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// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_STRINGS_STRING_TOKENIZER_H_
#define BASE_STRINGS_STRING_TOKENIZER_H_
#include <algorithm>
#include <string>
#include "base/strings/string_piece.h"
#include "base/strings/string_util.h"
namespace gurl_base {
// StringTokenizerT is a simple string tokenizer class. It works like an
// iterator that with each step (see the Advance method) updates members that
// refer to the next token in the input string. The user may optionally
// configure the tokenizer to return delimiters. For the optional
// WhitespacePolicy parameter, kSkipOver will cause the tokenizer to skip
// over whitespace characters. The tokenizer never stops on a whitespace
// character.
//
// EXAMPLE 1:
//
// char input[] = "this is a test";
// CStringTokenizer t(input, input + strlen(input), " ");
// while (t.GetNext()) {
// printf("%s\n", t.token().c_str());
// }
//
// Output:
//
// this
// is
// a
// test
//
//
// EXAMPLE 2:
//
// std::string input = "no-cache=\"foo, bar\", private";
// StringTokenizer t(input, ", ");
// t.set_quote_chars("\"");
// while (t.GetNext()) {
// printf("%s\n", t.token().c_str());
// }
//
// Output:
//
// no-cache="foo, bar"
// private
//
//
// EXAMPLE 3:
//
// bool next_is_option = false, next_is_value = false;
// std::string input = "text/html; charset=UTF-8; foo=bar";
// StringTokenizer t(input, "; =");
// t.set_options(StringTokenizer::RETURN_DELIMS);
// while (t.GetNext()) {
// if (t.token_is_delim()) {
// switch (*t.token_begin()) {
// case ';':
// next_is_option = true;
// break;
// case '=':
// next_is_value = true;
// break;
// }
// } else {
// const char* label;
// if (next_is_option) {
// label = "option-name";
// next_is_option = false;
// } else if (next_is_value) {
// label = "option-value";
// next_is_value = false;
// } else {
// label = "mime-type";
// }
// printf("%s: %s\n", label, t.token().c_str());
// }
// }
//
//
// EXAMPLE 4:
//
// std::string input = "this, \t is, \t a, \t test";
// StringTokenizer t(input, ",",
// StringTokenizer::WhitespacePolicy::kSkipOver);
// while (t.GetNext()) {
// printf("%s\n", t.token().c_str());
// }
//
// Output:
//
// this
// is
// a
// test
//
//
template <class str, class const_iterator>
class StringTokenizerT {
public:
typedef typename str::value_type char_type;
// Options that may be pass to set_options()
enum {
// Specifies the delimiters should be returned as tokens
RETURN_DELIMS = 1 << 0,
// Specifies that empty tokens should be returned. Treats the beginning and
// ending of the string as implicit delimiters, though doesn't return them
// as tokens if RETURN_DELIMS is also used.
RETURN_EMPTY_TOKENS = 1 << 1,
};
// Policy indicating what to do with whitespace characters. Whitespace is
// defined to be the characters indicated here:
// https://www.w3schools.com/jsref/jsref_regexp_whitespace.asp
enum class WhitespacePolicy {
// Whitespace should be treated the same as any other non-delimiter
// character.
kIncludeInTokens,
// Whitespace is skipped over and not included in the resulting token.
// Whitespace will also delimit other tokens, however it is never returned
// even if RETURN_DELIMS is set. If quote chars are set (See set_quote_chars
// below) Whitespace will be included in a token when processing quotes.
kSkipOver,
};
// The string object must live longer than the tokenizer. In particular, this
// should not be constructed with a temporary. The deleted rvalue constructor
// blocks the most obvious instances of this (e.g. passing a string literal to
// the constructor), but caution must still be exercised.
StringTokenizerT(
const str& string,
const str& delims,
WhitespacePolicy whitespace_policy = WhitespacePolicy::kIncludeInTokens) {
Init(string.begin(), string.end(), delims, whitespace_policy);
}
// Don't allow temporary strings to be used with string tokenizer, since
// Init() would otherwise save iterators to a temporary string.
StringTokenizerT(str&&, const str& delims) = delete;
StringTokenizerT(
const_iterator string_begin,
const_iterator string_end,
const str& delims,
WhitespacePolicy whitespace_policy = WhitespacePolicy::kIncludeInTokens) {
Init(string_begin, string_end, delims, whitespace_policy);
}
// Set the options for this tokenizer. By default, this is 0.
void set_options(int options) { options_ = options; }
// Set the characters to regard as quotes. By default, this is empty. When
// a quote char is encountered, the tokenizer will switch into a mode where
// it ignores delimiters that it finds. It switches out of this mode once it
// finds another instance of the quote char. If a backslash is encountered
// within a quoted string, then the next character is skipped.
void set_quote_chars(const str& quotes) { quotes_ = quotes; }
// Call this method to advance the tokenizer to the next delimiter. This
// returns false if the tokenizer is complete. This method must be called
// before calling any of the token* methods.
bool GetNext() {
if (quotes_.empty() && options_ == 0)
return QuickGetNext();
else
return FullGetNext();
}
// Start iterating through tokens from the beginning of the string.
