filesystem example (#2236)

Cargo.lock

@@ -813,6 +813,10 @@ dependencies = [
 name = "example-fib-debug-wasm"
 version = "0.0.0"
 
+[[package]]
+name = "example-wasi-fs-wasm"
+version = "0.0.0"
+
 [[package]]
 name = "example-wasi-wasm"
 version = "0.0.0"

Cargo.toml

@@ -70,6 +70,7 @@ members = [
   "crates/wiggle/wasmtime",
   "examples/fib-debug/wasm",
   "examples/wasi/wasm",
+  "examples/wasi-fs/wasm",
   "fuzz",
 ]
 

crates/wasi-common/src/virtfs.rs

@@ -127,16 +127,20 @@ impl FileContents for VecFileContents {
     }
 }
 
-struct VecFileContents {
+pub struct VecFileContents {
     content: Vec<u8>,
 }
 
 impl VecFileContents {
-    fn new() -> Self {
+    pub fn new() -> Self {
         Self {
             content: Vec::new(),
         }
     }
+
+    pub fn with_content(content: Vec<u8>) -> Self {
+        Self { content }
+    }
 }
 
 /// An `InMemoryFile` is a shared handle to some underlying data. The relationship is analagous to

crates/wasi/src/lib.rs

@@ -2,6 +2,7 @@ use wasmtime::Trap;
 
 pub mod old;
 
+pub use wasi_common::virtfs;
 pub use wasi_common::{WasiCtx, WasiCtxBuilder};
 
 // Defines a `struct Wasi` with member fields and appropriate APIs for dealing

docs/examples-rust-wasi-fs.md

@@ -0,0 +1,21 @@
+# WASI
+
+You can also [browse this source code online][code] and clone the wasmtime
+repository to run the example locally.
+
+[code]: https://github.com/bytecodealliance/wasmtime/blob/main/examples/wasi/main.rs
+
+This example shows off how to run a wasi binary with a memory filesystem.
+
+## Wasm Source code
+
+```rust,ignore
+{{#include ../examples/wasi-fs/wasm/wasi-fs.rs}}
+```
+
+
+## `wasi-fs.rs`
+
+```rust,ignore
+{{#include ../examples/wasi-fs/main.rs}}
+```

examples/externref.c

@@ -3,7 +3,7 @@ Example of using `externref` values.
 
 You can compile and run this example on Linux with:
 
-   cargo build --release -p wasmtime
+   cargo build --release -p wasmtime-c-api
    cc examples/externref.c \
        -I crates/c-api/include \
        -I crates/c-api/wasm-c-api/include \

examples/gcd.c

@@ -4,7 +4,7 @@ function.
 
 You can compile and run this example on Linux with:
 
-   cargo build --release -p wasmtime
+   cargo build --release -p wasmtime-c-api
    cc examples/gcd.c \
        -I crates/c-api/include \
        -I crates/c-api/wasm-c-api/include \

examples/hello.c

@@ -4,7 +4,7 @@ function.
 
 You can compile and run this example on Linux with:
 
-   cargo build --release -p wasmtime
+   cargo build --release -p wasmtime-c-api
    cc examples/hello.c \
        -I crates/c-api/include \
        -I crates/c-api/wasm-c-api/include \

examples/hello.cc

@@ -4,7 +4,7 @@ function.
 
 You can compile and run this example on Linux with:
 
-   cargo build --release -p wasmtime
+   cargo build --release -p wasmtime-c-api
    cc examples/hello.cc \
        -I crates/c-api/include \
        -I crates/c-api/wasm-c-api/include \

examples/interrupt.c

@@ -4,7 +4,7 @@ function.
 
 You can compile and run this example on Linux with:
 
-   cargo build --release -p wasmtime
+   cargo build --release -p wasmtime-c-api
    cc examples/interrupt.c \
        -I crates/c-api/include \
        -I crates/c-api/wasm-c-api/include \

examples/linking.c

@@ -4,7 +4,7 @@ together.
 
 You can compile and run this example on Linux with:
 
-   cargo build --release -p wasmtime
+   cargo build --release -p wasmtime-c-api
    cc examples/linking.c \
        -I crates/c-api/include \
        -I crates/c-api/wasm-c-api/include \

examples/memory.c

@@ -4,7 +4,7 @@ function.
 
