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Virtual file support (#701)

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* Add support for virtual files (eg, not backed by an OS file).

Virtual files are implemented through trait objects, with a default
implementation that tries to behave like on-disk files, but entirely
backed by in-memory structures.

Co-authored-by: Dan Gohman <sunfish@mozilla.com>
This commit is contained in:
iximeow
2020-03-06 11:08:13 -08:00
committed by GitHub
parent 7f7196a655
commit 7e0d9decbf
19 changed files with 1568 additions and 188 deletions
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44
crates/test-programs/tests/wasm_tests/runtime.rs
View File

@@ -1,30 +1,44 @@
use anyhow::{bail, Context};
use std::fs::File;
use std::path::Path;
use wasi_common::VirtualDirEntry;
use wasmtime::{Instance, Module, Store};
pub fn instantiate(data: &[u8], bin_name: &str, workspace: Option<&Path>) -> anyhow::Result<()> {
#[derive(Clone, Copy, Debug)]
pub enum PreopenType {
/// Preopens should be satisfied with real OS files.
OS,
/// Preopens should be satisfied with virtual files.
Virtual,
}
pub fn instantiate(
data: &[u8],
bin_name: &str,
workspace: Option<&Path>,
preopen_type: PreopenType,
) -> anyhow::Result<()> {
let store = Store::default();
let get_preopens = |workspace: Option<&Path>| -> anyhow::Result<Vec<_>> {
if let Some(workspace) = workspace {
let preopen_dir = wasi_common::preopen_dir(workspace)
.context(format!("error while preopening {:?}", workspace))?;
Ok(vec![(".".to_owned(), preopen_dir)])
} else {
Ok(vec![])
}
};
// Create our wasi context with pretty standard arguments/inheritance/etc.
// Additionally register andy preopened directories if we have them.
// Additionally register any preopened directories if we have them.
let mut builder = wasi_common::WasiCtxBuilder::new();
builder.arg(bin_name).arg(".").inherit_stdio();
for (dir, file) in get_preopens(workspace)? {
builder.preopened_dir(file, dir);
if let Some(workspace) = workspace {
match preopen_type {
PreopenType::OS => {
let preopen_dir = wasi_common::preopen_dir(workspace)
.context(format!("error while preopening {:?}", workspace))?;
builder.preopened_dir(preopen_dir, ".");
}
PreopenType::Virtual => {
// we can ignore the workspace path for virtual preopens because virtual preopens
// don't exist in the filesystem anyway - no name conflict concerns.
builder.preopened_virt(VirtualDirEntry::empty_directory(), ".");
}
}
}
// The nonstandard thing we do with `WasiCtxBuilder` is to ensure that