runtime/utils.cc

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * 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 "utils.h"

#include <inttypes.h>
#include <pthread.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <memory>

#include "android-base/strings.h"

#include "base/stl_util.h"
#include "base/unix_file/fd_file.h"
#include "dex_file-inl.h"
#include "dex_instruction.h"
#include "oat_quick_method_header.h"
#include "os.h"
#include "scoped_thread_state_change-inl.h"
#include "utf-inl.h"

#if defined(__APPLE__)
#include "AvailabilityMacros.h"  // For MAC_OS_X_VERSION_MAX_ALLOWED
#include <sys/syscall.h>
#include <crt_externs.h>
#endif

#if defined(__linux__)
#include <linux/unistd.h>
#endif

namespace art {

static const uint8_t kBase64Map[256] = {
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255,  62, 255, 255, 255,  63,
  52,  53,  54,  55,  56,  57,  58,  59,  60,  61, 255, 255,
  255, 254, 255, 255, 255,   0,   1,   2,   3,   4,   5,   6,
    7,   8,   9,  10,  11,  12,  13,  14,  15,  16,  17,  18,  // NOLINT
   19,  20,  21,  22,  23,  24,  25, 255, 255, 255, 255, 255,  // NOLINT
  255,  26,  27,  28,  29,  30,  31,  32,  33,  34,  35,  36,
   37,  38,  39,  40,  41,  42,  43,  44,  45,  46,  47,  48,  // NOLINT
   49,  50,  51, 255, 255, 255, 255, 255, 255, 255, 255, 255,  // NOLINT
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
  255, 255, 255, 255
};

uint8_t* DecodeBase64(const char* src, size_t* dst_size) {
  std::vector<uint8_t> tmp;
  uint32_t t = 0, y = 0;
  int g = 3;
  for (size_t i = 0; src[i] != '\0'; ++i) {
    uint8_t c = kBase64Map[src[i] & 0xFF];
    if (c == 255) continue;
    // the final = symbols are read and used to trim the remaining bytes
    if (c == 254) {
      c = 0;
      // prevent g < 0 which would potentially allow an overflow later
      if (--g < 0) {
        *dst_size = 0;
        return nullptr;
      }
    } else if (g != 3) {
      // we only allow = to be at the end
      *dst_size = 0;
      return nullptr;
    }
    t = (t << 6) | c;
    if (++y == 4) {
      tmp.push_back((t >> 16) & 255);
      if (g > 1) {
        tmp.push_back((t >> 8) & 255);
      }
      if (g > 2) {
        tmp.push_back(t & 255);
      }
      y = t = 0;
    }
  }
  if (y != 0) {
    *dst_size = 0;
    return nullptr;
  }
  std::unique_ptr<uint8_t[]> dst(new uint8_t[tmp.size()]);
  if (dst_size != nullptr) {
    *dst_size = tmp.size();
  } else {
    *dst_size = 0;
  }
  std::copy(tmp.begin(), tmp.end(), dst.get());
  return dst.release();
}

pid_t GetTid() {
#if defined(__APPLE__)
  uint64_t owner;
  CHECK_PTHREAD_CALL(pthread_threadid_np, (nullptr, &owner), __FUNCTION__);  // Requires Mac OS 10.6
  return owner;
#elif defined(__BIONIC__)
  return gettid();
#else
  return syscall(__NR_gettid);
#endif
}

std::string GetThreadName(pid_t tid) {
  std::string result;
  if (ReadFileToString(StringPrintf("/proc/self/task/%d/comm", tid), &result)) {
    result.resize(result.size() - 1);  // Lose the trailing '\n'.
  } else {
    result = "<unknown>";
  }
  return result;
}

bool ReadFileToString(const std::string& file_name, std::string* result) {
  File file(file_name, O_RDONLY, false);
  if (!file.IsOpened()) {
    return false;
  }

  std::vector<char> buf(8 * KB);
  while (true) {
    int64_t n = TEMP_FAILURE_RETRY(read(file.Fd(), &buf[0], buf.size()));
    if (n == -1) {
      return false;
    }
    if (n == 0) {
      return true;
    }
    result->append(&buf[0], n);
  }
}