 You can compile and run this example on Linux with:
 
-   cargo build --release -p wasmtime
+   cargo build --release -p wasmtime-c-api
    cc examples/memory.c \
        -I crates/c-api/include \
        -I crates/c-api/wasm-c-api/include \

examples/multi.c

@@ -4,7 +4,7 @@ function.
 
 You can compile and run this example on Linux with:
 
-   cargo build --release -p wasmtime
+   cargo build --release -p wasmtime-c-api
    cc examples/multi.c \
        -I crates/c-api/include \
        -I crates/c-api/wasm-c-api/include \

examples/serialize.c

@@ -4,7 +4,7 @@ function.
 
 You can compile and run this example on Linux with:
 
-   cargo build --release -p wasmtime
+   cargo build --release -p wasmtime-c-api
    cc examples/hello.c \
        -I crates/c-api/include \
        -I crates/c-api/wasm-c-api/include \

examples/wasi-fs/main.c

@@ -0,0 +1,119 @@
+/*
+Example of instantiating a WebAssembly which uses WASI imports.
+
+You can compile and run this example on Linux with:
+
+   cargo build --release -p wasmtime-c-api
+   cc examples/wasi-fs/main.c \
+       -I crates/c-api/include \
+       -I crates/c-api/wasm-c-api/include \
+       target/release/libwasmtime.a \
+       -lpthread -ldl -lm \
+       -o wasi-fs
+   ./wasi-fs
+
+Note that on Windows and macOS the command will be similar, but you'll need
+to tweak the `-lpthread` and such annotations.
+*/
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <wasm.h>
+#include <wasi.h>
+#include <wasmtime.h>
+
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+
+static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap);
+
+int main() {
+  int ret = 0;
+  // Set up our context
+  wasm_engine_t *engine = wasm_engine_new();
+  assert(engine != NULL);
+  wasm_store_t *store = wasm_store_new(engine);
+  assert(store != NULL);
+
+  wasm_byte_vec_t wasm;
+  // Load our input file to parse it next
+  FILE* file = fopen("target/wasm32-wasi/debug/wasi-fs.wasm", "rb");
+  if (!file) {
+    printf("> Error loading file!\n");
+    exit(1);
+  }
+  fseek(file, 0L, SEEK_END);
+  size_t file_size = ftell(file);
+  wasm_byte_vec_new_uninitialized(&wasm, file_size);
+  fseek(file, 0L, SEEK_SET);
+  if (fread(wasm.data, file_size, 1, file) != 1) {
+    printf("> Error loading module!\n");
+    exit(1);
+  }
+  fclose(file);
+
+  // Compile our modules
+  wasm_module_t *module = NULL;
+  wasmtime_error_t *error = wasmtime_module_new(engine, &wasm, &module);
+  if (!module)
+    exit_with_error("failed to compile module", error, NULL);
+  wasm_byte_vec_delete(&wasm);
+
+  // Instantiate wasi
+  wasi_config_t *wasi_config = wasi_config_new();
+  assert(wasi_config);
+  wasi_config_inherit_argv(wasi_config);
+  wasi_config_inherit_env(wasi_config);
+  wasi_config_inherit_stdin(wasi_config);
+  wasi_config_inherit_stdout(wasi_config);
+  wasi_config_inherit_stderr(wasi_config);
+  wasi_config_preopen_dir(wasi_config, "examples/wasi-fs", ".");
+  wasm_trap_t *trap = NULL;
+  wasi_instance_t *wasi = wasi_instance_new(store, "wasi_snapshot_preview1", wasi_config, &trap);
+  if (wasi == NULL)
+    exit_with_error("failed to instantiate WASI", NULL, trap);
+
+  wasmtime_linker_t *linker = wasmtime_linker_new(store);
+  error = wasmtime_linker_define_wasi(linker, wasi);
+  if (error != NULL)
+    exit_with_error("failed to link wasi", error, NULL);
+
+  // Instantiate the module
+  wasm_name_t empty;
+  wasm_name_new_from_string(&empty, "");
+  wasm_instance_t *instance = NULL;
+  error = wasmtime_linker_module(linker, &empty, module);
+  if (error != NULL)
+    exit_with_error("failed to instantiate module", error, NULL);
+
+  // Run it.
+  wasm_func_t* func;
+  wasmtime_linker_get_default(linker, &empty, &func);
+  if (error != NULL)
+    exit_with_error("failed to locate default export for module", error, NULL);
+  error = wasmtime_func_call(func, NULL, 0, NULL, 0, &trap);
+  if (error != NULL)
+    exit_with_error("error calling default export", error, trap);
+
+  // Clean up after ourselves at this point
+  wasm_name_delete(&empty);
+  wasm_module_delete(module);
+  wasm_store_delete(store);
+  wasm_engine_delete(engine);
+  return 0;
+}
+
+static void exit_with_error(const char *message, wasmtime_error_t *error, wasm_trap_t *trap) {
+  fprintf(stderr, "error: %s\n", message);
+  wasm_byte_vec_t error_message;
+  if (error != NULL) {
+    wasmtime_error_message(error, &error_message);
+    wasmtime_error_delete(error);
+  } else {
+    wasm_trap_message(trap, &error_message);
+    wasm_trap_delete(trap);
+  }
+  fprintf(stderr, "%.*s\n", (int) error_message.size, error_message.data);
+  wasm_byte_vec_delete(&error_message);
+  exit(1);
+}

