//
//Copyright (C) 2002-2005  3Dlabs Inc. Ltd.
//Copyright (C) 2013 LunarG, Inc.
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#ifndef _GLSLANG_SCAN_INCLUDED_
#define _GLSLANG_SCAN_INCLUDED_

#include "Versions.h"

namespace glslang {

// Use a global end-of-input character, so no tranlation is needed across
// layers of encapsulation.  Characters are all 8 bit, and positive, so there is
// no aliasing of character 255 onto -1, for example.
const int EndOfInput = -1;

//
// A character scanner that seamlessly, on read-only strings, reads across an
// array of strings without assuming null termination.
//
class TInputScanner {
public:
    TInputScanner(int n, const char* const s[], size_t L[], const char* const* names = nullptr, int b = 0, int f = 0) :
        numSources(n),
        sources(reinterpret_cast<const unsigned char* const *>(s)), // up to this point, common usage is "char*", but now we need positive 8-bit characters
        lengths(L), currentSource(0), currentChar(0), stringBias(b), finale(f)
    {
        loc = new TSourceLoc[numSources];
        for (int i = 0; i < numSources; ++i) {
            loc[i].init();
        }
        if (names != nullptr) {
            for (int i = 0; i < numSources; ++i)
                loc[i].name = names[i];
        }
        loc[currentSource].string = -stringBias;
        loc[currentSource].line = 1;
        loc[currentSource].column = 0;
    }

    virtual ~TInputScanner()
    {
        delete [] loc;
    }

    // retrieve the next character and advance one character
    int get()
    {
        if (currentSource >= numSources)
            return EndOfInput;

        int ret = peek();
        ++loc[currentSource].column;
        if (ret == '\n') {
            ++loc[currentSource].line;
            loc[currentSource].column = 0;
        }
        advance();

        return ret;
    }

    // retrieve the next character, no advance
    int peek()
    {
        if (currentSource >= numSources)
            return EndOfInput;
        // Make sure we do not read off the end of a string.
        // N.B. Sources can have a length of 0.
        int sourceToRead = currentSource;
        size_t charToRead = currentChar;
        while(charToRead >= lengths[sourceToRead]) {
            charToRead = 0;
            sourceToRead += 1;
            if (sourceToRead >= numSources) {
                return EndOfInput;
            }
        }

        // Here, we care about making negative valued characters positive
        return sources[sourceToRead][charToRead];
    }

    // go back one character
    void unget()
    {
        if (currentChar > 0) {
            --currentChar;
            --loc[currentSource].column;
            if (loc[currentSource].column < 0) {
                // We've moved back past a new line. Find the
                // previous newline (or start of the file) to compute
                // the column count on the now current line.
                size_t chIndex = currentChar;
                while (chIndex > 0) {
                    if (sources[currentSource][chIndex] == '\n') {
                        break;
                    }
                    --chIndex;
                }
                loc[currentSource].column = (int)(currentChar - chIndex);
            }
        } else {
            do {
                --currentSource;
            } while (currentSource > 0 && lengths[currentSource] == 0);
            if (lengths[currentSource] == 0) {
                // set to 0 if we've backed up to the start of an empty string
                currentChar = 0;
            } else
                currentChar = lengths[currentSource] - 1;
        }
        if (peek() == '\n')
            --loc[currentSource].line;
    }

    // for #line override
    void setLine(int newLine) { loc[getLastValidSourceIndex()].line = newLine; }
    void setFile(const char* filename) { loc[getLastValidSourceIndex()].name = filename; }
    void setString(int newString)
    {
        loc[getLastValidSourceIndex()].string = newString;
        loc[getLastValidSourceIndex()].name = nullptr;
    }

    const TSourceLoc& getSourceLoc() const { return loc[std::max(0, std::min(currentSource, numSources - finale - 1))]; }
    // Returns the index (starting from 0) of the most recent valid source string we are reading from.
    int getLastValidSourceIndex() const { return std::min(currentSource, numSources - 1); }

    void consumeWhiteSpace(bool& foundNonSpaceTab);
    bool consumeComment();
    void consumeWhitespaceComment(bool& foundNonSpaceTab);
    bool scanVersion(int& version, EProfile& profile, bool& notFirstToken);

protected:

    // advance one character
    void advance()
    {
        ++currentChar;
        if (currentChar >= static_cast<int>(lengths[currentSource])) {
            ++currentSource;
            if (currentSource < numSources) {
                loc[currentSource].string = loc[currentSource - 1].string + 1;
                loc[currentSource].line = 1;
                loc[currentSource].column = 0;
            }
            while (currentSource < numSources && lengths[currentSource] == 0) {
                ++currentSource;
                if (currentSource < numSources) {
                    loc[currentSource].string = loc[currentSource - 1].string + 1;
                    loc[currentSource].line = 1;
                    loc[currentSource].column = 0;
                }
            }
            currentChar = 0;
        }
    }

    int numSources;                      // number of strings in source
    const unsigned char* const *sources; // array of strings; must be converted to positive values on use, to avoid aliasing with -1 as EndOfInput
    const size_t *lengths;               // length of each string
    int currentSource;
    size_t currentChar;

    // This is for reporting what string/line an error occurred on, and can be overridden by #line.
    // It remembers the last state of each source string as it is left for the next one, so unget() 
    // can restore that state.
    TSourceLoc* loc;  // an array

    int stringBias;   // the first string that is the user's string number 0
    int finale;       // number of internal strings after user's last string
};

} // end namespace glslang

#endif // _GLSLANG_SCAN_INCLUDED_