//===- TGLexer.cpp - Lexer for TableGen -----------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Implement the Lexer for TableGen.
//
//===----------------------------------------------------------------------===//

#include "TGLexer.h"
#include "llvm/Support/Streams.h"
#include "llvm/Support/MemoryBuffer.h"
#include <ostream>
#include "llvm/Config/config.h"
#include <cctype>
using namespace llvm;

TGLexer::TGLexer(MemoryBuffer *StartBuf) : CurLineNo(1), CurBuf(StartBuf) {
  CurPtr = CurBuf->getBufferStart();
  TokStart = 0;
}

TGLexer::~TGLexer() {
  while (!IncludeStack.empty()) {
    delete IncludeStack.back().Buffer;
    IncludeStack.pop_back();
  }
  delete CurBuf;
}

/// ReturnError - Set the error to the specified string at the specified
/// location.  This is defined to always return tgtok::Error.
tgtok::TokKind TGLexer::ReturnError(const char *Loc, const std::string &Msg) {
  PrintError(Loc, Msg);
  return tgtok::Error;
}

void TGLexer::PrintIncludeStack(std::ostream &OS) const {
  for (unsigned i = 0, e = IncludeStack.size(); i != e; ++i)
    OS << "Included from " << IncludeStack[i].Buffer->getBufferIdentifier()
       << ":" << IncludeStack[i].LineNo << ":\n";
  OS << "Parsing " << CurBuf->getBufferIdentifier() << ":"
     << CurLineNo << ": ";
}

/// PrintError - Print the error at the specified location.
void TGLexer::PrintError(const char *ErrorLoc,  const std::string &Msg) const {
  PrintIncludeStack(*cerr.stream());
  cerr << Msg << "\n";
  assert(ErrorLoc && "Location not specified!");
  
  // Scan backward to find the start of the line.
  const char *LineStart = ErrorLoc;
  while (LineStart != CurBuf->getBufferStart() && 
         LineStart[-1] != '\n' && LineStart[-1] != '\r')
    --LineStart;
  // Get the end of the line.
  const char *LineEnd = ErrorLoc;
  while (LineEnd != CurBuf->getBufferEnd() && 
         LineEnd[0] != '\n' && LineEnd[0] != '\r')
    ++LineEnd;
  // Print out the line.
  cerr << std::string(LineStart, LineEnd) << "\n";
  // Print out spaces before the carat.
  for (const char *Pos = LineStart; Pos != ErrorLoc; ++Pos)
    cerr << (*Pos == '\t' ? '\t' : ' ');
  cerr << "^\n";
}

int TGLexer::getNextChar() {
  char CurChar = *CurPtr++;
  switch (CurChar) {
  default:
    return (unsigned char)CurChar;
  case 0:
    // A nul character in the stream is either the end of the current buffer or
    // a random nul in the file.  Disambiguate that here.
    if (CurPtr-1 != CurBuf->getBufferEnd())
      return 0;  // Just whitespace.
    
    // If this is the end of an included file, pop the parent file off the
    // include stack.
    if (!IncludeStack.empty()) {
      delete CurBuf;
      CurBuf = IncludeStack.back().Buffer;
      CurLineNo = IncludeStack.back().LineNo;
      CurPtr = IncludeStack.back().CurPtr;
      IncludeStack.pop_back();
      return getNextChar();
    }
    
    // Otherwise, return end of file.
    --CurPtr;  // Another call to lex will return EOF again.  
    return EOF;
  case '\n':
  case '\r':
    // Handle the newline character by ignoring it and incrementing the line
    // count.  However, be careful about 'dos style' files with \n\r in them.
    // Only treat a \n\r or \r\n as a single line.
    if ((*CurPtr == '\n' || (*CurPtr == '\r')) &&
        *CurPtr != CurChar)
      ++CurPtr;  // Eat the two char newline sequence.
      
    ++CurLineNo;
    return '\n';
  }  
}

tgtok::TokKind TGLexer::LexToken() {
  TokStart = CurPtr;
  // This always consumes at least one character.
  int CurChar = getNextChar();

  switch (CurChar) {
  default:
    // Handle letters: [a-zA-Z_]
    if (isalpha(CurChar) || CurChar == '_')
      return LexIdentifier();
      
    // Unknown character, emit an error.
    return ReturnError(TokStart, "Unexpected character");
  case EOF: return tgtok::Eof;
  case ':': return tgtok::colon;
  case ';': return tgtok::semi;
  case '.': return tgtok::period;
  case ',': return tgtok::comma;
  case '<': return tgtok::less;
  case '>': return tgtok::greater;
  case ']': return tgtok::r_square;
  case '{': return tgtok::l_brace;
  case '}': return tgtok::r_brace;
  case '(': return tgtok::l_paren;
  case ')': return tgtok::r_paren;
  case '=': return tgtok::equal;
  case '?': return tgtok::question;
      
  case 0:
  case ' ':
  case '\t':
  case '\n':
  case '\r':
    // Ignore whitespace.
    return LexToken();
  case '/':
    // If this is the start of a // comment, skip until the end of the line or
    // the end of the buffer.
    if (*CurPtr == '/')
      SkipBCPLComment();
    else if (*CurPtr == '*') {
      if (SkipCComment())
        return tgtok::Error;
    } else // Otherwise, this is an error.
      return ReturnError(TokStart, "Unexpected character");
    return LexToken();
  case '-': case '+':
  case '0': case '1': case '2': case '3': case '4': case '5': case '6':
  case '7': case '8': case '9':  
    return LexNumber();
  case '"': return LexString();
  case '$': return LexVarName();
  case '[': return LexBracket();
  case '!': return LexExclaim();
  }
}