examples/wasi-fs/main.rs

@@ -0,0 +1,46 @@
+//! Example of running a wasi binary in a memory filesystem
+
+// The corresponding wasm binary can be built with:
+// `cargo build -p example-wasi-fs-wasm --target wasm32-wasi`
+//
+// then you can execute this example with `cargo run --example wasi-fs`
+
+use anyhow::Result;
+use std::collections::HashMap;
+use wasmtime::*;
+use wasmtime_wasi::virtfs::{VecFileContents, VirtualDirEntry};
+use wasmtime_wasi::{Wasi, WasiCtxBuilder};
+
+fn main() -> Result<()> {
+    tracing_subscriber::FmtSubscriber::builder()
+        .with_env_filter(tracing_subscriber::EnvFilter::from_default_env())
+        .with_ansi(true)
+        .init();
+
+    let store = Store::default();
+    let mut linker = Linker::new(&store);
+
+    // Create an instance of `Wasi` which contains a `WasiCtx`. Note that
+    // `WasiCtx` provides a number of ways to configure what the target program
+    // will have access to.
+    let entry = VirtualDirEntry::File(Box::new(VecFileContents::with_content(
+        "world".as_bytes().to_owned(),
+    )));
+    let mut map = HashMap::new();
+    map.insert("test.txt".to_string(), entry);
+    let dir = VirtualDirEntry::Directory(map);
+    let ctx = WasiCtxBuilder::new()
+        .inherit_stdout()
+        .inherit_stderr()
+        .preopened_virt(dir, ".")
+        .build()?;
+    let wasi = Wasi::new(&store, ctx);
+    wasi.add_to_linker(&mut linker)?;
+
+    // Instantiate our module with the imports we've created, and run it.
+    let module = Module::from_file(store.engine(), "target/wasm32-wasi/debug/wasi-fs.wasm")?;
+    linker.module("", &module)?;
+    linker.get_default("")?.get0::<()>()?()?;
+
+    Ok(())
+}

examples/wasi-fs/test.txt

@@ -0,0 +1 @@
+world

examples/wasi-fs/wasm/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "example-wasi-fs-wasm"
+version = "0.0.0"
+authors = ["The Wasmtime Project Developers"]
+edition = "2018"
+publish = false
+
+[[bin]]
+path = "wasi-fs.rs"
+name = "wasi-fs"

examples/wasi-fs/wasm/wasi-fs.rs

@@ -0,0 +1,4 @@
+fn main() {
+    let contents = std::fs::read_to_string("test.txt").unwrap();
+    println!("Hello, {}!", contents);
+}

examples/wasi/main.c

@@ -3,8 +3,8 @@ Example of instantiating a WebAssembly which uses WASI imports.
 
 You can compile and run this example on Linux with:
 
-   cargo build --release -p wasmtime
+   cargo build --release -p wasmtime-c-api
-   cc examples/wasi.c \
+   cc examples/wasi/main.c \
        -I crates/c-api/include \
        -I crates/c-api/wasm-c-api/include \
        target/release/libwasmtime.a \