: INT = posix.access(path, posix.F_OK)
    if result == 0:
        return True
    return False


def isdir(path: str) -> bool:
    """Check whether the path is a directory"""
    st: posix.Stat = posix.Stat()
    result: INT = posix.stat(path, &st)
    if result != 0:
        return False
    if posix.S_ISDIR(st.st_mode):
        return True
    return False


def isfile(path: str) -> bool:
    """Check whether the path is a regular file"""
    st: posix.Stat = posix.Stat()
    result: INT = posix.stat(path, &st)
    if result != 0:
        return False
    if posix.S_ISREG(st.st_mode):
        return True
    return False


def getsize(path: str) -> int64:
    """Return the file size in bytes. Return -1 on failure."""
    st: posix.Stat = posix.Stat()
    result: INT = posix.stat(path, &st)
    if result != 0:
        return -1
    return st.st_size


# =============================================================================
# Working Directory
# =============================================================================

def getcwd_impl() -> str:
    """Return the current working directory (memory allocated via _mbuddy)"""
    buf: bytes = _mbuddy.alloc(MAX_PATH_LEN)
    if buf == None: return None
    result: CHARPTR = posix.getcwd(buf, MAX_PATH_LEN)
    if result == None:
        return None
    return str(buf)


def chdir_impl(path: str) -> int:
    """Switch the current working directory. Return 0 on success, -1 on failure."""
    result: INT = posix.chdir(path)
    if result != 0:
        return -1
    return 0


# =============================================================================
# File/Directory Operations
# =============================================================================

def mkdir_impl(path: str) -> int:
    """Create a directory. Return 0 on success, -1 on failure.
    Default permissions are 0o755 (rwxr-xr-x)."""
    result: INT = posix.mkdir(path, 0o755)
    if result != 0:
        return -1
    return 0


def remove(path: str) -> int:
    """Delete a file. Return 0 on success, -1 on failure."""
    result: INT = posix.unlink(path)
    if result != 0:
        return -1
    return 0


def rmdir_impl(path: str) -> int:
    """Delete an empty directory. Return 0 on success, -1 on failure."""
    result: INT = posix.rmdir(path)
    if result != 0:
        return -1
    return 0


def rename_impl(old_path: str, new_path: str) -> int:
    """Rename/move a file or directory. Return 0 on success, -1 on failure."""
    result: INT = posix.rename(old_path, new_path)
    if result != 0:
        return -1
    return 0


def chmod_impl(path: str, mode: int) -> int:
    """Modify file permissions. Return 0 on success, -1 on failure.
    mode is POSIX permission bits (e.g. 0o755)."""
    result: INT = posix.chmod(path, posix.mode_t(mode))
    if result != 0:
        return -1
    return 0


# =============================================================================
# Directory Listing (opendir / readdir / closedir)
# =============================================================================

def listdir(path: str, out_names: str*, max_count: ULONG) -> ULONG:
    """List file/subdirectory names under a directory.
    out_names is a caller-provided char** array (each entry points to a filename allocated via _mbuddy); max_count is its capacity. Return the count, or 0 on failure."""
    dirp: posix.DIR = posix.opendir(path)
    if dirp == None:
        return 0

    count: ULONG = 0
    while count < max_count:
        entry: posix.Dirent* = posix.readdir(dirp)
        if entry == None:
            break

        # Read the d_name field
        name: str = entry.d_name
        if name[0] == '.':
            if name[1] == 0:
                # "."
                continue
            if name[1] == '.' and name[2] == 0:
                # ".."
                continue

        # Copy the filename into newly allocated memory
        name_len: sizet = len(name)
        name_buf: bytes = _mbuddy.alloc(name_len + 1)
        if name_buf == None: break
        i: sizet = 0
        for ch in name:
            name_buf[i] = ch
            i += 1
        name_buf[name_len] = 0
        out_names[count] = str(name_buf)
        count += 1

    posix.closedir(dirp)
    return count


# =============================================================================
# Command Execution
# =============================================================================

def system_impl(cmd: str) -> int:
    """Execute a command line command (via the C runtime system()).
    Output goes to the child terminal (inherits parent stdout/stderr). Return the exit code (0 = success)."""
    return stdlib.system(cmd)