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package util
import (
"context"
"os"
"path"
"strconv"
"time"
"github.com/tetratelabs/wazero/api"
)
// Wasm_Tempnam wraps Go_Tempnam to fulfill wazero's api.GoModuleFunc,
// the argument definition is (i32, i32) and return definition is (i32).
// NOTE: the calling module MUST have access to exported malloc / free.
func Wasm_Tempnam(ctx context.Context, mod api.Module, stack []uint64) {
dirptr := api.DecodeU32(stack[0])
pfxptr := api.DecodeU32(stack[1])
dir := readString(ctx, mod, dirptr, 0)
pfx := readString(ctx, mod, pfxptr, 0)
tmpstr := Go_Tempnam(dir, pfx)
tmpptr := writeString(ctx, mod, tmpstr)
stack[0] = api.EncodeU32(tmpptr)
}
// Go_Tempname is functionally similar to C's tempnam.
func Go_Tempnam(dir, prefix string) string {
now := time.Now().Unix()
prefix = path.Join(dir, prefix)
for i := 0; i < 1000; i++ {
n := murmur2(uint32(now + int64(i)))
name := prefix + strconv.FormatUint(uint64(n), 10)
_, err := os.Stat(name)
if err == nil {
continue
} else if os.IsNotExist(err) {
return name
} else {
panic(err)
}
}
panic("too many attempts")
}
// murmur2 is a simple uint32 murmur2 hash
// impl with fixed seed and input size.
func murmur2(k uint32) (h uint32) {
const (
// seed ^ bitlen
s = uint32(2147483647) ^ 8
M = 0x5bd1e995
R = 24
)
h = s
k *= M
k ^= k >> R
k *= M
h *= M
h ^= k
h ^= h >> 13
h *= M
h ^= h >> 15
return
}
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