forked from tetratelabs/wazero
/
argsenv.go
73 lines (60 loc) · 1.9 KB
/
argsenv.go
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package gojs
import (
"encoding/binary"
"errors"
"github.com/AR1011/wazero/api"
"github.com/AR1011/wazero/internal/gojs/util"
"github.com/AR1011/wazero/internal/wasm"
)
// Constants about memory layout. See REFERENCE.md
const (
endOfPageZero = uint32(4096) // runtime.minLegalPointer
maxArgsAndEnviron = uint32(8192) // ld.wasmMinDataAddr - runtime.minLegalPointer
wasmMinDataAddr = endOfPageZero + maxArgsAndEnviron // ld.wasmMinDataAddr
)
var le = binary.LittleEndian
// WriteArgsAndEnviron writes arguments and environment variables to memory, so
// they can be read by main, Go compiles as the function export "run".
func WriteArgsAndEnviron(mod api.Module) (argc, argv uint32, err error) {
mem := mod.Memory()
sysCtx := mod.(*wasm.ModuleInstance).Sys
args := sysCtx.Args()
environ := sysCtx.Environ()
argc = uint32(len(args))
offset := endOfPageZero
strPtr := func(val []byte, field string, i int) (ptr uint32) {
// TODO: return err and format "%s[%d], field, i"
ptr = offset
util.MustWrite(mem, field, offset, append(val, 0))
offset += uint32(len(val) + 1)
if pad := offset % 8; pad != 0 {
offset += 8 - pad
}
return
}
argvPtrLen := len(args) + 1 + len(environ) + 1
argvPtrs := make([]uint32, 0, argvPtrLen)
for i, arg := range args {
argvPtrs = append(argvPtrs, strPtr(arg, "args", i))
}
argvPtrs = append(argvPtrs, 0)
for i, env := range environ {
argvPtrs = append(argvPtrs, strPtr(env, "env", i))
}
argvPtrs = append(argvPtrs, 0)
argv = offset
stop := uint32(argvPtrLen << 3) // argvPtrLen * 8
if offset+stop >= wasmMinDataAddr {
err = errors.New("total length of command line and environment variables exceeds limit")
}
buf, ok := mem.Read(argv, stop)
if !ok {
panic("out of memory reading argvPtrs")
}
pos := uint32(0)
for _, ptr := range argvPtrs {
le.PutUint64(buf[pos:], uint64(ptr))
pos += 8
}
return
}