This patch makes the error codes in nsError.h be generated by a python script.
This gives us the opportunity to add rust code generation in parallel with the
C++ code generation, which will happen in part 2.
This patch also reworks the name calculation in ErrorNames.cpp to use generated
code by the python script.
MozReview-Commit-ID: 5wxbdZwxe7q
This patch makes the error codes in nsError.h be generated by a python script.
This gives us the opportunity to add rust code generation in parallel with the
C++ code generation, which will happen in part 2.
This patch also reworks the name calculation in ErrorNames.cpp to use generated
code by the python script.
MozReview-Commit-ID: 5wxbdZwxe7q
1. Set the capacity to 1 when IsExclusive is true.
2. Set it to 3 because Try shows we never have more the 3 elements when IsExclusive is false.
MozReview-Commit-ID: dmIeE6ZTeh
--HG--
extra : rebase_source : fc6b173d3a389d11424238f76cbae1f496155ba5
extra : source : c6203c27b8020999ed39ff43ddf5173f5111ef6b
This improves performance because we won't try to fix the permissions of the file every time the nsIHandlerService implementation wants to open it, and makes it easier to access the file path from xpcshell tests.
MozReview-Commit-ID: DZmLa92qUnZ
--HG--
extra : source : bd0fdce03cc7442079e96318d3a9b519a4d403a9
PLDHashTable takes the result of the hash function and multiplies it by
kGoldenRatio to ensure that it has a good distribution of bits across
the 32-bit hash value, and then zeroes out the low bit so that it can be
used for the collision flag. This result is called hash0. From hash0
it computes two different numbers used to find entries in the table
storage: hash1 is used to find an initial position in the table to
begin searching for an entry; hash2 is then used to repeatedly offset
that position (mod the size of the table) to build a chain of positions
to search.
In a table with capacity 2^c entries, hash1 is simply the upper c bits
of hash0. This patch does not change this.
Prior to this patch, hash2 was the c bits below hash1, padded at the low
end with zeroes when c > 16. (Note that bug 927705, changeset
1a02bec165e16f370cace3da21bb2b377a0a7242, increased the maximum capacity
from 2^23 to 2^26 since 2^23 was sometimes insufficient!) This manner
of computing hash2 is problematic because it increases the risk of long
chains for very large tables, since there is less variation in the hash2
result due to the zero padding.
So this patch changes the hash2 computation by using the low bits of
hash0 instead of shifting it around, thus avoiding 0 bits in parts of
the hash2 value that are significant.
Note that this changes what hash2 is in all cases except when the table
capacity is exactly 2^16, so it does change our hashing characteristics.
For tables with capacity less than 2^16, it should be using a different
second hash, but with the same amount of random-ish data. For tables
with capacity greater than 2^16, it should be using more random-ish
data.
MozReview-Commit-ID: JvnxAMBY711
--HG--
extra : transplant_source : %8A%25%FB%E3H%B8_%F1G%F6%3E%0B%29%DF%20%FF%D8%E1%AEw
PLDHashTable's entry store has two types of unoccupied entries: free
entries and removed entries. The search of a chain of entries
(determined by the hash value) in the entry store to search for an entry
can stop at free entries, but it continues across removed entries,
because removed entries are entries that may have been skipped over when
we were adding the value we're searching for to the hash, but have since
been removed. For live entries, we also maintain this distinction by
using one bit of storage for a collision flag, which notes that if the
hashtable entry is removed, its place in the entry store must become a
removed entry rather than a free entry.
When we add a new entry to the table, Add's semantics require that we
return an existing entry if there is one, and only create a new entry if
no existing entry exists. (Bug 1352198 suggests the possibility of a
faster alternative Add API where the caller guarantees that the key is
not already in the hashtable.) When we search for the existing entry,
we must thus continue the search across removed entries, even though we
record the first removed entry found to return if the search for an
existing entry fails.
The existing code adds the collision flag through the entire table
search during an Add. This patch changes that behavior so that we only
add the collision flag prior to finding the first removed entry. Adding
it after we find the first removed entry is unnecessary, since we are
not making that entry part of a path to a new entry. If it is part of a
path to an existing entry, it will already have the collision flag set.
