text: /*
   * Copyright (c) Meta Platforms, Inc. and affiliates.
   *
   * 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
   *
   *     http://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 <folly/String.h>
  
  #include <cctype>
  #include <cerrno>
  #include <cstdarg>
  #include <cstring>
  #include <iterator>
  #include <sstream>
  #include <stdexcept>
  
  #include <glog/logging.h>
  
  #include <folly/Portability.h>
  #include <folly/ScopeGuard.h>
  #include <folly/container/Array.h>
  
  namespace folly {
  
  static_assert(IsConvertible<float>::value, "");
  static_assert(IsConvertible<int>::value, "");
  static_assert(IsConvertible<bool>::value, "");
  static_assert(IsConvertible<int>::value, "");
  static_assert(!IsConvertible<std::vector<int>>::value, "");
  
  namespace detail {
  
  struct string_table_c_escape_make_item {
    constexpr char operator()(std::size_t index) const {
      // clang-format off
      return
          index == '"' ? '"' :
          index == '\\' ? '\\' :
          index == '?' ? '?' :
          index == '\n' ? 'n' :
          index == '\r' ? 'r' :
          index == '\t' ? 't' :
          index < 32 || index > 126 ? 'O' : // octal
          'P'; // printable
      // clang-format on
    }
  };
  
  struct string_table_c_unescape_make_item {
    constexpr char operator()(std::size_t index) const {
      // clang-format off
      return
          index == '\'' ? '\'' :
          index == '?' ? '?' :
          index == '\\' ? '\\' :
          index == '"' ? '"' :
          index == 'a' ? '\a' :
          index == 'b' ? '\b' :
          index == 'f' ? '\f' :
          index == 'n' ? '\n' :
          index == 'r' ? '\r' :
          index == 't' ? '\t' :
          index == 'v' ? '\v' :
          index >= '0' && index <= '7' ? 'O' : // octal
          index == 'x' ? 'X' : // hex
          'I'; // invalid
      // clang-format on
    }
  };
  
  struct string_table_hex_make_item {
    constexpr unsigned char operator()(std::size_t index) const {
      // clang-format off
      return static_cast<unsigned char>(
          index >= '0' && index <= '9' ? index - '0' :
          index >= 'a' && index <= 'f' ? index - 'a' + 10 :
          index >= 'A' && index <= 'F' ? index - 'A' + 10 :
          16);
      // clang-format on
    }
  };
  
  struct string_table_uri_escape_make_item {
    //  0 = passthrough
    //  1 = unused
    //  2 = safe in path (/)
    //  3 = space (replace with '+' in query)
    //  4 = always percent-encode
    constexpr unsigned char operator()(std::size_t index) const {
      // clang-format off
      return
          index >= '0' && index <= '9' ? 0 :
          index >= 'A' && index <= 'Z' ? 0 :
          index >= 'a' && index <= 'z' ? 0 :
          index == '-' ? 0 :
          index == '_' ? 0 :
          index == '.' ? 0 :
          index == '~' ? 0 :
          index == '/' ? 2 :
          index == ' ' ? 3 :
          4;
      // clang-format on
    }
  };
  
  FOLLY_STORAGE_CONSTEXPR decltype(cEscapeTable) cEscapeTable =
      make_array_with<256>(string_table_c_escape_make_item{});
  FOLLY_STORAGE_CONSTEXPR decltype(cUnescapeTable) cUnescapeTable =
      make_array_with<256>(string_table_c_unescape_make_item{});
  FOLLY_STORAGE_CONSTEXPR decltype(hexTable) hexTable =
      make_array_with<256>(string_table_hex_make_item{});
  FOLLY_STORAGE_CONSTEXPR decltype(uriEscapeTable) uriEscapeTable =
      make_array_with<256>(string_table_uri_escape_make_item{});
  
