From 36ccdba805f1322c23714dbeb227fb632b54ae45 Mon Sep 17 00:00:00 2001 From: Colin Cross Date: Mon, 24 Jan 2022 20:27:14 -0800 Subject: Update webrtc's abseil-cpp Copy external/abseil-cpp into webrtc to update to version 20211102.0 to pick up changes that fix compiling against musl libc. Bug: 190084016 Test: m USE_HOST_MUSL=true host-native Test: m checkbuild Change-Id: I0ab600cd8db93a55eda8358cdbecd21c2f78d8fb --- .../absl/strings/internal/cord_rep_btree_reader.h | 211 +++++++++++++++++++++ 1 file changed, 211 insertions(+) create mode 100644 third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h (limited to 'third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h') diff --git a/third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h b/third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h new file mode 100644 index 0000000000..7aa79dbf10 --- /dev/null +++ b/third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h @@ -0,0 +1,211 @@ +// Copyright 2021 The Abseil Authors +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#ifndef ABSL_STRINGS_INTERNAL_CORD_REP_BTREE_READER_H_ +#define ABSL_STRINGS_INTERNAL_CORD_REP_BTREE_READER_H_ + +#include + +#include "absl/base/config.h" +#include "absl/strings/internal/cord_internal.h" +#include "absl/strings/internal/cord_rep_btree.h" +#include "absl/strings/internal/cord_rep_btree_navigator.h" +#include "absl/strings/internal/cord_rep_flat.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace cord_internal { + +// CordRepBtreeReader implements logic to iterate over cord btrees. +// References to the underlying data are returned as absl::string_view values. +// The most typical use case is a forward only iteration over tree data. +// The class also provides `Skip()`, `Seek()` and `Read()` methods similar to +// CordRepBtreeNavigator that allow more advanced navigation. +// +// Example: iterate over all data inside a cord btree: +// +// CordRepBtreeReader reader; +// for (string_view sv = reader.Init(tree); !sv.Empty(); sv = sv.Next()) { +// DoSomethingWithDataIn(sv); +// } +// +// All navigation methods always return the next 'chunk' of data. The class +// assumes that all data is directly 'consumed' by the caller. For example: +// invoking `Skip()` will skip the desired number of bytes, and directly +// read and return the next chunk of data directly after the skipped bytes. +// +// Example: iterate over all data inside a btree skipping the first 100 bytes: +// +// CordRepBtreeReader reader; +// absl::string_view sv = reader.Init(tree); +// if (sv.length() > 100) { +// sv.RemovePrefix(100); +// } else { +// sv = reader.Skip(100 - sv.length()); +// } +// while (!sv.empty()) { +// DoSomethingWithDataIn(sv); +// absl::string_view sv = reader.Next(); +// } +// +// It is important to notice that `remaining` is based on the end position of +// the last data edge returned to the caller, not the cumulative data returned +// to the caller which can be less in cases of skipping or seeking over data. +// +// For example, consider a cord btree with five data edges: "abc", "def", "ghi", +// "jkl" and "mno": +// +// absl::string_view sv; +// CordRepBtreeReader reader; +// +// sv = reader.Init(tree); // sv = "abc", remaining = 12 +// sv = reader.Skip(4); // sv = "hi", remaining = 6 +// sv = reader.Skip(2); // sv = "l", remaining = 3 +// sv = reader.Next(); // sv = "mno", remaining = 0 +// sv = reader.Seek(1); // sv = "bc", remaining = 12 +// +class CordRepBtreeReader { + public: + using ReadResult = CordRepBtreeNavigator::ReadResult; + using Position = CordRepBtreeNavigator::Position; + + // Returns true if this instance is not empty. + explicit operator bool() const { return navigator_.btree() != nullptr; } + + // Returns the tree referenced by this instance or nullptr if empty. + CordRepBtree* btree() const { return navigator_.btree(); } + + // Returns the current data edge inside the referenced btree. + // Requires that the current instance is not empty. + CordRep* node() const { return navigator_.Current(); } + + // Returns the length of the referenced tree. + // Requires that the current instance is not empty. + size_t length() const; + + // Returns the number of remaining bytes available for iteration, which is the + // number of bytes directly following the end of the last chunk returned. + // This value will be zero if we iterated over the last edge in the bound + // tree, in which case any call to Next() or Skip() will return an empty + // string_view reflecting the EOF state. + // Note that a call