upip: Switch to stream mode of operation using uzlib.DecompIO.

So, there's no longer requirement that uncompressed file fit into memory,
though for stream mode, max dictionary size of 32K is used so far.

upip/upip.py

@@ -13,8 +13,8 @@ def upip_import(mod, sub=None):
 sys = upip_import("sys")
 import uos as os
 import uerrno as errno
+import uzlib
 
-gzip = upip_import("gzip")
 try:
     tarfile = upip_import("utarfile")
 except ImportError:
@@ -28,7 +28,7 @@ except ImportError:
 DEFAULT_MICROPYPATH = "~/.micropython/lib:/usr/lib/micropython"
 
 debug = False
-cleanup_files = [".pkg.tar"]
+cleanup_files = []
 
 class NotFoundError(Exception):
     pass
@@ -113,7 +113,7 @@ try:
     import ussl
     import usocket
     warn_ussl = True
-    def download(url, local_name):
+    def url_open(url):
         global warn_ussl
         proto, _, host, urlpath = url.split('/', 3)
         ai = usocket.getaddrinfo(host, 443)
@@ -142,12 +142,8 @@ try:
                 raise OSError()
             if l == b'\r\n':
                 break
-        with open(local_name, "wb") as f:
-            while 1:
-                l = s.read(1024)
-                if not l:
-                    break
-                f.write(l)
+
+        return s
 
 except ImportError:
 
@@ -162,9 +158,9 @@ except ImportError:
 
 
 def get_pkg_metadata(name):
-    download("https://pypi.python.org/pypi/%s/json" % name, ".pkg.json")
-    with open(".pkg.json") as f:
-        s = f.read()
+    f = url_open("https://pypi.python.org/pypi/%s/json" % name)
+    s = f.read()
+    f.close()
     return json.loads(s)
 
 
@@ -192,16 +188,12 @@ def install_pkg(pkg_spec, install_path):
     package_url = packages[0]["url"]
     print("Installing %s %s from %s" % (pkg_spec, latest_ver, package_url))
     package_fname = op_basename(package_url)
-    download(package_url, package_fname)
-
-    data = gzdecompress(package_fname)
-
-    f = open(".pkg.tar", "wb")
-    f.write(data)
-    f.close()
-
-    f = tarfile.TarFile(".pkg.tar")
-    return install_tar(f, install_path)
+    f1 = url_open(package_url)
+    f2 = uzlib.DecompIO(f1, 16 + 15)
+    f3 = tarfile.TarFile(fileobj=f2)
+    meta = install_tar(f3, install_path)
+    f1.close()
+    return meta
 
 def cleanup():
     for fname in cleanup_files: