From 1eac97eea4ec0bcef0be061a2cba93a584355283 Mon Sep 17 00:00:00 2001
From: Chuyan Zhang <me@zcy.moe>
Date: Thu, 30 Nov 2023 02:15:06 -0800
Subject: Add real disk i/o, add mkfs.aya (not yet implemented)

---
 ayafs/src/disk/bitmap.rs | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 ayafs/src/disk/bitmap.rs

(limited to 'ayafs/src/disk/bitmap.rs')

diff --git a/ayafs/src/disk/bitmap.rs b/ayafs/src/disk/bitmap.rs
new file mode 100644
index 0000000..b68c341
--- /dev/null
+++ b/ayafs/src/disk/bitmap.rs
@@ -0,0 +1,48 @@
+use crate::block_device::{BlockDevice, BLOCK_SIZE};
+use std::sync::Arc;
+
+pub struct Bitmap {
+    pub starting_block: usize,
+    pub length: usize,
+    pub device: Arc<dyn BlockDevice>,
+    pub data: Vec<u8>,
+}
+
+impl Bitmap {
+    pub(crate) fn new(starting_block: usize, length: usize, device: Arc<dyn BlockDevice>) -> Self {
+        Self {
+            starting_block,
+            length,
+            device,
+            data: vec![0u8; length * BLOCK_SIZE],
+        }
+    }
+    pub(crate) fn allocate(&mut self) -> Option<usize> {
+        for (i, byte) in self.data.iter_mut().enumerate() {
+            let leading_ones = byte.leading_ones();
+            if leading_ones != 8 {
+                *byte |= (1 << (7 - leading_ones)) as u8;
+                return Some(i * 8 + leading_ones as usize);
+            }
+        }
+        None
+    }
+
+    pub(crate) fn query(&self, index: usize) -> bool {
+        if index == 0 {
+            false
+        } else {
+            self.data[index / 8] & ((1 << (7 - index % 8)) as u8) != 0
+        }
+    }
+
+    pub(crate) fn deallocate(&mut self, index: usize) -> bool {
+        if self.query(index) {
+            let mask = !(1u8 << (7 - index % 8));
+            self.data[index / 8] &= mask;
+            true
+        } else {
+            false
+        }
+    }
+}
-- 
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