From 777d5e01a34b8ebe6f1a5751b593266f93e88499 Mon Sep 17 00:00:00 2001
From: Chuyan Zhang <me@zcy.moe>
Date: Sat, 25 Nov 2023 19:36:31 -0800
Subject: Add dir entry operations

---
 src/memory/dir_entry.rs | 103 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 src/memory/dir_entry.rs

(limited to 'src/memory/dir_entry.rs')

diff --git a/src/memory/dir_entry.rs b/src/memory/dir_entry.rs
new file mode 100644
index 0000000..0ade23f
--- /dev/null
+++ b/src/memory/dir_entry.rs
@@ -0,0 +1,103 @@
+use std::ffi::OsStr;
+use std::os::unix::ffi::OsStrExt;
+use libc::{c_int, ENOENT, ENOSPC};
+use crate::disk::block::{DirectoryBlock, DirectoryEntry};
+use crate::disk::inode::{Inode};
+use crate::AyaFS;
+
+impl AyaFS {
+    pub(crate) fn remove_direntry(
+        &mut self,
+        parent_inode: &mut Inode,
+        entry_index: u32
+    ) -> Result<(), c_int> {
+        let block_index_within_inode = (entry_index / 15) as usize;
+        let entry_index_within_block = (entry_index % 15) as usize;
+
+        match self.access_block_mut::<DirectoryBlock>(parent_inode, block_index_within_inode) {
+            Some(directory_block) => {
+                if directory_block.block.query(entry_index_within_block) {
+                    directory_block.block.deallocate(entry_index_within_block);
+                    directory_block.block.entries[entry_index_within_block] = DirectoryEntry::default();
+                    Ok(())
+                } else {
+                    Err(ENOENT)
+                }
+            }
+            None => Err(ENOENT),
+        }
+    }
+
+    pub(crate) fn add_direntry(
+        &mut self,
+        parent_inode: &mut Inode,
+        child_inode_index: u32,
+        child_inode_name: &OsStr,
+        child_inode: &Inode,
+    ) -> Result<u32, c_int> {
+        // 找到第一个有空闲 DirEntry 的块, 从中分配一个 entry
+        let mut block_index_within_inode: usize = 0;
+        loop {
+            // 所有已经分配的块都用完, 需要额外分配一个块了
+            if block_index_within_inode as u32 == parent_inode.n_blocks {
+                if self.allocate_block_for(parent_inode).is_none() {
+                    return Err(ENOSPC);
+                }
+            }
+            // 寻找当前块里有没有空闲空间
+            if let Some(directory_block) = self.access_block_mut::<DirectoryBlock>(parent_inode, block_index_within_inode) {
+                if let Some(entry_index_within_block) = directory_block.block.allocate() {
+                    // 如果有空闲空间, 可以分配一个块
+                    let name_len = child_inode_name.len() as u8;
+                    let file_type = child_inode.mode.into();
+                    let mut name = [0u8; 256];
+                    name.copy_from_slice(child_inode_name.as_bytes());
+
+                    let dir_entry = DirectoryEntry {
+                        inode: child_inode_index,
+                        record_len: 264,
+                        name_len,
+                        file_type,
+                        name,
+                    };
+                    directory_block.block.entries[entry_index_within_block] = dir_entry;
+                    let entry_index = block_index_within_inode * 15 + entry_index_within_block;
+                    return Ok(entry_index as u32);
+                }
+            }
+            block_index_within_inode += 1;
+        };
+    }
+    pub(crate) fn get_direntry(
+        &mut self,
+        parent_inode: &Inode,
+        entry_index: u32
+    ) -> Option<DirectoryEntry> {
+        let block_index_within_inode = (entry_index / 15) as usize;
+        let entry_index_within_block = (entry_index % 15) as usize;
+
+        self.access_block::<DirectoryBlock>(parent_inode, block_index_within_inode)
+            .and_then(|directory_block| {
+                if directory_block.block.query(entry_index_within_block) {
+                    Some(directory_block.block.entries[entry_index_within_block].clone())
+                } else {
+                    None
+                }
+            })
+    }
+
+    // TODO 实现一个带 cache 的版本
+    pub fn lookup_name(&mut self, parent_inode: &Inode, name: &OsStr) -> Result<(u32, u32, Inode), c_int> {
+        let mut entry_index = 0;
+        while entry_index < parent_inode.size {
+            if let Some(entry) = self.get_direntry(parent_inode, entry_index) {
+                if entry.name() == name {
+                    let inode = self.get_inode(entry.inode as usize).unwrap().clone();
+                    return Ok((entry.inode, entry_index, inode))
+                }
+            }
+            entry_index += 1;
+        }
+        Err(ENOENT)
+    }
+}
-- 
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