go-wasm
A WebAssembly binary file parser in go.
The parser takes an io.Reader and parses a WebAssembly module from it, which
allows the user to see into the binary file. All data is read, future version
may allow to write it out too, which would allow modifying the binary.
For example:
package main
import (
"flag"
"fmt"
"os"
"text/tabwriter"
wasm "github.com/akupila/go-wasm"
)
func main() {
file := flag.String("file", "", "file to parse (.wasm)")
flag.Parse()
if *file == "" {
flag.Usage()
os.Exit(2)
}
f, err := os.Open(*file)
if err != nil {
fmt.Fprintf(os.Stderr, "open file: %v", err)
os.Exit(1)
}
defer f.Close()
mod, err := wasm.Parse(f)
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(1)
}
w := tabwriter.NewWriter(os.Stdout, 0, 0, 4, ' ', 0)
fmt.Fprintf(w, "Index\tName\tSize (bytes)\n")
for i, s := range mod.Sections {
fmt.Fprintf(w, "%d\t%s\t%d\n", i, s.Name(), s.Size())
}
w.Flush()
}
when passed in a .wasm file compiled with go1.11:
Index Name Size (bytes)
0 Custom 103
1 Type 58
2 Import 363
3 Function 1588
4 Table 5
5 Memory 5
6 Global 51
7 Export 14
8 Element 3066
9 Code 1174891
10 Data 1169054
11 Custom 45428
Much more information is available by type asserting on the items in
.Sections, for example:
for i, s := range mod.Sections {
switch section := s.(type) {
case *wasm.SectionCode:
// can now read function bytecode from section.
}
}
Installation
go get github.com/akupila/go-wasm/...
Notes
This is a experimental, early and definitely not properly tested. There are
probably bugs. If you find one, please open an issue!