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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Assertions.h>
#include <AK/StdLibExtras.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <syscall.h>
#include <unistd.h>
extern "C" {
DIR* opendir(const char* name)
{
int fd = open(name, O_RDONLY | O_DIRECTORY);
if (fd == -1)
return nullptr;
DIR* dirp = (DIR*)malloc(sizeof(DIR));
dirp->fd = fd;
dirp->buffer = nullptr;
dirp->buffer_size = 0;
dirp->nextptr = nullptr;
return dirp;
}
int closedir(DIR* dirp)
{
if (!dirp || dirp->fd == -1)
return -EBADF;
free(dirp->buffer);
int rc = close(dirp->fd);
if (rc == 0)
dirp->fd = -1;
free(dirp);
return rc;
}
void rewinddir(DIR* dirp)
{
free(dirp->buffer);
dirp->buffer = nullptr;
dirp->buffer_size = 0;
dirp->nextptr = nullptr;
lseek(dirp->fd, 0, SEEK_SET);
}
struct [[gnu::packed]] sys_dirent {
ino_t ino;
u8 file_type;
size_t namelen;
char name[];
size_t total_size()
{
return sizeof(ino_t) + sizeof(u8) + sizeof(size_t) + sizeof(char) * namelen;
}
};
static void create_struct_dirent(sys_dirent* sys_ent, struct dirent* str_ent)
{
str_ent->d_ino = sys_ent->ino;
str_ent->d_type = sys_ent->file_type;
str_ent->d_off = 0;
str_ent->d_reclen = sizeof(struct dirent);
int size = min((sys_ent->namelen + 1) * sizeof(char), sizeof(str_ent->d_name));
[[maybe_unused]] auto n = strlcpy(str_ent->d_name, sys_ent->name, size);
}
static int allocate_dirp_buffer(DIR* dirp)
{
if (dirp->buffer) {
return 0;
}
struct stat st;
// preserve errno since this could be a reentrant call
int old_errno = errno;
int rc = fstat(dirp->fd, &st);
if (rc < 0) {
int new_errno = errno;
errno = old_errno;
return new_errno;
}
size_t size_to_allocate = max(st.st_size, static_cast<off_t>(4096));
dirp->buffer = (char*)malloc(size_to_allocate);
ssize_t nread = syscall(SC_get_dir_entries, dirp->fd, dirp->buffer, size_to_allocate);
if (nread < 0) {
// uh-oh, the syscall returned an error
free(dirp->buffer);
dirp->buffer = nullptr;
return -nread;
}
dirp->buffer_size = nread;
dirp->nextptr = dirp->buffer;
return 0;
}
dirent* readdir(DIR* dirp)
{
if (!dirp)
return nullptr;
if (dirp->fd == -1)
return nullptr;
if (int new_errno = allocate_dirp_buffer(dirp)) {
// readdir is allowed to mutate errno
errno = new_errno;
return nullptr;
}
if (dirp->nextptr >= (dirp->buffer + dirp->buffer_size))
return nullptr;
auto* sys_ent = (sys_dirent*)dirp->nextptr;
create_struct_dirent(sys_ent, &dirp->cur_ent);
dirp->nextptr += sys_ent->total_size();
return &dirp->cur_ent;
}
static bool compare_sys_struct_dirent(sys_dirent* sys_ent, struct dirent* str_ent)
{
size_t namelen = min((size_t)256, sys_ent->namelen);
// These fields are guaranteed by create_struct_dirent to be the same
return sys_ent->ino == str_ent->d_ino
&& sys_ent->file_type == str_ent->d_type
&& sys_ent->total_size() == str_ent->d_reclen
&& strncmp(sys_ent->name, str_ent->d_name, namelen) == 0;
}
int readdir_r(DIR* dirp, struct dirent* entry, struct dirent** result)
{
if (!dirp || dirp->fd == -1) {
*result = nullptr;
return EBADF;
}
if (int new_errno = allocate_dirp_buffer(dirp)) {
*result = nullptr;
return new_errno;
}
// This doesn't care about dirp state; seek until we find the entry.
// Unfortunately, we can't just compare struct dirent to sys_dirent, so
// manually compare the fields. This seems a bit risky, but could work.
auto* buffer = dirp->buffer;
auto* sys_ent = (sys_dirent*)buffer;
bool found = false;
while (!(found || buffer >= dirp->buffer + dirp->buffer_size)) {
found = compare_sys_struct_dirent(sys_ent, entry);
// Make sure if we found one, it's the one after (end of buffer or not)
buffer += sys_ent->total_size();
sys_ent = (sys_dirent*)buffer;
}
// If we found one, but hit end of buffer, then EOD
if (found && buffer >= dirp->buffer + dirp->buffer_size) {
*result = nullptr;
return 0;
}
// If we never found a match for entry in buffer, start from the beginning
else if (!found) {
buffer = dirp->buffer;
sys_ent = (sys_dirent*)buffer;
}
*result = entry;
create_struct_dirent(sys_ent, entry);
return 0;
}
int dirfd(DIR* dirp)
{
VERIFY(dirp);
return dirp->fd;
}
}
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