  } // namespace detail
  
  static inline bool is_oddspace(char c) {
    return c == '\n' || c == '\t' || c == '\r';
  }
  
  StringPiece ltrimWhitespace(StringPiece sp) {
    // Spaces other than ' ' characters are less common but should be
    // checked.  This configuration where we loop on the ' '
    // separately from oddspaces was empirically fastest.
  
    while (true) {
      while (!sp.empty() && sp.front() == ' ') {
        sp.pop_front();
      }
      if (!sp.empty() && is_oddspace(sp.front())) {
        sp.pop_front();
        continue;
      }
  
      return sp;
    }
  }
  
  StringPiece rtrimWhitespace(StringPiece sp) {
    // Spaces other than ' ' characters are less common but should be
    // checked.  This configuration where we loop on the ' '
    // separately from oddspaces was empirically fastest.
  
    while (true) {
      while (!sp.empty() && sp.back() == ' ') {
        sp.pop_back();
      }
      if (!sp.empty() && is_oddspace(sp.back())) {
        sp.pop_back();
        continue;
      }
  
      return sp;
    }
  }
  
  namespace {
  
  int stringAppendfImplHelper(
      char* buf, size_t bufsize, const char* format, va_list args) {
    va_list args_copy;
    va_copy(args_copy, args);
    int bytes_used = vsnprintf(buf, bufsize, format, args_copy);
    va_end(args_copy);
    return bytes_used;
  }
  
  void stringAppendfImpl(std::string& output, const char* format, va_list args) {
    // Very simple; first, try to avoid an allocation by using an inline
    // buffer.  If that fails to hold the output string, allocate one on
    // the heap, use it instead.
    //
    // It is hard to guess the proper size of this buffer; some
    // heuristics could be based on the number of format characters, or
    // static analysis of a codebase.  Or, we can just pick a number
    // that seems big enough for simple cases (say, one line of text on
    // a terminal) without being large enough to be concerning as a
    // stack variable.
    std::array<char, 128> inline_buffer;
  
    int bytes_used = stringAppendfImplHelper(
        inline_buffer.data(), inline_buffer.size(), format, args);
    if (bytes_used < 0) {
      throw std::runtime_error(to<std::string>(
          "Invalid format string; snprintf returned negative "
          "with format string: ",
          format));
    }
  
    if (static_cast<size_t>(bytes_used) < inline_buffer.size()) {
      output.append(inline_buffer.data(), size_t(bytes_used));
      return;
    }
  
    // Couldn't fit.  Heap allocate a buffer, oh well.
    std::unique_ptr<char[]> heap_buffer(new char[size_t(bytes_used + 1)]);
    int final_bytes_used = stringAppendfImplHelper(
        heap_buffer.get(), size_t(bytes_used + 1), format, args);
    // The second call can take fewer bytes if, for example, we were printing a
    // string buffer with null-terminating char using a width specifier -
    // vsnprintf("%.*s", buf.size(), buf)
    CHECK(bytes_used >= final_bytes_used);
  
    // We don't keep the trailing '\0' in our output string
    output.append(heap_buffer.get(), size_t(final_bytes_used));
  }
  
  } // namespace
  
  std::string stringPrintf(const char* format, ...) {
    va_list ap;
    va_start(ap, format);
    SCOPE_EXIT { va_end(ap); };
    return stringVPrintf(format, ap);
  }
  
  std::string stringVPrintf(const char* format, va_list ap) {
    std::string ret;
    stringAppendfImpl(ret, format, ap);
    return ret;
  }
  
