servo_base/generic_channel/
shared_memory.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5use std::fmt;
6use std::ops::Deref;
7use std::sync::Arc;
8
9use ipc_channel::ipc::IpcSharedMemory;
10use malloc_size_of::MallocSizeOf;
11use serde::de::VariantAccess;
12use serde::{Deserialize, Deserializer, Serialize, Serializer};
13use servo_config::opts;
14
15#[derive(Clone)]
16pub struct GenericSharedMemory(GenericSharedMemoryVariant);
17
18#[derive(Clone)]
19enum GenericSharedMemoryVariant {
20    Ipc(IpcSharedMemory),
21    InProcess(Arc<Vec<u8>>),
22}
23
24impl Deref for GenericSharedMemory {
25    type Target = [u8];
26
27    #[inline]
28    fn deref(&self) -> &[u8] {
29        match &self.0 {
30            GenericSharedMemoryVariant::Ipc(ipc_shared_memory) => ipc_shared_memory,
31            GenericSharedMemoryVariant::InProcess(items) => items.as_slice(),
32        }
33    }
34}
35
36impl MallocSizeOf for GenericSharedMemory {
37    fn size_of(&self, ops: &mut malloc_size_of::MallocSizeOfOps) -> usize {
38        match &self.0 {
39            GenericSharedMemoryVariant::Ipc(_) => 0,
40            GenericSharedMemoryVariant::InProcess(items) => items.size_of(ops),
41        }
42    }
43}
44
45impl GenericSharedMemory {
46    pub fn from_bytes(bytes: &[u8]) -> Self {
47        if servo_config::opts::get().multiprocess || servo_config::opts::get().force_ipc {
48            GenericSharedMemory(GenericSharedMemoryVariant::Ipc(
49                IpcSharedMemory::from_bytes(bytes),
50            ))
51        } else {
52            GenericSharedMemory(GenericSharedMemoryVariant::InProcess(Arc::new(
53                bytes.to_owned(),
54            )))
55        }
56    }
57
58    pub fn from_byte(data: u8, length: usize) -> Self {
59        if servo_config::opts::get().multiprocess || servo_config::opts::get().force_ipc {
60            GenericSharedMemory(GenericSharedMemoryVariant::Ipc(IpcSharedMemory::from_byte(
61                data, length,
62            )))
63        } else {
64            GenericSharedMemory(GenericSharedMemoryVariant::InProcess(Arc::new(vec![
65                data;
66                length
67            ])))
68        }
69    }
70
71    /// Free operation in single process mode.
72    /// If multiple `GenericSharedmemory` point to the same value this is safe to use and only effects the value currently hold.
73    pub fn into_arc_vec(self) -> Arc<Vec<u8>> {
74        match self.0 {
75            GenericSharedMemoryVariant::Ipc(ipc_shared_memory) => {
76                Arc::new(ipc_shared_memory.to_vec())
77            },
78            GenericSharedMemoryVariant::InProcess(arc) => arc,
79        }
80    }
81}
82
83impl fmt::Debug for GenericSharedMemory {
84    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
85        f.debug_tuple("GenericSharedMemory").finish()
86    }
87}
88
89impl Serialize for GenericSharedMemory {
90    fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
91        match &self.0 {
92            GenericSharedMemoryVariant::Ipc(memory) => {
93                s.serialize_newtype_variant("GenericSharedMemory", 0, "Ipc", memory)
94            },
95            GenericSharedMemoryVariant::InProcess(arc) => {
96                if opts::get().multiprocess || opts::get().force_ipc {
97                    return Err(serde::ser::Error::custom(
98                        "Arc<Vec<u8>> found in multiprocess mode!",
99                    ));
100                } // We know everything is in one address-space, so we can "serialize" the receiver by
101                // sending a leaked Arc pointer.
102                let address = Arc::into_raw(arc.clone()) as *mut Vec<u8> as usize;
103                s.serialize_newtype_variant("GenericSharedMemory", 1, "InProcess", &address)
104            },
105        }
106    }
107}
108
109struct GenericSharedMemoryVisitor {}
110
111impl<'de> serde::de::Visitor<'de> for GenericSharedMemoryVisitor {
112    type Value = GenericSharedMemory;
113
114    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
115        formatter.write_str("a GenericReceiver variant")
116    }
117
118    fn visit_enum<A>(self, data: A) -> Result<Self::Value, A::Error>
119    where
120        A: serde::de::EnumAccess<'de>,
121    {
122        #[derive(Deserialize)]
123        enum GenericSharedMemoryVariantNames {
124            Ipc,
125            InProcess,
126        }
127
128        let (variant_name, variant_data): (GenericSharedMemoryVariantNames, _) = data.variant()?;
129
130        match variant_name {
131            GenericSharedMemoryVariantNames::Ipc => variant_data
132                .newtype_variant::<IpcSharedMemory>()
133                .map(|receiver| GenericSharedMemory(GenericSharedMemoryVariant::Ipc(receiver))),
134            GenericSharedMemoryVariantNames::InProcess => {
135                if opts::get().multiprocess || servo_config::opts::get().force_ipc {
136                    return Err(serde::de::Error::custom(
137                        "Arc data found in multiprocess mode!",
138                    ));
139                }
140                let addr = variant_data.newtype_variant::<usize>()?;
141                let ptr = addr as *mut Vec<u8>;
142                // SAFETY: We know we are in the same address space as the sender, so we can safely
143                // reconstruct the Arc.
144                #[expect(unsafe_code)]
145                let arc = unsafe { Arc::from_raw(ptr) };
146                Ok(GenericSharedMemory(GenericSharedMemoryVariant::InProcess(
147                    arc,
148                )))
149            },
150        }
151    }
152}
153
154impl<'a> Deserialize<'a> for GenericSharedMemory {
155    fn deserialize<D>(d: D) -> Result<GenericSharedMemory, D::Error>
156    where
157        D: Deserializer<'a>,
158    {
159        d.deserialize_enum(
160            "GenericSharedMemory",
161            &["Ipc", "InProcess"],
162            GenericSharedMemoryVisitor {},
163        )
164    }
165}
166
167#[cfg(test)]
168mod single_process_shared_memory_test {
169    use std::sync::Arc;
170
171    use ipc_channel::ipc::IpcSharedMemory;
172
173    use super::GenericSharedMemory;
174    use crate::generic_channel::{self};
175
176    #[test]
177    fn test_ipc() {
178        let bytes = vec![0xba; 10];
179        let bytes_copy = bytes.clone();
180        let shared_memory = GenericSharedMemory(super::GenericSharedMemoryVariant::Ipc(
181            IpcSharedMemory::from_bytes(&bytes),
182        ));
183
184        let (send, recv) = generic_channel::channel().unwrap();
185        send.send(shared_memory).expect("Could not send");
186        assert_eq!(recv.recv().unwrap().to_vec(), bytes_copy);
187    }
188
189    #[test]
190    fn test_inprocess() {
191        let bytes = vec![0xba; 10];
192        let bytes_copy = bytes.clone();
193        let shared_memory = GenericSharedMemory(super::GenericSharedMemoryVariant::InProcess(
194            Arc::new(bytes.clone()),
195        ));
196
197        let (send, recv) = generic_channel::channel().unwrap();
198        send.send(shared_memory).expect("Could not send");
199        assert_eq!(recv.recv().unwrap().to_vec(), bytes_copy);
200    }
201}
servo_base/generic_channel/shared_memory.rs

servo_base/generic_channel/
shared_memory.rs
