Addresses #1531 Reimplemented setenv, unsetenv correctly

git-svn-id: file:///svn/toku/tokudb@9974 c7de825b-a66e-492c-adef-691d508d4ae1

windows/env.c

 #include <windows.h>
 #include <toku_stdlib.h>
+#include "toku_portability.h"
+#include <assert.h>
 
 int
 setenv(const char *name, const char *value, int overwrite) {
-    char buf[2]; //Need a dummy buffer
-    BOOL exists = TRUE;
-    int r = GetEnvironmentVariable(name, buf, sizeof(buf));
-    if (r==0) {
-        r = GetLastError();
-        if (r==ERROR_ENVVAR_NOT_FOUND) exists = FALSE;
-        else {
-            errno = r;
-            r = -1;
-            goto cleanup;
-        }
-    } 
+    char * current = getenv(name);
+    BOOL exists = current!=NULL;
+
+    int r;
     if (overwrite || !exists) {
-        r = SetEnvironmentVariable(name, value);
-        if (r==0) {
+        char setstring[sizeof("=") + strlen(name) + strlen(value)];
+        int bytes = snprintf(setstring, sizeof(setstring), "%s=%s", name, value);
+        assert(bytes>=0);
+        assert((size_t)bytes < sizeof(setstring));
+        r = _putenv(setstring);
+        if (r==-1) {
             errno = GetLastError();
-            r = -1;
             goto cleanup;
         }
     }
@@ -30,12 +27,7 @@ cleanup:
 
 int
 unsetenv(const char *name) {
-    int r = SetEnvironmentVariable(name, NULL);
-    if (r==0) { //0 is failure
-        r = -1;
-        errno = GetLastError();
-    }
-    else r = 0;
+    int r = setenv(name, "", 1);
     return r;
 }