From 3a2d6572d06709da32a17f053ca1e3c8e2af90df Mon Sep 17 00:00:00 2001 From: Abseil Team Date: Thu, 21 Jan 2021 12:04:50 -0800 Subject: Export of internal Abseil changes -- 3b43586da865534cf86401d2cae09c65c60b8474 by Abseil Team : Introduce CordRepRingReader class PiperOrigin-RevId: 353070937 -- 0bff6e4bcca34fdd1e6610da5fb3c37fd49b2940 by Abseil Team : Fix docstring typo "Exmaple" -> "Example" PiperOrigin-RevId: 352927688 -- 1ef4e0a1100cfa7bc9d9e8f155acf0e469348b56 by Abseil Team : Refactor tree initialization of ChunkIterator and CordReader PiperOrigin-RevId: 352916786 -- 919c3eb175b87294184a405785eef4fab520d47e by Abseil Team : Disable `preserve_most` when compiling with sanitizers. PiperOrigin-RevId: 352890630 GitOrigin-RevId: 3b43586da865534cf86401d2cae09c65c60b8474 Change-Id: I8a733494b353af69a46862a4019a7f9b40148f49 --- absl/strings/internal/cord_rep_ring_reader.h | 114 +++++++++++++++++++++++++++ 1 file changed, 114 insertions(+) create mode 100644 absl/strings/internal/cord_rep_ring_reader.h (limited to 'absl/strings/internal/cord_rep_ring_reader.h') diff --git a/absl/strings/internal/cord_rep_ring_reader.h b/absl/strings/internal/cord_rep_ring_reader.h new file mode 100644 index 00000000..396c0e2c --- /dev/null +++ b/absl/strings/internal/cord_rep_ring_reader.h @@ -0,0 +1,114 @@ +// 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_RING_READER_H_ +#define ABSL_STRINGS_INTERNAL_CORD_REP_RING_READER_H_ + +#include +#include +#include + +#include "absl/strings/internal/cord_internal.h" +#include "absl/strings/internal/cord_rep_ring.h" +#include "absl/strings/string_view.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace cord_internal { + +// CordRepRingReader provides basic navigation over CordRepRing data. +class CordRepRingReader { + public: + // Returns true if this instance is not empty. + explicit operator bool() const { return ring_ != nullptr; } + + // Returns the ring buffer reference for this instance, or nullptr if empty. + CordRepRing* ring() const { return ring_; } + + // Returns the current node index inside the ring buffer for this instance. + // The returned value is undefined if this instance is empty. + CordRepRing::index_type index() const { return index_; } + + // Returns the length of the referenced ring buffer. + // Requires the current instance to be non empty. + size_t length() const { + assert(ring_); + return ring_->length; + } + + // Returns the end offset of the last navigated-to chunk, which represents the + // total bytes 'consumed' relative to the start of the ring. The returned + // value is never zero. For example, initializing a reader with a ring buffer + // with a first chunk of 19 bytes will return consumed() = 19. + // Requires the current instance to be non empty. + size_t consumed() const { + assert(ring_); + return ring_->entry_end_offset(index_); + } + + // Returns the number of bytes remaining beyond the last navigated-to chunk. + // Requires the current instance to be non empty. + size_t remaining() const { + assert(ring_); + return length() - consumed(); + } + + // Resets this instance to an empty value + void Reset() { ring_ = nullptr; } + + // Resets this instance to the start of `ring`. `ring` must not be null. + // Returns a reference into the first chunk of the provided ring. + absl::string_view Reset(CordRepRing* ring) { + assert(ring); + ring_ = ring; + index_ = ring_->head(); + return ring_->entry_data(index_); + } + + // Navigates to the next chunk inside the reference ring buffer. + // Returns a reference into the navigated-to chunk. + // Requires remaining() to be non zero. + absl::string_view Next() { + assert(remaining()); + index_ = ring_->advance(index_); + return ring_->entry_data(index_); + } + + // 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 + // ring buffer 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. + // Requires `offset` to be less than `length()` + absl::string_view Seek(size_t offset) { + assert(offset < length()); + size_t current = ring_->entry_end_offset(index_); + CordRepRing::index_type hint = (offset >= current) ? index_ : ring_->head(); + const CordRepRing::Position head = ring_->Find(hint, offset); + index_ = head.index; + auto data = ring_->entry_data(head.index); + data.remove_prefix(head.offset); + return data; + } + + private: + CordRepRing* ring_ = nullptr; + CordRepRing::index_type index_; +}; + +} // namespace cord_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_STRINGS_INTERNAL_CORD_REP_RING_READER_H_ -- cgit v1.2.3