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Add support for read-only mapping #100

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Add support for read-only mapping #100

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34 changes: 30 additions & 4 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -44,16 +44,32 @@ cfg_if! {
}
}

#[derive(Clone, Default)]
#[derive(Clone)]
/// Struct used to configure different parameters before creating a shared memory mapping
pub struct ShmemConf {
owner: bool,
writable: bool,
os_id: Option<String>,
overwrite_flink: bool,
flink_path: Option<PathBuf>,
size: usize,
ext: os_impl::ShmemConfExt,
}

impl Default for ShmemConf {
fn default() -> Self {
Self {
owner: false,
writable: true,
os_id: None,
overwrite_flink: false,
flink_path: None,
size: Default::default(),
ext: Default::default(),
}
}
}

impl Drop for ShmemConf {
fn drop(&mut self) {
// Delete the flink if we are the owner of the mapping
Expand Down Expand Up @@ -100,6 +116,14 @@ impl ShmemConf {
self
}

/// Specifies whether the region should be writable by this process.
///
/// Enabled by default.
pub fn writable(mut self, writable: bool) -> Self {
self.writable = writable;
self
}

/// Create a new mapping using the current configuration
pub fn create(mut self) -> Result<Shmem, ShmemError> {
if self.size == 0 {
Expand All @@ -118,7 +142,7 @@ impl ShmemConf {
// Generate random ID until one works
loop {
let cur_id = format!("/shmem_{:X}", rand::random::<u64>());
match os_impl::create_mapping(&cur_id, self.size) {
match os_impl::create_mapping(&cur_id, self.size, self.writable) {
Err(ShmemError::MappingIdExists) => continue,
Ok(m) => break m,
Err(e) => {
Expand All @@ -127,7 +151,9 @@ impl ShmemConf {
};
}
}
Some(ref specific_id) => os_impl::create_mapping(specific_id, self.size)?,
Some(ref specific_id) => {
os_impl::create_mapping(specific_id, self.size, self.writable)?
}
};
debug!("Created shared memory mapping '{}'", mapping.unique_id);

Expand Down Expand Up @@ -204,7 +230,7 @@ impl ShmemConf {
flink_uid.as_str()
};

match os_impl::open_mapping(unique_id, self.size, &self.ext) {
match os_impl::open_mapping(unique_id, self.size, &self.ext, self.writable) {
Ok(m) => {
self.size = m.map_size;
self.owner = false;
Expand Down
45 changes: 30 additions & 15 deletions src/unix.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -81,7 +81,11 @@ impl MapData {
}

/// Creates a mapping specified by the uid and size
pub fn create_mapping(unique_id: &str, map_size: usize) -> Result<MapData, ShmemError> {
pub fn create_mapping(
unique_id: &str,
map_size: usize,
writable: bool,
) -> Result<MapData, ShmemError> {
//Create shared memory file descriptor
debug!("Creating persistent mapping at {}", unique_id);

Expand Down Expand Up @@ -124,21 +128,26 @@ pub fn create_mapping(unique_id: &str, map_size: usize) -> Result<MapData, Shmem

//Put the mapping in our address space
debug!("Loading mapping into address space");
let access = if writable {
ProtFlags::PROT_READ | ProtFlags::PROT_WRITE
} else {
ProtFlags::PROT_READ
};
new_map.map_ptr = match unsafe {
mmap(
None, //Desired addr
nz_map_size, //size of mapping
ProtFlags::PROT_READ | ProtFlags::PROT_WRITE, //Permissions on pages
MapFlags::MAP_SHARED, //What kind of mapping
new_map.map_fd, //fd
0, //Offset into fd
None, //Desired addr
nz_map_size, //size of mapping
access, //Permissions on pages
MapFlags::MAP_SHARED, //What kind of mapping
new_map.map_fd, //fd
0, //Offset into fd
)
} {
Ok(v) => {
trace!(
"mmap(NULL, {}, {:X}, {:X}, {}, 0) == {:p}",
new_map.map_size,
ProtFlags::PROT_READ | ProtFlags::PROT_WRITE,
access,
MapFlags::MAP_SHARED,
new_map.map_fd,
v
Expand All @@ -156,6 +165,7 @@ pub fn open_mapping(
unique_id: &str,
_map_size: usize,
_ext: &ShmemConfExt,
writable: bool,
) -> Result<MapData, ShmemError> {
//Open shared memory
debug!("Openning persistent mapping at {}", unique_id);
Expand Down Expand Up @@ -195,21 +205,26 @@ pub fn open_mapping(

//Map memory into our address space
debug!("Loading mapping into address space");
let access = if writable {
ProtFlags::PROT_READ | ProtFlags::PROT_WRITE
} else {
ProtFlags::PROT_READ
};
new_map.map_ptr = match unsafe {
mmap(
None, //Desired addr
nz_map_size, //size of mapping
ProtFlags::PROT_READ | ProtFlags::PROT_WRITE, //Permissions on pages
MapFlags::MAP_SHARED, //What kind of mapping
new_map.map_fd, //fd
0, //Offset into fd
None, //Desired addr
nz_map_size, //size of mapping
access, //Permissions on pages
MapFlags::MAP_SHARED, //What kind of mapping
new_map.map_fd, //fd
0, //Offset into fd
)
} {
Ok(v) => {
trace!(
"mmap(NULL, {}, {:X}, {:X}, {}, 0) == {:p}",
new_map.map_size,
ProtFlags::PROT_READ | ProtFlags::PROT_WRITE,
access,
MapFlags::MAP_SHARED,
new_map.map_fd,
v
Expand Down
25 changes: 16 additions & 9 deletions src/windows.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,7 @@ fn new_map(
mut map_size: usize,
create: bool,
allow_raw: bool,
writable: bool,
) -> Result<MapData, ShmemError> {
// Create file to back the shared memory
let mut file_path = get_tmp_dir()?;
Expand Down Expand Up @@ -230,12 +231,13 @@ fn new_map(

//Map mapping into address space
debug!("Loading mapping into address space");
trace!(
"MapViewOfFile(0x{:X}, {:X}, 0, 0, 0)",
map_h,
(FILE_MAP_READ | FILE_MAP_WRITE).0,
);
let map_ptr = match MapViewOfFile(map_h.as_handle(), FILE_MAP_READ | FILE_MAP_WRITE, 0, 0, 0) {
let access = if writable {
FILE_MAP_READ | FILE_MAP_WRITE
} else {
FILE_MAP_READ
};
trace!("MapViewOfFile(0x{:X}, {:X}, 0, 0, 0)", map_h, access.0,);
let map_ptr = match MapViewOfFile(map_h.as_handle(), access, 0, 0, 0) {
Ok(v) => v,
Err(e) => {
return Err(if create {
Expand Down Expand Up @@ -267,15 +269,20 @@ fn new_map(
}

//Creates a mapping specified by the uid and size
pub fn create_mapping(unique_id: &str, map_size: usize) -> Result<MapData, ShmemError> {
new_map(unique_id, map_size, true, false)
pub fn create_mapping(
unique_id: &str,
map_size: usize,
writable: bool,
) -> Result<MapData, ShmemError> {
new_map(unique_id, map_size, true, false, writable)
}

//Opens an existing mapping specified by its uid
pub fn open_mapping(
unique_id: &str,
map_size: usize,
ext: &ShmemConfExt,
writable: bool,
) -> Result<MapData, ShmemError> {
new_map(unique_id, map_size, false, ext.allow_raw)
new_map(unique_id, map_size, false, ext.allow_raw, writable)
}