Interface ClassReader

All Superinterfaces:
ConstantPool, Iterable<PoolEntry>

public sealed interface ClassReader extends ConstantPool
Advanced class file reading support for AttributeMappers. Supports reading arbitrary offsets within a class file and reading data of various numeric types (e.g., u2, u4) in addition to constant pool access.

All numeric values in the class file format are big endian.

Unless otherwise specified, all out-of-bounds access result in an IllegalArgumentException to indicate the class file data is malformed. Since the class file data is arbitrary, users should sanity-check the structural integrity of the data before attempting to interpret the potentially malformed data.

Since:
24
See Also:
  • Method Summary

    Modifier and Type
    Method
    Description
    int
    Returns the length of the class file, in number of bytes.
    void
    copyBytesTo(BufWriter buf, int offset, int len)
    Copy a range of bytes from the class file to a BufWriter.
    Returns the table of custom attribute mappers.
    int
    Returns the access flags for the class, as a bit mask.
    byte[]
    readBytes(int offset, int len)
    Returns a copy of the bytes at the specified range in the class file.
    double
    readDouble(int offset)
    Returns the double value at the specified offset within the class file.
    readEntry(int offset)
    Returns the constant pool entry whose index is given at the specified offset within the class file.
    <T extends PoolEntry>
    T
    readEntry(int offset, Class<T> cls)
    Returns the constant pool entry of a given type whose index is given at the specified offset within the class file.
    readEntryOrNull(int offset)
    Returns the constant pool entry whose index is given at the specified offset within the class file, or null if the index at the specified offset is zero.
    <T extends PoolEntry>
    T
    readEntryOrNull(int offset, Class<T> cls)
    Returns the constant pool entry of a given type whose index is given at the specified offset within the class file, or null if the index at the specified offset is zero.
    float
    readFloat(int offset)
    Returns the float value at the specified offset within the class file.
    int
    readInt(int offset)
    Returns the signed int at the specified offset within the class file.
    long
    readLong(int offset)
    Returns the signed long at the specified offset within the class file.
    int
    readS1(int offset)
    Returns the signed byte at the specified offset within the class file.
    int
    readS2(int offset)
    Returns the signed byte at the specified offset within the class file.
    int
    readU1(int offset)
    Returns the unsigned byte at the specified offset within the class file.
    int
    readU2(int offset)
    Returns the unsigned short at the specified offset within the class file.
    Returns the constant pool entry describing the name of the superclass, if any.
    Returns the constant pool entry describing the name of class.

    Methods inherited from interface Iterable

    forEach, spliterator
  • Method Details

    • customAttributes

      Function<Utf8Entry, AttributeMapper<?>> customAttributes()
      Returns the table of custom attribute mappers. This is derived from the processing option ClassFile.AttributeMapperOption.
      Returns:
      the table of custom attribute mappers
    • flags

      int flags()
      Returns the access flags for the class, as a bit mask.
      Returns:
      the access flags for the class, as a bit mask
      See Also:
    • thisClassEntry

      ClassEntry thisClassEntry()
      Returns the constant pool entry describing the name of class.
      Returns:
      the constant pool entry describing the name of class
      See Also:
    • superclassEntry

      Optional<ClassEntry> superclassEntry()
      Returns the constant pool entry describing the name of the superclass, if any.
      Returns:
      the constant pool entry describing the name of the superclass, if any
      See Also:
    • classfileLength

      int classfileLength()
      Returns the length of the class file, in number of bytes.
      Returns:
      the length of the class file, in number of bytes
    • readEntry

      PoolEntry readEntry(int offset)
      Returns the constant pool entry whose index is given at the specified offset within the class file.
      API Note:
      If only a particular type of entry is expected, use readEntry(int, Class).
      Parameters:
      offset - the offset of the index within the class file
      Returns:
      the constant pool entry whose index is given at the specified offset within the class file
      Throws:
      ConstantPoolException - if the index is out of range of the constant pool size, or zero
    • readEntry

