// Copyright 2017 The Abseil Authors.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//      https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include "absl/strings/string_view.h"

#ifndef ABSL_USES_STD_STRING_VIEW

#include <algorithm>

#include <climits>

#include <cstring>

#include <ostream>

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace {

// This is significantly faster for case-sensitive matches with very

// few possible matches.

const char* memmatch(const char* phaystack, size_t haylen, const char* pneedle,

                     size_t neelen) {

  if (0 == neelen) {

    return phaystack;  // even if haylen is 0

  }

  if (haylen < neelen) return nullptr;

  const char* match;

  const char* hayend = phaystack + haylen - neelen + 1;

  // A static cast is used here as memchr returns a const void *, and pointer

  // arithmetic is not allowed on pointers to void.

  while (

      (match = static_cast<const char*>(memchr(

           phaystack, pneedle[0], static_cast<size_t>(hayend - phaystack))))) {

    if (memcmp(match, pneedle, neelen) == 0)

      return match;

    else

      phaystack = match + 1;

  }

  return nullptr;

}

void WritePadding(std::ostream& o, size_t pad) {

  char fill_buf[32];

  memset(fill_buf, o.fill(), sizeof(fill_buf));

  while (pad) {

    size_t n = std::min(pad, sizeof(fill_buf));

    o.write(fill_buf, static_cast<std::streamsize>(n));

    pad -= n;

  }

}

class LookupTable {

 public:

  // For each character in wanted, sets the index corresponding

  // to the ASCII code of that character. This is used by

  // the find_.*_of methods below to tell whether or not a character is in

  // the lookup table in constant time.

  explicit LookupTable(string_view wanted) {

    for (char c : wanted) {

      table_[Index(c)] = true;

    }

  }

  bool operator[](char c) const { return table_[Index(c)]; }

 private:

  static unsigned char Index(char c) { return static_cast<unsigned char>(c); }

  bool table_[UCHAR_MAX + 1] = {};

};

}  // namespace

std::ostream& operator<<(std::ostream& o, string_view piece) {

  std::ostream::sentry sentry(o);

  if (sentry) {

    size_t lpad = 0;

    size_t rpad = 0;

    if (static_cast<size_t>(o.width()) > piece.size()) {

      size_t pad = static_cast<size_t>(o.width()) - piece.size();

      if ((o.flags() & o.adjustfield) == o.left) {

        rpad = pad;

      } else {

        lpad = pad;

      }

    }

    if (lpad) WritePadding(o, lpad);

    o.write(piece.data(), static_cast<std::streamsize>(piece.size()));

    if (rpad) WritePadding(o, rpad);

    o.width(0);

  }

  return o;

}

string_view::size_type string_view::find(string_view s,

                                         size_type pos) const noexcept {

  if (empty() || pos > length_) {

    if (empty() && pos == 0 && s.empty()) return 0;

    return npos;

  }

  const char* result = memmatch(ptr_ + pos, length_ - pos, s.ptr_, s.length_);

  return result ? static_cast<size_type>(result - ptr_) : npos;

}

string_view::size_type string_view::find(char c, size_type pos) const noexcept {

  if (empty() || pos >= length_) {

    return npos;

  }

  const char* result =

      static_cast<const char*>(memchr(ptr_ + pos, c, length_ - pos));

  return result != nullptr ? static_cast<size_type>(result - ptr_) : npos;

}

string_view::size_type string_view::rfind(string_view s,

                                          size_type pos) const noexcept {

  if (length_ < s.length_) return npos;

  if (s.empty()) return std::min(length_, pos);

  const char* last = ptr_ + std::min(length_ - s.length_, pos) + s.length_;

  const char* result = std::find_end(ptr_, last, s.ptr_, s.ptr_ + s.length_);

  return result != last ? static_cast<size_type>(result - ptr_) : npos;

}

// Search range is [0..pos] inclusive.  If pos == npos, search everything.

string_view::size_type string_view::rfind(char c,

                                          size_type pos) const noexcept {

  // Note: memrchr() is not available on Windows.

  if (empty()) return npos;

  for (size_type i = std::min(pos, length_ - 1);; --i) {

    if (ptr_[i] == c) {

      return i;

    }

    if (i == 0) break;

  }

  return npos;

}

string_view::size_type string_view::find_first_of(

    string_view s, size_type pos) const noexcept {

  if (empty() || s.empty()) {

    return npos;

  }

  // Avoid the cost of LookupTable() for a single-character search.

  if (s.length_ == 1) return find_first_of(s.ptr_[0], pos);

  LookupTable tbl(s);

  for (size_type i = pos; i < length_; ++i) {

    if (tbl[ptr_[i]]) {

      return i;

    }

  }

  return npos;

}

string_view::size_type string_view::find_first_not_of(

    string_view s, size_type pos) const noexcept {

  if (empty()) return npos;

  // Avoid the cost of LookupTable() for a single-character search.

  if (s.length_ == 1) return find_first_not_of(s.ptr_[0], pos);

  LookupTable tbl(s);

  for (size_type i = pos; i < length_; ++i) {

    if (!tbl[ptr_[i]]) {

      return i;

    }

  }

  return npos;

}

string_view::size_type string_view::find_first_not_of(

    char c, size_type pos) const noexcept {

  if (empty()) return npos;

  for (; pos < length_; ++pos) {

    if (ptr_[pos] != c) {

      return pos;

    }

  }

  return npos;

}

string_view::size_type string_view::find_last_of(string_view s,

                                                 size_type pos) const noexcept {

  if (empty() || s.empty()) return npos;

  // Avoid the cost of LookupTable() for a single-character search.

  if (s.length_ == 1) return find_last_of(s.ptr_[0], pos);

  LookupTable tbl(s);

  for (size_type i = std::min(pos, length_ - 1);; --i) {

    if (tbl[ptr_[i]]) {

      return i;

    }

    if (i == 0) break;

  }

  return npos;

}

string_view::size_type string_view::find_last_not_of(

    string_view s, size_type pos) const noexcept {

  if (empty()) return npos;

  size_type i = std::min(pos, length_ - 1);

  if (s.empty()) return i;

  // Avoid the cost of LookupTable() for a single-character search.

  if (s.length_ == 1) return find_last_not_of(s.ptr_[0], pos);

  LookupTable tbl(s);

  for (;; --i) {

    if (!tbl[ptr_[i]]) {

      return i;

    }

    if (i == 0) break;

  }

  return npos;

}

string_view::size_type string_view::find_last_not_of(

    char c, size_type pos) const noexcept {

  if (empty()) return npos;

  size_type i = std::min(pos, length_ - 1);

  for (;; --i) {

    if (ptr_[i] != c) {

      return i;

    }

    if (i == 0) break;

  }

  return npos;

}

#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL

constexpr string_view::size_type string_view::npos;

constexpr string_view::size_type string_view::kMaxSize;

#endif

ABSL_NAMESPACE_END

}  // namespace absl

#endif  // ABSL_USES_STD_STRING_VIEW