bool PrintFileToLog(const std::string& file_name, LogSeverity level) {
  File file(file_name, O_RDONLY, false);
  if (!file.IsOpened()) {
    return false;
  }

  constexpr size_t kBufSize = 256;  // Small buffer. Avoid stack overflow and stack size warnings.
  char buf[kBufSize + 1];           // +1 for terminator.
  size_t filled_to = 0;
  while (true) {
    DCHECK_LT(filled_to, kBufSize);
    int64_t n = TEMP_FAILURE_RETRY(read(file.Fd(), &buf[filled_to], kBufSize - filled_to));
    if (n <= 0) {
      // Print the rest of the buffer, if it exists.
      if (filled_to > 0) {
        buf[filled_to] = 0;
        LOG(level) << buf;
      }
      return n == 0;
    }
    // Scan for '\n'.
    size_t i = filled_to;
    bool found_newline = false;
    for (; i < filled_to + n; ++i) {
      if (buf[i] == '\n') {
        // Found a line break, that's something to print now.
        buf[i] = 0;
        LOG(level) << buf;
        // Copy the rest to the front.
        if (i + 1 < filled_to + n) {
          memmove(&buf[0], &buf[i + 1], filled_to + n - i - 1);
          filled_to = filled_to + n - i - 1;
        } else {
          filled_to = 0;
        }
        found_newline = true;
        break;
      }
    }
    if (found_newline) {
      continue;
    } else {
      filled_to += n;
      // Check if we must flush now.
      if (filled_to == kBufSize) {
        buf[kBufSize] = 0;
        LOG(level) << buf;
        filled_to = 0;
      }
    }
  }
}

std::string PrettyDescriptor(const char* descriptor) {
  // Count the number of '['s to get the dimensionality.
  const char* c = descriptor;
  size_t dim = 0;
  while (*c == '[') {
    dim++;
    c++;
  }

  // Reference or primitive?
  if (*c == 'L') {
    // "[[La/b/C;" -> "a.b.C[][]".
    c++;  // Skip the 'L'.
  } else {
    // "[[B" -> "byte[][]".
    // To make life easier, we make primitives look like unqualified
    // reference types.
    switch (*c) {
    case 'B': c = "byte;"; break;
    case 'C': c = "char;"; break;
    case 'D': c = "double;"; break;
    case 'F': c = "float;"; break;
    case 'I': c = "int;"; break;
    case 'J': c = "long;"; break;
    case 'S': c = "short;"; break;
    case 'Z': c = "boolean;"; break;
    case 'V': c = "void;"; break;  // Used when decoding return types.
    default: return descriptor;
    }
  }

  // At this point, 'c' is a string of the form "fully/qualified/Type;"
  // or "primitive;". Rewrite the type with '.' instead of '/':
  std::string result;
  const char* p = c;
  while (*p != ';') {
    char ch = *p++;
    if (ch == '/') {
      ch = '.';
    }
    result.push_back(ch);
  }
  // ...and replace the semicolon with 'dim' "[]" pairs:
  for (size_t i = 0; i < dim; ++i) {
    result += "[]";
  }
  return result;
}

std::string PrettyArguments(const char* signature) {
  std::string result;
  result += '(';
  CHECK_EQ(*signature, '(');
  ++signature;  // Skip the '('.
  while (*signature != ')') {
    size_t argument_length = 0;
    while (signature[argument_length] == '[') {
      ++argument_length;
    }
    if (signature[argument_length] == 'L') {
      argument_length = (strchr(signature, ';') - signature + 1);
    } else {
      ++argument_length;
    }
    {
      std::string argument_descriptor(signature, argument_length);
      result += PrettyDescriptor(argument_descriptor.c_str());
    }
    if (signature[argument_length] != ')') {
      result += ", ";
    }
    signature += argument_length;
  }
  CHECK_EQ(*signature, ')');
  ++signature;  // Skip the ')'.
  result += ')';
  return result;
}

std::string PrettyReturnType(const char* signature) {
  const char* return_type = strchr(signature, ')');
  CHECK(return_type != nullptr);
  ++return_type;  // Skip ')'.
  return PrettyDescriptor(return_type);
}

