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/*
* Copyright 2017 Google
*
* 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
*
* http://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 IPHONE_FIRESTORE_SOURCE_LOCAL_STRING_VIEW_H_
#define IPHONE_FIRESTORE_SOURCE_LOCAL_STRING_VIEW_H_
#ifndef __cplusplus
#error "StringView is Objective-C++ and can only be included from .mm files"
#endif
#import <Foundation/Foundation.h>
#include <leveldb/slice.h>
#include <string>
namespace Firestore {
// A simple wrapper for the character data of any string-like type to which
// we'd like to temporarily refer as an argument.
//
// This is superficially similar to StringPiece and leveldb::Slice except
// that it also supports implicit conversion from NSString *, which is useful
// when writing Objective-C++ methods that accept any string-like type.
//
// Note that much like any other view-type class in C++, the caller is
// responsible for ensuring that the lifetime of the string-like data is longer
// than the lifetime of the StringView.
//
// Functions that take a StringView argument promise that they won't keep the
// pointer beyond the immediate scope of their own stack frame.
class StringView {
public:
// Creates a StringView from an NSString. When StringView is an argument type
// into which an NSString* is passed, the caller should ensure that the
// NSString is retained.
StringView(NSString *str)
: data_([str UTF8String]), size_([str lengthOfBytesUsingEncoding:NSUTF8StringEncoding]) {
}
// Creates a StringView from the given char* pointer with an explicit size.
// The character data can contain NUL bytes as a result.
StringView(const char *data, size_t size) : data_(data), size_(size) {
}
// Creates a StringView from the given char* pointer but computes the size
// with strlen. This is really only suitable for passing C string literals.
StringView(const char *data) : data_(data), size_(strlen(data)) {
}
// Creates a StringView from the given slice.
StringView(leveldb::Slice slice) : data_(slice.data()), size_(slice.size()) {
}
// Creates a StringView from the given std::string. The string must be an
// lvalue for the lifetime requirements to be satisfied.
StringView(const std::string &str) : data_(str.data()), size_(str.size()) {
}
// Converts this StringView to a Slice, which is an equivalent (and more
// functional) type. The returned slice has the same lifetime as this
// StringView.
operator leveldb::Slice() {
return leveldb::Slice(data_, size_);
}
private:
const char *data_;
const size_t size_;
};
} // namespace Firestore
#endif // IPHONE_FIRESTORE_SOURCE_LOCAL_STRING_VIEW_H_
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