#include "tensorflow/core/lib/strings/strcat.h"

#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

#include "tensorflow/core/platform/logging.h"
#include "tensorflow/core/lib/gtl/stl_util.h"

namespace tensorflow {
namespace strings {

AlphaNum gEmptyAlphaNum("");

AlphaNum::AlphaNum(Hex hex) {
  char *const end = &digits_[kFastToBufferSize];
  char *writer = end;
  uint64 value = hex.value;
  uint64 width = hex.spec;
  // We accomplish minimum width by OR'ing in 0x10000 to the user's value,
  // where 0x10000 is the smallest hex number that is as wide as the user
  // asked for.
  uint64 mask = ((static_cast<uint64>(1) << (width - 1) * 4)) | value;
  static const char hexdigits[] = "0123456789abcdef";
  do {
    *--writer = hexdigits[value & 0xF];
    value >>= 4;
    mask >>= 4;
  } while (mask != 0);
  piece_.set(writer, end - writer);
}

// ----------------------------------------------------------------------
// StrCat()
//    This merges the given strings or integers, with no delimiter.  This
//    is designed to be the fastest possible way to construct a string out
//    of a mix of raw C strings, StringPieces, strings, and integer values.
// ----------------------------------------------------------------------

// Append is merely a version of memcpy that returns the address of the byte
// after the area just overwritten.  It comes in multiple flavors to minimize
// call overhead.
static char *Append1(char *out, const AlphaNum &x) {
  memcpy(out, x.data(), x.size());
  return out + x.size();
}

static char *Append2(char *out, const AlphaNum &x1, const AlphaNum &x2) {
  memcpy(out, x1.data(), x1.size());
  out += x1.size();

  memcpy(out, x2.data(), x2.size());
  return out + x2.size();
}

static char *Append4(char *out, const AlphaNum &x1, const AlphaNum &x2,
                     const AlphaNum &x3, const AlphaNum &x4) {
  memcpy(out, x1.data(), x1.size());
  out += x1.size();

  memcpy(out, x2.data(), x2.size());
  out += x2.size();

  memcpy(out, x3.data(), x3.size());
  out += x3.size();

  memcpy(out, x4.data(), x4.size());
  return out + x4.size();
}

string StrCat(const AlphaNum &a, const AlphaNum &b) {
  string result;
  gtl::STLStringResizeUninitialized(&result, a.size() + b.size());
  char *const begin = &*result.begin();
  char *out = Append2(begin, a, b);
  DCHECK_EQ(out, begin + result.size());
  return result;
}

string StrCat(const AlphaNum &a, const AlphaNum &b, const AlphaNum &c) {
  string result;
  gtl::STLStringResizeUninitialized(&result, a.size() + b.size() + c.size());
  char *const begin = &*result.begin();
  char *out = Append2(begin, a, b);
  out = Append1(out, c);
  DCHECK_EQ(out, begin + result.size());
  return result;
}

string StrCat(const AlphaNum &a, const AlphaNum &b, const AlphaNum &c,
              const AlphaNum &d) {
  string result;
  gtl::STLStringResizeUninitialized(&result,
                                    a.size() + b.size() + c.size() + d.size());
  char *const begin = &*result.begin();
  char *out = Append4(begin, a, b, c, d);
  DCHECK_EQ(out, begin + result.size());
  return result;
}

namespace internal {

// Do not call directly - these are not part of the public API.
string CatPieces(std::initializer_list<StringPiece> pieces) {
  string result;
  size_t total_size = 0;
  for (const StringPiece piece : pieces) total_size += piece.size();
  gtl::STLStringResizeUninitialized(&result, total_size);

  char *const begin = &*result.begin();
  char *out = begin;
  for (const StringPiece piece : pieces) {
    const size_t this_size = piece.size();
    memcpy(out, piece.data(), this_size);
    out += this_size;
  }
  DCHECK_EQ(out, begin + result.size());
  return result;
}

// It's possible to call StrAppend with a StringPiece that is itself a fragment
// of the string we're appending to.  However the results of this are random.
// Therefore, check for this in debug mode.  Use unsigned math so we only have
// to do one comparison.
#define DCHECK_NO_OVERLAP(dest, src) \
  DCHECK_GE(uintptr_t((src).data() - (dest).data()), uintptr_t((dest).size()))

void AppendPieces(string *result, std::initializer_list<StringPiece> pieces) {
  size_t old_size = result->size();
  size_t total_size = old_size;
  for (const StringPiece piece : pieces) {
    DCHECK_NO_OVERLAP(*result, piece);
    total_size += piece.size();
  }
  gtl::STLStringResizeUninitialized(result, total_size);

  char *const begin = &*result->begin();
  char *out = begin + old_size;
  for (const StringPiece piece : pieces) {
    const size_t this_size = piece.size();
    memcpy(out, piece.data(), this_size);
    out += this_size;
  }
  DCHECK_EQ(out, begin + result->size());
}

}  // namespace internal

void StrAppend(string *result, const AlphaNum &a) {
  DCHECK_NO_OVERLAP(*result, a);
  result->append(a.data(), a.size());
}

void StrAppend(string *result, const AlphaNum &a, const AlphaNum &b) {
  DCHECK_NO_OVERLAP(*result, a);
  DCHECK_NO_OVERLAP(*result, b);
  string::size_type old_size = result->size();
  gtl::STLStringResizeUninitialized(result, old_size + a.size() + b.size());
  char *const begin = &*result->begin();
  char *out = Append2(begin + old_size, a, b);
  DCHECK_EQ(out, begin + result->size());
}

void StrAppend(string *result, const AlphaNum &a, const AlphaNum &b,
               const AlphaNum &c) {
  DCHECK_NO_OVERLAP(*result, a);
  DCHECK_NO_OVERLAP(*result, b);
  DCHECK_NO_OVERLAP(*result, c);
  string::size_type old_size = result->size();
  gtl::STLStringResizeUninitialized(result,
                                    old_size + a.size() + b.size() + c.size());
  char *const begin = &*result->begin();
  char *out = Append2(begin + old_size, a, b);
  out = Append1(out, c);
  DCHECK_EQ(out, begin + result->size());
}

void StrAppend(string *result, const AlphaNum &a, const AlphaNum &b,
               const AlphaNum &c, const AlphaNum &d) {
  DCHECK_NO_OVERLAP(*result, a);
  DCHECK_NO_OVERLAP(*result, b);
  DCHECK_NO_OVERLAP(*result, c);
  DCHECK_NO_OVERLAP(*result, d);
  string::size_type old_size = result->size();
  gtl::STLStringResizeUninitialized(
      result, old_size + a.size() + b.size() + c.size() + d.size());
  char *const begin = &*result->begin();
  char *out = Append4(begin + old_size, a, b, c, d);
  DCHECK_EQ(out, begin + result->size());
}

}  // namespace strings
}  // namespace tensorflow