std::string PrettyJavaAccessFlags(uint32_t access_flags) {
  std::string result;
  if ((access_flags & kAccPublic) != 0) {
    result += "public ";
  }
  if ((access_flags & kAccProtected) != 0) {
    result += "protected ";
  }
  if ((access_flags & kAccPrivate) != 0) {
    result += "private ";
  }
  if ((access_flags & kAccFinal) != 0) {
    result += "final ";
  }
  if ((access_flags & kAccStatic) != 0) {
    result += "static ";
  }
  if ((access_flags & kAccAbstract) != 0) {
    result += "abstract ";
  }
  if ((access_flags & kAccInterface) != 0) {
    result += "interface ";
  }
  if ((access_flags & kAccTransient) != 0) {
    result += "transient ";
  }
  if ((access_flags & kAccVolatile) != 0) {
    result += "volatile ";
  }
  if ((access_flags & kAccSynchronized) != 0) {
    result += "synchronized ";
  }
  return result;
}

std::string PrettySize(int64_t byte_count) {
  // The byte thresholds at which we display amounts.  A byte count is displayed
  // in unit U when kUnitThresholds[U] <= bytes < kUnitThresholds[U+1].
  static const int64_t kUnitThresholds[] = {
    0,              // B up to...
    3*1024,         // KB up to...
    2*1024*1024,    // MB up to...
    1024*1024*1024  // GB from here.
  };
  static const int64_t kBytesPerUnit[] = { 1, KB, MB, GB };
  static const char* const kUnitStrings[] = { "B", "KB", "MB", "GB" };
  const char* negative_str = "";
  if (byte_count < 0) {
    negative_str = "-";
    byte_count = -byte_count;
  }
  int i = arraysize(kUnitThresholds);
  while (--i > 0) {
    if (byte_count >= kUnitThresholds[i]) {
      break;
    }
  }
  return StringPrintf("%s%" PRId64 "%s",
                      negative_str, byte_count / kBytesPerUnit[i], kUnitStrings[i]);
}

static inline constexpr bool NeedsEscaping(uint16_t ch) {
  return (ch < ' ' || ch > '~');
}

std::string PrintableChar(uint16_t ch) {
  std::string result;
  result += '\'';
  if (NeedsEscaping(ch)) {
    StringAppendF(&result, "\\u%04x", ch);
  } else {
    result += ch;
  }
  result += '\'';
  return result;
}

std::string PrintableString(const char* utf) {
  std::string result;
  result += '"';
  const char* p = utf;
  size_t char_count = CountModifiedUtf8Chars(p);
  for (size_t i = 0; i < char_count; ++i) {
    uint32_t ch = GetUtf16FromUtf8(&p);
    if (ch == '\\') {
      result += "\\\\";
    } else if (ch == '\n') {
      result += "\\n";
    } else if (ch == '\r') {
      result += "\\r";
    } else if (ch == '\t') {
      result += "\\t";
    } else {
      const uint16_t leading = GetLeadingUtf16Char(ch);

      if (NeedsEscaping(leading)) {
        StringAppendF(&result, "\\u%04x", leading);
      } else {
        result += leading;
      }

      const uint32_t trailing = GetTrailingUtf16Char(ch);
      if (trailing != 0) {
        // All high surrogates will need escaping.
        StringAppendF(&result, "\\u%04x", trailing);
      }
    }
  }
  result += '"';
  return result;
}

// See http://java.sun.com/j2se/1.5.0/docs/guide/jni/spec/design.html#wp615 for the full rules.
std::string MangleForJni(const std::string& s) {
  std::string result;
  size_t char_count = CountModifiedUtf8Chars(s.c_str());
  const char* cp = &s[0];
  for (size_t i = 0; i < char_count; ++i) {
    uint32_t ch = GetUtf16FromUtf8(&cp);
    if ((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9')) {
      result.push_back(ch);
    } else if (ch == '.' || ch == '/') {
      result += "_";
    } else if (ch == '_') {
      result += "_1";
    } else if (ch == ';') {
      result += "_2";
    } else if (ch == '[') {
      result += "_3";
    } else {
      const uint16_t leading = GetLeadingUtf16Char(ch);
      const uint32_t trailing = GetTrailingUtf16Char(ch);