void Reset() {
token_end_ = start_pos_;
}
// Returns true if token is a delimiter. When the tokenizer is constructed
// with the RETURN_DELIMS option, this method can be used to check if the
// returned token is actually a delimiter. Returns true before the first
// time GetNext() has been called, and after GetNext() returns false.
bool token_is_delim() const { return token_is_delim_; }
// If GetNext() returned true, then these methods may be used to read the
// value of the token.
const_iterator token_begin() const { return token_begin_; }
const_iterator token_end() const { return token_end_; }
str token() const { return str(token_begin_, token_end_); }
BasicStringPiece<char_type> token_piece() const {
return MakeBasicStringPiece<char_type>(token_begin_, token_end_);
}
private:
void Init(const_iterator string_begin,
const_iterator string_end,
const str& delims,
WhitespacePolicy whitespace_policy) {
start_pos_ = string_begin;
token_begin_ = string_begin;
token_end_ = string_begin;
end_ = string_end;
delims_ = delims;
options_ = 0;
token_is_delim_ = true;
whitespace_policy_ = whitespace_policy;
}
bool ShouldSkip(char_type c) const {
return whitespace_policy_ == WhitespacePolicy::kSkipOver &&
IsAsciiWhitespace(c);
}
// Skip over any contiguous whitespace characters according to the whitespace
// policy.
void SkipWhitespace() {
while (token_end_ != end_ && ShouldSkip(*token_end_))
++token_end_;
}
// Implementation of GetNext() for when we have no quote characters. We have
// two separate implementations because AdvanceOne() is a hot spot in large
// text files with large tokens.
bool QuickGetNext() {
token_is_delim_ = false;
for (;;) {
token_begin_ = token_end_;
if (token_end_ == end_) {
token_is_delim_ = true;
return false;
}
++token_end_;
if (delims_.find(*token_begin_) == str::npos &&
!ShouldSkip(*token_begin_)) {
break;
}
// else skip over delimiter or skippable character.
}
while (token_end_ != end_ && delims_.find(*token_end_) == str::npos &&
!ShouldSkip(*token_end_)) {
++token_end_;
}
return true;
}
// Implementation of GetNext() for when we have to take quotes into account.
bool FullGetNext() {
AdvanceState state;
SkipWhitespace();
for (;;) {
if (token_is_delim_) {
// Last token was a delimiter. Note: This is also the case at the start.
//
// ... D T T T T D ...
// ^ ^
// | |
// | |token_end_| : The next character to look at or |end_|.
// |
// |token_begin_| : Points to delimiter or |token_end_|.
//
// The next token is always a non-delimiting token. It could be empty,
// however.
token_is_delim_ = false;
token_begin_ = token_end_;
// Slurp all non-delimiter characters into the token.
while (token_end_ != end_ && AdvanceOne(&state, *token_end_)) {
++token_end_;
}
// If it's non-empty, or empty tokens were requested, return the token.
if (token_begin_ != token_end_ || (options_ & RETURN_EMPTY_TOKENS))
return true;
}
GURL_DCHECK(!token_is_delim_);
// Last token was a regular token.
//
// ... T T T D T T ...
// ^ ^
// | |
// | token_end_ : The next character to look at. Always one
// | char beyond the token boundary.
// |
// token_begin_ : Points to beginning of token. Note: token could
// be empty, in which case
// token_begin_ == token_end_.
//
// The next token is always a delimiter. It could be |end_| however, but
// |end_| is also an implicit delimiter.
token_is_delim_ = true;
token_begin_ = token_end_;
if (token_end_ == end_)
return false;
// Look at the delimiter.
++token_end_;
if (options_ & RETURN_DELIMS)
return true;
}
return false;
}
bool IsDelim(char_type c) const { return delims_.find(c) != str::npos; }
bool IsQuote(char_type c) const { return quotes_.find(c) != str::npos; }
struct AdvanceState {
bool in_quote;
bool in_escape;
char_type quote_char;
AdvanceState() : in_quote(false), in_escape(false), quote_char('\0') {}
};
// Returns true if a delimiter or, depending on policy, whitespace was not
// hit.
bool AdvanceOne(AdvanceState* state, char_type c) {
if (state->in_quote) {
if (state->in_escape) {
state->in_escape = false;
} else if (c == '\\') {
state->in_escape = true;
} else if (c == state->quote_char) {
state->in_quote = false;
}
} else {
if (IsDelim(c) || ShouldSkip(c))
return false;
state->in_quote = IsQuote(state->quote_char = c);
}
return true;
}
const_iterator start_pos_;
const_iterator token_begin_;
const_iterator token_end_;
const_iterator end_;
str delims_;
str quotes_;
int options_;
bool token_is_delim_;
WhitespacePolicy whitespace_policy_;
};
typedef StringTokenizerT<std::string, std::string::const_iterator>
StringTokenizer;
typedef StringTokenizerT<std::u16string, std::u16string::const_iterator>
String16Tokenizer;
typedef StringTokenizerT<std::string, const char*> CStringTokenizer;
} // namespace base
#endif // BASE_STRINGS_STRING_TOKENIZER_H_