403 lines
15 KiB
C
403 lines
15 KiB
C
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// Protocol Buffers - Google's data interchange format
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// Copyright 2008 Google Inc. All rights reserved.
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// https://developers.google.com/protocol-buffers/
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// A StringPiece points to part or all of a string, Cord, double-quoted string
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// literal, or other string-like object. A StringPiece does *not* own the
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// string to which it points. A StringPiece is not null-terminated.
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//
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// You can use StringPiece as a function or method parameter. A StringPiece
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// parameter can receive a double-quoted string literal argument, a "const
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// char*" argument, a string argument, or a StringPiece argument with no data
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// copying. Systematic use of StringPiece for arguments reduces data
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// copies and strlen() calls.
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//
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// Prefer passing StringPieces by value:
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// void MyFunction(StringPiece arg);
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// If circumstances require, you may also pass by const reference:
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// void MyFunction(const StringPiece& arg); // not preferred
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// Both of these have the same lifetime semantics. Passing by value
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// generates slightly smaller code. For more discussion, see the thread
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// go/stringpiecebyvalue on c-users.
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//
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// StringPiece is also suitable for local variables if you know that
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// the lifetime of the underlying object is longer than the lifetime
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// of your StringPiece variable.
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//
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// Beware of binding a StringPiece to a temporary:
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// StringPiece sp = obj.MethodReturningString(); // BAD: lifetime problem
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//
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// This code is okay:
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// string str = obj.MethodReturningString(); // str owns its contents
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// StringPiece sp(str); // GOOD, because str outlives sp
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//
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// StringPiece is sometimes a poor choice for a return value and usually a poor
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// choice for a data member. If you do use a StringPiece this way, it is your
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// responsibility to ensure that the object pointed to by the StringPiece
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// outlives the StringPiece.
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//
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// A StringPiece may represent just part of a string; thus the name "Piece".
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// For example, when splitting a string, vector<StringPiece> is a natural data
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// type for the output. For another example, a Cord is a non-contiguous,
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// potentially very long string-like object. The Cord class has an interface
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// that iteratively provides StringPiece objects that point to the
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// successive pieces of a Cord object.
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//
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// A StringPiece is not null-terminated. If you write code that scans a
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// StringPiece, you must check its length before reading any characters.
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// Common idioms that work on null-terminated strings do not work on
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// StringPiece objects.
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//
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// There are several ways to create a null StringPiece:
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// StringPiece()
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// StringPiece(nullptr)
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// StringPiece(nullptr, 0)
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// For all of the above, sp.data() == nullptr, sp.length() == 0,
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// and sp.empty() == true. Also, if you create a StringPiece with
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// a non-null pointer then sp.data() != nullptr. Once created,
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// sp.data() will stay either nullptr or not-nullptr, except if you call
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// sp.clear() or sp.set().
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//
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// Thus, you can use StringPiece(nullptr) to signal an out-of-band value
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// that is different from other StringPiece values. This is similar
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// to the way that const char* p1 = nullptr; is different from
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// const char* p2 = "";.
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//
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// There are many ways to create an empty StringPiece:
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// StringPiece()
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// StringPiece(nullptr)
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// StringPiece(nullptr, 0)
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// StringPiece("")
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// StringPiece("", 0)
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// StringPiece("abcdef", 0)
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// StringPiece("abcdef"+6, 0)
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// For all of the above, sp.length() will be 0 and sp.empty() will be true.
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// For some empty StringPiece values, sp.data() will be nullptr.
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// For some empty StringPiece values, sp.data() will not be nullptr.
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//
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// Be careful not to confuse: null StringPiece and empty StringPiece.
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// The set of empty StringPieces properly includes the set of null StringPieces.
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// That is, every null StringPiece is an empty StringPiece,
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// but some non-null StringPieces are empty Stringpieces too.
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//
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// All empty StringPiece values compare equal to each other.
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// Even a null StringPieces compares equal to a non-null empty StringPiece:
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// StringPiece() == StringPiece("", 0)
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// StringPiece(nullptr) == StringPiece("abc", 0)
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// StringPiece(nullptr, 0) == StringPiece("abcdef"+6, 0)
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//
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// Look carefully at this example:
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// StringPiece("") == nullptr
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// True or false? TRUE, because StringPiece::operator== converts
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// the right-hand side from nullptr to StringPiece(nullptr),
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// and then compares two zero-length spans of characters.
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// However, we are working to make this example produce a compile error.
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//
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// Suppose you want to write:
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// bool TestWhat?(StringPiece sp) { return sp == nullptr; } // BAD
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// Do not do that. Write one of these instead:
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// bool TestNull(StringPiece sp) { return sp.data() == nullptr; }
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// bool TestEmpty(StringPiece sp) { return sp.empty(); }
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// The intent of TestWhat? is unclear. Did you mean TestNull or TestEmpty?
