gecko-dev/xpcom/ds/Tokenizer.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef Tokenizer_h__
#define Tokenizer_h__
#include "nsString.h"
#include "mozilla/CheckedInt.h"
namespace mozilla {
/**
* This is a simple implementation of a lexical analyzer or maybe better
* called a tokenizer. It doesn't allow any user dictionaries or
* user define token types.
*
* It is limited only to ASCII input for now. UTF-8 or any other input
* encoding must yet be implemented.
*/
class Tokenizer {
public:
/**
* The analyzer works with elements in the input cut to a sequence of token
* where each token has an elementary type
*/
enum TokenType {
TOKEN_UNKNOWN,
TOKEN_ERROR,
TOKEN_INTEGER,
TOKEN_WORD,
TOKEN_CHAR,
TOKEN_WS,
TOKEN_EOL,
TOKEN_EOF
};
/**
* Class holding the type and the value of a token. It can be manually created
* to allow checks against it via methods of Tokenizer or are results of some of
* the Tokenizer's methods.
*/
class Token {
TokenType mType;
nsDependentCSubstring mWord;
char mChar;
uint64_t mInteger;
// If this token is a result of the parsing process, this member is referencing
// a sub-string in the input buffer. If this is externally created Token this
// member is left an empty string.
nsDependentCSubstring mFragment;
friend class Tokenizer;
void AssignFragment(nsACString::const_char_iterator begin,
nsACString::const_char_iterator end);
public:
Token() : mType(TOKEN_UNKNOWN), mChar(0), mInteger(0) {}
Token(const Token& aOther);
Token& operator=(const Token& aOther);
// Static constructors of tokens by type and value
static Token Word(const nsACString& aWord);
static Token Char(const char aChar);
static Token Number(const uint64_t aNumber);
static Token Whitespace();
static Token NewLine();
static Token EndOfFile();
static Token Error();
// Compares the two tokens, type must be identical and value
// of one of the tokens must be 'any' or equal.
bool Equals(const Token& aOther) const;
TokenType Type() const { return mType; }
char AsChar() const;
nsDependentCSubstring AsString() const;
uint64_t AsInteger() const;
nsDependentCSubstring Fragment() const { return mFragment; }
};
public:
/**
* @param aSource
* The string to parse.
* IMPORTANT NOTE: Tokenizer doesn't ensure the input string buffer lifetime.
* It's up to the consumer to make sure the string's buffer outlives the Tokenizer!
* @param aWhitespaces
* If non-null Tokenizer will use this custom set of whitespaces for CheckWhite()
* and SkipWhites() calls.
* By default the list consists of space and tab.
* @param aAdditionalWordChars
* If non-null it will be added to the list of characters that consist a word.
* This is useful when you want to accept e.g. '-' in HTTP headers.
* By default a word character is consider any character for which upper case
* is different from lower case.
*
* If there is an overlap between aWhitespaces and aAdditionalWordChars, the check for
* word characters is made first.
*/
explicit Tokenizer(const nsACString& aSource,
const char* aWhitespaces = nullptr,
const char* aAdditionalWordChars = nullptr);
explicit Tokenizer(const char* aSource,
const char* aWhitespaces = nullptr,
const char* aAdditionalWordChars = nullptr);
/**
* When there is still anything to read from the input, tokenize it, store the token type
* and value to aToken result and shift the cursor past this just parsed token. Each call
* to Next() reads another token from the input and shifts the cursor.
* Returns false if we have passed the end of the input.
*/
MOZ_MUST_USE
bool Next(Token& aToken);
/**
* Parse the token on the input read cursor position, check its type is equal to aTokenType
* and if so, put it into aResult, shift the cursor and return true. Otherwise, leave
* the input read cursor position intact and return false.
*/
MOZ_MUST_USE
bool Check(const TokenType aTokenType, Token& aResult);
/**
* Same as above method, just compares both token type and token value passed in aToken.
