File Descriptor

File Descriptor 的协作图:

函数
int	fdt_fd_new (struct dfs_fdtable *fdt)
struct dfs_file *	fdt_get_file (struct dfs_fdtable *fdt, int fd)
void	fd_release (int fd)

详细描述

函数说明

fdt_fd_new()

int fdt_fd_new

(

struct dfs_fdtable *

fdt

)

This function will allocate a file descriptor.

返回

-1 on failed or the allocated file descriptor.

在文件 dfs.c 第 199 行定义.

{
    int idx = -1;
 
    /* lock filesystem */
    if (dfs_file_lock() != RT_EOK)
    {
        return -RT_ENOSYS;
    }
 
    /* find an empty fd entry */
    idx = _fdt_fd_alloc(fdt, (fdt == &_fdtab) ? DFS_STDIO_OFFSET : 0);
    /* can't find an empty fd entry */
    if (idx < 0)
    {
        LOG_E("DFS fd new is failed! Could not found an empty fd entry.");
    }
    else if (!fdt->fds[idx])
    {
        struct dfs_file *file;
 
        file = (struct dfs_file *)rt_calloc(1, sizeof(struct dfs_file));
 
        if (file)
        {
            file->magic = DFS_FD_MAGIC;
            file->ref_count = 1;
            rt_mutex_init(&file->pos_lock, "fpos", RT_IPC_FLAG_PRIO);
            fdt->fds[idx] = file;
 
            LOG_D("allocate a new fd @ %d", idx);
        }
        else
        {
            fdt->fds[idx] = RT_NULL;
            idx = -1;
        }
    }
    else
    {
        LOG_E("DFS not found an empty fds entry.");
        idx = -1;
    }
 
    dfs_file_unlock();
 
    return idx;
}

引用了 DFS_FD_MAGIC, dfs_file_lock(), dfs_file_unlock(), DFS_STDIO_OFFSET, dfs_fdtable::fds, LOG_D, LOG_E, dfs_file::magic, dfs_file::pos_lock, dfs_file::ref_count, rt_calloc(), RT_IPC_FLAG_PRIO, rt_mutex_init() , 以及 RT_NULL.

函数调用图:

这是这个函数的调用关系图:

fdt_get_file()

struct dfs_file * fdt_get_file	(	struct dfs_fdtable *	fdt,
		int	fd )

This function will return a file descriptor structure according to file descriptor.

返回

NULL on on this file descriptor or the file descriptor structure pointer.

在文件 dfs.c 第 286 行定义.

{
    struct dfs_file *f;
 
    if (fd < 0 || fd >= (int)fdt->maxfd)
    {
        return NULL;
    }
 
    f = fdt->fds[fd];
 
    /* check file valid or not */
    if ((f == NULL) || (f->magic != DFS_FD_MAGIC))
    {
        return NULL;
    }
 
    return f;
}

引用了 DFS_FD_MAGIC, dfs_fdtable::fds, dfs_file::magic , 以及 dfs_fdtable::maxfd.

这是这个函数的调用关系图:

fd_release()

void fd_release

(

int

fd

)

This function will put the file descriptor.

在文件 dfs.c 第 359 行定义.

{
    struct dfs_fdtable *fdt;
 
    fdt = dfs_fdtable_get();
    fdt_fd_release(fdt, fd);
}

引用了 dfs_fdtable_get() , 以及 fdt_fd_release().

函数调用图:

这是这个函数的调用关系图: