//===- Disassembler.cpp - Disassembler for hex strings --------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This class implements the disassembler of strings of bytes written in
// hexadecimal, from standard input or from a file.
//
//===----------------------------------------------------------------------===//

#include "Disassembler.h"
#include "../../lib/MC/MCDisassembler/EDDisassembler.h"
#include "../../lib/MC/MCDisassembler/EDInst.h"
#include "../../lib/MC/MCDisassembler/EDOperand.h"
#include "../../lib/MC/MCDisassembler/EDToken.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCDisassembler.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstPrinter.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/MemoryObject.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;

typedef std::vector<std::pair<unsigned char, const char*> > ByteArrayTy;

namespace {
class VectorMemoryObject : public MemoryObject {
private:
  const ByteArrayTy &Bytes;
public:
  VectorMemoryObject(const ByteArrayTy &bytes) : Bytes(bytes) {}

  uint64_t getBase() const { return 0; }
  uint64_t getExtent() { return Bytes.size(); }

  int readByte(uint64_t Addr, uint8_t *Byte) {
    if (Addr >= getExtent())
      return -1;
    *Byte = Bytes[Addr].first;
    return 0;
  }
};
}

static bool PrintInsts(const MCDisassembler &DisAsm,
                       MCInstPrinter &Printer, const ByteArrayTy &Bytes,
                       SourceMgr &SM, raw_ostream &Out) {
  // Wrap the vector in a MemoryObject.
  VectorMemoryObject memoryObject(Bytes);

  // Disassemble it to strings.
  uint64_t Size;
  uint64_t Index;

  for (Index = 0; Index < Bytes.size(); Index += Size) {
    MCInst Inst;

    MCDisassembler::DecodeStatus S;
    S = DisAsm.getInstruction(Inst, Size, memoryObject, Index,
                              /*REMOVE*/ nulls(), nulls());
    switch (S) {
    case MCDisassembler::Fail:
      SM.PrintMessage(SMLoc::getFromPointer(Bytes[Index].second),
                      SourceMgr::DK_Warning,
                      "invalid instruction encoding");
      if (Size == 0)
        Size = 1; // skip illegible bytes
      break;

    case MCDisassembler::SoftFail:
      SM.PrintMessage(SMLoc::getFromPointer(Bytes[Index].second),
                      SourceMgr::DK_Warning,
                      "potentially undefined instruction encoding");
      // Fall through

    case MCDisassembler::Success:
      Printer.printInst(&Inst, Out, "");
      Out << "\n";
      break;
    }
  }

  return false;
}

static bool ByteArrayFromString(ByteArrayTy &ByteArray,
                                StringRef &Str,
                                SourceMgr &SM) {
  while (!Str.empty()) {
    // Strip horizontal whitespace.
    if (size_t Pos = Str.find_first_not_of(" \t\r")) {
      Str = Str.substr(Pos);
      continue;
    }

    // If this is the end of a line or start of a comment, remove the rest of
    // the line.
    if (Str[0] == '\n' || Str[0] == '#') {
      // Strip to the end of line if we already processed any bytes on this
      // line.  This strips the comment and/or the \n.
      if (Str[0] == '\n') {
        Str = Str.substr(1);
      } else {
        Str = Str.substr(Str.find_first_of('\n'));
        if (!Str.empty())
          Str = Str.substr(1);
      }
      continue;
    }

    // Get the current token.
    size_t Next = Str.find_first_of(" \t\n\r#");
    StringRef Value = Str.substr(0, Next);

    // Convert to a byte and add to the byte vector.
    unsigned ByteVal;
    if (Value.getAsInteger(0, ByteVal) || ByteVal > 255) {
      // If we have an error, print it and skip to the end of line.
      SM.PrintMessage(SMLoc::getFromPointer(Value.data()), SourceMgr::DK_Error,
                      "invalid input token");
      Str = Str.substr(Str.find('\n'));
      ByteArray.clear();
      continue;
    }

    ByteArray.push_back(std::make_pair((unsigned char)ByteVal, Value.data()));
    Str = Str.substr(Next);
  }

  return false;
}

int Disassembler::disassemble(const Target &T,
                              const std::string &Triple,
                              const std::string &Cpu,
                              const std::string &FeaturesStr,
                              MemoryBuffer &Buffer,
                              raw_ostream &Out) {
  // Set up disassembler.
  OwningPtr<const MCAsmInfo> AsmInfo(T.createMCAsmInfo(Triple));

  if (!AsmInfo) {
    errs() << "error: no assembly info for target " << Triple << "\n";
    return -1;
  }

  OwningPtr<const MCSubtargetInfo> STI(T.createMCSubtargetInfo(Triple, Cpu, FeaturesStr));
  if (!STI) {
    errs() << "error: no subtarget info for target " << Triple << "\n";
    return -1;
  }
  
  OwningPtr<const MCDisassembler> DisAsm(T.createMCDisassembler(*STI));
  if (!DisAsm) {
    errs() << "error: no disassembler for target " << Triple << "\n";
    return -1;
  }

  int AsmPrinterVariant = AsmInfo->getAssemblerDialect();
  OwningPtr<MCInstPrinter> IP(T.createMCInstPrinter(AsmPrinterVariant,
                                                    *AsmInfo, *STI));
  if (!IP) {
    errs() << "error: no instruction printer for target " << Triple << '\n';
    return -1;
  }

  bool ErrorOccurred = false;

  SourceMgr SM;
  SM.AddNewSourceBuffer(&Buffer, SMLoc());

  // Convert the input to a vector for disassembly.
  ByteArrayTy ByteArray;
  StringRef Str = Buffer.getBuffer();

  ErrorOccurred |= ByteArrayFromString(ByteArray, Str, SM);

  if (!ByteArray.empty())
    ErrorOccurred |= PrintInsts(*DisAsm, *IP, ByteArray, SM, Out);

  return ErrorOccurred;
}

static int byteArrayReader(uint8_t *B, uint64_t A, void *Arg) {
  ByteArrayTy &ByteArray = *((ByteArrayTy*)Arg);

  if (A >= ByteArray.size())
    return -1;

  *B = ByteArray[A].first;

  return 0;
}

static int verboseEvaluator(uint64_t *V, unsigned R, void *Arg) {
  EDDisassembler &disassembler = *(EDDisassembler *)((void **)Arg)[0];
  raw_ostream &Out = *(raw_ostream *)((void **)Arg)[1];

  if (const char *regName = disassembler.nameWithRegisterID(R))
    Out << "[" << regName << "/" << R << "]";

  if (disassembler.registerIsStackPointer(R))
    Out << "(sp)";
  if (disassembler.registerIsProgramCounter(R))
    Out << "(pc)";

  *V = 0;
  return 0;
}

int Disassembler::disassembleEnhanced(const std::string &TS,
                                      MemoryBuffer &Buffer,
                                      raw_ostream &Out) {
  ByteArrayTy ByteArray;
  StringRef Str = Buffer.getBuffer();
  SourceMgr SM;

  SM.AddNewSourceBuffer(&Buffer, SMLoc());

  if (ByteArrayFromString(ByteArray, Str, SM)) {
    return -1;
  }

  Triple T(TS);
  EDDisassembler::AssemblySyntax AS;

  switch (T.getArch()) {
  default:
    errs() << "error: no default assembly syntax for " << TS.c_str() << "\n";
    return -1;
  case Triple::arm:
  case Triple::thumb:
    AS = EDDisassembler::kEDAssemblySyntaxARMUAL;
    break;
  case Triple::x86:
  case Triple::x86_64:
    AS = EDDisassembler::kEDAssemblySyntaxX86ATT;
    break;
  }

  OwningPtr<EDDisassembler>
    disassembler(EDDisassembler::getDisassembler(TS.c_str(), AS));

  if (disassembler == 0) {
    errs() << "error: couldn't get disassembler for " << TS << '\n';
    return -1;
  }

  while (ByteArray.size()) {
    OwningPtr<EDInst>
      inst(disassembler->createInst(byteArrayReader, 0, &ByteArray));

    if (inst == 0) {
      errs() << "error: Didn't get an instruction\n";
      return -1;
    }

    ByteArray.erase (ByteArray.begin(), ByteArray.begin() + inst->byteSize());

    unsigned numTokens = inst->numTokens();
    if ((int)numTokens < 0) {
      errs() << "error: couldn't count the instruction's tokens\n";
      return -1;
    }

    for (unsigned tokenIndex = 0; tokenIndex != numTokens; ++tokenIndex) {
      EDToken *token;

      if (inst->getToken(token, tokenIndex)) {
        errs() << "error: Couldn't get token\n";
        return -1;
      }

      const char *buf;
      if (token->getString(buf)) {
        errs() << "error: Couldn't get string for token\n";
        return -1;
      }

      Out << '[';
      int operandIndex = token->operandID();

      if (operandIndex >= 0)
        Out << operandIndex << "-";

      switch (token->type()) {
      case EDToken::kTokenWhitespace: Out << "w"; break;
      case EDToken::kTokenPunctuation: Out << "p"; break;
      case EDToken::kTokenOpcode: Out << "o"; break;
      case EDToken::kTokenLiteral: Out << "l"; break;
      case EDToken::kTokenRegister: Out << "r"; break;
      }

      Out << ":" << buf;

      if (token->type() == EDToken::kTokenLiteral) {
        Out << "=";
        if (token->literalSign())
          Out << "-";
        uint64_t absoluteValue;
        if (token->literalAbsoluteValue(absoluteValue)) {
          errs() << "error: Couldn't get the value of a literal token\n";
          return -1;
        }
        Out << absoluteValue;
      } else if (token->type() == EDToken::kTokenRegister) {
        Out << "=";
        unsigned regID;
        if (token->registerID(regID)) {
          errs() << "error: Couldn't get the ID of a register token\n";
          return -1;
        }
        Out << "r" << regID;
      }

      Out << "]";
    }

    Out << " ";

    if (inst->isBranch())
      Out << "<br> ";
    if (inst->isMove())
      Out << "<mov> ";

    unsigned numOperands = inst->numOperands();

    if ((int)numOperands < 0) {
      errs() << "error: Couldn't count operands\n";
      return -1;
    }

    for (unsigned operandIndex = 0; operandIndex != numOperands;
         ++operandIndex) {
      Out << operandIndex << ":";

      EDOperand *operand;
      if (inst->getOperand(operand, operandIndex)) {
        errs() << "error: couldn't get operand\n";
        return -1;
      }

      uint64_t evaluatedResult;
      void *Arg[] = { disassembler.get(), &Out };
      if (operand->evaluate(evaluatedResult, verboseEvaluator, Arg)) {
        errs() << "error: Couldn't evaluate an operand\n";
        return -1;
      }
      Out << "=" << evaluatedResult << " ";
    }

    Out << '\n';
  }

  return 0;
}