* When both the type and the value equals, shift the cursor and return true. Otherwise
* return false.
*/
MOZ_MUST_USE
bool Check(const Token& aToken);
/**
* Return false iff the last Check*() call has returned false or when we've read past
* the end of the input string.
*/
MOZ_MUST_USE
bool HasFailed() const;
/**
* SkipWhites method (below) may also skip new line characters automatically.
*/
enum WhiteSkipping {
/**
* SkipWhites will only skip what is defined as a white space (default).
*/
DONT_INCLUDE_NEW_LINE = 0,
/**
* SkipWhites will skip definited white spaces as well as new lines
* automatically.
*/
INCLUDE_NEW_LINE = 1
};
/**
* Skips any occurence of whitespaces specified in mWhitespaces member,
* optionally skip also new lines.
*/
void SkipWhites(WhiteSkipping aIncludeNewLines = DONT_INCLUDE_NEW_LINE);
/**
* Skips all tokens until the given one is found or EOF is hit. The token
* or EOF are next to read.
*/
void SkipUntil(Token const& aToken);
// These are mostly shortcuts for the Check() methods above.
/**
* Check whitespace character is present.
*/
MOZ_MUST_USE
bool CheckWhite() { return Check(Token::Whitespace()); }
/**
* Check there is a single character on the read cursor position. If so, shift the read
* cursor position and return true. Otherwise false.
*/
MOZ_MUST_USE
bool CheckChar(const char aChar) { return Check(Token::Char(aChar)); }
/**
* This is a customizable version of CheckChar. aClassifier is a function called with
* value of the character on the current input read position. If this user function
* returns true, read cursor is shifted and true returned. Otherwise false.
* The user classifiction function is not called when we are at or past the end and
* false is immediately returned.
*/
MOZ_MUST_USE
bool CheckChar(bool (*aClassifier)(const char aChar));
/**
* Check for a whole expected word.
*/
MOZ_MUST_USE
bool CheckWord(const nsACString& aWord) { return Check(Token::Word(aWord)); }
/**
* Shortcut for literal const word check with compile time length calculation.
*/
template <uint32_t N>
MOZ_MUST_USE
bool CheckWord(const char (&aWord)[N]) { return Check(Token::Word(nsDependentCString(aWord, N - 1))); }
/**
* Checks \r, \n or \r\n.
*/
MOZ_MUST_USE
bool CheckEOL() { return Check(Token::NewLine()); }
/**
* Checks we are at the end of the input string reading. If so, shift past the end
* and returns true. Otherwise does nothing and returns false.
*/
MOZ_MUST_USE
bool CheckEOF() { return Check(Token::EndOfFile()); }
/**
* These are shortcuts to obtain the value immediately when the token type matches.
*/
MOZ_MUST_USE bool ReadChar(char* aValue);
MOZ_MUST_USE bool ReadChar(bool (*aClassifier)(const char aChar),
char* aValue);
MOZ_MUST_USE bool ReadWord(nsACString& aValue);
MOZ_MUST_USE bool ReadWord(nsDependentCSubstring& aValue);
/**
* This is an integer read helper. It returns false and doesn't move the read
* cursor when any of the following happens:
* - the token at the read cursor is not an integer
* - the final number doesn't fit the T type
* Otherwise true is returned, aValue is filled with the integral number
* and the cursor is moved forward.
*/
template <typename T>
MOZ_MUST_USE bool ReadInteger(T* aValue)
{
MOZ_RELEASE_ASSERT(aValue);
nsACString::const_char_iterator rollback = mRollback;
nsACString::const_char_iterator cursor = mCursor;
Token t;
if (!Check(TOKEN_INTEGER, t)) {
return false;
}
mozilla::CheckedInt<T> checked(t.AsInteger());
if (!checked.isValid()) {
// Move to a state as if Check() call has failed
mRollback = rollback;
mCursor = cursor;
mHasFailed = true;
return false;
}
*aValue = checked.value();
return true;
}
/**
* Returns the read cursor position back as it was before the last call of any parsing
* method of Tokenizer (Next, Check*, Skip*, Read*) so that the last operation
* can be repeated.
