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//go:build darwin || nintendoswitch || wasip1
package syscall
import (
"unsafe"
)
func Environ() []string {
// This function combines all the environment into a single allocation.
// While this optimizes for memory usage and garbage collector
// overhead, it does run the risk of potentially pinning a "large"
// allocation if a user holds onto a single environment variable or
// value. Having each variable be its own allocation would make the
// trade-off in the other direction.
// calculate total memory required
var length uintptr
var vars int
for environ := libc_environ; *environ != nil; {
length += libc_strlen(*environ)
vars++
environ = (*unsafe.Pointer)(unsafe.Add(unsafe.Pointer(environ), unsafe.Sizeof(environ)))
}
// allocate our backing slice for the strings
b := make([]byte, length)
// and the slice we're going to return
envs := make([]string, 0, vars)
// loop over the environment again, this time copying over the data to the backing slice
for environ := libc_environ; *environ != nil; {
length = libc_strlen(*environ)
// construct a Go string pointing at the libc-allocated environment variable data
var envVar string
rawEnvVar := (*struct {
ptr unsafe.Pointer
length uintptr
})(unsafe.Pointer(&envVar))
rawEnvVar.ptr = *environ
rawEnvVar.length = length
// pull off the number of bytes we need for this environment variable
var bs []byte
bs, b = b[:length], b[length:]
// copy over the bytes to the Go heap
copy(bs, envVar)
// convert trimmed slice to string
s := *(*string)(unsafe.Pointer(&bs))
// add s to our list of environment variables
envs = append(envs, s)
// environ++
environ = (*unsafe.Pointer)(unsafe.Add(unsafe.Pointer(environ), unsafe.Sizeof(environ)))
}
return envs
}
//go:extern environ
var libc_environ *unsafe.Pointer
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