added doc

README.md

@@ -208,6 +208,27 @@ zip_stream_close(zip);
 free(buf);
 ```
 
+* Extract a partial zip entry
+
+```c
+unsigned char buf[16];
+size_t bufsize = sizeof(buf);
+
+struct zip_t *zip = zip_open("foo.zip", 0, 'r');
+{
+    zip_entry_open(zip, "foo-1.txt");
+    {
+        size_t offset = 4;
+        ssize_t nread = zip_entry_noallocread_offset(zip, offset, bufsize, (void *)buf);
+    }
+
+    zip_entry_close(zip);
+}
+zip_close(zip);
+
+free(buf);
+```
+
 * List of all zip entries
 
 ```c