Fall back to reading instead of mmap on windows

Windows doesn't have support for mmap (at least not with the same apis)

Author: Colecf

src/file_pool.rs

@@ -1,83 +1,127 @@
 use anyhow::bail;
 use core::slice;
-use libc::{
-    c_void, mmap, munmap, sysconf, MAP_ANONYMOUS, MAP_FAILED, MAP_FIXED, MAP_PRIVATE, PROT_READ,
-    PROT_WRITE, _SC_PAGESIZE,
-};
-use std::{
-    os::fd::{AsFd, AsRawFd},
-    path::Path,
-    ptr::null_mut,
-    sync::Mutex,
-};
+use std::{path::Path, sync::Mutex};
 
-/// FilePool is a datastructure that is intended to hold onto byte buffers and give out immutable
-/// references to them. But it can also accept new byte buffers while old ones are still lent out.
-/// This requires interior mutability / unsafe code. Appending to a Vec while references to other
-/// elements are held is generally unsafe, because the Vec can reallocate all the prior elements
-/// to a new memory location. But if the elements themselves are pointers to stable memory, the
-/// contents of those pointers can be referenced safely. This also requires guarding the outer
-/// Vec with a Mutex so that two threads don't append to it at the same time.
-pub struct FilePool {
-    files: Mutex<Vec<(*mut c_void, usize)>>,
-}
-impl FilePool {
-    pub fn new() -> FilePool {
-        FilePool {
-            files: Mutex::new(Vec::new()),
-        }
+#[cfg(unix)]
+mod mmap {
+    use super::*;
+    use libc::{
+        c_void, mmap, munmap, sysconf, MAP_ANONYMOUS, MAP_FAILED, MAP_FIXED, MAP_PRIVATE,
+        PROT_READ, PROT_WRITE, _SC_PAGESIZE,
+    };
+    use std::{
+        os::fd::{AsFd, AsRawFd},
+        ptr::null_mut,
+    };
+    /// FilePool is a datastructure that is intended to hold onto byte buffers and give out immutable
+    /// references to them. But it can also accept new byte buffers while old ones are still lent out.
+    /// This requires interior mutability / unsafe code. Appending to a Vec while references to other
+    /// elements are held is generally unsafe, because the Vec can reallocate all the prior elements
+    /// to a new memory location. But if the elements themselves are pointers to stable memory, the
+    /// contents of those pointers can be referenced safely. This also requires guarding the outer
+    /// Vec with a Mutex so that two threads don't append to it at the same time.
+    pub struct FilePool {
+        files: Mutex<Vec<(*mut c_void, usize)>>,
     }
-
-    pub fn read_file(&self, path: &Path) -> anyhow::Result<&[u8]> {
-        let page_size = unsafe { sysconf(_SC_PAGESIZE) } as usize;
-        let file = std::fs::File::open(path)?;
-        let fd = file.as_fd().as_raw_fd();
-        let file_size = file.metadata()?.len() as usize;
-        let mapping_size = (file_size + page_size).next_multiple_of(page_size);
-        unsafe {
-            // size + 1 to add a null terminator.
-            let addr = mmap(null_mut(), mapping_size, PROT_READ, MAP_PRIVATE, fd, 0);
-            if addr == MAP_FAILED {
-                bail!("mmap failed");
+    impl FilePool {
+        pub fn new() -> FilePool {
+            FilePool {
+                files: Mutex::new(Vec::new()),
             }
+        }
+
+        pub fn read_file(&self, path: &Path) -> anyhow::Result<&[u8]> {
+            let page_size = unsafe { sysconf(_SC_PAGESIZE) } as usize;
+            let file = std::fs::File::open(path)?;
+            let fd = file.as_fd().as_raw_fd();
+            let file_size = file.metadata()?.len() as usize;
+            let mapping_size = (file_size + page_size).next_multiple_of(page_size);
+            unsafe {
+                // size + 1 to add a null terminator.
+                let addr = mmap(null_mut(), mapping_size, PROT_READ, MAP_PRIVATE, fd, 0);
+                if addr == MAP_FAILED {
+                    bail!("mmap failed");
+                }
+
+                let addr2 = mmap(
+                    addr.add(mapping_size).sub(page_size),
+                    page_size,
+                    PROT_READ | PROT_WRITE,
+                    MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
+                    -1,
+                    0,
+                );
+                if addr2 == MAP_FAILED {
+                    bail!("mmap failed");
+                }
+                *(addr.add(mapping_size).sub(page_size) as *mut u8) = 0;
+                // The manpages say the extra bytes past the end of the file are
+                // zero-filled, but just to make sure:
+                assert!(*(addr.add(file_size) as *mut u8) == 0);
+
+                let files = &mut self.files.lock().unwrap();
+                files.push((addr, mapping_size));
 