  // Basic declarations; allow for parameters of strings and string
  // pieces to be specified.
  std::string& stringAppendf(std::string* output, const char* format, ...) {
    va_list ap;
    va_start(ap, format);
    SCOPE_EXIT { va_end(ap); };
    return stringVAppendf(output, format, ap);
  }
  
  std::string& stringVAppendf(
      std::string* output, const char* format, va_list ap) {
    stringAppendfImpl(*output, format, ap);
    return *output;
  }
  
  void stringPrintf(std::string* output, const char* format, ...) {
    va_list ap;
    va_start(ap, format);
    SCOPE_EXIT { va_end(ap); };
    return stringVPrintf(output, format, ap);
  }
  
  void stringVPrintf(std::string* output, const char* format, va_list ap) {
    output->clear();
    stringAppendfImpl(*output, format, ap);
  }
  
  namespace {
  
  struct PrettySuffix {
    const char* suffix;
    double val;
  };
  
  const PrettySuffix kPrettyTimeSuffixes[] = {
      {"s ", 1e0L},
      {"ms", 1e-3L},
      {"us", 1e-6L},
      {"ns", 1e-9L},
      {"ps", 1e-12L},
      {"s ", 0},
      {nullptr, 0},
  };
  
  const PrettySuffix kPrettyTimeHmsSuffixes[] = {
      {"h ", 60L * 60L},
      {"m ", 60L},
      {"s ", 1e0L},
      {"ms", 1e-3L},
      {"us", 1e-6L},
      {"ns", 1e-9L},
      {"ps", 1e-12L},
      {"s ", 0},
      {nullptr, 0},
  };
  
  const PrettySuffix kPrettyBytesMetricSuffixes[] = {
      {"EB", 1e18L},
      {"PB", 1e15L},
      {"TB", 1e12L},
      {"GB", 1e9L},
      {"MB", 1e6L},
      {"kB", 1e3L},
      {"B ", 0L},
      {nullptr, 0},
  };
  
  const PrettySuffix kPrettyBytesBinarySuffixes[] = {
      {"EB", int64_t(1) << 60},
      {"PB", int64_t(1) << 50},
      {"TB", int64_t(1) << 40},
      {"GB", int64_t(1) << 30},
      {"MB", int64_t(1) << 20},
      {"kB", int64_t(1) << 10},
      {"B ", 0L},
      {nullptr, 0},
  };
  
  const PrettySuffix kPrettyBytesBinaryIECSuffixes[] = {
      {"EiB", int64_t(1) << 60},
      {"PiB", int64_t(1) << 50},
      {"TiB", int64_t(1) << 40},
      {"GiB", int64_t(1) << 30},
      {"MiB", int64_t(1) << 20},
      {"KiB", int64_t(1) << 10},
      {"B  ", 0L},
      {nullptr, 0},
  };
  
  const PrettySuffix kPrettyUnitsMetricSuffixes[] = {
      {"qntl", 1e18L},
      {"qdrl", 1e15L},
      {"tril", 1e12L},
      {"bil", 1e9L},
      {"M", 1e6L},
      {"k", 1e3L},
      {" ", 0},
      {nullptr, 0},
  };
  
  const PrettySuffix kPrettyUnitsBinarySuffixes[] = {
      {"E", int64_t(1) << 60},
      {"P", int64_t(1) << 50},
      {"T", int64_t(1) << 40},
      {"G", int64_t(1) << 30},
      {"M", int64_t(1) << 20},
      {"k", int64_t(1) << 10},
      {" ", 0},
      {nullptr, 0},
  };
  
  const PrettySuffix kPrettyUnitsBinaryIECSuffixes[] = {
      {"Ei", int64_t(1) << 60},
      {"Pi", int64_t(1) << 50},
      {"Ti", int64_t(1) << 40},
      {"Gi", int64_t(1) << 30},
      {"Mi", int64_t(1) << 20},
      {"Ki", int64_t(1) << 10},
      {"  ", 0},
      {nullptr, 0},
  };
  
