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
72impl fmt::Debug for GenericSharedMemory {
73    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
74        f.debug_tuple("GenericSharedMemory").finish()
75    }
76}
77
78impl Serialize for GenericSharedMemory {
79    fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
80        match &self.0 {
81            GenericSharedMemoryVariant::Ipc(memory) => {
82                s.serialize_newtype_variant("GenericSharedMemory", 0, "Ipc", memory)
83            },
84            GenericSharedMemoryVariant::InProcess(arc) => {
85                if opts::get().multiprocess || opts::get().force_ipc {
86                    return Err(serde::ser::Error::custom(
87                        "Arc<Vec<u8>> found in multiprocess mode!",
88                    ));
89                } // We know everything is in one address-space, so we can "serialize" the receiver by
90                // sending a leaked Arc pointer.
91                let address = Arc::into_raw(arc.clone()) as *mut Vec<u8> as usize;
92                s.serialize_newtype_variant("GenericSharedMemory", 1, "InProcess", &address)
93            },
94        }
95    }
96}
97
98struct GenericSharedMemoryVisitor {}
99
100impl<'de> serde::de::Visitor<'de> for GenericSharedMemoryVisitor {
101    type Value = GenericSharedMemory;
102
103    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
104        formatter.write_str("a GenericReceiver variant")
105    }
106
107    fn visit_enum<A>(self, data: A) -> Result<Self::Value, A::Error>
108    where
109        A: serde::de::EnumAccess<'de>,
110    {
111        #[derive(Deserialize)]
112        enum GenericSharedMemoryVariantNames {
113            Ipc,
114            InProcess,
115        }
116
117        let (variant_name, variant_data): (GenericSharedMemoryVariantNames, _) = data.variant()?;
118
119        match variant_name {
120            GenericSharedMemoryVariantNames::Ipc => variant_data
121                .newtype_variant::<IpcSharedMemory>()
122                .map(|receiver| GenericSharedMemory(GenericSharedMemoryVariant::Ipc(receiver))),
123            GenericSharedMemoryVariantNames::InProcess => {
124                if opts::get().multiprocess || servo_config::opts::get().force_ipc {
125                    return Err(serde::de::Error::custom(
126                        "Arc data found in multiprocess mode!",
127                    ));
128                }
129                let addr = variant_data.newtype_variant::<usize>()?;
130                let ptr = addr as *mut Vec<u8>;
131                // SAFETY: We know we are in the same address space as the sender, so we can safely
132                // reconstruct the Arc.
133                #[expect(unsafe_code)]
134                let arc = unsafe { Arc::from_raw(ptr) };
135                Ok(GenericSharedMemory(GenericSharedMemoryVariant::InProcess(
136                    arc,
137                )))
138            },
139        }
140    }
141}
142
143impl<'a> Deserialize<'a> for GenericSharedMemory {
144    fn deserialize<D>(d: D) -> Result<GenericSharedMemory, D::Error>
145    where
146        D: Deserializer<'a>,
147    {
148        d.deserialize_enum(
149            "GenericSharedMemory",
150            &["Ipc", "InProcess"],
151            GenericSharedMemoryVisitor {},
152        )
153    }
154}
155
156#[cfg(test)]
157mod single_process_shared_memory_test {
158    use std::sync::Arc;
159
160    use ipc_channel::ipc::IpcSharedMemory;
161
162    use super::GenericSharedMemory;
163    use crate::generic_channel::{self};
164
165    #[test]
166    fn test_ipc() {
167        let bytes = vec![0xba; 10];
168        let bytes_copy = bytes.clone();
169        let shared_memory = GenericSharedMemory(super::GenericSharedMemoryVariant::Ipc(
170            IpcSharedMemory::from_bytes(&bytes),
171        ));
172
173        let (send, recv) = generic_channel::channel().unwrap();
174        send.send(shared_memory).expect("Could not send");
175        assert_eq!(recv.recv().unwrap().to_vec(), bytes_copy);
176    }
177
178    #[test]
179    fn test_inprocess() {
180        let bytes = vec![0xba; 10];
181        let bytes_copy = bytes.clone();
182        let shared_memory = GenericSharedMemory(super::GenericSharedMemoryVariant::InProcess(
183            Arc::new(bytes.clone()),
184        ));
185
186        let (send, recv) = generic_channel::channel().unwrap();
187        send.send(shared_memory).expect("Could not send");
188        assert_eq!(recv.recv().unwrap().to_vec(), bytes_copy);
189    }
190}
base/generic_channel/shared_memory.rs

base/generic_channel/
shared_memory.rs