      <T extends PoolEntry> T readEntry(int offset, Class<T> cls)
      Returns the constant pool entry of a given type whose index is given at the specified offset within the class file.
      Type Parameters:
      T - the entry type
      Parameters:
      offset - the offset of the index within the class file
      cls - the entry type
      Returns:
      the constant pool entry of a given type whose index is given at the specified offset within the class file
      Throws:
      ConstantPoolException - if the index is out of range of the constant pool size, or zero, or the entry is not of the given type
    • readEntryOrNull

      PoolEntry readEntryOrNull(int offset)
      Returns the constant pool entry whose index is given at the specified offset within the class file, or null if the index at the specified offset is zero.
      API Note:
      If only a particular type of entry is expected, use readEntryOrNull(int, Class).
      Parameters:
      offset - the offset of the index within the class file
      Returns:
      the constant pool entry whose index is given at the specified offset within the class file, or null if the index at the specified offset is zero
      Throws:
      ConstantPoolException - if the index is out of range of the constant pool size
    • readEntryOrNull

      <T extends PoolEntry> T readEntryOrNull(int offset, Class<T> cls)
      Returns the constant pool entry of a given type whose index is given at the specified offset within the class file, or null if the index at the specified offset is zero.
      Type Parameters:
      T - the entry type
      Parameters:
      offset - the offset of the index within the class file
      cls - the entry type
      Returns:
      the constant pool entry of a given type whose index is given at the specified offset within the class file, or null if the index at the specified offset is zero
      Throws:
      ConstantPoolException - if the index is out of range of the constant pool size, or zero, or the entry is not of the given type
    • readU1

      int readU1(int offset)
      Returns the unsigned byte at the specified offset within the class file. Reads a byte and zero-extends it to an int.
      Parameters:
      offset - the offset within the class file
      Returns:
      the unsigned byte at the specified offset within the class file
    • readU2

      int readU2(int offset)
      Returns the unsigned short at the specified offset within the class file. Reads a 2-byte value and zero-extends it to an int.
      Parameters:
      offset - the offset within the class file
      Returns:
      the unsigned short at the specified offset within the class file
    • readS1

      int readS1(int offset)
      Returns the signed byte at the specified offset within the class file. Reads a byte and sign-extends it to an int.
      Parameters:
      offset - the offset within the class file
      Returns:
      the signed byte at the specified offset within the class file
    • readS2

      int readS2(int offset)
      Returns the signed byte at the specified offset within the class file. Reads a 2-byte value and sign-extends it to an int.
      Parameters:
      offset - the offset within the class file
      Returns:
      the signed byte at the specified offset within the class file
    • readInt

      int readInt(int offset)
      Returns the signed int at the specified offset within the class file. Reads 4 bytes of value.
      Parameters:
      offset - the offset within the class file
      Returns:
      the signed int at the specified offset within the class file
    • readLong

      long readLong(int offset)
      Returns the signed long at the specified offset within the class file. Reads 8 bytes of value.
      Parameters:
      offset - the offset within the class file
      Returns:
      the signed long at the specified offset within the class file
    • readFloat

      float readFloat(int offset)
      Returns the float value at the specified offset within the class file. Reads 4 bytes of value.

      In the conversions, all NaN values of the float may or may not be collapsed into a single "canonical" NaN value.

      Parameters:
      offset - the offset within the class file
      Returns:
      the float value at the specified offset within the class file
    • readDouble

      double readDouble(int offset)
      Returns the double value at the specified offset within the class file. Reads 8 bytes of value.

      In the conversions, all NaN values of the double may or may not be collapsed into a single "canonical" NaN value.

      Parameters:
      offset - the offset within the class file
      Returns:
      the double value at the specified offset within the class file
    • readBytes

      byte[] readBytes(int offset, int len)
      Returns a copy of the bytes at the specified range in the class file.
      Parameters:
      offset - the offset within the class file
      len - the length of the range
      Returns:
      a copy of the bytes at the specified range in the class file
    • copyBytesTo

      void copyBytesTo(BufWriter buf, int offset, int len)
      Copy a range of bytes from the class file to a BufWriter.
      Parameters:
      buf - the BufWriter
      offset - the offset within the class file
      len - the length of the range