  const PrettySuffix kPrettySISuffixes[] = {
      {"Y", 1e24L},  {"Z", 1e21L},  {"E", 1e18L},  {"P", 1e15L},  {"T", 1e12L},
      {"G", 1e9L},   {"M", 1e6L},   {"k", 1e3L},   {"h", 1e2L},   {"da", 1e1L},
      {"d", 1e-1L},  {"c", 1e-2L},  {"m", 1e-3L},  {"u", 1e-6L},  {"n", 1e-9L},
      {"p", 1e-12L}, {"f", 1e-15L}, {"a", 1e-18L}, {"z", 1e-21L}, {"y", 1e-24L},
      {" ", 0},      {nullptr, 0},
  };
  
  const PrettySuffix* const kPrettySuffixes[PRETTY_NUM_TYPES] = {
      kPrettyTimeSuffixes,
      kPrettyTimeHmsSuffixes,
      kPrettyBytesMetricSuffixes,
      kPrettyBytesBinarySuffixes,
      kPrettyBytesBinaryIECSuffixes,
      kPrettyUnitsMetricSuffixes,
      kPrettyUnitsBinarySuffixes,
      kPrettyUnitsBinaryIECSuffixes,
      kPrettySISuffixes,
  };
  
  } // namespace
  
  std::string prettyPrint(double val, PrettyType type, bool addSpace) {
    char buf[100];
  
    // pick the suffixes to use
    assert(type >= 0);
    assert(type < PRETTY_NUM_TYPES);
    const PrettySuffix* suffixes = kPrettySuffixes[type];
  
    // find the first suffix we're bigger than -- then use it
    double abs_val = fabs(val);
    for (int i = 0; suffixes[i].suffix; ++i) {
      if (abs_val >= suffixes[i].val) {
        snprintf(
            buf,
            sizeof buf,
            "%.4g%s%s",
            (suffixes[i].val ? (val / suffixes[i].val) : val),
            (addSpace ? " " : ""),
            suffixes[i].suffix);
        return std::string(buf);
      }
    }
  
    // no suffix, we've got a tiny value -- just print it in sci-notation
    snprintf(buf, sizeof buf, "%.4g", val);
    return std::string(buf);
  }
  
  // TODO:
  // 1) Benchmark & optimize
  double prettyToDouble(
      folly::StringPiece* const prettyString, const PrettyType type) {
    auto value = folly::to<double>(prettyString);
    while (!prettyString->empty() && std::isspace(prettyString->front())) {
      prettyString->advance(1); // Skipping spaces between number and suffix
    }
    const PrettySuffix* suffixes = kPrettySuffixes[type];
    int longestPrefixLen = -1;
    int bestPrefixId = -1;
    for (int j = 0; suffixes[j].suffix; ++j) {
      if (suffixes[j].suffix[0] == ' ') { // Checking for " " -> number rule.
        if (longestPrefixLen == -1) {
          longestPrefixLen = 0; // No characters to skip
          bestPrefixId = j;
        }
      } else if (prettyString->startsWith(suffixes[j].suffix)) {
        int suffixLen = int(strlen(suffixes[j].suffix));
        // We are looking for a longest suffix matching prefix of the string
        // after numeric value. We need this in case suffixes have common prefix.
        if (suffixLen > longestPrefixLen) {
          longestPrefixLen = suffixLen;
          bestPrefixId = j;
        }
      }
    }
    if (bestPrefixId == -1) { // No valid suffix rule found
      throw std::invalid_argument(folly::to<std::string>(
          "Unable to parse suffix \"", *prettyString, "\""));
    }
    prettyString->advance(size_t(longestPrefixLen));
    return suffixes[bestPrefixId].val ? value * suffixes[bestPrefixId].val
                                      : value;
  }
  
  double prettyToDouble(folly::StringPiece prettyString, const PrettyType type) {
    double result = prettyToDouble(&prettyString, type);
    detail::enforceWhitespace(prettyString);
    return result;
  }
  
  std::string hexDump(const void* ptr, size_t size) {
    std::ostringstream os;
    hexDump(ptr, size, std::ostream_iterator<StringPiece>(os, "\n"));
    return os.str();
  }
  
  // There are two variants of `strerror_r` function, one returns
  // `int`, and another returns `char*`. Selecting proper version using
  // preprocessor macros portably is extremely hard.
  //
  // For example, on Android function signature depends on `__USE_GNU` and
  // `__ANDROID_API__` macros (https://git.io/fjBBE).
  //
  // So we are using C++ overloading trick: we pass a pointer of
  // `strerror_r` to `invoke_strerror_r` function, and C++ compiler
  // selects proper function.
  
