// Copyright 2011 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/parsing/duplicate-finder.h"

#include "src/conversions.h"
#include "src/unicode-cache.h"

namespace v8 {
namespace internal {

int DuplicateFinder::AddOneByteSymbol(Vector<const uint8_t> key, int value) {
  return AddSymbol(key, true, value);
}

int DuplicateFinder::AddTwoByteSymbol(Vector<const uint16_t> key, int value) {
  return AddSymbol(Vector<const uint8_t>::cast(key), false, value);
}

int DuplicateFinder::AddSymbol(Vector<const uint8_t> key, bool is_one_byte,
                               int value) {
  uint32_t hash = Hash(key, is_one_byte);
  byte* encoding = BackupKey(key, is_one_byte);
  base::HashMap::Entry* entry = map_.LookupOrInsert(encoding, hash);
  int old_value = static_cast<int>(reinterpret_cast<intptr_t>(entry->value));
  entry->value =
      reinterpret_cast<void*>(static_cast<intptr_t>(value | old_value));
  return old_value;
}

int DuplicateFinder::AddNumber(Vector<const uint8_t> key, int value) {
  DCHECK(key.length() > 0);
  // Quick check for already being in canonical form.
  if (IsNumberCanonical(key)) {
    return AddOneByteSymbol(key, value);
  }

  int flags = ALLOW_HEX | ALLOW_OCTAL | ALLOW_IMPLICIT_OCTAL | ALLOW_BINARY;
  double double_value = StringToDouble(unicode_constants_, key, flags, 0.0);
  int length;
  const char* string;
  if (!std::isfinite(double_value)) {
    string = "Infinity";
    length = 8;  // strlen("Infinity");
  } else {
    string = DoubleToCString(double_value,
                             Vector<char>(number_buffer_, kBufferSize));
    length = StrLength(string);
  }
  return AddSymbol(
      Vector<const byte>(reinterpret_cast<const byte*>(string), length), true,
      value);
}

bool DuplicateFinder::IsNumberCanonical(Vector<const uint8_t> number) {
  // Test for a safe approximation of number literals that are already
  // in canonical form: max 15 digits, no leading zeroes, except an
  // integer part that is a single zero, and no trailing zeros below
  // the decimal point.
  int pos = 0;
  int length = number.length();
  if (number.length() > 15) return false;
  if (number[pos] == '0') {
    pos++;
  } else {
    while (pos < length &&
           static_cast<unsigned>(number[pos] - '0') <= ('9' - '0'))
      pos++;
  }
  if (length == pos) return true;
  if (number[pos] != '.') return false;
  pos++;
  bool invalid_last_digit = true;
  while (pos < length) {
    uint8_t digit = number[pos] - '0';
    if (digit > '9' - '0') return false;
    invalid_last_digit = (digit == 0);
    pos++;
  }
  return !invalid_last_digit;
}

uint32_t DuplicateFinder::Hash(Vector<const uint8_t> key, bool is_one_byte) {
  // Primitive hash function, almost identical to the one used
  // for strings (except that it's seeded by the length and representation).
  int length = key.length();
  uint32_t hash = (length << 1) | (is_one_byte ? 1 : 0);
  for (int i = 0; i < length; i++) {
    uint32_t c = key[i];
    hash = (hash + c) * 1025;
    hash ^= (hash >> 6);
  }
  return hash;
}

bool DuplicateFinder::Match(void* first, void* second) {
  // Decode lengths.
  // Length + representation is encoded as base 128, most significant heptet
  // first, with a 8th bit being non-zero while there are more heptets.
  // The value encodes the number of bytes following, and whether the original
  // was Latin1.
  byte* s1 = reinterpret_cast<byte*>(first);
  byte* s2 = reinterpret_cast<byte*>(second);
  uint32_t length_one_byte_field = 0;
  byte c1;
  do {
    c1 = *s1;
    if (c1 != *s2) return false;
    length_one_byte_field = (length_one_byte_field << 7) | (c1 & 0x7f);
    s1++;
    s2++;
  } while ((c1 & 0x80) != 0);
  int length = static_cast<int>(length_one_byte_field >> 1);
  return memcmp(s1, s2, length) == 0;
}

byte* DuplicateFinder::BackupKey(Vector<const uint8_t> bytes,
                                 bool is_one_byte) {
  uint32_t one_byte_length = (bytes.length() << 1) | (is_one_byte ? 1 : 0);
  backing_store_.StartSequence();
  // Emit one_byte_length as base-128 encoded number, with the 7th bit set
  // on the byte of every heptet except the last, least significant, one.
  if (one_byte_length >= (1 << 7)) {
    if (one_byte_length >= (1 << 14)) {
      if (one_byte_length >= (1 << 21)) {
        if (one_byte_length >= (1 << 28)) {
          backing_store_.Add(
              static_cast<uint8_t>((one_byte_length >> 28) | 0x80));
        }
        backing_store_.Add(
            static_cast<uint8_t>((one_byte_length >> 21) | 0x80u));
      }
      backing_store_.Add(static_cast<uint8_t>((one_byte_length >> 14) | 0x80u));
    }
    backing_store_.Add(static_cast<uint8_t>((one_byte_length >> 7) | 0x80u));
  }
  backing_store_.Add(static_cast<uint8_t>(one_byte_length & 0x7f));

  backing_store_.AddBlock(bytes);
  return backing_store_.EndSequence().start();
}

}  // namespace internal
}  // namespace v8