gecko-dev/xpcom/ds/nsCharSeparatedTokenizer.h

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* 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 __nsCharSeparatedTokenizer_h
#define __nsCharSeparatedTokenizer_h

#include "mozilla/RangedPtr.h"

#include "nsDependentSubstring.h"
#include "nsCRT.h"

/**
 * This parses a SeparatorChar-separated string into tokens.
 * Whitespace surrounding tokens is not treated as part of tokens, however
 * whitespace inside a token is. If the final token is the empty string, it is
 * not returned.
 *
 * Some examples, with SeparatorChar = ',':
 *
 * "foo, bar, baz" ->      "foo" "bar" "baz"
 * "foo,bar,baz" ->        "foo" "bar" "baz"
 * "foo , bar hi , baz" -> "foo" "bar hi" "baz"
 * "foo, ,bar,baz" ->      "foo" "" "bar" "baz"
 * "foo,,bar,baz" ->       "foo" "" "bar" "baz"
 * "foo,bar,baz," ->       "foo" "bar" "baz"
 *
 * The function used for whitespace detection is a template argument.
 * By default, it is NS_IsAsciiWhitespace.
 */
template<typename DependentSubstringType, bool IsWhitespace(char16_t)>
class nsTCharSeparatedTokenizer
{
  typedef typename DependentSubstringType::char_type CharType;
  typedef typename DependentSubstringType::substring_type SubstringType;

public:
    // Flags -- only one for now. If we need more, they should be defined to
    // be 1 << 1, 1 << 2, etc. (They're masks, and aFlags is a bitfield.)
    enum {
        SEPARATOR_OPTIONAL = 1
    };

    nsTCharSeparatedTokenizer(const SubstringType& aSource,
                              CharType aSeparatorChar,
                              uint32_t aFlags = 0)
        : mIter(aSource.Data(), aSource.Length()),
          mEnd(aSource.Data() + aSource.Length(), aSource.Data(),
               aSource.Length()),
          mSeparatorChar(aSeparatorChar),
          mWhitespaceBeforeFirstToken(false),
          mWhitespaceAfterCurrentToken(false),
          mSeparatorAfterCurrentToken(false),
          mSeparatorOptional(aFlags & SEPARATOR_OPTIONAL)
    {
        // Skip initial whitespace
        while (mIter < mEnd && IsWhitespace(*mIter)) {
            mWhitespaceBeforeFirstToken = true;
            ++mIter;
        }
    }

    /**
     * Checks if any more tokens are available.
     */
    bool hasMoreTokens() const
    {
        MOZ_ASSERT(mIter == mEnd || !IsWhitespace(*mIter),
                   "Should be at beginning of token if there is one");

        return mIter < mEnd;
    }

    /*
     * Returns true if there is whitespace prior to the first token.
     */
    bool whitespaceBeforeFirstToken() const
    {
        return mWhitespaceBeforeFirstToken;
    }

    /*
     * Returns true if there is a separator after the current token.
     * Useful if you want to check whether the last token has a separator
     * after it which may not be valid.
     */
    bool separatorAfterCurrentToken() const
    {
        return mSeparatorAfterCurrentToken;
    }

    /*
     * Returns true if there is any whitespace after the current token.
     */
    bool whitespaceAfterCurrentToken() const
    {
        return mWhitespaceAfterCurrentToken;
    }

    /**
     * Returns the next token.
     */
    const DependentSubstringType nextToken()
    {
        mozilla::RangedPtr<const CharType> tokenStart = mIter;
        mozilla::RangedPtr<const CharType> tokenEnd = mIter;

        MOZ_ASSERT(mIter == mEnd || !IsWhitespace(*mIter),
                   "Should be at beginning of token if there is one");

        // Search until we hit separator or end (or whitespace, if a separator
        // isn't required -- see clause with 'break' below).
        while (mIter < mEnd && *mIter != mSeparatorChar) {
          // Skip to end of the current word.
          while (mIter < mEnd &&
                 !IsWhitespace(*mIter) && *mIter != mSeparatorChar) {
              ++mIter;
          }
          tokenEnd = mIter;

          // Skip whitespace after the current word.
          mWhitespaceAfterCurrentToken = false;
          while (mIter < mEnd && IsWhitespace(*mIter)) {
              mWhitespaceAfterCurrentToken = true;
              ++mIter;
          }
          if (mSeparatorOptional) {
            // We've hit (and skipped) whitespace, and that's sufficient to end
            // our token, regardless of whether we've reached a SeparatorChar.
            break;
          } // (else, we'll keep looping until we hit mEnd or SeparatorChar)
        }

        mSeparatorAfterCurrentToken = (mIter != mEnd &&
                                       *mIter == mSeparatorChar);
        MOZ_ASSERT(mSeparatorOptional ||
                   (mSeparatorAfterCurrentToken == (mIter < mEnd)),
                   "If we require a separator and haven't hit the end of "
                   "our string, then we shouldn't have left the loop "
                   "unless we hit a separator");

        // Skip separator (and any whitespace after it), if we're at one.
        if (mSeparatorAfterCurrentToken) {
            ++mIter;

            while (mIter < mEnd && IsWhitespace(*mIter)) {
                mWhitespaceAfterCurrentToken = true;
                ++mIter;
            }
        }

        return Substring(tokenStart.get(), tokenEnd.get());
    }

private:
    mozilla::RangedPtr<const CharType> mIter;
    const mozilla::RangedPtr<const CharType> mEnd;
    CharType mSeparatorChar;
    bool mWhitespaceBeforeFirstToken;
    bool mWhitespaceAfterCurrentToken;
    bool mSeparatorAfterCurrentToken;
    bool mSeparatorOptional;
};

template<bool IsWhitespace(char16_t) = NS_IsAsciiWhitespace>
class nsCharSeparatedTokenizerTemplate
  : public nsTCharSeparatedTokenizer<nsDependentSubstring, IsWhitespace>
{
public:
  nsCharSeparatedTokenizerTemplate(const nsSubstring& aSource,
                                   char16_t aSeparatorChar,
                                   uint32_t aFlags = 0)
    : nsTCharSeparatedTokenizer<nsDependentSubstring,
                                IsWhitespace>(aSource, aSeparatorChar, aFlags)
  {
  }
};

typedef nsCharSeparatedTokenizerTemplate<> nsCharSeparatedTokenizer;

template<bool IsWhitespace(char16_t) = NS_IsAsciiWhitespace>
class nsCCharSeparatedTokenizerTemplate
  : public nsTCharSeparatedTokenizer<nsDependentCSubstring, IsWhitespace>
{
public:
  nsCCharSeparatedTokenizerTemplate(const nsCSubstring& aSource,
                                    char aSeparatorChar,
                                    uint32_t aFlags = 0)
    : nsTCharSeparatedTokenizer<nsDependentCSubstring,
                                IsWhitespace>(aSource, aSeparatorChar, aFlags)
  {
  }
};

typedef nsCCharSeparatedTokenizerTemplate<> nsCCharSeparatedTokenizer;

#endif /* __nsCharSeparatedTokenizer_h */