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// Copyright 2010 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
// A string-like object that points to a sized piece of memory.
// Functions or methods may use const StringPiece& parameters to accept either
// a "const char*" or a "string" value that will be implicitly converted to
// a StringPiece. The implicit conversion means that it is often appropriate
// to include this .h file in other files rather than forward-declaring
// StringPiece as would be appropriate for most other Google classes.
// Systematic usage of StringPiece is encouraged as it will reduce unnecessary
// conversions from "const char*" to "string" and back again.
#include <string.h>
#include <algorithm>
#include <iosfwd>
#include <string>
namespace art {
class StringPiece {
const char* ptr_;
int length_;
// We provide non-explicit singleton constructors so users can pass
// in a "const char*" or a "string" wherever a "StringPiece" is
// expected.
StringPiece() : ptr_(NULL), length_(0) { }
StringPiece(const char* str) // NOLINT
: ptr_(str), length_((str == NULL) ? 0 : static_cast<int>(strlen(str))) { }
StringPiece(const std::string& str) // NOLINT
: ptr_(, length_(static_cast<int>(str.size())) { }
StringPiece(const char* offset, int len) : ptr_(offset), length_(len) { }
// data() may return a pointer to a buffer with embedded NULs, and the
// returned buffer may or may not be null terminated. Therefore it is
// typically a mistake to pass data() to a routine that expects a NUL
// terminated string.
const char* data() const { return ptr_; }
int size() const { return length_; }
int length() const { return length_; }
bool empty() const { return length_ == 0; }
void clear() {
ptr_ = NULL;
length_ = 0;
void set(const char* data, int len) {
ptr_ = data;
length_ = len;
void set(const char* str) {
ptr_ = str;
if (str != NULL)
length_ = static_cast<int>(strlen(str));
length_ = 0;
void set(const void* data, int len) {
ptr_ = reinterpret_cast<const char*>(data);
length_ = len;
char operator[](int i) const { return ptr_[i]; }
void remove_prefix(int n) {
ptr_ += n;
length_ -= n;
void remove_suffix(int n) {
length_ -= n;
int compare(const StringPiece& x) const;
std::string as_string() const {
return std::string(data(), size());
// We also define ToString() here, since many other string-like
// interfaces name the routine that converts to a C++ string
// "ToString", and it's confusing to have the method that does that
// for a StringPiece be called "as_string()". We also leave the
// "as_string()" method defined here for existing code.
std::string ToString() const {
return std::string(data(), size());
void CopyToString(std::string* target) const;
void AppendToString(std::string* target) const;
// Does "this" start with "x"
bool starts_with(const StringPiece& x) const {
return ((length_ >= x.length_) &&
(memcmp(ptr_, x.ptr_, x.length_) == 0));
// Does "this" end with "x"
bool ends_with(const StringPiece& x) const {
return ((length_ >= x.length_) &&
(memcmp(ptr_ + (length_-x.length_), x.ptr_, x.length_) == 0));
// standard STL container boilerplate
typedef char value_type;
typedef const char* pointer;
typedef const char& reference;
typedef const char& const_reference;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
static const size_type npos;
typedef const char* const_iterator;
typedef const char* iterator;
typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
typedef std::reverse_iterator<iterator> reverse_iterator;
iterator begin() const { return ptr_; }
iterator end() const { return ptr_ + length_; }
const_reverse_iterator rbegin() const {
return const_reverse_iterator(ptr_ + length_);
const_reverse_iterator rend() const {
return const_reverse_iterator(ptr_);
// STLS says return size_type, but Google says return int
int max_size() const { return length_; }
int capacity() const { return length_; }
int copy(char* buf, size_type n, size_type pos = 0) const;
size_type find(const StringPiece& s, size_type pos = 0) const;
size_type find(char c, size_type pos = 0) const;
size_type rfind(const StringPiece& s, size_type pos = npos) const;
size_type rfind(char c, size_type pos = npos) const;
StringPiece substr(size_type pos, size_type n = npos) const;
// This large function is defined inline so that in a fairly common case where
// one of the arguments is a literal, the compiler can elide a lot of the
// following comparisons.
inline bool operator==(const StringPiece& x, const StringPiece& y) {
int len = x.size();
if (len != y.size()) {
return false;
const char* p1 =;
const char* p2 =;
if (p1 == p2) {
return true;
if (len <= 0) {
return true;
// Test last byte in case strings share large common prefix
if (p1[len-1] != p2[len-1]) return false;
if (len == 1) return true;
// At this point we can, but don't have to, ignore the last byte. We use
// this observation to fold the odd-length case into the even-length case.
len &= ~1;
return memcmp(p1, p2, len) == 0;
inline bool operator!=(const StringPiece& x, const StringPiece& y) {
return !(x == y);
bool operator<(const StringPiece& x, const StringPiece& y);
inline bool operator>(const StringPiece& x, const StringPiece& y) {
return y < x;
inline bool operator<=(const StringPiece& x, const StringPiece& y) {
return !(x > y);
inline bool operator>=(const StringPiece& x, const StringPiece& y) {
return !(x < y);
extern std::ostream& operator<<(std::ostream& o, const StringPiece& piece);
struct StringPieceHash {
size_t operator()(const StringPiece& string_piece) const {
size_t string_size = string_piece.size();
const char* string_data =;
// This is the java.lang.String hashcode for convenience, not interoperability.
size_t hash = 0;
while (string_size--) {
hash = hash * 31 + *string_data++;
return hash;
} // namespace art