      StringAppendF(&result, "_0%04x", leading);
      if (trailing != 0) {
        StringAppendF(&result, "_0%04x", trailing);
      }
    }
  }
  return result;
}

std::string DotToDescriptor(const char* class_name) {
  std::string descriptor(class_name);
  std::replace(descriptor.begin(), descriptor.end(), '.', '/');
  if (descriptor.length() > 0 && descriptor[0] != '[') {
    descriptor = "L" + descriptor + ";";
  }
  return descriptor;
}

std::string DescriptorToDot(const char* descriptor) {
  size_t length = strlen(descriptor);
  if (length > 1) {
    if (descriptor[0] == 'L' && descriptor[length - 1] == ';') {
      // Descriptors have the leading 'L' and trailing ';' stripped.
      std::string result(descriptor + 1, length - 2);
      std::replace(result.begin(), result.end(), '/', '.');
      return result;
    } else {
      // For arrays the 'L' and ';' remain intact.
      std::string result(descriptor);
      std::replace(result.begin(), result.end(), '/', '.');
      return result;
    }
  }
  // Do nothing for non-class/array descriptors.
  return descriptor;
}

std::string DescriptorToName(const char* descriptor) {
  size_t length = strlen(descriptor);
  if (descriptor[0] == 'L' && descriptor[length - 1] == ';') {
    std::string result(descriptor + 1, length - 2);
    return result;
  }
  return descriptor;
}

// Helper for IsValidPartOfMemberNameUtf8(), a bit vector indicating valid low ascii.
uint32_t DEX_MEMBER_VALID_LOW_ASCII[4] = {
  0x00000000,  // 00..1f low control characters; nothing valid
  0x03ff2010,  // 20..3f digits and symbols; valid: '0'..'9', '$', '-'
  0x87fffffe,  // 40..5f uppercase etc.; valid: 'A'..'Z', '_'
  0x07fffffe   // 60..7f lowercase etc.; valid: 'a'..'z'
};

// Helper for IsValidPartOfMemberNameUtf8(); do not call directly.
bool IsValidPartOfMemberNameUtf8Slow(const char** pUtf8Ptr) {
  /*
   * It's a multibyte encoded character. Decode it and analyze. We
   * accept anything that isn't (a) an improperly encoded low value,
   * (b) an improper surrogate pair, (c) an encoded '\0', (d) a high
   * control character, or (e) a high space, layout, or special
   * character (U+00a0, U+2000..U+200f, U+2028..U+202f,
   * U+fff0..U+ffff). This is all specified in the dex format
   * document.
   */

  const uint32_t pair = GetUtf16FromUtf8(pUtf8Ptr);
  const uint16_t leading = GetLeadingUtf16Char(pair);

  // We have a surrogate pair resulting from a valid 4 byte UTF sequence.
  // No further checks are necessary because 4 byte sequences span code
  // points [U+10000, U+1FFFFF], which are valid codepoints in a dex
  // identifier. Furthermore, GetUtf16FromUtf8 guarantees that each of
  // the surrogate halves are valid and well formed in this instance.
  if (GetTrailingUtf16Char(pair) != 0) {
    return true;
  }


  // We've encountered a one, two or three byte UTF-8 sequence. The
  // three byte UTF-8 sequence could be one half of a surrogate pair.
  switch (leading >> 8) {
    case 0x00:
      // It's only valid if it's above the ISO-8859-1 high space (0xa0).
      return (leading > 0x00a0);
    case 0xd8:
    case 0xd9:
    case 0xda:
    case 0xdb:
      {
        // We found a three byte sequence encoding one half of a surrogate.
        // Look for the other half.
        const uint32_t pair2 = GetUtf16FromUtf8(pUtf8Ptr);
        const uint16_t trailing = GetLeadingUtf16Char(pair2);

        return (GetTrailingUtf16Char(pair2) == 0) && (0xdc00 <= trailing && trailing <= 0xdfff);
      }
    case 0xdc:
    case 0xdd:
    case 0xde:
    case 0xdf:
      // It's a trailing surrogate, which is not valid at this point.
      return false;
    case 0x20:
    case 0xff:
      // It's in the range that has spaces, controls, and specials.
      switch (leading & 0xfff8) {
        case 0x2000:
        case 0x2008:
        case 0x2028:
        case 0xfff0:
        case 0xfff8:
          return false;
      }
      return true;
    default:
      return true;
  }