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// Right now, TestWhat? behaves likes TestEmpty.
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// We are working to make TestWhat? produce a compile error.
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// TestNull is good to test for an out-of-band signal.
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// TestEmpty is good to test for an empty StringPiece.
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//
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// Caveats (again):
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// (1) The lifetime of the pointed-to string (or piece of a string)
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// must be longer than the lifetime of the StringPiece.
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// (2) There may or may not be a '\0' character after the end of
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// StringPiece data.
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// (3) A null StringPiece is empty.
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// An empty StringPiece may or may not be a null StringPiece.
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#ifndef GOOGLE_PROTOBUF_STUBS_STRINGPIECE_H_
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#define GOOGLE_PROTOBUF_STUBS_STRINGPIECE_H_
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#include <assert.h>
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#include <stddef.h>
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#include <string.h>
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#include <iosfwd>
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#include <limits>
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#include <string>
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#if defined(__cpp_lib_string_view)
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#include <string_view>
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#endif
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#include <google/protobuf/stubs/hash.h>
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#include <google/protobuf/port_def.inc>
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namespace google {
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namespace protobuf {
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namespace stringpiece_internal {
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class PROTOBUF_EXPORT StringPiece {
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public:
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using traits_type = std::char_traits<char>;
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using value_type = char;
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using pointer = char*;
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using const_pointer = const char*;
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using reference = char&;
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using const_reference = const char&;
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using const_iterator = const char*;
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using iterator = const_iterator;
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using const_reverse_iterator = std::reverse_iterator<const_iterator>;
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using reverse_iterator = const_reverse_iterator;
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using size_type = size_t;
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using difference_type = std::ptrdiff_t;
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private:
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const char* ptr_;
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size_type length_;
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static constexpr size_type kMaxSize =
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(std::numeric_limits<difference_type>::max)();
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static size_type CheckSize(size_type size) {
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#if !defined(NDEBUG) || defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0
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if (PROTOBUF_PREDICT_FALSE(size > kMaxSize)) {
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// Some people grep for this message in logs
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// so take care if you ever change it.
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LogFatalSizeTooBig(size, "string length exceeds max size");
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}
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#endif
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return size;
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}
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// Out-of-line error path.
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static void LogFatalSizeTooBig(size_type size, const char* details);
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public:
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// We provide non-explicit singleton constructors so users can pass
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// in a "const char*" or a "string" wherever a "StringPiece" is
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// expected.
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//
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// Style guide exception granted:
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// http://goto/style-guide-exception-20978288
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StringPiece() : ptr_(nullptr), length_(0) {}
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StringPiece(const char* str) // NOLINT(runtime/explicit)
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: ptr_(str), length_(0) {
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if (str != nullptr) {
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length_ = CheckSize(strlen(str));
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}
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}
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template <class Allocator>
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StringPiece( // NOLINT(runtime/explicit)
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const std::basic_string<char, std::char_traits<char>, Allocator>& str)
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: ptr_(str.data()), length_(0) {
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length_ = CheckSize(str.size());
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}
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#if defined(__cpp_lib_string_view)
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StringPiece( // NOLINT(runtime/explicit)
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std::string_view str)
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: ptr_(str.data()), length_(0) {
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length_ = CheckSize(str.size());
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}
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#endif
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StringPiece(const char* offset, size_type len)
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: ptr_(offset), length_(CheckSize(len)) {}
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// data() may return a pointer to a buffer with embedded NULs, and the
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// returned buffer may or may not be null terminated. Therefore it is
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// typically a mistake to pass data() to a routine that expects a NUL
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// terminated string.
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const_pointer data() const { return ptr_; }
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size_type size() const { return length_; }
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size_type length() const { return length_; }
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bool empty() const { return length_ == 0; }
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char operator[](size_type i) const {
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assert(i < length_);
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return ptr_[i];
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}
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void remove_prefix(size_type n) {
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assert(length_ >= n);
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ptr_ += n;
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length_ -= n;
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}
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void remove_suffix(size_type n) {
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assert(length_ >= n);
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length_ -= n;
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}
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// returns {-1, 0, 1}
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int compare(StringPiece x) const {
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size_type min_size = length_ < x.length_ ? length_ : x.length_;
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int r = memcmp(ptr_, x.ptr_, static_cast<size_t>(min_size));
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if (r < 0) return -1;
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if (r > 0) return 1;
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if (length_ < x.length_) return -1;
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if (length_ > x.length_) return 1;
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return 0;
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}
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std::string as_string() const { return ToString(); }
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// We also define ToString() here, since many other string-like
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// interfaces name the routine that converts to a C++ string
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// "ToString", and it's confusing to have the method that does that
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// for a StringPiece be called "as_string()". We also leave the
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// "as_string()" method defined here for existing code.