* Rollback cannot be used multiple times, it only reverts the last successfull parse
* operation. It also cannot be used before any parsing operation has been called
* on the Tokenizer.
*/
void Rollback();
/**
* Record() and Claim() are collecting the input as it is being parsed to obtain
* a substring between particular syntax bounderies defined by any recursive
* descent parser or simple parser the Tokenizer is used to read the input for.
* Inlucsion of a token that has just been parsed can be controlled using an arguemnt.
*/
enum ClaimInclusion {
/**
* Include resulting (or passed) token of the last lexical analyzer operation in the result.
*/
INCLUDE_LAST,
/**
* Do not include it.
*/
EXCLUDE_LAST
};
/**
* Start the process of recording. Based on aInclude value the begining of the recorded
* sub-string is at the current position (EXCLUDE_LAST) or at the position before the last
* parsed token (INCLUDE_LAST).
*/
void Record(ClaimInclusion aInclude = EXCLUDE_LAST);
/**
* Claim result of the record started with Record() call before. Depending on aInclude
* the ending of the sub-string result includes or excludes the last parsed or checked
* token.
*/
void Claim(nsACString& aResult, ClaimInclusion aInclude = EXCLUDE_LAST);
void Claim(nsDependentCSubstring& aResult, ClaimInclusion aInclude = EXCLUDE_LAST);
/**
* If aToken is found, aResult is set to the substring between the current
* position and the position of aToken, potentially including aToken depending
* on aInclude.
* If aToken isn't found aResult is set to the substring between the current
* position and the end of the string.
* If aToken is found, the method returns true. Otherwise it returns false.
*
* Calling Rollback() after ReadUntil() will return the read cursor to the
* position it had before ReadUntil was called.
*/
MOZ_MUST_USE bool ReadUntil(Token const& aToken, nsDependentCSubstring& aResult,
ClaimInclusion aInclude = EXCLUDE_LAST);
MOZ_MUST_USE bool ReadUntil(Token const& aToken, nsACString& aResult,
ClaimInclusion aInclude = EXCLUDE_LAST);
protected:
// false if we have already read the EOF token.
bool HasInput() const;
// Main parsing function, it doesn't shift the read cursor, just returns the next
// token position.
nsACString::const_char_iterator Parse(Token& aToken) const;
// Is read cursor at the end?
bool IsEnd(const nsACString::const_char_iterator& caret) const;
// Is read cursor on a character that is a word start?
bool IsWordFirst(const char aInput) const;
// Is read cursor on a character that is an in-word letter?
bool IsWord(const char aInput) const;
// Is read cursor on a character that is a valid number?
// TODO - support multiple radix
bool IsNumber(const char aInput) const;
// true iff we have already read the EOF token
bool mPastEof;
// true iff the last Check*() call has returned false, reverts to true on Rollback() call
bool mHasFailed;
// Customizable list of whitespaces
const char* mWhitespaces;
// Additinal custom word characters
const char* mAdditionalWordChars;
// All these point to the original buffer passed to the Tokenizer
nsACString::const_char_iterator mRecord; // Position where the recorded sub-string for Claim() is
nsACString::const_char_iterator mRollback; // Position of the previous token start
nsACString::const_char_iterator mCursor; // Position of the current (actually next to read) token start
nsACString::const_char_iterator mEnd; // End of the input position
private:
Tokenizer() = delete;
Tokenizer(const Tokenizer&) = delete;
Tokenizer(Tokenizer&&) = delete;
Tokenizer(const Tokenizer&&) = delete;
Tokenizer &operator=(const Tokenizer&) = delete;
};
} // mozilla
#endif // Tokenizer_h__