This patch effectively puts an if (!firstRemoved) around the else branch
of the if (MOZ_UNLIKELY(EntryIsRemoved(entry))), and then refactors that
condition outwards since it is now around the contents of both the if
and else branches.
MozReview-Commit-ID: CsXnMYttHVy
--HG--
extra : transplant_source : 0T%B0%FA%C0%85v%8B%16%E7%81%03p%F5K%97%B1%9E%92%27
This uses std::atomic rather than mozilla::Atomic since mozilla::Atomic
does not support using different memory synchronization for different
atomic operations on the same variable.
The added comments could use careful review since, while they reflect my
understanding of the issue, I don't consider myself an expert on the
topic.
MozReview-Commit-ID: 7xByCXt17Dr
--HG--
extra : transplant_source : 8%8Ci%CC%EA%0F%CF%C7%3E%F1%93%F5%C9%ED9%84%F9%3Evx
PLDHashTable's entry store has two types of unoccupied entries: free
entries and removed entries. The search of a chain of entries
(determined by the hash value) in the entry store to search for an entry
can stop at free entries, but it continues across removed entries,
because removed entries are entries that may have been skipped over when
we were adding the value we're searching for to the hash, but have since
been removed. For live entries, we also maintain this distinction by
using one bit of storage for a collision flag, which notes that if the
hashtable entry is removed, its place in the entry store must become a
removed entry rather than a free entry.
When we add a new entry to the table, Add's semantics require that we
return an existing entry if there is one, and only create a new entry if
no existing entry exists. (Bug 1352198 suggests the possibility of a
faster alternative Add API where the caller guarantees that the key is
not already in the hashtable.) When we search for the existing entry,
we must thus continue the search across removed entries, even though we
record the first removed entry found to return if the search for an
existing entry fails.
The existing code adds the collision flag through the entire table
search during an Add. This patch changes that behavior so that we only
add the collision flag prior to finding the first removed entry. Adding
it after we find the first removed entry is unnecessary, since we are
not making that entry part of a path to a new entry. If it is part of a
path to an existing entry, it will already have the collision flag set.
This patch effectively puts an if (!firstRemoved) around the else branch
of the if (MOZ_UNLIKELY(EntryIsRemoved(entry))), and then refactors that
condition outwards since it is now around the contents of both the if
and else branches.
MozReview-Commit-ID: CsXnMYttHVy
--HG--
extra : transplant_source : W4%B8%BA%D5p%102%1B%8D%83%23%E0s%B3%B0f%0D%05%AE
This is the same optimization made for ThreadSafeAutoRefCnt in bug
1277709. However, nsStringBuffer uses a 32-bit reference count all the
time, so it can't easily use ThreadSafeAutoRefCnt.
MozReview-Commit-ID: LpB3xaYbaEE
--HG--
extra : transplant_source : %89%FA%02%402%B1%83%17%81%09%EEw%B0%85%A0%B2%8DK/%D6
This uses std::atomic rather than mozilla::Atomic since mozilla::Atomic
does not support using different memory synchronization for different
atomic operations on the same variable.
The added comments could use careful review since, while they reflect my
understanding of the issue, I don't consider myself an expert on the
topic.
MozReview-Commit-ID: 7xByCXt17Dr
--HG--
extra : transplant_source : %8DM%88%E8%B7%B4%D8a%D6%F5%3F%9B%DC%09X%F3%7C%98%DE%21
We need this because the stored values in the hash table may themselves
be main-thread only objects, and destroying them off the main thread
will cause crashes.
Michael Layzell
Petr Sumbera
Andrea Marchesini
Iris Hsiao
Florian Queze
Bill McCloskey
Ricky Chien
Jan de Mooij
Phil Ringnalda
Carsten "Tomcat" Book
Wes Kocher
Eric Rahm
Carl Corcoran
Daniel Holbert
Byron Campen [:bwc]
JW Wang
Paolo Amadini
L. David Baron
Olli Pettay
Bevis Tseng
Nathan Froyd