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std::string ToString() const {
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if (ptr_ == nullptr) return "";
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return std::string(data(), static_cast<size_type>(size()));
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}
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explicit operator std::string() const { return ToString(); }
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void CopyToString(std::string* target) const;
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void AppendToString(std::string* target) const;
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bool starts_with(StringPiece x) const {
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return (length_ >= x.length_) &&
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(memcmp(ptr_, x.ptr_, static_cast<size_t>(x.length_)) == 0);
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}
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bool ends_with(StringPiece x) const {
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return ((length_ >= x.length_) &&
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(memcmp(ptr_ + (length_-x.length_), x.ptr_,
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static_cast<size_t>(x.length_)) == 0));
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}
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// Checks whether StringPiece starts with x and if so advances the beginning
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// of it to past the match. It's basically a shortcut for starts_with
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// followed by remove_prefix.
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bool Consume(StringPiece x);
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// Like above but for the end of the string.
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bool ConsumeFromEnd(StringPiece x);
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// standard STL container boilerplate
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static const size_type npos;
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const_iterator begin() const { return ptr_; }
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const_iterator end() const { return ptr_ + length_; }
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const_reverse_iterator rbegin() const {
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return const_reverse_iterator(ptr_ + length_);
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}
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const_reverse_iterator rend() const {
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return const_reverse_iterator(ptr_);
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}
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size_type max_size() const { return length_; }
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size_type capacity() const { return length_; }
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// cpplint.py emits a false positive [build/include_what_you_use]
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size_type copy(char* buf, size_type n, size_type pos = 0) const; // NOLINT
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bool contains(StringPiece s) const;
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size_type find(StringPiece s, size_type pos = 0) const;
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size_type find(char c, size_type pos = 0) const;
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size_type rfind(StringPiece s, size_type pos = npos) const;
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size_type rfind(char c, size_type pos = npos) const;
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size_type find_first_of(StringPiece s, size_type pos = 0) const;
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size_type find_first_of(char c, size_type pos = 0) const {
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return find(c, pos);
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}
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size_type find_first_not_of(StringPiece s, size_type pos = 0) const;
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size_type find_first_not_of(char c, size_type pos = 0) const;
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size_type find_last_of(StringPiece s, size_type pos = npos) const;
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size_type find_last_of(char c, size_type pos = npos) const {
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return rfind(c, pos);
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}
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size_type find_last_not_of(StringPiece s, size_type pos = npos) const;
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size_type find_last_not_of(char c, size_type pos = npos) const;
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StringPiece substr(size_type pos, size_type n = npos) const;
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};
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// This large function is defined inline so that in a fairly common case where
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// one of the arguments is a literal, the compiler can elide a lot of the
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// following comparisons.
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inline bool operator==(StringPiece x, StringPiece y) {
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StringPiece::size_type len = x.size();
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if (len != y.size()) {
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return false;
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}
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return x.data() == y.data() || len <= 0 ||
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memcmp(x.data(), y.data(), static_cast<size_t>(len)) == 0;
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}
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inline bool operator!=(StringPiece x, StringPiece y) {
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return !(x == y);
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}
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inline bool operator<(StringPiece x, StringPiece y) {
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const StringPiece::size_type min_size =
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x.size() < y.size() ? x.size() : y.size();
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const int r = memcmp(x.data(), y.data(), static_cast<size_t>(min_size));
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return (r < 0) || (r == 0 && x.size() < y.size());
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}
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inline bool operator>(StringPiece x, StringPiece y) {
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return y < x;
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}
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inline bool operator<=(StringPiece x, StringPiece y) {
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return !(x > y);
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}
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inline bool operator>=(StringPiece x, StringPiece y) {
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return !(x < y);
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}
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// allow StringPiece to be logged
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extern std::ostream& operator<<(std::ostream& o, StringPiece piece);
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} // namespace stringpiece_internal
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using ::google::protobuf::stringpiece_internal::StringPiece;
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} // namespace protobuf
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} // namespace google
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GOOGLE_PROTOBUF_HASH_NAMESPACE_DECLARATION_START
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template<> struct hash<StringPiece> {
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size_t operator()(const StringPiece& s) const {
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size_t result = 0;
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for (const char *str = s.data(), *end = str + s.size(); str < end; str++) {
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result = 5 * result + static_cast<size_t>(*str);
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}
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return result;
|
||
|
}
|
||
|
};
|
||
|
GOOGLE_PROTOBUF_HASH_NAMESPACE_DECLARATION_END
|
||
|
|
||
|
#include <google/protobuf/port_undef.inc>
|
||
|
|
||
|
#endif // STRINGS_STRINGPIECE_H_
|