to `Seek()` resets `remaining` to a value based on the + // end position of the chunk returned by that call. + size_t remaining() const { return remaining_; } + + // Resets this instance to an empty value. + void Reset() { navigator_.Reset(); } + + // Initializes this instance with `tree`. `tree` must not be null. + // Returns a reference to the first data edge of the provided tree. + absl::string_view Init(CordRepBtree* tree); + + // Navigates to and returns the next data edge of the referenced tree. + // Returns an empty string_view if an attempt is made to read beyond the end + // of the tree, i.e.: if `remaining()` is zero indicating an EOF condition. + // Requires that the current instance is not empty. + absl::string_view Next(); + + // Skips the provided amount of bytes and returns a reference to the data + // directly following the skipped bytes. + absl::string_view Skip(size_t skip); + + // Reads `n` bytes into `tree`. + // If `chunk_size` is zero, starts reading at the next data edge. If + // `chunk_size` is non zero, the read starts at the last `chunk_size` bytes of + // the last returned data edge. Effectively, this means that the read starts + // at offset `consumed() - chunk_size`. + // Requires that `chunk_size` is less than or equal to the length of the + // last returned data edge. The purpose of `chunk_size` is to simplify code + // partially consuming a returned chunk and wanting to include the remaining + // bytes in the Read call. For example, the below code will read 1000 bytes of + // data into a cord tree if the first chunk starts with "big:": + // + // CordRepBtreeReader reader; + // absl::string_view sv = reader.Init(tree); + // if (absl::StartsWith(sv, "big:")) { + // CordRepBtree tree; + // sv = reader.Read(1000, sv.size() - 4 /* "big:" */, &tree); + // } + // + // This method will return an empty string view if all remaining data was + // read. If `n` exceeded the amount of remaining data this function will + // return an empty string view and `tree` will be set to nullptr. + // In both cases, `consumed` will be set to `length`. + absl::string_view Read(size_t n, size_t chunk_size, CordRep*& tree); + + // Navigates to the chunk at offset `offset`. + // Returns a reference into the navigated to chunk, adjusted for the relative + // position of `offset` into that chunk. For example, calling `Seek(13)` on a + // cord tree containing 2 chunks of 10 and 20 bytes respectively will return + // a string view into the second chunk starting at offset 3 with a size of 17. + // Returns an empty string view if `offset` is equal to or greater than the + // length of the referenced tree. + absl::string_view Seek(size_t offset); + + private: + size_t remaining_ = 0; + CordRepBtreeNavigator navigator_; +}; + +inline size_t CordRepBtreeReader::length() const { + assert(btree() != nullptr); + return btree()->length; +} + +inline absl::string_view CordRepBtreeReader::Init(CordRepBtree* tree) { + assert(tree != nullptr); + const CordRep* edge = navigator_.InitFirst(tree); + remaining_ = tree->length - edge->length; + return CordRepBtree::EdgeData(edge); +} + +inline absl::string_view CordRepBtreeReader::Next() { + if (remaining_ == 0) return {}; + const CordRep* edge = navigator_.Next(); + assert(edge != nullptr); + remaining_ -= edge->length; + return CordRepBtree::EdgeData(edge); +} + +inline absl::string_view CordRepBtreeReader::Skip(size_t skip) { + // As we are always positioned on the last 'consumed' edge, we + // need to skip the current edge as well as `skip`. + const size_t edge_length = navigator_.Current()->length; + CordRepBtreeNavigator::Position pos = navigator_.Skip(skip + edge_length); + if (ABSL_PREDICT_FALSE(pos.edge == nullptr)) { + remaining_ = 0; + return {}; + } + // The combined length of all edges skipped before `pos.edge` is `skip - + // pos.offset`, all of which are 'consumed', as well as the current edge. + remaining_ -= skip - pos.offset + pos.edge->length; + return CordRepBtree::EdgeData(pos.edge).substr(pos.offset); +} + +inline absl::string_view CordRepBtreeReader::Seek(size_t offset) { + const CordRepBtreeNavigator::Position pos = navigator_.Seek(offset); + if (ABSL_PREDICT_FALSE(pos.edge == nullptr)) { + remaining_ = 0; + return {}; + } + absl::string_view chunk = CordRepBtree::EdgeData(pos.edge).substr(pos.offset); + remaining_ = length() - offset - chunk.length(); + return chunk; +} + +} // namespace cord_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_STRINGS_INTERNAL_CORD_REP_BTREE_READER_H_ -- cgit v1.2.3