From 1918ad2ae38aa32c74b558b322479a8efdd76363 Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Fri, 11 Dec 2020 14:49:17 -0800 Subject: Export of internal Abseil changes MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit -- 0bfa836596a9c787a2f0bdc283011dd1f6810c6e by Benjamin Barenblat : Ignore missing CPU frequency on more architectures Linux on MIPS, PA-RISC, RISC-V, and SystemZ doesn’t expose the nominal CPU frequency via /sys, so don’t worry if `NominalCPUFrequency` returns 1.0 on those platforms. Some POWER machines expose the CPU frequency; others do not. Since we can’t predict which type of machine the tests will run on, simply disable testing for `NominalCPUFrequency` on POWER. PiperOrigin-RevId: 347079873 -- 492b6834ed4a07cbc3abccd846f7e37d8c556ee5 by Benjamin Barenblat : Use ABSL_HAVE_THREAD_LOCAL macro instead of copying code Reduce code duplication by checking the ABSL_HAVE_THREAD_LOCAL macro instead of copying code from base/config.h. PiperOrigin-RevId: 347079561 -- 8d656efce4da9cb032094377e58493d98427a536 by Abseil Team : Rollback PiperOrigin-RevId: 347078779 -- 221bc69ec6dd7e2777ffcff6942584f979ef6382 by Abseil Team : Add flag for 'shallow subcord' feature for experimental ring buffer rollout There is a potential trade-off of CPU cost vs over-sharing cord data for subcord of large cords. This flag allows making subcords shallow for ringbuffers (with a potential larger waste of referenced source cords), which allows us to make subcord fast for this apps that do no persist (unmodified / plain copied) sub cords. This change also introduces constants for the default settings, intended to keep the internal cord settings concistent with external flags. PiperOrigin-RevId: 347053271 -- 00a56c24293566734009f6bf2169a83fb37a35ba by Abseil Team : Revert the usage of variant<> in Cord iterator and reader. The introduction of the variant may lead to some missed compiler optimizations. PiperOrigin-RevId: 347053041 -- c7b7b5ed7e3ab46b1e75b80f1a7de0bda26c8f70 by Chris Kennelly : Release library for integer power-of-2 functions and bit counting. PiperOrigin-RevId: 347035065 -- 5a035c0d9840b251967f9e7039fc6a4e01dd52f3 by Abseil Team : Restructure Cord::ChunkIterator for future ring buffer support. PiperOrigin-RevId: 346890054 GitOrigin-RevId: 0bfa836596a9c787a2f0bdc283011dd1f6810c6e Change-Id: I3a58e2a44cb4c6f2116c43e2a4ccbc319d3ccecf --- absl/strings/cord.h | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) (limited to 'absl/strings/cord.h') diff --git a/absl/strings/cord.h b/absl/strings/cord.h index b9cdc435..5fc61a73 100644 --- a/absl/strings/cord.h +++ b/absl/strings/cord.h @@ -362,6 +362,8 @@ class Cord { friend class CharIterator; private: + using Stack = absl::InlinedVector; + // Constructs a `begin()` iterator from `cord`. explicit ChunkIterator(const Cord* cord); @@ -370,6 +372,10 @@ class Cord { void RemoveChunkPrefix(size_t n); Cord AdvanceAndReadBytes(size_t n); void AdvanceBytes(size_t n); + + // Stack specific operator++ + ChunkIterator& AdvanceStack(); + // Iterates `n` bytes, where `n` is expected to be greater than or equal to // `current_chunk_.size()`. void AdvanceBytesSlowPath(size_t n); @@ -383,8 +389,10 @@ class Cord { absl::cord_internal::CordRep* current_leaf_ = nullptr; // The number of bytes left in the `Cord` over which we are iterating. size_t bytes_remaining_ = 0; - absl::InlinedVector - stack_of_right_children_; + // Context of this chunk iterator, can be one of: + // - monostate: iterator holds only one chunk or is empty. + // - Stack : iterator holds a concat / substring tree + absl::variant context_; }; // Cord::ChunkIterator::chunk_begin() @@ -1100,13 +1108,29 @@ inline Cord::ChunkIterator::ChunkIterator(const Cord* cord) : bytes_remaining_(cord->size()) { if (cord->empty()) return; if (cord->contents_.is_tree()) { - stack_of_right_children_.push_back(cord->contents_.tree()); + Stack& stack_of_right_children = context_.emplace(); + stack_of_right_children.push_back(cord->contents_.tree()); operator++(); } else { current_chunk_ = absl::string_view(cord->contents_.data(), cord->size()); } } +inline Cord::ChunkIterator& Cord::ChunkIterator::operator++() { + ABSL_HARDENING_ASSERT(bytes_remaining_ > 0 && + "Attempted to iterate past `end()`"); + assert(bytes_remaining_ >= current_chunk_.size()); + bytes_remaining_ -= current_chunk_.size(); + if (bytes_remaining_ > 0) { + if (absl::holds_alternative(context_)) { + return AdvanceStack(); + } + } else { + current_chunk_ = {}; + } + return *this; +} + inline Cord::ChunkIterator Cord::ChunkIterator::operator++(int) { ChunkIterator tmp(*this); operator++(); -- cgit v1.2.3