Module openj9.dtfj
Package com.ibm.dtfj.corereaders.zos.util

Class Clib

java.lang.Object
com.ibm.dtfj.corereaders.zos.util.Clib
public class Clib extends Object
This class provides a low level interface to some of the z/OS C library. This approach was inspired by the SWT design in that we have a one-to-one mapping between JNI calls and C library calls: no extra work is done in the native functions. This is much easier to maintain because this library should rarely need recompiling.

Please refer to the C library documentation for more details about arguments to these calls.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    SEEK_CUR
    fseek whence argument to indicate that offset is from the current position of the file pointer
    static final int
    SEEK_END
    fseek whence argument to indicate that offset is from the end of the file
    static final int
    SEEK_SET
    fseek whence argument to indicate that offset is from the beginning of the file

  • Constructor Summary

    Constructors
    Constructor
    Description
    Clib()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static int
    fgetpos(long fp, int[] pos)
    This method is a wrapper around fgetpos.
    static long
    fopen(byte[] filename, byte[] mode)
    This method is a wrapper around fopen.
    static long
    fopen(String filename, String mode)
    This method is a slightly friendlier version of the native fopen call (the parameters are Strings rather than byte arrays otherwise everything is the same).
    static int
    fread(byte[] buf, int size, int count, long fp)
    This method is a wrapper around fread.
    static int
    fseek(long fp, long offset, int whence)
    This method is a wrapper around fseek.
    static int
    fsetpos(long fp, int[] pos)
    This method is a wrapper around fsetpos.
    static void
    perror(byte[] prefix)
    This method is a wrapper around perror.
    static void
    perror(String prefix)
    Friendlier version of the native perror call that accepts a String parameter.

    Methods declared in class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • SEEK_SET

      public static final int SEEK_SET
      fseek whence argument to indicate that offset is from the beginning of the file
      See Also:

    • SEEK_CUR

      public static final int SEEK_CUR
      fseek whence argument to indicate that offset is from the current position of the file pointer
      See Also:

    • SEEK_END

      public static final int SEEK_END
      fseek whence argument to indicate that offset is from the end of the file
      See Also:

  • Constructor Details

    • Clib

      public Clib()

  • Method Details

    • fopen

      public static long fopen(byte[] filename, byte[] mode)
      This method is a wrapper around fopen.
      Parameters:
      filename - the name of the file to open as a null-terminated ebcdic byte array
      mode - the open mode which must be a null-terminated ebcdic byte array. See the C library fopen documentation for more details
      Returns:
      the FILE stream pointer from fopen cast to a long

    • fopen

      public static long fopen(String filename, String mode)
      This method is a slightly friendlier version of the native fopen call (the parameters are Strings rather than byte arrays otherwise everything is the same).

    • fgetpos

      public static int fgetpos(long fp, int[] pos)
      This method is a wrapper around fgetpos. Here we make use of the knowledge that a C fpos_t on z/OS is actually an array of 8 ints.
      Parameters:
      fp - the stream obtained from an earlier call to fopen
      pos - this must be an array of 8 ints. The position indicator is stored in this array. The same array contents may be passed to a subsequent fsetpos call.
      Returns:
      the return code from the fgetpos call (zero if successful)

    • fsetpos

      public static int fsetpos(long fp, int[] pos)
      This method is a wrapper around fsetpos.
      Parameters:
      fp - the stream obtained from an earlier call to fopen
      pos - this must be an array of 8 ints whose contents were obtained in a previous call to fgetpos.
      Returns:
      the return code from the fsetpos call (zero if successful)

    • fseek

      public static int fseek(long fp, long offset, int whence)
      This method is a wrapper around fseek. (Note: this hasn't been tested for seeks over 2GB yet).
      Parameters:
      fp - the stream obtained from an earlier call to fopen
      offset - the offset to seek to
      whence - specifies where to seek from
      Returns:
      the return code from the fseek call (zero if successful)

    • fread

      public static int fread(byte[] buf, int size, int count, long fp)
      This method is a wrapper around fread.
      Parameters:
      buf - the buffer to contain the read data
      size - the size of each element
      count - the number of elements to read
      fp - the stream obtained from an earlier call to fopen
      Returns:
      the number of elements read

    • perror

      public static void perror(byte[] prefix)
      This method is a wrapper around perror.
      Parameters:
      prefix - the message prefix as a null-terminated ebcdic byte array

    • perror

      public static void perror(String prefix)
      Friendlier version of the native perror call that accepts a String parameter.