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    pub fn from_bytes_with_mutator(bytes: &[u8], mutator: impl FnOnce(&mut [u8])) -> Self {
83        let mut shared_memory = Self::from_bytes(bytes);
84        match &mut shared_memory.0 {
85            GenericSharedMemoryVariant::Ipc(ipc_shared_memory) => {
86                #[expect(unsafe_code)]
87                unsafe {
88                    mutator(ipc_shared_memory.deref_mut())
89                }
90            },
91            GenericSharedMemoryVariant::InProcess(arc) => mutator(
92                Arc::get_mut(arc)
93                    .expect("Arc just created from bytes")
94                    .as_mut_slice(),
95            ),
96        }
97        shared_memory
98    }
99}
100
101impl fmt::Debug for GenericSharedMemory {
102    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
103        f.debug_tuple("GenericSharedMemory").finish()
104    }
105}
106
107impl Serialize for GenericSharedMemory {
108    fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
109        match &self.0 {
110            GenericSharedMemoryVariant::Ipc(memory) => {
111                s.serialize_newtype_variant("GenericSharedMemory", 0, "Ipc", memory)
112            },
113            GenericSharedMemoryVariant::InProcess(arc) => {
114                if opts::get().multiprocess || opts::get().force_ipc {
115                    return Err(serde::ser::Error::custom(
116                        "Arc<Vec<u8>> found in multiprocess mode!",
117                    ));
118                } // We know everything is in one address-space, so we can "serialize" the receiver by
119                // sending a leaked Arc pointer.
120                let address = Arc::into_raw(arc.clone()) as *mut Vec<u8> as usize;
121                s.serialize_newtype_variant("GenericSharedMemory", 1, "InProcess", &address)
122            },
123        }
124    }
125}
126
127struct GenericSharedMemoryVisitor {}
128
129impl<'de> serde::de::Visitor<'de> for GenericSharedMemoryVisitor {
130    type Value = GenericSharedMemory;
131
132    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
133        formatter.write_str("a GenericReceiver variant")
134    }
135
136    fn visit_enum<A>(self, data: A) -> Result<Self::Value, A::Error>
137    where
138        A: serde::de::EnumAccess<'de>,
139    {
140        #[derive(Deserialize)]
141        enum GenericSharedMemoryVariantNames {
142            Ipc,
143            InProcess,
144        }
145
146        let (variant_name, variant_data): (GenericSharedMemoryVariantNames, _) = data.variant()?;
147
148        match variant_name {
149            GenericSharedMemoryVariantNames::Ipc => variant_data
150                .newtype_variant::<IpcSharedMemory>()
151                .map(|receiver| GenericSharedMemory(GenericSharedMemoryVariant::Ipc(receiver))),
152            GenericSharedMemoryVariantNames::InProcess => {
153                if opts::get().multiprocess || servo_config::opts::get().force_ipc {
154                    return Err(serde::de::Error::custom(
155                        "Arc data found in multiprocess mode!",
156                    ));
157                }
158                let addr = variant_data.newtype_variant::<usize>()?;
159                let ptr = addr as *mut Vec<u8>;
160                // SAFETY: We know we are in the same address space as the sender, so we can safely
161                // reconstruct the Arc.
162                #[expect(unsafe_code)]
163                let arc = unsafe { Arc::from_raw(ptr) };
164                Ok(GenericSharedMemory(GenericSharedMemoryVariant::InProcess(
165                    arc,
166                )))
167            },
168        }
169    }
170}
171
172impl<'a> Deserialize<'a> for GenericSharedMemory {
173    fn deserialize<D>(d: D) -> Result<GenericSharedMemory, D::Error>
174    where
175        D: Deserializer<'a>,
176    {
177        d.deserialize_enum(
178            "GenericSharedMemory",
179            &["Ipc", "InProcess"],
180            GenericSharedMemoryVisitor {},
181        )
182    }
183}
184
185#[cfg(test)]
186mod single_process_shared_memory_test {
187    use std::sync::Arc;
188
189    use ipc_channel::ipc::IpcSharedMemory;
190
191    use super::GenericSharedMemory;
192    use crate::generic_channel::{self};
193
194    #[test]
195    fn test_ipc() {
196        let bytes = vec![0xba; 10];
197        let bytes_copy = bytes.clone();
198        let shared_memory = GenericSharedMemory(super::GenericSharedMemoryVariant::Ipc(
199            IpcSharedMemory::from_bytes(&bytes),
200        ));
201
202        let (send, recv) = generic_channel::channel().unwrap();
203        send.send(shared_memory).expect("Could not send");
204        assert_eq!(recv.recv().unwrap().to_vec(), bytes_copy);
205    }
206
207    #[test]
208    fn test_inprocess() {
209        let bytes = vec![0xba; 10];
210        let bytes_copy = bytes.clone();
211        let shared_memory = GenericSharedMemory(super::GenericSharedMemoryVariant::InProcess(
212            Arc::new(bytes.clone()),
213        ));
214
215        let (send, recv) = generic_channel::channel().unwrap();
216        send.send(shared_memory).expect("Could not send");
217        assert_eq!(recv.recv().unwrap().to_vec(), bytes_copy);
218    }
219}
servo_base/generic_channel/shared_memory.rs

servo_base/generic_channel/
shared_memory.rs
