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| author | Amaury Pouly <pamaury@rockbox.org> | 2010-02-02 20:49:35 +0000 |
|---|---|---|
| committer | Amaury Pouly <pamaury@rockbox.org> | 2010-02-02 20:49:35 +0000 |
| commit | 75fc9ee84b73287bdca627f414bc91c964b238d8 (patch) | |
| tree | 5761f3a0a2373c7f1c283092074ec19ad18af275 /apps | |
| parent | a54cacb508b7904d1923135a2d27e31d3f5a4b41 (diff) | |
| download | rockbox-75fc9ee84b73287bdca627f414bc91c964b238d8.tar.gz rockbox-75fc9ee84b73287bdca627f414bc91c964b238d8.zip | |
FS#8967: Fix autoscore computation overflow when the playtime is huge.
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@24471 a1c6a512-1295-4272-9138-f99709370657
Diffstat (limited to 'apps')
| -rw-r--r-- | apps/tagcache.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/apps/tagcache.c b/apps/tagcache.c index 79c96ff186..9ffb6f86fe 100644 --- a/apps/tagcache.c +++ b/apps/tagcache.c | |||
| @@ -772,9 +772,19 @@ static long check_virtual_tags(int tag, const struct index_entry *idx) | |||
| 772 | } | 772 | } |
| 773 | else | 773 | else |
| 774 | { | 774 | { |
| 775 | data = 100 * idx->tag_seek[tag_playtime] | 775 | /* A straight calculus gives: |
| 776 | / idx->tag_seek[tag_length] | 776 | autoscore = 100 * playtime / length / playcout (1) |
| 777 | / idx->tag_seek[tag_playcount]; | 777 | Now, consider the euclidian division of playtime by length: |
| 778 | playtime = alpha * length + beta | ||
| 779 | With: | ||
| 780 | 0 <= beta < length | ||
| 781 | Now, (1) becomes: | ||
| 782 | autoscore = 100 * (alpha / playcout + beta / length / playcount) | ||
| 783 | Both terms should be small enough to avoid any overflow | ||
| 784 | */ | ||
| 785 | data = 100 * (idx->tag_seek[tag_playtime] / idx->tag_seek[tag_length]) | ||
| 786 | + (100 * (idx->tag_seek[tag_playtime] % idx->tag_seek[tag_length])) / idx->tag_seek[tag_length]; | ||
| 787 | data /= idx->tag_seek[tag_playcount]; | ||
| 778 | } | 788 | } |
| 779 | break; | 789 | break; |
| 780 | 790 | ||