Entry storage allocation now occurs on the first lookupForAdd()/put()/putNew().
This removes the need for init() and initialized(), and matches how
PLDHashTable/nsTHashtable work. It also removes the need for init() functions
in a lot of types that are built on top of mozilla::Hash{Map,Set}.
Pros:
- No need for init() calls and subsequent checks.
- No memory allocated for empty tables, which are not that uncommon.
Cons:
- An extra branch in lookup() and lookupForAdd(), but not in put()/putNew(),
because the existing checkOverloaded() can handle it.
Specifics:
- Construction now can take a length parameter.
- init() is removed. Explicit length-setting, when necessary, now occurs in the
constructors.
- initialized() is removed.
- capacity() now returns zero when the entry storage is absent.
- lookupForAdd() is no longer `const`, because it can instantiate the storage,
which requires modifications.
- lookupForAdd() can now return an invalid AddPtr in two cases:
- old: hashing failure (due to OOM in the hasher)
- new: OOM while instantiating entry storage
The existing failure handling paths for the old case work for the new case.
- clear(), finish(), and clearAndShrink() are replaced by clear(), compact(),
and reserve(). The old compactIfUnderloaded() is also removed.
- Capacity computation code is now in its own functions, bestCapacity() and
hashShift(). setTableSizeLog2() is removed.
- uint32_t is used throughout for capacities, instead of size_t, for
consistency with other similar values.
- changeTableSize() now takes a capacity instead of a deltaLog2, and it can now
handle !mTable.
Measurements:
- Total source code size is reduced by over 900 lines. Also, lots of existing
lines got shorter (i.e. two checks were reduced to one).
- Executable size barely changed, down by 2 KiB on Linux64. The extra branches
are compensated for by the lack of init() calls.
- Speed changed negligibly. The instruction count for Bench_Cpp_MozHash
increased from 2.84 billion to 2.89 billion but any execution time change was
well below noise.
c_char isn't i8 on some platforms such as Android/arm, so we should use c_char
instead.
MozReview-Commit-ID: 486BCGvYAE0
--HG--
extra : rebase_source : 0ee9d510de5cd8ab20daa1709c7425ca95dc8793
(patch is actually r=erahm,mystor)
nsTFixedString<T> is only used as a base class for nsTAutoStringN<T, N>, so
this patch merges the former into the latter, cutting some code and simplifying
the string class hierarchy.
Because the "Fixed" name is now gone, the patch also renames
StringDataFlags::FIXED as INLINE and ClassDataFlags::FIXED as INLINE.
The patch also removes nsFixed[C]String and ns_auto_[c]string! from Rust code
because nsAutoString can't be implemented directly in Rust due to its move
semantics. There were only two uses of ns_auto_string! outside of tests so this
seems like a minor loss.
MozReview-Commit-ID: 8ntximghiut
--HG--
extra : rebase_source : f36edbae0553adcfee356fb8b311097ff7424786
This is needed for patch 4.
MozReview-Commit-ID: 5ikQFIL9O0i
--HG--
extra : transplant_source : %88%80%E3%04%11%7E%7F%A4%7E%15%1B%1A%84%E2%13%3E%F6%E8%2A%1C
Thanks to Manish for help in reflecting this idiomatically in rust.
MozReview-Commit-ID: 8tB7vsc5yxc
--HG--
extra : transplant_source : F%87%16%82.P%BD%F3%B1%A4%19%BA%F0%3DQ%F6%ED%BD%95%60
We now have code that unconditionally requires the rust
compiler and are committed to adding more. Remove this
last vestige of conditional support.
MozReview-Commit-ID: EK6FBnAbR
--HG--
extra : rebase_source : 6efda10a74f9ca0482304c2b1ffe6941e42138f8
This patch adds a series of fallible methods for the rust ns[C]String
bindings, as well as the `set_length` method, which is the same as the
`SetLength` method in C++. `set_length` is marked as unsafe.
The decision was made to make the fallible methods seperate from the
infallible methods, and to use seperate Rust->C++ bindings for each of
them, rather than only binding the fallible bindings, and unwrapping
them in rust-land. This is to try to match the C++ API as closely as
possible, and to ensure that the behavior matches.
MozReview-Commit-ID: FkSomkFUFGD