  UNREACHABLE();
}

/* Return whether the pointed-at modified-UTF-8 encoded character is
 * valid as part of a member name, updating the pointer to point past
 * the consumed character. This will consume two encoded UTF-16 code
 * points if the character is encoded as a surrogate pair. Also, if
 * this function returns false, then the given pointer may only have
 * been partially advanced.
 */
static bool IsValidPartOfMemberNameUtf8(const char** pUtf8Ptr) {
  uint8_t c = (uint8_t) **pUtf8Ptr;
  if (LIKELY(c <= 0x7f)) {
    // It's low-ascii, so check the table.
    uint32_t wordIdx = c >> 5;
    uint32_t bitIdx = c & 0x1f;
    (*pUtf8Ptr)++;
    return (DEX_MEMBER_VALID_LOW_ASCII[wordIdx] & (1 << bitIdx)) != 0;
  }

  // It's a multibyte encoded character. Call a non-inline function
  // for the heavy lifting.
  return IsValidPartOfMemberNameUtf8Slow(pUtf8Ptr);
}

bool IsValidMemberName(const char* s) {
  bool angle_name = false;

  switch (*s) {
    case '\0':
      // The empty string is not a valid name.
      return false;
    case '<':
      angle_name = true;
      s++;
      break;
  }

  while (true) {
    switch (*s) {
      case '\0':
        return !angle_name;
      case '>':
        return angle_name && s[1] == '\0';
    }

    if (!IsValidPartOfMemberNameUtf8(&s)) {
      return false;
    }
  }
}

enum ClassNameType { kName, kDescriptor };
template<ClassNameType kType, char kSeparator>
static bool IsValidClassName(const char* s) {
  int arrayCount = 0;
  while (*s == '[') {
    arrayCount++;
    s++;
  }

  if (arrayCount > 255) {
    // Arrays may have no more than 255 dimensions.
    return false;
  }

  ClassNameType type = kType;
  if (type != kDescriptor && arrayCount != 0) {
    /*
     * If we're looking at an array of some sort, then it doesn't
     * matter if what is being asked for is a class name; the
     * format looks the same as a type descriptor in that case, so
     * treat it as such.
     */
    type = kDescriptor;
  }

  if (type == kDescriptor) {
    /*
     * We are looking for a descriptor. Either validate it as a
     * single-character primitive type, or continue on to check the
     * embedded class name (bracketed by "L" and ";").
     */
    switch (*(s++)) {
    case 'B':
    case 'C':
    case 'D':
    case 'F':
    case 'I':
    case 'J':
    case 'S':
    case 'Z':
      // These are all single-character descriptors for primitive types.
      return (*s == '\0');
    case 'V':
      // Non-array void is valid, but you can't have an array of void.
      return (arrayCount == 0) && (*s == '\0');
    case 'L':
      // Class name: Break out and continue below.
      break;
    default:
      // Oddball descriptor character.
      return false;
    }
  }

  /*
   * We just consumed the 'L' that introduces a class name as part
   * of a type descriptor, or we are looking for an unadorned class
   * name.
   */

  bool sepOrFirst = true;  // first character or just encountered a separator.
  for (;;) {
    uint8_t c = (uint8_t) *s;
    switch (c) {
    case '\0':
      /*
       * Premature end for a type descriptor, but valid for
       * a class name as long as we haven't encountered an
       * empty component (including the degenerate case of
       * the empty string "").
       */
      return (type == kName) && !sepOrFirst;
    case ';':
      /*
       * Invalid character for a class name, but the
       * legitimate end of a type descriptor. In the latter
       * case, make sure that this is the end of the string
       * and that it doesn't end with an empty component
       * (including the degenerate case of "L;").
       */
      return (type == kDescriptor) && !sepOrFirst && (s[1] == '\0');
    case '/':
    case '.':
      if (c != kSeparator) {
        // The wrong separator character.
        return false;
      }
      if (sepOrFirst) {
        // Separator at start or two separators in a row.
        return false;
      }
      sepOrFirst = true;
      s++;
      break;
    default:
      if (!IsValidPartOfMemberNameUtf8(&s)) {
        return false;
      }
      sepOrFirst = false;
      break;
    }
  }
}

