content: /*
   * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package javac.internal.jimage;
  
  import java.io.UTFDataFormatException;
  import java.nio.ByteBuffer;
  import java.nio.charset.StandardCharsets;
  import java.util.Objects;
  
  /**
   * @implNote This class needs to maintain JDK 8 source compatibility.
   *
   * It is used internally in the JDK to implement jimage/jrtfs access,
   * but also compiled and delivered as part of the jrtfs.jar to support access
   * to the jimage file provided by the shipped JDK by tools running on JDK 8.
   */
  public class ImageStringsReader implements ImageStrings {
      public static final int HASH_MULTIPLIER = 0x01000193;
      public static final int POSITIVE_MASK = 0x7FFFFFFF;
  
      private final BasicImageReader reader;
  
      ImageStringsReader(BasicImageReader reader) {
          this.reader = Objects.requireNonNull(reader);
      }
  
      @Override
      public String get(int offset) {
          return reader.getString(offset);
      }
  
      @Override
      public int match(int offset, String string, int stringOffset) {
          return reader.match(offset, string, stringOffset);
      }
  
      @Override
      public int add(final String string) {
          throw new InternalError("Can not add strings at runtime");
      }
  
      public static int hashCode(String s) {
          return hashCode(s, HASH_MULTIPLIER);
      }
  
      public static int hashCode(String s, int seed) {
          return unmaskedHashCode(s, seed) & POSITIVE_MASK;
      }
  
      public static int hashCode(String module, String name) {
          return hashCode(module, name, HASH_MULTIPLIER);
      }
  
      public static int hashCode(String module, String name, int seed) {
          seed = (seed * HASH_MULTIPLIER) ^ ('/');
          seed = unmaskedHashCode(module, seed);
          seed = (seed * HASH_MULTIPLIER) ^ ('/');
          seed = unmaskedHashCode(name, seed);
          return seed & POSITIVE_MASK;
      }
  
      public static int unmaskedHashCode(String s, int seed) {
          int slen = s.length();
          byte[] buffer = null;
  
          for (int i = 0; i < slen; i++) {
              int uch = s.charAt(i);
  
              if ((uch & ~0x7F) != 0) {
                  if (buffer == null) {
                      buffer = new byte[8];
                  }
                  int mask = ~0x3F;
                  int n = 0;
  
                  do {
                      buffer[n++] = (byte)(0x80 | (uch & 0x3F));
                      uch >>= 6;
                      mask >>= 1;
                  } while ((uch & mask) != 0);
  
                  buffer[n] = (byte)((mask << 1) | uch);
  
                  do {
                      seed = (seed * HASH_MULTIPLIER) ^ (buffer[n--] & 0xFF);
                  } while (0 <= n);
              } else if (uch == 0) {
                  seed = (seed * HASH_MULTIPLIER) ^ (0xC0);
                  seed = (seed * HASH_MULTIPLIER) ^ (0x80);
              } else {
                  seed = (seed * HASH_MULTIPLIER) ^ (uch);
              }
          }
          return seed;
      }
  
      static int charsFromMUTF8Length(byte[] bytes, int offset, int count) {
          int length = 0;
  
          for (int i = offset; i < offset + count; i++) {
              byte ch = bytes[i];
  
              if (ch == 0) {
                  break;
              }
  
              if ((ch & 0xC0) != 0x80) {
                  length++;
              }
          }
  
          return length;
      }
  
      static void charsFromMUTF8(char[] chars, byte[] bytes, int offset, int count) throws UTFDataFormatException {
          int j = 0;
  
          for (int i = offset; i < offset + count; i++) {
              byte ch = bytes[i];
  
              if (ch == 0) {
                  break;
              }
  
              boolean is_unicode = (ch & 0x80) != 0;
              int uch = ch & 0x7F;
  
              if (is_unicode) {
                  int mask = 0x40;
  
                  while ((uch & mask) != 0) {
                      ch = bytes[++i];
  
                      if ((ch & 0xC0) != 0x80) {
                          throw new UTFDataFormatException("bad continuation 0x" + Integer.toHexString(ch));
                      }
  
                      uch = ((uch & ~mask) << 6) | (ch & 0x3F);
                      mask <<= 6 - 1;
                  }
  
                  if ((uch & 0xFFFF) != uch) {
                      throw new UTFDataFormatException("character out of range \\u" + Integer.toHexString(uch));
                  }
              }
  
              chars[j++] = (char)uch;
          }
      }
  
      public static String stringFromMUTF8(byte[] bytes, int offset, int count) {
          int length = charsFromMUTF8Length(bytes, offset, count);
          char[] chars = new char[length];
  
          try {
              charsFromMUTF8(chars, bytes, offset, count);
          } catch (UTFDataFormatException ex) {
              throw new InternalError("Attempt to convert non modified UTF-8 byte sequence", ex);
          }
  
          return new String(chars);
      }
  
      public static String stringFromMUTF8(byte[] bytes) {
          return stringFromMUTF8(bytes, 0, bytes.length);
      }
  
      /**
       * Calculates the number of characters in the String present at the
       * specified offset. As an optimization, the length returned will
       * be positive if the characters are all ASCII, and negative otherwise.
       */
      private static int charsFromByteBufferLength(ByteBuffer buffer, int offset) {
          int length = 0;
  
          int limit = buffer.limit();
          boolean asciiOnly = true;
          while (offset < limit) {
              byte ch = buffer.get(offset++);
  
              if (ch < 0) {
                  asciiOnly = false;
              } else if (ch == 0) {
                  return asciiOnly ? length : -length;
              }
  
              if ((ch & 0xC0) != 0x80) {
                  length++;
              }
          }
          throw new InternalError("No terminating zero byte for modified UTF-8 byte sequence");
      }
  
      private static void charsFromByteBuffer(char[] chars, ByteBuffer buffer, int offset) {
          int j = 0;
  
          int limit = buffer.limit();
          while (offset < limit) {
              byte ch = buffer.get(offset++);
  
              if (ch == 0) {
                  return;
              }
  
              boolean is_unicode = (ch & 0x80) != 0;
              int uch = ch & 0x7F;
  
              if (is_unicode) {
                  int mask = 0x40;
  
                  while ((uch & mask) != 0) {
                      ch = buffer.get(offset++);
  
                      if ((ch & 0xC0) != 0x80) {
                          throw new InternalError("Bad continuation in " +
                              "modified UTF-8 byte sequence: " + ch);
                      }
  
                      uch = ((uch & ~mask) << 6) | (ch & 0x3F);
                      mask <<= 6 - 1;
                  }
              }
  
              if ((uch & 0xFFFF) != uch) {
                  throw new InternalError("UTF-32 char in modified UTF-8 " +
                      "byte sequence: " + uch);
              }
  
              chars[j++] = (char)uch;
          }
  
          throw new InternalError("No terminating zero byte for modified UTF-8 byte sequence");
      }
  
      public static String stringFromByteBuffer(ByteBuffer buffer) {
          return stringFromByteBuffer(buffer, 0);
      }
  
      /* package-private */
      static String stringFromByteBuffer(ByteBuffer buffer, int offset) {
          int length = charsFromByteBufferLength(buffer, offset);
          if (length > 0) {
              byte[] asciiBytes = new byte[length];
              // Ideally we could use buffer.get(offset, asciiBytes, 0, length)
              // here, but that was introduced in JDK 13
              for (int i = 0; i < length; i++) {
                  asciiBytes[i] = buffer.get(offset++);
              }
              return new String(asciiBytes, StandardCharsets.US_ASCII);
          }
          char[] chars = new char[-length];
          charsFromByteBuffer(chars, buffer, offset);
          return new String(chars);
      }
  
      /* package-private */
      static int stringFromByteBufferMatches(ByteBuffer buffer, int offset, String string, int stringOffset) {
          // ASCII fast-path
          int limit = buffer.limit();
          int current = offset;
          int slen = string.length();
          while (current < limit) {
              byte ch = buffer.get(current);
              if (ch <= 0) {
                  if (ch == 0) {
                      // Match
                      return current - offset;
                  }
                  // non-ASCII byte, run slow-path from current offset
                  break;
              }
              if (slen <= stringOffset || string.charAt(stringOffset) != (char)ch) {
                  // No match
                  return -1;
              }
              stringOffset++;
              current++;
          }
          // invariant: remainder of the string starting at current is non-ASCII,
          // so return value from charsFromByteBufferLength will be negative
          int length = -charsFromByteBufferLength(buffer, current);
          char[] chars = new char[length];
          charsFromByteBuffer(chars, buffer, current);
          for (int i = 0; i < length; i++) {
              if (string.charAt(stringOffset++) != chars[i]) {
                  return -1;
              }
          }
          return length;
      }
  
      static int mutf8FromStringLength(String s) {
          int length = 0;
          int slen = s.length();
  
          for (int i = 0; i < slen; i++) {
              char ch = s.charAt(i);
              int uch = ch & 0xFFFF;
  
              if ((uch & ~0x7F) != 0) {
                  int mask = ~0x3F;
                  int n = 0;
  
                  do {
                      n++;
                      uch >>= 6;
                      mask >>= 1;
                  } while ((uch & mask) != 0);
  
                  length += n + 1;
              } else if (uch == 0) {
                  length += 2;
              } else {
                  length++;
              }
          }
  
          return length;
      }
  
      static void mutf8FromString(byte[] bytes, int offset, String s) {
          int j = offset;
          byte[] buffer = null;
          int slen = s.length();
  
          for (int i = 0; i < slen; i++) {
              char ch = s.charAt(i);
              int uch = ch & 0xFFFF;
  
              if ((uch & ~0x7F) != 0) {
                  if (buffer == null) {
                      buffer = new byte[8];
                  }
                  int mask = ~0x3F;
                  int n = 0;
  
                  do {
                      buffer[n++] = (byte)(0x80 | (uch & 0x3F));
                      uch >>= 6;
                      mask >>= 1;
                  } while ((uch & mask) != 0);
  
                  buffer[n] = (byte)((mask << 1) | uch);
  
                  do {
                      bytes[j++] = buffer[n--];
                  } while (0 <= n);
              } else if (uch == 0) {
                  bytes[j++] = (byte)0xC0;
                  bytes[j++] = (byte)0x80;
              } else {
                  bytes[j++] = (byte)uch;
              }
          }
      }
  
      public static byte[] mutf8FromString(String string) {
          int length = mutf8FromStringLength(string);
          byte[] bytes = new byte[length];
          mutf8FromString(bytes, 0, string);
  
          return bytes;
      }
  }
  