-            let addr2 = mmap(
-                addr.add(mapping_size).sub(page_size),
-                page_size,
-                PROT_READ | PROT_WRITE,
-                MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
-                -1,
-                0,
-            );
-            if addr2 == MAP_FAILED {
-                bail!("mmap failed");
+                Ok(slice::from_raw_parts(addr as *mut u8, file_size + 1))
             }
-            *(addr.add(mapping_size).sub(page_size) as *mut u8) = 0;
-            // The manpages say the extra bytes past the end of the file are
-            // zero-filled, but just to make sure:
-            assert!(*(addr.add(file_size) as *mut u8) == 0);
+        }
+    }
 
-            let files = &mut self.files.lock().unwrap();
-            files.push((addr, mapping_size));
+    // SAFETY: Sync isn't implemented automatically because we have a *mut pointer,
+    // but that pointer isn't used at all aside from the drop implementation, so
+    // we won't have data races.
+    unsafe impl Sync for FilePool {}
+    unsafe impl Send for FilePool {}
 
-            Ok(slice::from_raw_parts(addr as *mut u8, file_size + 1))
+    impl Drop for FilePool {
+        fn drop(&mut self) {
+            let files = self.files.lock().unwrap();
+            for &(addr, len) in files.iter() {
+                unsafe {
+                    munmap(addr, len);
+                }
+            }
         }
     }
 }
 
-// SAFETY: Sync isn't implemented automatically because we have a *mut pointer,
-// but that pointer isn't used at all aside from the drop implementation, so
-// we won't have data races.
-unsafe impl Sync for FilePool {}
-unsafe impl Send for FilePool {}
+#[cfg(not(unix))]
+mod read {
+    use crate::scanner::read_file_with_nul;
 
-impl Drop for FilePool {
-    fn drop(&mut self) {
-        let files = self.files.lock().unwrap();
-        for &(addr, len) in files.iter() {
-            unsafe {
-                munmap(addr, len);
+    use super::*;
+
+    /// FilePool is a datastructure that is intended to hold onto byte buffers and give out immutable
+    /// references to them. But it can also accept new byte buffers while old ones are still lent out.
+    /// This requires interior mutability / unsafe code. Appending to a Vec while references to other
+    /// elements are held is generally unsafe, because the Vec can reallocate all the prior elements
+    /// to a new memory location. But if the elements themselves are unchanging Vecs, the
+    /// contents of those Vecs can be referenced safely. This also requires guarding the outer
+    /// Vec with a Mutex so that two threads don't append to it at the same time.
+    pub struct FilePool {
+        files: Mutex<Vec<Vec<u8>>>,
+    }
+
+    impl FilePool {
+        pub fn new() -> FilePool {
+            FilePool {
+                files: Mutex::new(Vec::new()),
             }
         }
+
+        pub fn read_file(&self, path: &Path) -> anyhow::Result<&[u8]> {
+            let bytes = read_file_with_nul(path)?;
+            let addr = bytes.as_ptr();
+            let len = bytes.len();
+            self.files.lock().unwrap().push(bytes);
+
+            unsafe { Ok(slice::from_raw_parts(addr as *mut u8, len)) }
+        }
     }
 }
+
+#[cfg(unix)]
+pub use mmap::FilePool;
+
+#[cfg(not(unix))]
+pub use read::FilePool;