bool IsValidBinaryClassName(const char* s) {
  return IsValidClassName<kName, '.'>(s);
}

bool IsValidJniClassName(const char* s) {
  return IsValidClassName<kName, '/'>(s);
}

bool IsValidDescriptor(const char* s) {
  return IsValidClassName<kDescriptor, '/'>(s);
}

void Split(const std::string& s, char separator, std::vector<std::string>* result) {
  const char* p = s.data();
  const char* end = p + s.size();
  while (p != end) {
    if (*p == separator) {
      ++p;
    } else {
      const char* start = p;
      while (++p != end && *p != separator) {
        // Skip to the next occurrence of the separator.
      }
      result->push_back(std::string(start, p - start));
    }
  }
}

void SetThreadName(const char* thread_name) {
  int hasAt = 0;
  int hasDot = 0;
  const char* s = thread_name;
  while (*s) {
    if (*s == '.') {
      hasDot = 1;
    } else if (*s == '@') {
      hasAt = 1;
    }
    s++;
  }
  int len = s - thread_name;
  if (len < 15 || hasAt || !hasDot) {
    s = thread_name;
  } else {
    s = thread_name + len - 15;
  }
#if defined(__linux__)
  // pthread_setname_np fails rather than truncating long strings.
  char buf[16];       // MAX_TASK_COMM_LEN=16 is hard-coded in the kernel.
  strncpy(buf, s, sizeof(buf)-1);
  buf[sizeof(buf)-1] = '\0';
  errno = pthread_setname_np(pthread_self(), buf);
  if (errno != 0) {
    PLOG(WARNING) << "Unable to set the name of current thread to '" << buf << "'";
  }
#else  // __APPLE__
  pthread_setname_np(thread_name);
#endif
}

void GetTaskStats(pid_t tid, char* state, int* utime, int* stime, int* task_cpu) {
  *utime = *stime = *task_cpu = 0;
  std::string stats;
  if (!ReadFileToString(StringPrintf("/proc/self/task/%d/stat", tid), &stats)) {
    return;
  }
  // Skip the command, which may contain spaces.
  stats = stats.substr(stats.find(')') + 2);
  // Extract the three fields we care about.
  std::vector<std::string> fields;
  Split(stats, ' ', &fields);
  *state = fields[0][0];
  *utime = strtoull(fields[11].c_str(), nullptr, 10);
  *stime = strtoull(fields[12].c_str(), nullptr, 10);
  *task_cpu = strtoull(fields[36].c_str(), nullptr, 10);
}

const char* GetAndroidRoot() {
  const char* android_root = getenv("ANDROID_ROOT");
  if (android_root == nullptr) {
    if (OS::DirectoryExists("/system")) {
      android_root = "/system";
    } else {
      LOG(FATAL) << "ANDROID_ROOT not set and /system does not exist";
      return "";
    }
  }
  if (!OS::DirectoryExists(android_root)) {
    LOG(FATAL) << "Failed to find ANDROID_ROOT directory " << android_root;
    return "";
  }
  return android_root;
}

const char* GetAndroidData() {
  std::string error_msg;
  const char* dir = GetAndroidDataSafe(&error_msg);
  if (dir != nullptr) {
    return dir;
  } else {
    LOG(FATAL) << error_msg;
    return "";
  }
}

const char* GetAndroidDataSafe(std::string* error_msg) {
  const char* android_data = getenv("ANDROID_DATA");
  if (android_data == nullptr) {
    if (OS::DirectoryExists("/data")) {
      android_data = "/data";
    } else {
      *error_msg = "ANDROID_DATA not set and /data does not exist";
      return nullptr;
    }
  }
  if (!OS::DirectoryExists(android_data)) {
    *error_msg = StringPrintf("Failed to find ANDROID_DATA directory %s", android_data);
    return nullptr;
  }
  return android_data;
}

