feat(assets): implement AssetFile with seeking, buffering, and reading mechanics

crates/molotov-core/src/assets/asset.rs

@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+use super::types::{SEEK_CUR, SEEK_END, SEEK_SET};
+use std::ffi::c_void;
+
+pub struct AssetFile {
+    data: Vec<u8>,
+    cursor: usize,
+}
+
+impl AssetFile {
+    pub fn new(data: Vec<u8>) -> Self {
+        Self { data, cursor: 0 }
+    }
+
+    pub fn length(&self) -> i64 {
+        self.data.len() as i64
+    }
+
+    pub fn remaining_length(&self) -> i64 {
+        self.data.len().saturating_sub(self.cursor) as i64
+    }
+
+    pub fn get_buffer(&self) -> *const c_void {
+        self.data.as_ptr() as *const c_void
+    }
+
+    pub fn read(&mut self, buf: &mut [u8]) -> usize {
+        let available = self.data.len().saturating_sub(self.cursor);
+        let to_read = buf.len().min(available);
+        if to_read > 0 {
+            buf[..to_read].copy_from_slice(&self.data[self.cursor..self.cursor + to_read]);
+            self.cursor += to_read;
+        }
+        to_read
+    }
+
+    pub fn seek(&mut self, offset: i64, whence: i32) -> i64 {
+        let new_pos: i64 = match whence {
+            SEEK_SET => offset,
+            SEEK_CUR => self.cursor as i64 + offset,
+            SEEK_END => self.data.len() as i64 + offset,
+            _ => return -1,
+        };
+
+        if new_pos >= 0 && (new_pos as usize) <= self.data.len() {
+            self.cursor = new_pos as usize;
+            self.cursor as i64
+        } else {
+            -1
+        }
+    }
+}

crates/molotov-core/src/assets/mod.rs

@@ -0,0 +1,3 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+pub mod asset;
+pub mod types;

crates/molotov-core/src/assets/types.rs

@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+pub const AASSET_MODE_UNKNOWN: i32 = 0;
+pub const AASSET_MODE_RANDOM: i32 = 1;
+pub const AASSET_MODE_STREAMING: i32 = 2;
+pub const AASSET_MODE_BUFFER: i32 = 3;
+
+pub const SEEK_SET: i32 = 0;
+pub const SEEK_CUR: i32 = 1;
+pub const SEEK_END: i32 = 2;

crates/molotov-core/src/lib.rs

@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
+pub mod assets;
 pub mod audio;
 pub mod dynamic;
 pub mod elf;

crates/molotov-core/tests/asset_read_test.rs

@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+use molotov_core::assets::asset::AssetFile;
+
+#[test]
+fn test_asset_read_and_seek_flow() {
+    let data = b"ROBLOX_ASSET_CONTENT_12345".to_vec();
+    let mut asset = AssetFile::new(data);
+
+    assert_eq!(asset.length(), 26);
+    assert_eq!(asset.remaining_length(), 26);
+
+    let mut buf = [0u8; 6];
+    assert_eq!(asset.read(&mut buf), 6);
+    assert_eq!(&buf, b"ROBLOX");
+    assert_eq!(asset.remaining_length(), 20);
+
+    // Seek to offset 7 (SEEK_SET = 0)
+    assert_eq!(asset.seek(7, 0), 7);
+    assert_eq!(asset.remaining_length(), 19);
+
+    let mut next_buf = [0u8; 5];
+    assert_eq!(asset.read(&mut next_buf), 5);
+    assert_eq!(&next_buf, b"ASSET");
+}