/// LexString - Lex "[^"]*"
tgtok::TokKind TGLexer::LexString() {
  const char *StrStart = CurPtr;
  
  while (*CurPtr != '"') {
    // If we hit the end of the buffer, report an error.
    if (*CurPtr == 0 && CurPtr == CurBuf->getBufferEnd())
      return ReturnError(StrStart, "End of file in string literal");
    
    if (*CurPtr == '\n' || *CurPtr == '\r')
      return ReturnError(StrStart, "End of line in string literal");
    
    ++CurPtr;
  }
  
  CurStrVal.assign(StrStart, CurPtr);
  ++CurPtr;
  return tgtok::StrVal;
}

tgtok::TokKind TGLexer::LexVarName() {
  if (!isalpha(CurPtr[0]) && CurPtr[0] != '_')
    return ReturnError(TokStart, "Invalid variable name");
  
  // Otherwise, we're ok, consume the rest of the characters.
  const char *VarNameStart = CurPtr++;
  
  while (isalpha(*CurPtr) || isdigit(*CurPtr) || *CurPtr == '_')
    ++CurPtr;

  CurStrVal.assign(VarNameStart, CurPtr);
  return tgtok::VarName;
}


tgtok::TokKind TGLexer::LexIdentifier() {
  // The first letter is [a-zA-Z_].
  const char *IdentStart = TokStart;
  
  // Match the rest of the identifier regex: [0-9a-zA-Z_]*
  while (isalpha(*CurPtr) || isdigit(*CurPtr) || *CurPtr == '_')
    ++CurPtr;
  
  // Check to see if this identifier is a keyword.
  unsigned Len = CurPtr-IdentStart;
  
  if (Len == 3 && !memcmp(IdentStart, "int", 3)) return tgtok::Int;
  if (Len == 3 && !memcmp(IdentStart, "bit", 3)) return tgtok::Bit;
  if (Len == 4 && !memcmp(IdentStart, "bits", 4)) return tgtok::Bits;
  if (Len == 6 && !memcmp(IdentStart, "string", 6)) return tgtok::String;
  if (Len == 4 && !memcmp(IdentStart, "list", 4)) return tgtok::List;
  if (Len == 4 && !memcmp(IdentStart, "code", 4)) return tgtok::Code;
  if (Len == 3 && !memcmp(IdentStart, "dag", 3)) return tgtok::Dag;
  
  if (Len == 5 && !memcmp(IdentStart, "class", 5)) return tgtok::Class;
  if (Len == 3 && !memcmp(IdentStart, "def", 3)) return tgtok::Def;
  if (Len == 4 && !memcmp(IdentStart, "defm", 4)) return tgtok::Defm;
  if (Len == 10 && !memcmp(IdentStart, "multiclass", 10))
    return tgtok::MultiClass;
  if (Len == 5 && !memcmp(IdentStart, "field", 5)) return tgtok::Field;
  if (Len == 3 && !memcmp(IdentStart, "let", 3)) return tgtok::Let;
  if (Len == 2 && !memcmp(IdentStart, "in", 2)) return tgtok::In;
  
  if (Len == 7 && !memcmp(IdentStart, "include", 7)) {
    if (LexInclude()) return tgtok::Error;
    return Lex();
  }
    
  CurStrVal.assign(IdentStart, CurPtr);
  return tgtok::Id;
}

/// LexInclude - We just read the "include" token.  Get the string token that
/// comes next and enter the include.
bool TGLexer::LexInclude() {
  // The token after the include must be a string.
  tgtok::TokKind Tok = LexToken();
  if (Tok == tgtok::Error) return true;
  if (Tok != tgtok::StrVal) {
    PrintError(getLoc(), "Expected filename after include");
    return true;
  }

  // Get the string.
  std::string Filename = CurStrVal;

  // Try to find the file.
  MemoryBuffer *NewBuf = MemoryBuffer::getFile(&Filename[0], Filename.size());

  // If the file didn't exist directly, see if it's in an include path.
  for (unsigned i = 0, e = IncludeDirectories.size(); i != e && !NewBuf; ++i) {
    std::string IncFile = IncludeDirectories[i] + "/" + Filename;
    NewBuf = MemoryBuffer::getFile(&IncFile[0], IncFile.size());
  }
    
  if (NewBuf == 0) {
    PrintError(getLoc(), "Could not find include file '" + Filename + "'");
    return true;
  }
  
