/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef LIBTEXTCLASSIFIER_UTILS_STRINGS_STRINGPIECE_H_
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#define LIBTEXTCLASSIFIER_UTILS_STRINGS_STRINGPIECE_H_
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#include <stddef.h>
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#include <string>
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#include "utils/base/logging.h"
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namespace libtextclassifier3 {
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// Read-only "view" of a piece of data. Does not own the underlying data.
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class StringPiece {
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public:
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StringPiece() : StringPiece(nullptr, 0) {}
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StringPiece(const char *str) // NOLINT(runtime/explicit)
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: start_(str), size_(str == nullptr ? 0 : strlen(str)) {}
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StringPiece(const char *start, size_t size) : start_(start), size_(size) {}
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// Intentionally no "explicit" keyword: in function calls, we want strings to
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// be converted to StringPiece implicitly.
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StringPiece(const std::string &s) // NOLINT(runtime/explicit)
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: StringPiece(s.data(), s.size()) {}
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StringPiece(const std::string &s, int offset, int len)
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: StringPiece(s.data() + offset, len) {}
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char operator[](size_t i) const { return start_[i]; }
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// Returns start address of underlying data.
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const char *data() const { return start_; }
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// Returns number of bytes of underlying data.
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size_t size() const { return size_; }
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size_t length() const { return size_; }
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bool empty() const { return size_ == 0; }
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// Returns a std::string containing a copy of the underlying data.
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std::string ToString() const { return std::string(data(), size()); }
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// Returns whether string ends with a given suffix.
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bool EndsWith(StringPiece suffix) const {
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return suffix.empty() || (size_ >= suffix.size() &&
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memcmp(start_ + (size_ - suffix.size()),
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suffix.data(), suffix.size()) == 0);
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}
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// Returns whether the string begins with a given prefix.
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bool StartsWith(StringPiece prefix) const {
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return prefix.empty() ||
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(size_ >= prefix.size() &&
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memcmp(start_, prefix.data(), prefix.size()) == 0);
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}
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bool Equals(StringPiece other) const {
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return size() == other.size() && memcmp(start_, other.data(), size_) == 0;
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}
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// Removes the first `n` characters from the string piece. Note that the
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// underlying string is not changed, only the view.
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void RemovePrefix(int n) {
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TC3_CHECK_LE(n, size_);
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start_ += n;
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size_ -= n;
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}
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private:
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const char *start_; // Not owned.
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size_t size_;
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};
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inline bool EndsWith(StringPiece text, StringPiece suffix) {
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return text.EndsWith(suffix);
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}
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inline bool StartsWith(StringPiece text, StringPiece prefix) {
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return text.StartsWith(prefix);
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}
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inline bool ConsumePrefix(StringPiece *text, StringPiece prefix) {
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if (!text->StartsWith(prefix)) {
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return false;
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}
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text->RemovePrefix(prefix.size());
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return true;
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}
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} // namespace libtextclassifier3
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#endif // LIBTEXTCLASSIFIER_UTILS_STRINGS_STRINGPIECE_H_
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