use nix to remove many uses of unsafe

db/upgrade/v1_to_v2.rs

@@ -32,7 +32,7 @@
 
 use crate::dir;
 use failure::{Error, bail, format_err};
-use libc;
+use nix::fcntl::FlockArg;
 use protobuf::prelude::MessageField;
 use rusqlite::types::ToSql;
 use crate::schema::DirMeta;
@@ -47,7 +47,7 @@ pub fn run(args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
                                         schema version 1 to 2."))?;
 
     let d = dir::Fd::open(sample_file_path, false)?;
-    d.lock(libc::LOCK_EX | libc::LOCK_NB)?;
+    d.lock(FlockArg::LockExclusiveNonblock)?;
     verify_dir_contents(sample_file_path, tx)?;
 
     // These create statements match the schema.sql when version 2 was the latest.

db/upgrade/v2_to_v3.rs

@@ -35,12 +35,11 @@
 use crate::db::{self, FromSqlUuid};
 use crate::dir;
 use failure::Error;
-use libc;
 use crate::schema;
 use protobuf::prelude::MessageField;
 use rusqlite::types::ToSql;
-use std::io::{self, Write};
-use std::mem;
+use std::io::Write;
+use std::os::unix::io::AsRawFd;
 use std::sync::Arc;
 use uuid::Uuid;
 
@@ -90,10 +89,10 @@ pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
         let id = db::CompositeId(row.get(0)?);
         let sample_file_uuid: FromSqlUuid = row.get(1)?;
         let from_path = get_uuid_pathname(sample_file_uuid.0);
-        let to_path = get_id_pathname(id);
-        let r = unsafe { dir::renameat(&d.fd, from_path.as_ptr(), &d.fd, to_path.as_ptr()) };
-        if let Err(e) = r {
-            if e.kind() == io::ErrorKind::NotFound {
+        let to_path = crate::dir::CompositeIdPath::from(id);
+        if let Err(e) = nix::fcntl::renameat(d.fd.as_raw_fd(), &from_path[..],
+                                             d.fd.as_raw_fd(), &to_path) {
+            if e == nix::Error::Sys(nix::errno::Errno::ENOENT) {
                 continue;  // assume it was already moved.
             }
             Err(e)?;
@@ -122,17 +121,9 @@ pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
 }
 
 /// Gets a pathname for a sample file suitable for passing to open or unlink.
-fn get_uuid_pathname(uuid: Uuid) -> [libc::c_char; 37] {
+fn get_uuid_pathname(uuid: Uuid) -> [u8; 37] {
     let mut buf = [0u8; 37];
     write!(&mut buf[..36], "{}", uuid.to_hyphenated_ref())
         .expect("can't format uuid to pathname buf");
-
-    // libc::c_char seems to be i8 on some platforms (Linux/arm) and u8 on others (Linux/amd64).
-    unsafe { mem::transmute::<[u8; 37], [libc::c_char; 37]>(buf) }
-}
-
-fn get_id_pathname(id: db::CompositeId) -> [libc::c_char; 17] {
-    let mut buf = [0u8; 17];
-    write!(&mut buf[..16], "{:016x}", id.0).expect("can't format id to pathname buf");
-    unsafe { mem::transmute::<[u8; 17], [libc::c_char; 17]>(buf) }
+    buf
 }

db/upgrade/v4_to_v5.rs

@@ -37,9 +37,12 @@ use crate::db::FromSqlUuid;
 use crate::{dir, schema};
 use cstr::*;
 use failure::{Error, Fail, bail};
+use nix::fcntl::{FlockArg, OFlag};
+use nix::sys::stat::Mode;
 use protobuf::{Message, prelude::MessageField};
 use rusqlite::params;
 use std::io::{Read, Write};
+use std::os::unix::io::AsRawFd;
 
 const FIXED_DIR_META_LEN: usize = 512;
 
@@ -76,10 +79,10 @@ pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
         }
 
         let dir = dir::Fd::open(path, false)?;
-        dir.lock(libc::LOCK_EX)?;
+        dir.lock(FlockArg::LockExclusiveNonblock)?;
         let tmp_path = cstr!("meta.tmp");
         let path = cstr!("meta");
-        let mut f = unsafe { dir.openat(path.as_ptr(), libc::O_RDONLY, 0) }?;
+        let mut f = dir.openat(path, OFlag::O_RDONLY, Mode::empty())?;
         let mut data = Vec::new();
         f.read_to_end(&mut data)?;
         if data.len() == FIXED_DIR_META_LEN {
@@ -92,8 +95,8 @@ pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
         if !dir::SampleFileDir::consistent(&db_meta, &dir_meta) {
             bail!("Inconsistent db_meta={:?} dir_meta={:?}", &db_meta, &dir_meta);
         }
-        let mut f = unsafe { dir.openat(tmp_path.as_ptr(),
-                                        libc::O_CREAT | libc::O_TRUNC | libc::O_WRONLY, 0o600)? };
+        let mut f = dir.openat(tmp_path, OFlag::O_CREAT | OFlag::O_TRUNC | OFlag::O_WRONLY,
+                               Mode::S_IRUSR | Mode::S_IWUSR)?;
         let mut data =
             dir_meta.write_length_delimited_to_bytes().expect("proto3->vec is infallible");
         if data.len() > FIXED_DIR_META_LEN {
@@ -103,7 +106,7 @@ pub fn run(_args: &super::Args, tx: &rusqlite::Transaction) -> Result<(), Error>
         data.resize(FIXED_DIR_META_LEN, 0);  // pad to required length.
         f.write_all(&data)?;
         f.sync_all()?;
-        unsafe { dir::renameat(&dir, tmp_path.as_ptr(), &dir, path.as_ptr())? };
+        nix::fcntl::renameat(dir.as_raw_fd(), tmp_path, dir.as_raw_fd(), path)?;
         dir.sync()?;
     }
     Ok(())