#include "tensorflow/core/lib/core/coding.h"

namespace tensorflow {
namespace core {

void EncodeFixed32(char* buf, uint32 value) {
  if (port::kLittleEndian) {
    memcpy(buf, &value, sizeof(value));
  } else {
    buf[0] = value & 0xff;
    buf[1] = (value >> 8) & 0xff;
    buf[2] = (value >> 16) & 0xff;
    buf[3] = (value >> 24) & 0xff;
  }
}

void EncodeFixed64(char* buf, uint64 value) {
  if (port::kLittleEndian) {
    memcpy(buf, &value, sizeof(value));
  } else {
    buf[0] = value & 0xff;
    buf[1] = (value >> 8) & 0xff;
    buf[2] = (value >> 16) & 0xff;
    buf[3] = (value >> 24) & 0xff;
    buf[4] = (value >> 32) & 0xff;
    buf[5] = (value >> 40) & 0xff;
    buf[6] = (value >> 48) & 0xff;
    buf[7] = (value >> 56) & 0xff;
  }
}

void PutFixed32(string* dst, uint32 value) {
  char buf[sizeof(value)];
  EncodeFixed32(buf, value);
  dst->append(buf, sizeof(buf));
}

void PutFixed64(string* dst, uint64 value) {
  char buf[sizeof(value)];
  EncodeFixed64(buf, value);
  dst->append(buf, sizeof(buf));
}

char* EncodeVarint32(char* dst, uint32 v) {
  // Operate on characters as unsigneds
  unsigned char* ptr = reinterpret_cast<unsigned char*>(dst);
  static const int B = 128;
  if (v < (1 << 7)) {
    *(ptr++) = v;
  } else if (v < (1 << 14)) {
    *(ptr++) = v | B;
    *(ptr++) = v >> 7;
  } else if (v < (1 << 21)) {
    *(ptr++) = v | B;
    *(ptr++) = (v >> 7) | B;
    *(ptr++) = v >> 14;
  } else if (v < (1 << 28)) {
    *(ptr++) = v | B;
    *(ptr++) = (v >> 7) | B;
    *(ptr++) = (v >> 14) | B;
    *(ptr++) = v >> 21;
  } else {
    *(ptr++) = v | B;
    *(ptr++) = (v >> 7) | B;
    *(ptr++) = (v >> 14) | B;
    *(ptr++) = (v >> 21) | B;
    *(ptr++) = v >> 28;
  }
  return reinterpret_cast<char*>(ptr);
}

void PutVarint32(string* dst, uint32 v) {
  char buf[5];
  char* ptr = EncodeVarint32(buf, v);
  dst->append(buf, ptr - buf);
}

char* EncodeVarint64(char* dst, uint64 v) {
  static const int B = 128;
  unsigned char* ptr = reinterpret_cast<unsigned char*>(dst);
  while (v >= B) {
    *(ptr++) = (v & (B - 1)) | B;
    v >>= 7;
  }
  *(ptr++) = static_cast<unsigned char>(v);
  return reinterpret_cast<char*>(ptr);
}

void PutVarint64(string* dst, uint64 v) {
  char buf[10];
  char* ptr = EncodeVarint64(buf, v);
  dst->append(buf, ptr - buf);
}

int VarintLength(uint64_t v) {
  int len = 1;
  while (v >= 128) {
    v >>= 7;
    len++;
  }
  return len;
}

const char* GetVarint32PtrFallback(const char* p, const char* limit,
                                   uint32* value) {
  uint32 result = 0;
  for (uint32 shift = 0; shift <= 28 && p < limit; shift += 7) {
    uint32 byte = *(reinterpret_cast<const unsigned char*>(p));
    p++;
    if (byte & 128) {
      // More bytes are present
      result |= ((byte & 127) << shift);
    } else {
      result |= (byte << shift);
      *value = result;
      return reinterpret_cast<const char*>(p);
    }
  }
  return NULL;
}

bool GetVarint32(StringPiece* input, uint32* value) {
  const char* p = input->data();
  const char* limit = p + input->size();
  const char* q = GetVarint32Ptr(p, limit, value);
  if (q == NULL) {
    return false;
  } else {
    *input = StringPiece(q, limit - q);
    return true;
  }
}

const char* GetVarint64Ptr(const char* p, const char* limit, uint64* value) {
  uint64 result = 0;
  for (uint32 shift = 0; shift <= 63 && p < limit; shift += 7) {
    uint64 byte = *(reinterpret_cast<const unsigned char*>(p));
    p++;
    if (byte & 128) {
      // More bytes are present
      result |= ((byte & 127) << shift);
    } else {
      result |= (byte << shift);
      *value = result;
      return reinterpret_cast<const char*>(p);
    }
  }
  return NULL;
}

bool GetVarint64(StringPiece* input, uint64* value) {
  const char* p = input->data();
  const char* limit = p + input->size();
  const char* q = GetVarint64Ptr(p, limit, value);
  if (q == NULL) {
    return false;
  } else {
    *input = StringPiece(q, limit - q);
    return true;
  }
}

}  // namespace core
}  // namespace tensorflow