Function dfs_aspace_read

components/dfs/dfs_v2/src/dfs_pcache.c:1558–1617

* @brief Read data from file through address space page cache * * This function reads data from a file using its address space page cache. It handles * the lookup of pages containing the requested data, copies the data to the provided * buffer, and manages page references. * * @param[in] file Pointer to the file structure containing vnode and aspace * @param[in] buf Buffer to store the r

 * @return Number of bytes successfully read, or negative error code
 */
int dfs_aspace_read(struct dfs_file *file, void *buf, size_t count, off_t *pos)
{
    int ret = -EINVAL;

    if (file && file->vnode && file->vnode->aspace)
    {
        if (!(file->vnode->aspace->ops->read))
            return ret;
        struct dfs_vnode *vnode = file->vnode;
        struct dfs_aspace *aspace = vnode->aspace;

        struct dfs_page *page;
        char *ptr = (char *)buf;

        ret = 0;

        while (count)
        {
            page = dfs_page_lookup(file, *pos);
            if (page)
            {
                off_t len;

                dfs_aspace_lock(aspace);
                if (aspace->vnode->size < page->fpos + ARCH_PAGE_SIZE)
                {
                    len = aspace->vnode->size - *pos;
                }
                else
                {
                    len = page->fpos + ARCH_PAGE_SIZE - *pos;
                }

                len = count > len ? len : count;
                if (len > 0)
                {
                    rt_memcpy(ptr, page->page + *pos - page->fpos, len);
                    ptr += len;
                    *pos += len;
                    count -= len;
                    ret += len;
                }
                else
                {
                    dfs_page_release(page);
                    dfs_aspace_unlock(aspace);
                    break;
                }
                dfs_page_release(page);
                dfs_aspace_unlock(aspace);
            }
            else
            {
                break;
            }
        }
    }