runtime: make windows goenvs look more like Go

Change-Id: I4f84a89553f77382a8064f49db0f5eb575b64313
Reviewed-on: https://go-review.googlesource.com/2714
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/runtime/os1_windows.go b/src/runtime/os1_windows.go
index 7ac1cfe5b1cc8496ffb7f0a84bfc868500b4f455..653a7b34c7b01e0468b83dfe1ac8da74b5914fc3 100644 (file)
--- a/src/runtime/os1_windows.go
+++ b/src/runtime/os1_windows.go
@@ -182,24 +182,34 @@ func getRandomData(r []byte) {
 }
 
 func goenvs() {
-       var p *uint16
-
-       env := (*uint16)(unsafe.Pointer(stdcall0(_GetEnvironmentStringsW)))
+       // strings is a pointer to environment variable pairs in the form:
+       //     "envA=valA\x00envB=valB\x00\x00" (in UTF-16)
+       // Two consecutive zero bytes end the list.
+       strings := unsafe.Pointer(stdcall0(_GetEnvironmentStringsW))
+       p := (*[1 << 24]uint16)(strings)[:]
 
        n := 0
-       for p = env; *p != 0; n++ {
-               p = (*uint16)(add(unsafe.Pointer(p), uintptr(findnullw(p)+1)*unsafe.Sizeof(*p)))
+       for from, i := 0, 0; true; i++ {
+               if p[i] == 0 {
+                       // empty string marks the end
+                       if i == from {
+                               break
+                       }
+                       from = i + 1
+                       n++
+               }
        }
+       envs = makeStringSlice(n)
 
-       envs = makeStringSlice(int(n))
-
-       p = env
-       for i := 0; i < n; i++ {
-               envs[i] = gostringw(p)
-               p = (*uint16)(add(unsafe.Pointer(p), uintptr(findnullw(p)+1)*unsafe.Sizeof(*p)))
+       for i := range envs {
+               envs[i] = gostringw(&p[0])
+               for p[0] != 0 {
+                       p = p[1:]
+               }
+               p = p[1:] // skip nil byte
        }
 
-       stdcall1(_FreeEnvironmentStringsW, uintptr(unsafe.Pointer(env)))
+       stdcall1(_FreeEnvironmentStringsW, uintptr(strings))
 }
 
 //go:nosplit