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#include "errno.h"
#include "fs/fcntl.h"
#include "fs/file.h"
#include "fs/vfs.h"
#include "fs/vfs_syscall.h"
#include "fs/vnode.h"
#include "globals.h"
#include "util/debug.h"
#include <fs/vnode.h>
// NOTE: IF DOING MULTI-THREADED PROCS, NEED TO SYNCHRONIZE ACCESS TO FILE
// DESCRIPTORS, AND, MORE GENERALLY SPEAKING, p_files, IN PARTICULAR IN THIS
// FUNCTION AND ITS CALLERS.
/*
* Go through curproc->p_files and find the first null entry.
* If one exists, set fd to that index and return 0.
*
* Error cases get_empty_fd is responsible for generating:
* - EMFILE: no empty file descriptor
*/
long get_empty_fd(int *fd)
{
for (*fd = 0; *fd < NFILES; (*fd)++)
{
if (!curproc->p_files[*fd])
{
return 0;
}
}
*fd = -1;
return -EMFILE;
}
/*
* Open the file at the provided path with the specified flags.
*
* Returns the file descriptor on success, or error cases:
* - EINVAL: Invalid oflags
* - EISDIR: Trying to open a directory with write access
* - ENXIO: Blockdev or chardev vnode does not have an actual underlying device
* - ENOMEM: Not enough kernel memory (if fcreate() fails)
*
* Hints:
* 1) Use get_empty_fd() to get an available fd.
* 2) Use namev_open() with oflags, mode S_IFREG, and devid 0.
* 3) Check for EISDIR and ENXIO errors.
* 4) Convert oflags (O_RDONLY, O_WRONLY, O_RDWR, O_APPEND) into corresponding
* file access flags (FMODE_READ, FMODE_WRITE, FMODE_APPEND).
* 5) Use fcreate() to create and initialize the corresponding file descriptor
* with the vnode from 2) and the mode from 4).
*
* When checking oflags, you only need to check that the read and write
* permissions are consistent. However, because O_RDONLY is 0 and O_RDWR is 2,
* there's no way to tell if both were specified. So, you really only need
* to check if O_WRONLY and O_RDWR were specified.
*
* If O_TRUNC specified and the vnode represents a regular file, make sure to call the
* the vnode's truncate routine (to reduce the size of the file to 0).
*
* If a vnode represents a chardev or blockdev, then the appropriate field of
* the vnode->vn_dev union will point to the device. Otherwise, the union will be NULL.
*/
long do_open(const char *filename, int oflags)
{
// Check if oflags is valid
if ((oflags & O_WRONLY) && (oflags & O_RDWR))
{
return -EINVAL;
}
// Get an empty file descriptor
int fd = -1;
long ret = get_empty_fd(&fd);
if (ret < 0)
{
return ret;
}
// Check if the file is a directory
if (filename[strlen(filename) - 1] == '/' && (oflags & O_WRONLY))
{
return -EISDIR;
}
// Open the file
vnode_t *res_vnode = NULL;
vnode_t *base = curproc->p_cwd;
ret = namev_open(base, filename, oflags, S_IFREG, 0, &res_vnode);
if (ret < 0)
{
if (res_vnode != NULL)
{
vput(&res_vnode);
}
return ret;
}
// Check if the vnode is a directory
if (S_ISDIR(res_vnode->vn_mode) && ((oflags & O_WRONLY) || (oflags & O_RDWR)))
{
vput(&res_vnode);
return -EISDIR;
}
// Check if the vnode is a blockdev or chardev
if (S_ISCHR(res_vnode->vn_mode) && res_vnode->vn_dev.chardev == NULL)
{
vput(&res_vnode);
return -ENXIO;
}
if (S_ISBLK(res_vnode->vn_mode) && res_vnode->vn_dev.blockdev == NULL)
{
vput(&res_vnode);
return -ENXIO;
}
// Convert oflags to file access flags
int fmode = 0;
if (oflags & O_RDONLY)
{
fmode |= FMODE_READ;
}
if (oflags & O_WRONLY)
{
fmode |= FMODE_WRITE;
}
else
{
fmode |= FMODE_READ;
}
if (oflags & O_RDWR)
{
fmode |= FMODE_READ | FMODE_WRITE;
}
if (oflags & O_APPEND)
{
fmode |= FMODE_APPEND;
}
// Truncate the file if O_TRUNC is specified
if (oflags & O_TRUNC && S_ISREG(res_vnode->vn_mode))
{
res_vnode->vn_ops->truncate_file(res_vnode);
}
// Create the file descriptor
file_t *file = fcreate(fd, res_vnode, fmode);
if (file == NULL)
{
vput(&res_vnode);
return -ENOMEM;
}
vput(&res_vnode);
return fd;
}
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