//
// Copyright (C) 2016 Google, Inc.
//
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#include "hlslTokenStream.h"

namespace glslang {

void HlslTokenStream::pushPreToken(const HlslToken& tok)
{
    assert(preTokenStackSize < tokenBufferSize);
    preTokenStack[preTokenStackSize++] = tok;
}

HlslToken HlslTokenStream::popPreToken()
{
    assert(preTokenStackSize > 0);

    return preTokenStack[--preTokenStackSize];
}

void HlslTokenStream::pushTokenBuffer(const HlslToken& tok)
{
    tokenBuffer[tokenBufferPos] = tok;
    tokenBufferPos = (tokenBufferPos+1) % tokenBufferSize;
}

HlslToken HlslTokenStream::popTokenBuffer()
{
    // Back up
    tokenBufferPos = (tokenBufferPos+tokenBufferSize-1) % tokenBufferSize;

    return tokenBuffer[tokenBufferPos];
}

//
// Make a new source of tokens, not from the source, but from an
// already pre-processed token stream.
//
// This interrupts current token processing which must be restored
// later.  Some simplifying assumptions are made (and asserted).
//
void HlslTokenStream::pushTokenStream(const TVector<HlslToken>* tokens)
{
    // not yet setup to interrupt a stream that has been receded
    // and not yet reconsumed
    assert(preTokenStackSize == 0);

    // save current state
    currentTokenStack.push_back(token);

    // set up new token stream
    tokenStreamStack.push_back(tokens);

    // start position at first token:
    token = (*tokens)[0];
    tokenPosition.push_back(0);
}

// Undo pushTokenStream(), see above
void HlslTokenStream::popTokenStream()
{
    tokenStreamStack.pop_back();
    tokenPosition.pop_back();
    token = currentTokenStack.back();
    currentTokenStack.pop_back();
}

// Load 'token' with the next token in the stream of tokens.
void HlslTokenStream::advanceToken()
{
    pushTokenBuffer(token);
    if (preTokenStackSize > 0)
        token = popPreToken();
    else {
        if (tokenStreamStack.size() == 0)
            scanner.tokenize(token);
        else {
            ++tokenPosition.back();
            if (tokenPosition.back() >= (int)tokenStreamStack.back()->size())
                token.tokenClass = EHTokNone;
            else
                token = (*tokenStreamStack.back())[tokenPosition.back()];
        }
    }
}

void HlslTokenStream::recedeToken()
{
    pushPreToken(token);
    token = popTokenBuffer();
}

// Return the current token class.
EHlslTokenClass HlslTokenStream::peek() const
{
    return token.tokenClass;
}

// Return true, without advancing to the next token, if the current token is
// the expected (passed in) token class.
bool HlslTokenStream::peekTokenClass(EHlslTokenClass tokenClass) const
{
    return peek() == tokenClass;
}

// Return true and advance to the next token if the current token is the
// expected (passed in) token class.
bool HlslTokenStream::acceptTokenClass(EHlslTokenClass tokenClass)
{
    if (peekTokenClass(tokenClass)) {
        advanceToken();
        return true;
    }

    return false;
}

} // end namespace glslang