void GetDalvikCache(const char* subdir, const bool create_if_absent, std::string* dalvik_cache,
                    bool* have_android_data, bool* dalvik_cache_exists, bool* is_global_cache) {
  CHECK(subdir != nullptr);
  std::string error_msg;
  const char* android_data = GetAndroidDataSafe(&error_msg);
  if (android_data == nullptr) {
    *have_android_data = false;
    *dalvik_cache_exists = false;
    *is_global_cache = false;
    return;
  } else {
    *have_android_data = true;
  }
  const std::string dalvik_cache_root(StringPrintf("%s/dalvik-cache/", android_data));
  *dalvik_cache = dalvik_cache_root + subdir;
  *dalvik_cache_exists = OS::DirectoryExists(dalvik_cache->c_str());
  *is_global_cache = strcmp(android_data, "/data") == 0;
  if (create_if_absent && !*dalvik_cache_exists && !*is_global_cache) {
    // Don't create the system's /data/dalvik-cache/... because it needs special permissions.
    *dalvik_cache_exists = ((mkdir(dalvik_cache_root.c_str(), 0700) == 0 || errno == EEXIST) &&
                            (mkdir(dalvik_cache->c_str(), 0700) == 0 || errno == EEXIST));
  }
}

std::string GetDalvikCache(const char* subdir) {
  CHECK(subdir != nullptr);
  const char* android_data = GetAndroidData();
  const std::string dalvik_cache_root(StringPrintf("%s/dalvik-cache/", android_data));
  const std::string dalvik_cache = dalvik_cache_root + subdir;
  if (!OS::DirectoryExists(dalvik_cache.c_str())) {
    // TODO: Check callers. Traditional behavior is to not abort.
    return "";
  }
  return dalvik_cache;
}

bool GetDalvikCacheFilename(const char* location, const char* cache_location,
                            std::string* filename, std::string* error_msg) {
  if (location[0] != '/') {
    *error_msg = StringPrintf("Expected path in location to be absolute: %s", location);
    return false;
  }
  std::string cache_file(&location[1]);  // skip leading slash
  if (!android::base::EndsWith(location, ".dex") &&
      !android::base::EndsWith(location, ".art") &&
      !android::base::EndsWith(location, ".oat")) {
    cache_file += "/";
    cache_file += DexFile::kClassesDex;
  }
  std::replace(cache_file.begin(), cache_file.end(), '/', '@');
  *filename = StringPrintf("%s/%s", cache_location, cache_file.c_str());
  return true;
}

static void InsertIsaDirectory(const InstructionSet isa, std::string* filename) {
  // in = /foo/bar/baz
  // out = /foo/bar/<isa>/baz
  size_t pos = filename->rfind('/');
  CHECK_NE(pos, std::string::npos) << *filename << " " << isa;
  filename->insert(pos, "/", 1);
  filename->insert(pos + 1, GetInstructionSetString(isa));
}

std::string GetSystemImageFilename(const char* location, const InstructionSet isa) {
  // location = /system/framework/boot.art
  // filename = /system/framework/<isa>/boot.art
  std::string filename(location);
  InsertIsaDirectory(isa, &filename);
  return filename;
}

int ExecAndReturnCode(std::vector<std::string>& arg_vector, std::string* error_msg) {
  const std::string command_line(android::base::Join(arg_vector, ' '));
  CHECK_GE(arg_vector.size(), 1U) << command_line;

  // Convert the args to char pointers.
  const char* program = arg_vector[0].c_str();
  std::vector<char*> args;
  for (size_t i = 0; i < arg_vector.size(); ++i) {
    const std::string& arg = arg_vector[i];
    char* arg_str = const_cast<char*>(arg.c_str());
    CHECK(arg_str != nullptr) << i;
    args.push_back(arg_str);
  }
  args.push_back(nullptr);

  // fork and exec
  pid_t pid = fork();
  if (pid == 0) {
    // no allocation allowed between fork and exec

    // change process groups, so we don't get reaped by ProcessManager
    setpgid(0, 0);

    // (b/30160149): protect subprocesses from modifications to LD_LIBRARY_PATH, etc.
    // Use the snapshot of the environment from the time the runtime was created.
    char** envp = (Runtime::Current() == nullptr) ? nullptr : Runtime::Current()->GetEnvSnapshot();
    if (envp == nullptr) {
      execv(program, &args[0]);
    } else {
      execve(program, &args[0], envp);
    }
    PLOG(ERROR) << "Failed to execve(" << command_line << ")";
    // _exit to avoid atexit handlers in child.
    _exit(1);
  } else {
    if (pid == -1) {
      *error_msg = StringPrintf("Failed to execv(%s) because fork failed: %s",
                                command_line.c_str(), strerror(errno));
      return -1;
    }

    // wait for subprocess to finish
    int status = -1;
    pid_t got_pid = TEMP_FAILURE_RETRY(waitpid(pid, &status, 0));
    if (got_pid != pid) {
      *error_msg = StringPrintf("Failed after fork for execv(%s) because waitpid failed: "
                                "wanted %d, got %d: %s",
                                command_line.c_str(), pid, got_pid, strerror(errno));
      return -1;
    }
    if (WIFEXITED(status)) {
      return WEXITSTATUS(status);
    }
    return -1;
  }
}

bool Exec(std::vector<std::string>& arg_vector, std::string* error_msg) {
  int status = ExecAndReturnCode(arg_vector, error_msg);
  if (status != 0) {
    const std::string command_line(android::base::Join(arg_vector, ' '));
    *error_msg = StringPrintf("Failed execv(%s) because non-0 exit status",
                              command_line.c_str());
    return false;
  }
  return true;
}

bool FileExists(const std::string& filename) {
  struct stat buffer;
  return stat(filename.c_str(), &buffer) == 0;
}

bool FileExistsAndNotEmpty(const std::string& filename) {
  struct stat buffer;
  if (stat(filename.c_str(), &buffer) != 0) {
    return false;
  }
  return buffer.st_size > 0;
}

std::string ReplaceFileExtension(const std::string& filename, const std::string& new_extension) {
  const size_t last_ext = filename.find_last_of('.');
  if (last_ext == std::string::npos) {
    return filename + "." + new_extension;
  } else {
    return filename.substr(0, last_ext + 1) + new_extension;
  }
}

std::string PrettyDescriptor(Primitive::Type type) {
  return PrettyDescriptor(Primitive::Descriptor(type));
}

static void ParseStringAfterChar(const std::string& s,
                                 char c,
                                 std::string* parsed_value,
                                 UsageFn Usage) {
  std::string::size_type colon = s.find(c);
  if (colon == std::string::npos) {
    Usage("Missing char %c in option %s\n", c, s.c_str());
  }
  // Add one to remove the char we were trimming until.
  *parsed_value = s.substr(colon + 1);
}

void ParseDouble(const std::string& option,
                 char after_char,
                 double min,
                 double max,
                 double* parsed_value,
                 UsageFn Usage) {
  std::string substring;
  ParseStringAfterChar(option, after_char, &substring, Usage);
  bool sane_val = true;
  double value;
  if ((false)) {
    // TODO: this doesn't seem to work on the emulator.  b/15114595
    std::stringstream iss(substring);
    iss >> value;
    // Ensure that we have a value, there was no cruft after it and it satisfies a sensible range.
    sane_val = iss.eof() && (value >= min) && (value <= max);
  } else {
    char* end = nullptr;
    value = strtod(substring.c_str(), &end);
    sane_val = *end == '\0' && value >= min && value <= max;
  }
  if (!sane_val) {
    Usage("Invalid double value %s for option %s\n", substring.c_str(), option.c_str());
  }
  *parsed_value = value;
}

int64_t GetFileSizeBytes(const std::string& filename) {
  struct stat stat_buf;
  int rc = stat(filename.c_str(), &stat_buf);
  return rc == 0 ? stat_buf.st_size : -1;
}

void SleepForever() {
  while (true) {
    usleep(1000000);
  }
}

}  // namespace art