  FOLLY_MAYBE_UNUSED
  static std::string invoke_strerror_r(
      int (*strerror_r)(int, char*, size_t), int err, char* buf, size_t buflen) {
    // Using XSI-compatible strerror_r
    int r = strerror_r(err, buf, buflen);
  
    // OSX/FreeBSD use EINVAL and Linux uses -1 so just check for non-zero
    if (r != 0) {
      return to<std::string>(
          "Unknown error ", err, " (strerror_r failed with error ", errno, ")");
    } else {
      return buf;
    }
  }
  
  FOLLY_MAYBE_UNUSED
  static std::string invoke_strerror_r(
      char* (*strerror_r)(int, char*, size_t),
      int err,
      char* buf,
      size_t buflen) {
    // Using GNU strerror_r
    return strerror_r(err, buf, buflen);
  }
  
  std::string errnoStr(int err) {
    int savedErrno = errno;
  
    // Ensure that we reset errno upon exit.
    auto guard(makeGuard([&] { errno = savedErrno; }));
  
    char buf[1024];
    buf[0] = '\0';
  
    std::string result;
  
    // https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/strerror_r.3.html
    // http://www.kernel.org/doc/man-pages/online/pages/man3/strerror.3.html
  #if defined(_WIN32) && (defined(__MINGW32__) || defined(_MSC_VER))
    // mingw64 has no strerror_r, but Windows has strerror_s, which C11 added
    // as well. So maybe we should use this across all platforms (together
    // with strerrorlen_s). Note strerror_r and _s have swapped args.
    int r = strerror_s(buf, sizeof(buf), err);
    if (r != 0) {
      result = to<std::string>(
          "Unknown error ", err, " (strerror_r failed with error ", errno, ")");
    } else {
      result.assign(buf);
    }
  #else
    // Using any strerror_r
    result.assign(invoke_strerror_r(strerror_r, err, buf, sizeof(buf)));
  #endif
  
    return result;
  }
  
  namespace {
  
  void toLowerAscii8(char& c) {
    // Branchless tolower, based on the input-rotating trick described
    // at http://www.azillionmonkeys.com/qed/asmexample.html
    //
    // This algorithm depends on an observation: each uppercase
    // ASCII character can be converted to its lowercase equivalent
    // by adding 0x20.
  
    // Step 1: Clear the high order bit. We'll deal with it in Step 5.
    auto rotated = uint8_t(c & 0x7f);
    // Currently, the value of rotated, as a function of the original c is:
    //   below 'A':   0- 64
    //   'A'-'Z':    65- 90
    //   above 'Z':  91-127
  
    // Step 2: Add 0x25 (37)
    rotated += 0x25;
    // Now the value of rotated, as a function of the original c is:
    //   below 'A':   37-101
    //   'A'-'Z':    102-127
    //   above 'Z':  128-164
  
    // Step 3: clear the high order bit
    rotated &= 0x7f;
    //   below 'A':   37-101
    //   'A'-'Z':    102-127
    //   above 'Z':    0- 36
  
    // Step 4: Add 0x1a (26)
    rotated += 0x1a;
    //   below 'A':   63-127
    //   'A'-'Z':    128-153
    //   above 'Z':   25- 62
  
    // At this point, note that only the uppercase letters have been
    // transformed into values with the high order bit set (128 and above).
  
