[NaCl SDK] nacl_io: Replace allocated ino with hash of path.

native_client_sdk/src/libraries/nacl_io/html5fs/html5_fs.cc

Index: native_client_sdk/src/libraries/nacl_io/html5fs/html5_fs.cc
diff --git a/native_client_sdk/src/libraries/nacl_io/html5fs/html5_fs.cc b/native_client_sdk/src/libraries/nacl_io/html5fs/html5_fs.cc
index c747733231042d864218a51db54c9536ba8172d9..cf410fdc0bf9485aa7c04f376639a35b63ad46a3 100644
--- a/native_client_sdk/src/libraries/nacl_io/html5fs/html5_fs.cc
+++ b/native_client_sdk/src/libraries/nacl_io/html5fs/html5_fs.cc
@@ -29,6 +29,37 @@ int64_t strtoull(const char* nptr, char** endptr, int base) {
 
 }  // namespace
 
+
+// Use a simple rotating hash to modify all bits.
+static inline ino_t HashChar(ino_t hash, char c) {

[binji, 2014/09/25 15:01:17]

I'd add these to the anonymous namespace above rather than making them static

[noelallen1, 2014/09/25 18:10:08]

Done.

+  const ino_t bits = (ino_t) (sizeof(ino_t) * 8);
+  ino_t out = (hash << 5) + (hash >> (ino_t) (bits - 5));
+  return out ^ c;

[Sam Clegg, 2014/09/25 19:12:09]

Is this is well known hash function?  Perhaps at a reference to where it comes
from?

[noelallen1, 2014/09/25 21:01:38]

I actually went ahead and changed this to a well known function which has
similar properties.

+}
+
+static ino_t HashPath(const Path& path) {
+  ino_t hash = 0x12345678;
+  for (size_t segment = 0; segment < path.Size(); segment++) {
+    hash = HashChar(hash, '/');
+    const char *ptr = path.Part(segment).c_str();
+    while (ptr) {

[binji, 2014/09/25 15:01:17]

while (*ptr)

[noelallen1, 2014/09/25 18:10:08]

Interesting, why didn't our current tests catch this?

+      hash = HashChar(hash, *ptr++);
+    }
+  }
+  return hash;
+}
+
+// For HTML5, the INO should be the one used by the system, however PPAPI

[binji, 2014/09/25 15:01:17]

It is not clear from the comment that you are overriding this function to
prevent st_ino from being set by the default OnNodeCreated call. Can you clarify
that here?

[noelallen1, 2014/09/25 18:10:08]

Done.

+// does not provide access to the real INO.  Instead, since HTML5 does not
+// suport links, we assume that files are unique based on path to the base
+// of the mount.
+void Html5Fs::OnNodeCreated(Node* node) {
+  node->stat_.st_dev = dev_;
+}
+
+void Html5Fs::OnNodeDestroyed(Node* node) {}
+
+
 Error Html5Fs::OpenWithMode(const Path& path, int open_flags, mode_t mode,
                             ScopedNode* out_node) {
   out_node->reset(NULL);
@@ -43,6 +74,10 @@ Error Html5Fs::OpenWithMode(const Path& path, int open_flags, mode_t mode,
 
   ScopedNode node(new Html5FsNode(this, fileref));
   error = node->Init(open_flags);
+
+  // Set the INO based on the path
+  node->stat_.st_ino = HashPath(path);

[binji, 2014/09/25 15:01:17]

This will fix GetStat, but GetDents is also returning an incorrect ino_t value.

[noelallen1, 2014/09/25 18:10:08]

Done.

+
   if (error)
     return error;