diff options
Diffstat (limited to 'fs/fd.cc')
| -rw-r--r-- | fs/fd.cc | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/fs/fd.cc b/fs/fd.cc new file mode 100644 index 0000000..5fc8ab0 --- /dev/null +++ b/fs/fd.cc @@ -0,0 +1,216 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* Copyright (C) 2026 Richard Qin */ + +/* + * fd.cc — File descriptor table management + */ + +#include <lume/fdtable.h> +#include <lume/file.h> +#include <lume/slab.h> +#include <lume/errno.h> + +/* ================================================================== */ +/* Bitmap helpers */ +/* ================================================================== */ + +static inline bool bit_test(const uint64* bmap, int bit) { + return (bmap[bit / 64] >> (bit % 64)) & 1; +} +static inline void bit_set(uint64* bmap, int bit) { + bmap[bit / 64] |= (1ULL << (bit % 64)); +} +static inline void bit_clear(uint64* bmap, int bit) { + bmap[bit / 64] &= ~(1ULL << (bit % 64)); +} + +/* ================================================================== */ +/* alloc_files_struct */ +/* ================================================================== */ + +files_struct* alloc_files_struct() +{ + auto* files = new files_struct{}; + if (!files) return nullptr; + + files->count.store(1); + files->next_fd = 0; + files->max_fds = NR_OPEN_DEFAULT; + + for (int i = 0; i < NR_OPEN_DEFAULT; i++) + files->fd_array[i] = nullptr; + + int bmap_words = (NR_OPEN_DEFAULT + 63) / 64; + for (int i = 0; i < bmap_words; i++) { + files->close_on_exec_init[i] = 0; + files->open_fds_init[i] = 0; + } + + return files; +} + +/* ================================================================== */ +/* put_files_struct — drop reference, free on last */ +/* ================================================================== */ + +void put_files_struct(files_struct* files) +{ + if (!files) return; + + int old = files->count.fetch_sub(1); + if (old > 1) return; + + /* Close all open fds */ + for (int i = 0; i < files->max_fds; i++) { + if (files->fd_array[i]) { + fput(files->fd_array[i]); + files->fd_array[i] = nullptr; + } + } + + delete files; +} + +/* ================================================================== */ +/* dup_fd — duplicate entire fd table (for fork) */ +/* ================================================================== */ + +files_struct* dup_fd(files_struct* old_files) +{ + auto* new_files = alloc_files_struct(); + if (!new_files) return nullptr; + + LockGuard guard(old_files->file_lock); + + for (int i = 0; i < old_files->max_fds; i++) { + file* fp = old_files->fd_array[i]; + if (fp) { + get_file(fp); + new_files->fd_array[i] = fp; + } + } + + /* Copy bitmaps */ + int bmap_words = (NR_OPEN_DEFAULT + 63) / 64; + for (int i = 0; i < bmap_words; i++) { + new_files->open_fds_init[i] = old_files->open_fds_init[i]; + new_files->close_on_exec_init[i] = old_files->close_on_exec_init[i]; + } + + new_files->next_fd = old_files->next_fd; + + return new_files; +} + +/* ================================================================== */ +/* alloc_fd — find lowest free fd >= start */ +/* ================================================================== */ + +int alloc_fd(files_struct* files, unsigned int start) +{ + LockGuard guard(files->file_lock); + + for (int fd = static_cast<int>(start); fd < files->max_fds; fd++) { + if (!bit_test(files->open_fds_init, fd)) { + bit_set(files->open_fds_init, fd); + files->fd_array[fd] = nullptr; /* placeholder, fd_install sets real file */ + if (fd >= files->next_fd) + files->next_fd = fd + 1; + return fd; + } + } + + return -EMFILE; +} + +/* ================================================================== */ +/* fd_install — place a file* at a given fd */ +/* ================================================================== */ + +void fd_install(files_struct* files, int fd, file* fp) +{ + LockGuard guard(files->file_lock); + files->fd_array[fd] = fp; +} + +/* ================================================================== */ +/* fcheck — look up file by fd (no refcount bump) */ +/* ================================================================== */ + +file* fcheck(files_struct* files, int fd) +{ + if (fd < 0 || fd >= files->max_fds) return nullptr; + return files->fd_array[fd]; +} + +/* ================================================================== */ +/* close_fd */ +/* ================================================================== */ + +int close_fd(files_struct* files, int fd) +{ + file* fp; + { + LockGuard guard(files->file_lock); + if (fd < 0 || fd >= files->max_fds) return -EBADF; + + fp = files->fd_array[fd]; + if (!fp) return -EBADF; + + files->fd_array[fd] = nullptr; + bit_clear(files->open_fds_init, fd); + bit_clear(files->close_on_exec_init, fd); + } + + fput(fp); + return 0; +} + +/* ================================================================== */ +/* do_dup2 — duplicate oldfd to newfd */ +/* ================================================================== */ + +int do_dup2(files_struct* files, int oldfd, int newfd, int flags) +{ + if (oldfd == newfd) return -EINVAL; + + file* existing = nullptr; + { + LockGuard guard(files->file_lock); + + if (oldfd < 0 || oldfd >= files->max_fds) return -EBADF; + if (newfd < 0 || newfd >= files->max_fds) return -EBADF; + + file* old_fp = files->fd_array[oldfd]; + if (!old_fp) return -EBADF; + + existing = files->fd_array[newfd]; + + get_file(old_fp); + files->fd_array[newfd] = old_fp; + bit_set(files->open_fds_init, newfd); + + if (flags & O_CLOEXEC) + bit_set(files->close_on_exec_init, newfd); + else + bit_clear(files->close_on_exec_init, newfd); + } + + if (existing) + fput(existing); + + return newfd; +} + +/* ================================================================== */ +/* do_close_on_exec — close all fds with CLOEXEC set */ +/* ================================================================== */ + +void do_close_on_exec(files_struct* files) +{ + for (int fd = 0; fd < files->max_fds; fd++) { + if (bit_test(files->close_on_exec_init, fd)) { + close_fd(files, fd); + } + } +} |