    // Step 5: Shift the high order bit 2 spaces to the right: the spot
    // where the only 1 bit in 0x20 is.  But first, how we ignored the
    // high order bit of the original c in step 1?  If that bit was set,
    // we may have just gotten a false match on a value in the range
    // 128+'A' to 128+'Z'.  To correct this, need to clear the high order
    // bit of rotated if the high order bit of c is set.  Since we don't
    // care about the other bits in rotated, the easiest thing to do
    // is invert all the bits in c and bitwise-and them with rotated.
    rotated &= ~c;
    rotated >>= 2;
  
    // Step 6: Apply a mask to clear everything except the 0x20 bit
    // in rotated.
    rotated &= 0x20;
  
    // At this point, rotated is 0x20 if c is 'A'-'Z' and 0x00 otherwise
  
    // Step 7: Add rotated to c
    c += char(rotated);
  }
  
  void toLowerAscii32(uint32_t& c) {
    // Besides being branchless, the algorithm in toLowerAscii8() has another
    // interesting property: None of the addition operations will cause
    // an overflow in the 8-bit value.  So we can pack four 8-bit values
    // into a uint32_t and run each operation on all four values in parallel
    // without having to use any CPU-specific SIMD instructions.
    uint32_t rotated = c & uint32_t(0x7f7f7f7fL);
    rotated += uint32_t(0x25252525L);
    rotated &= uint32_t(0x7f7f7f7fL);
    rotated += uint32_t(0x1a1a1a1aL);
  
    // Step 5 involves a shift, so some bits will spill over from each
    // 8-bit value into the next.  But that's okay, because they're bits
    // that will be cleared by the mask in step 6 anyway.
    rotated &= ~c;
    rotated >>= 2;
    rotated &= uint32_t(0x20202020L);
    c += rotated;
  }
  
  void toLowerAscii64(uint64_t& c) {
    // 64-bit version of toLower32
    uint64_t rotated = c & uint64_t(0x7f7f7f7f7f7f7f7fL);
    rotated += uint64_t(0x2525252525252525L);
    rotated &= uint64_t(0x7f7f7f7f7f7f7f7fL);
    rotated += uint64_t(0x1a1a1a1a1a1a1a1aL);
    rotated &= ~c;
    rotated >>= 2;
    rotated &= uint64_t(0x2020202020202020L);
    c += rotated;
  }
  
  } // namespace
  
  void toLowerAscii(char* str, size_t length) {
    static const size_t kAlignMask64 = 7;
    static const size_t kAlignMask32 = 3;
  
    // Convert a character at a time until we reach an address that
    // is at least 32-bit aligned
    auto n = (size_t)str;
    n &= kAlignMask32;
    n = std::min(n, length);
    size_t offset = 0;
    if (n != 0) {
      n = std::min(4 - n, length);
      do {
        toLowerAscii8(str[offset]);
        offset++;
      } while (offset < n);
    }
  
    n = (size_t)(str + offset);
    n &= kAlignMask64;
    if ((n != 0) && (offset + 4 <= length)) {
      // The next address is 32-bit aligned but not 64-bit aligned.
      // Convert the next 4 bytes in order to get to the 64-bit aligned
      // part of the input.
      toLowerAscii32(*(uint32_t*)(str + offset));
      offset += 4;
    }
  
    // Convert 8 characters at a time
    while (offset + 8 <= length) {
      toLowerAscii64(*(uint64_t*)(str + offset));
      offset += 8;
    }
  
    // Convert 4 characters at a time
    while (offset + 4 <= length) {
      toLowerAscii32(*(uint32_t*)(str + offset));
      offset += 4;
    }
  
