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Deletes the drifted Deeper dive section in REAMDE (#891)

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Signed-off-by: Takeshi Yoneda <takeshi@tetrate.io>
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Takeshi Yoneda
2022-12-06 16:30:59 +09:00
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commit 29e4f46d4a
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@@ -15,66 +15,10 @@ Import wazero and extend your Go application with code written in any language!
## Example ## Example
The best way to learn wazero is by trying one of our [examples](examples). The The best way to learn wazero is by trying one of our [examples](examples/README.md). The
most [basic example](examples/basic) extends a Go application with an addition most [basic example](examples/basic) extends a Go application with an addition
function defined in WebAssembly. function defined in WebAssembly.
## Deeper dive
The former example is a pure function. While a good start, you probably are
wondering how to do something more realistic, like read a file. WebAssembly
Modules (Wasm) are sandboxed similar to containers. They can't read anything
on your machine unless you explicitly allow it.
The WebAssembly Core Specification is a standard, governed by W3C process, but
it has no scope to specify how system resources like files are accessed.
Instead, WebAssembly defines "host functions" and the signatures they can use.
In wazero, "host functions" are written in Go, and let you do anything
including access files. The main constraint is that WebAssembly only allows
numeric types. wazero includes [imports](imports) for common languages and
compiler toolchains.
For example, you can grant WebAssembly code access to your console by exporting
a function written in Go. The below function can be imported into standard
WebAssembly as the module "env" and the function name "log_i32".
```go
_, err := r.NewHostModuleBuilder("env").
ExportFunction("log_i32", func(v uint32) {
fmt.Println("log_i32 >>", v)
}).
Instantiate(ctx, r)
if err != nil {
log.Panicln(err)
}
```
The WebAssembly community has [subgroups][4] which maintain work that may not
result in a Web Standard. One such group is the WebAssembly System Interface
([WASI][5]), which defines functions similar to Go's [x/sys/unix][6].
The [wasi_snapshot_preview1][13] tag of WASI is widely implemented, so wazero
bundles an implementation. That way, you don't have to write these functions.
For example, here's how you can allow WebAssembly modules to read
"/work/home/a.txt" as "/a.txt" or "./a.txt" as well the system clock:
```go
_, err := wasi_snapshot_preview1.Instantiate(ctx, r)
if err != nil {
log.Panicln(err)
}
config := wazero.NewModuleConfig().
WithFS(os.DirFS("/work/home")). // instead of no file system
WithSysWalltime().WithSysNanotime() // instead of fake time
module, err := r.InstantiateModule(ctx, compiled, config)
...
```
While we hope this deeper dive was useful, we also provide [examples](examples)
to elaborate each point. Please try these before raising usage questions as
they may answer them for you!
## Runtime ## Runtime
There are two runtime configurations supported in wazero: _Compiler_ is default: There are two runtime configurations supported in wazero: _Compiler_ is default: