Update some comments, fine-tune the streaming bid

diff --git a/libarchive/archive_read_support_format_zip.c b/libarchive/archive_read_support_format_zip.c
index 0395edf9033b9c3c71bd5ace0a8d4e54a458a5ec..866f37ee9c9ee350f3a2e38da569a5b8a5ec744e 100644 (file)
--- a/libarchive/archive_read_support_format_zip.c
+++ b/libarchive/archive_read_support_format_zip.c
@@ -1,5 +1,5 @@
 /*-
- * Copyright (c) 2004 Tim Kientzle
+ * Copyright (c) 2004-2013 Tim Kientzle
  * Copyright (c) 2011-2012 Michihiro NAKAJIMA
  * Copyright (c) 2013 Konrad Kleine
  * All rights reserved.
@@ -242,7 +242,7 @@ archive_read_format_zip_options(struct archive_read *a,
 
        zip = (struct zip *)(a->format->data);
        if (strcmp(key, "compat-2x")  == 0) {
-               /* Handle filnames as libarchive 2.x */
+               /* Handle filenames as libarchive 2.x */
                zip->init_default_conversion = (val != NULL) ? 1 : 0;
                return (ARCHIVE_OK);
        } else if (strcmp(key, "hdrcharset")  == 0) {
@@ -1071,9 +1071,12 @@ archive_read_format_zip_streamable_bid(struct archive_read *a, int best_bid)
                return (-1);
 
        /*
-        * Bid of 30 here is: 16 bits for "PK",
-        * next 16-bit field has four options (-2 bits).
-        * 16 + 16-2 = 30.
+        * Bid of 29 here comes from:
+        *  + 16 bits for "PK",
+        *  + next 16-bit field has 6 options so contributes
+        *    about 16 - log_2(6) ~= 16 - 2.6 ~= 13 bits
+        *
+        * So we've effectively verified ~29 total bits of check data.
         */
        if (p[0] == 'P' && p[1] == 'K') {
                if ((p[2] == '\001' && p[3] == '\002')
@@ -1082,7 +1085,7 @@ archive_read_format_zip_streamable_bid(struct archive_read *a, int best_bid)
                    || (p[2] == '\006' && p[3] == '\006')
                    || (p[2] == '\007' && p[3] == '\010')
                    || (p[2] == '0' && p[3] == '0'))
-                       return (30);
+                       return (29);
        }
 
        /* TODO: It's worth looking ahead a little bit for a valid