stream_libarchive: remember archive headers from initial open

The header probing hacks were previously all broken. They only worked
the first time the archive file was open. Since subsequent opens (on
seek) occured in the middle of the source stream rather than at the
beginning, the stream_read_peek calls meant to retrieve the headers were
instead returning random bytes in the middle of the file.

Perhaps the worst manifestation of this was when seeking within a
multi-volume .rar archive with the "legacy" file naming pattern. If the
seek required a reopen, the fact that the archive was multi-volume would
be forgotten and the file would appear truncated terminating playback.

To solve this, only perform the header probling the first time the
archive is opened. Save the results and reuse them on subsequent
reopens. Put this in a wrapper so this is transparent to
demux_libarchive.

1 files changed, 46 insertions, 16 deletions

diff --git a/stream/stream_libarchive.c b/stream/stream_libarchive.c
index ca6f9db032..61c95cc349 100644
--- a/stream/stream_libarchive.c
+++ b/stream/stream_libarchive.c
@@ -25,6 +25,10 @@
 
 #include "stream_libarchive.h"
 
+#define MP_ARCHIVE_FLAG_MAYBE_ZIP       (MP_ARCHIVE_FLAG_PRIV << 0)
+#define MP_ARCHIVE_FLAG_MAYBE_RAR       (MP_ARCHIVE_FLAG_PRIV << 1)
+#define MP_ARCHIVE_FLAG_MAYBE_VOLUMES   (MP_ARCHIVE_FLAG_PRIV << 2)
+
 struct mp_archive_volume {
     struct mp_archive *mpa;
     int index; // volume number (starting with 0, mp_archive.primary_src)
@@ -73,6 +77,21 @@ static bool probe_zip(struct stream *s)
     return false;
 }
 
+static int mp_archive_probe(struct stream *src)
+{
+    int flags = 0;
+    assert(stream_tell(src) == 0);
+    if (probe_zip(src))
+        flags |= MP_ARCHIVE_FLAG_MAYBE_ZIP;
+
+    if (probe_rar(src)) {
+        flags |= MP_ARCHIVE_FLAG_MAYBE_RAR;
+        if (probe_multi_rar(src))
+            flags |= MP_ARCHIVE_FLAG_MAYBE_VOLUMES;
+    }
+    return flags;
+}
+
 static bool volume_seek(struct mp_archive_volume *vol)
 {
     if (!vol->src || vol->seek_to < 0)
@@ -260,7 +279,7 @@ static const struct file_pattern patterns[] = {
     { NULL, NULL, NULL, 0, 0 },
 };
 
-static bool find_volumes(struct mp_archive *mpa, bool multivol_hint)
+static bool find_volumes(struct mp_archive *mpa, int flags)
 {
     struct bstr primary_url = bstr0(mpa->primary_src->url);
 
@@ -273,7 +292,7 @@ static bool find_volumes(struct mp_archive *mpa, bool multivol_hint)
 
     if (!pattern->match)
         return true;
-    if (pattern->legacy && !multivol_hint)
+    if (pattern->legacy && !(flags & MP_ARCHIVE_FLAG_MAYBE_VOLUMES))
         return true;
 
     struct bstr base = bstr_splice(primary_url, 0, -(int)strlen(pattern->match));
@@ -293,8 +312,9 @@ static bool find_volumes(struct mp_archive *mpa, bool multivol_hint)
     return true;
 }
 
-struct mp_archive *mp_archive_new(struct mp_log *log, struct stream *src,
-                                  int flags, int max_volumes)
+static struct mp_archive *mp_archive_new_raw(struct mp_log *log,
+                                             struct stream *src,
+                                             int flags, int max_volumes)
 {
     struct mp_archive *mpa = talloc_zero(NULL, struct mp_archive);
     mpa->log = log;
@@ -308,20 +328,17 @@ struct mp_archive *mp_archive_new(struct mp_log *log, struct stream *src,
     mpa->primary_src = src;
     if (!mpa->arch)
         goto err;
+
+    mpa->flags = flags;
     mpa->num_volumes = max_volumes ? max_volumes : INT_MAX;
 
     // first volume is the primary stream
     if (!add_volume(mpa, src, src->url, 0))
         goto err;
 
-    bool maybe_rar = probe_rar(src);
-    bool maybe_zip = probe_zip(src);
-    bool probe_all = flags & MP_ARCHIVE_FLAG_UNSAFE;
-    bool maybe_rar2_multivol = maybe_rar && probe_multi_rar(src);
-
-    if (!(flags & MP_ARCHIVE_FLAG_NO_RAR_VOLUMES)) {
+    if (!(flags & MP_ARCHIVE_FLAG_NO_VOLUMES)) {
         // try to open other volumes
-        if (!find_volumes(mpa, maybe_rar2_multivol))
+        if (!find_volumes(mpa, flags))
             goto err;
     }
 
@@ -333,7 +350,7 @@ struct mp_archive *mp_archive_new(struct mp_log *log, struct stream *src,
     // Exclude other formats if it's probably RAR, because other formats may
     // behave suboptimal with multiple volumes exposed, such as opening every
     // single volume by seeking at the end of the file.
-    if (!maybe_rar) {
+    if (!(flags & MP_ARCHIVE_FLAG_MAYBE_RAR)) {
         archive_read_support_format_7zip(mpa->arch);
         archive_read_support_format_iso9660(mpa->arch);
         archive_read_support_filter_bzip2(mpa->arch);
@@ -345,7 +362,7 @@ struct mp_archive *mp_archive_new(struct mp_log *log, struct stream *src,
         // of the file, which may be annoying (HTTP reconnect, volume skipping),
         // so use it only as last resort, or if it's relatively likely that it's
         // really zip.
-        if (maybe_zip || probe_all)
+        if (flags & (MP_ARCHIVE_FLAG_UNSAFE | MP_ARCHIVE_FLAG_MAYBE_ZIP))
             archive_read_support_format_zip_seekable(mpa->arch);
     }
 
@@ -370,6 +387,13 @@ err:
     return NULL;
 }
 
+struct mp_archive *mp_archive_new(struct mp_log *log, struct stream *src,
+                                  int flags, int max_volumes)
+{
+    flags |= mp_archive_probe(src);
+    return mp_archive_new_raw(log, src, flags, max_volumes);
+}
+
 // Iterate entries. The first call establishes the first entry. Returns false
 // if no entry found, otherwise returns true and sets mpa->entry/entry_filename.
 bool mp_archive_next_entry(struct mp_archive *mpa)
@@ -428,10 +452,16 @@ struct priv {
 static int reopen_archive(stream_t *s)
 {
     struct priv *p = s->priv;
-    int num_volumes = p->mpa ? p->mpa->num_volumes : 0;
-    mp_archive_free(p->mpa);
     s->pos = 0;
-    p->mpa = mp_archive_new(s->log, p->src, MP_ARCHIVE_FLAG_UNSAFE, num_volumes);
+    if (!p->mpa) {
+        p->mpa = mp_archive_new(s->log, p->src, MP_ARCHIVE_FLAG_UNSAFE, 0);
+    } else {
+        int flags = p->mpa->flags;
+        int num_volumes = p->mpa->num_volumes;
+        mp_archive_free(p->mpa);
+        p->mpa = mp_archive_new_raw(s->log, p->src, flags, num_volumes);
+    }
+
     if (!p->mpa)
         return STREAM_ERROR;