  // Save the line number and lex buffer of the includer.
  IncludeStack.push_back(IncludeRec(CurBuf, CurPtr, CurLineNo));
  
  CurLineNo = 1;  // Reset line numbering.
  CurBuf = NewBuf;
  CurPtr = CurBuf->getBufferStart();
  return false;
}

void TGLexer::SkipBCPLComment() {
  ++CurPtr;  // skip the second slash.
  while (1) {
    switch (*CurPtr) {
    case '\n':
    case '\r':
      return;  // Newline is end of comment.
    case 0:
      // If this is the end of the buffer, end the comment.
      if (CurPtr == CurBuf->getBufferEnd())
        return;
      break;
    }
    // Otherwise, skip the character.
    ++CurPtr;
  }
}

/// SkipCComment - This skips C-style /**/ comments.  The only difference from C
/// is that we allow nesting.
bool TGLexer::SkipCComment() {
  ++CurPtr;  // skip the star.
  unsigned CommentDepth = 1;
  
  while (1) {
    int CurChar = getNextChar();
    switch (CurChar) {
    case EOF:
      PrintError(TokStart, "Unterminated comment!");
      return true;
    case '*':
      // End of the comment?
      if (CurPtr[0] != '/') break;
      
      ++CurPtr;   // End the */.
      if (--CommentDepth == 0)
        return false;
      break;
    case '/':
      // Start of a nested comment?
      if (CurPtr[0] != '*') break;
      ++CurPtr;
      ++CommentDepth;
      break;
    }
  }
}

/// LexNumber - Lex:
///    [-+]?[0-9]+
///    0x[0-9a-fA-F]+
///    0b[01]+
tgtok::TokKind TGLexer::LexNumber() {
  if (CurPtr[-1] == '0') {
    if (CurPtr[0] == 'x') {
      ++CurPtr;
      const char *NumStart = CurPtr;
      while (isxdigit(CurPtr[0]))
        ++CurPtr;
      
      // Requires at least one hex digit.
      if (CurPtr == NumStart)
        return ReturnError(CurPtr-2, "Invalid hexadecimal number");

      CurIntVal = strtoll(NumStart, 0, 16);
      return tgtok::IntVal;
    } else if (CurPtr[0] == 'b') {
      ++CurPtr;
      const char *NumStart = CurPtr;
      while (CurPtr[0] == '0' || CurPtr[0] == '1')
        ++CurPtr;

      // Requires at least one binary digit.
      if (CurPtr == NumStart)
        return ReturnError(CurPtr-2, "Invalid binary number");
      CurIntVal = strtoll(NumStart, 0, 2);
      return tgtok::IntVal;
    }
  }

  // Check for a sign without a digit.
  if (!isdigit(CurPtr[0])) {
    if (CurPtr[-1] == '-')
      return tgtok::minus;
    else if (CurPtr[-1] == '+')
      return tgtok::plus;
  }
  
  while (isdigit(CurPtr[0]))
    ++CurPtr;
  CurIntVal = strtoll(TokStart, 0, 10);
  return tgtok::IntVal;
}

/// LexBracket - We just read '['.  If this is a code block, return it,
/// otherwise return the bracket.  Match: '[' and '[{ ( [^}]+ | }[^]] )* }]'
tgtok::TokKind TGLexer::LexBracket() {
  if (CurPtr[0] != '{')
    return tgtok::l_square;
  ++CurPtr;
  const char *CodeStart = CurPtr;
  while (1) {
    int Char = getNextChar();
    if (Char == EOF) break;
    
    if (Char != '}') continue;
    
    Char = getNextChar();
    if (Char == EOF) break;
    if (Char == ']') {
      CurStrVal.assign(CodeStart, CurPtr-2);
      return tgtok::CodeFragment;
    }
  }
  
  return ReturnError(CodeStart-2, "Unterminated Code Block");
}

/// LexExclaim - Lex '!' and '![a-zA-Z]+'.
tgtok::TokKind TGLexer::LexExclaim() {
  if (!isalpha(*CurPtr))
    return ReturnError(CurPtr-1, "Invalid \"!operator\"");
  
  const char *Start = CurPtr++;
  while (isalpha(*CurPtr))
    ++CurPtr;
  
  // Check to see which operator this is.
  unsigned Len = CurPtr-Start;
  
  if (Len == 3 && !memcmp(Start, "con", 3)) return tgtok::XConcat;
  if (Len == 3 && !memcmp(Start, "sra", 3)) return tgtok::XSRA;
  if (Len == 3 && !memcmp(Start, "srl", 3)) return tgtok::XSRL;
  if (Len == 3 && !memcmp(Start, "shl", 3)) return tgtok::XSHL;
  if (Len == 9 && !memcmp(Start, "strconcat", 9)) return tgtok::XStrConcat;
  
  return ReturnError(Start-1, "Unknown operator");
}