virtual filesystem: MMIO-based file I/O for Kov programs in the emulator

Author: visualstudioblyat

src/emu/mod.rs

@@ -1,4 +1,5 @@
 pub mod cpu;
 pub mod memory;
+pub mod vfs;
 
 pub use cpu::Cpu;

src/emu/vfs.rs

@@ -0,0 +1,153 @@
+// virtual filesystem for the emulator
+// MMIO addresses that map to host file operations
+// this lets Kov programs read/write files when running in the emulator
+
+use std::collections::HashMap;
+
+const VFS_BASE: u32 = 0xF000_0000;
+const VFS_OPEN: u32 = VFS_BASE; // write: ptr to path → read: fd
+const VFS_READ: u32 = VFS_BASE + 4; // write: fd | read: byte (-1 = EOF)
+const VFS_WRITE: u32 = VFS_BASE + 8; // write: fd << 8 | byte
+const VFS_CLOSE: u32 = VFS_BASE + 12; // write: fd
+const VFS_READDIR: u32 = VFS_BASE + 16; // write: ptr to path → fills buffer
+const VFS_STDOUT: u32 = VFS_BASE + 20; // write: byte → prints to stdout
+const VFS_STRLEN: u32 = VFS_BASE + 24; // write: ptr → read: length
+
+pub struct VirtualFS {
+    pub files: HashMap<u32, FileState>,
+    next_fd: u32,
+    pub stdout: Vec<u8>,
+    pub last_result: u32,
+}
+
+struct FileState {
+    data: Vec<u8>,
+    pos: usize,
+}
+
+impl VirtualFS {
+    pub fn new() -> Self {
+        Self {
+            files: HashMap::new(),
+            next_fd: 3, // 0=stdin, 1=stdout, 2=stderr
+            stdout: Vec::new(),
+            last_result: 0,
+        }
+    }
+
+    pub fn is_vfs_addr(addr: u32) -> bool {
+        addr >= VFS_BASE && addr < VFS_BASE + 0x100
+    }
+
+    // preload a file into the VFS (for testing or providing input)
+    pub fn preload(&mut self, path: &str, data: Vec<u8>) -> u32 {
+        let fd = self.next_fd;
+        self.next_fd += 1;
+        self.files.insert(fd, FileState { data, pos: 0 });
+        fd
+    }
+
+    pub fn handle_write(&mut self, addr: u32, value: u32, memory: &[u8]) {
+        match addr {
+            VFS_OPEN => {
+                // value is pointer to null-terminated path in memory
+                let path = read_cstring(memory, value);
+                match std::fs::read(&path) {
+                    Ok(data) => {
+                        let fd = self.next_fd;
+                        self.next_fd += 1;
+                        self.files.insert(fd, FileState { data, pos: 0 });
+                        self.last_result = fd;
+                    }
+                    Err(_) => {
+                        self.last_result = 0; // 0 = error
+                    }
+                }
+            }
+            VFS_READ => {
+                let fd = value;
+                if let Some(file) = self.files.get_mut(&fd) {
+                    if file.pos < file.data.len() {
+                        self.last_result = file.data[file.pos] as u32;
+                        file.pos += 1;
+                    } else {
+                        self.last_result = 0xFFFF_FFFF; // EOF
+                    }
+                } else {
+                    self.last_result = 0xFFFF_FFFF;
+                }
+            }
+            VFS_WRITE => {
+                let fd = value >> 8;
+                let byte = (value & 0xFF) as u8;
+                if fd == 1 {
+                    self.stdout.push(byte);
+                }
+                // for other fds, we'd append to a write buffer
+            }
+            VFS_CLOSE => {
+                self.files.remove(&value);
+            }
+            VFS_STDOUT => {
+                self.stdout.push(value as u8);
+                if value as u8 == b'\n' {
+                    let line = String::from_utf8_lossy(&self.stdout);
+                    print!("{}", line);
+                    self.stdout.clear();
+                }
+            }
+            _ => {}
+        }
+    }
+
+    pub fn handle_read(&self, addr: u32) -> u32 {
+        match addr {
+            VFS_OPEN | VFS_READ | VFS_STRLEN => self.last_result,
+            _ => 0,
+        }
+    }
+}
+
+fn read_cstring(memory: &[u8], addr: u32) -> String {
+    let mut s = Vec::new();
+    let mut i = addr as usize;
+    while i < memory.len() && memory[i] != 0 {
+        s.push(memory[i]);
+        i += 1;
+    }
+    String::from_utf8_lossy(&s).to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn vfs_stdout() {
+        let mut vfs = VirtualFS::new();
+        vfs.handle_write(VFS_STDOUT, b'h' as u32, &[]);
+        vfs.handle_write(VFS_STDOUT, b'i' as u32, &[]);
+        assert_eq!(&vfs.stdout, b"hi");
+    }
+
+    #[test]
+    fn vfs_preload_read() {
+        let mut vfs = VirtualFS::new();
+        let fd = vfs.preload("test.txt", b"abc".to_vec());
+        vfs.handle_write(VFS_READ, fd, &[]);
+        assert_eq!(vfs.last_result, b'a' as u32);
+        vfs.handle_write(VFS_READ, fd, &[]);
+        assert_eq!(vfs.last_result, b'b' as u32);
+        vfs.handle_write(VFS_READ, fd, &[]);
+        assert_eq!(vfs.last_result, b'c' as u32);
+        vfs.handle_write(VFS_READ, fd, &[]);
+        assert_eq!(vfs.last_result, 0xFFFF_FFFF); // EOF
+    }
+
+    #[test]
+    fn vfs_addr_detection() {
+        assert!(VirtualFS::is_vfs_addr(0xF000_0000));
+        assert!(VirtualFS::is_vfs_addr(0xF000_0020));
+        assert!(!VirtualFS::is_vfs_addr(0x2000_0000));
+    }
+}

tools/kovdocs/target/release/.fingerprint/kovdocs-f8a7353ebc002695/dep-bin-kovdocs

@@ -1,5 +1,10 @@
-C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\target\release\deps\kovdocs.d: src\main.rs
+C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\target\release\deps\kovdocs.d: src\main.rs src\config.rs src\highlight.rs src\markdown.rs src\style.css src\app.js
 
-C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\target\release\deps\kovdocs.exe: src\main.rs
+C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\target\release\deps\kovdocs.exe: src\main.rs src\config.rs src\highlight.rs src\markdown.rs src\style.css src\app.js
 
 src\main.rs:
+src\config.rs:
+src\highlight.rs:
+src\markdown.rs:
+src\style.css:
+src\app.js:

tools/kovdocs/target/release/deps/kovdocs.d

@@ -1 +1 @@
-C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\target\release\kovdocs.exe: C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\src\main.rs
+C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\target\release\kovdocs.exe: C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\src\app.js C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\src\config.rs C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\src\highlight.rs C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\src\main.rs C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\src\markdown.rs C:\Users\akrec\Desktop\kov-lang\tools\kovdocs\src\style.css