    // Convert any characters remaining after the last 4-byte aligned group
    while (offset < length) {
      toLowerAscii8(str[offset]);
      offset++;
    }
  }
  
  namespace detail {
  
  size_t hexDumpLine(
      const void* ptr, size_t offset, size_t size, std::string& line) {
    static char hexValues[] = "0123456789abcdef";
    // Line layout:
    // 8: address
    // 1: space
    // (1+2)*16: hex bytes, each preceded by a space
    // 1: space separating the two halves
    // 3: "  |"
    // 16: characters
    // 1: "|"
    // Total: 78
    line.clear();
    line.reserve(78);
    const uint8_t* p = reinterpret_cast<const uint8_t*>(ptr) + offset;
    size_t n = std::min(size - offset, size_t(16));
    line.push_back(hexValues[(offset >> 28) & 0xf]);
    line.push_back(hexValues[(offset >> 24) & 0xf]);
    line.push_back(hexValues[(offset >> 20) & 0xf]);
    line.push_back(hexValues[(offset >> 16) & 0xf]);
    line.push_back(hexValues[(offset >> 12) & 0xf]);
    line.push_back(hexValues[(offset >> 8) & 0xf]);
    line.push_back(hexValues[(offset >> 4) & 0xf]);
    line.push_back(hexValues[offset & 0xf]);
    line.push_back(' ');
  
    for (size_t i = 0; i < n; i++) {
      if (i == 8) {
        line.push_back(' ');
      }
  
      line.push_back(' ');
      line.push_back(hexValues[(p[i] >> 4) & 0xf]);
      line.push_back(hexValues[p[i] & 0xf]);
    }
  
    // 3 spaces for each byte we're not printing, one separating the halves
    // if necessary
    line.append(3 * (16 - n) + (n <= 8), ' ');
    line.append("  |");
  
    for (size_t i = 0; i < n; i++) {
      char c = (p[i] >= 32 && p[i] <= 126 ? static_cast<char>(p[i]) : '.');
      line.push_back(c);
    }
    line.append(16 - n, ' ');
    line.push_back('|');
    DCHECK_EQ(line.size(), 78u);
  
    return n;
  }
  
  } // namespace detail
  
  std::string stripLeftMargin(std::string s) {
    std::vector<StringPiece> pieces;
    split("\n", s, pieces);
    auto piecer = range(pieces);
  
    auto piece = (piecer.end() - 1);
    auto needle = std::find_if(piece->begin(), piece->end(), [](char c) {
      return c != ' ' && c != '\t';
    });
    if (needle == piece->end()) {
      (piecer.end() - 1)->clear();
    }
    piece = piecer.begin();
    needle = std::find_if(piece->begin(), piece->end(), [](char c) {
      return c != ' ' && c != '\t';
    });
    if (needle == piece->end()) {
      piecer.erase(piecer.begin(), piecer.begin() + 1);
    }
  
    const auto sentinel = std::numeric_limits<size_t>::max();
    auto indent = sentinel;
    size_t max_length = 0;
    for (piece = piecer.begin(); piece != piecer.end(); piece++) {
      needle = std::find_if(piece->begin(), piece->end(), [](char c) {
        return c != ' ' && c != '\t';
      });
      if (needle != piece->end()) {
        indent = std::min<size_t>(indent, size_t(needle - piece->begin()));
      } else {
        max_length = std::max<size_t>(piece->size(), max_length);
      }
    }
    indent = indent == sentinel ? max_length : indent;
    for (piece = piecer.begin(); piece != piecer.end(); piece++) {
      if (piece->size() < indent) {
        piece->clear();
      } else {
        piece->erase(piece->begin(), piece->begin() + indent);
      }
    }
    return join("\n", piecer);
  }
  
  } // namespace folly
  
  #ifdef FOLLY_DEFINED_DMGL
  #undef FOLLY_DEFINED_DMGL
  #undef DMGL_NO_OPTS
  #undef DMGL_PARAMS
  #undef DMGL_ANSI
  #undef DMGL_JAVA
  #undef DMGL_VERBOSE
  #undef DMGL_TYPES
  #undef DMGL_RET_POSTFIX
  #endif
  