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     CBT(3X)                                                   CBT(3X)

          bopen, bclose, bseek, bfirst, bkey, breclen, bread, bdelete,
          bwrite - compressed B-tree subroutines

          #include <cbt.h>

          bfile *bopen(name, typ) char *name;

          void bclose(b) bfile *b;

          bseek(b, key) bfile *b; mbuf key;

          bfirst(b) bfile *b;

          mbuf bkey(b) bfile *b;

          breclen(b) bfile *b;

          bread(b, key, val) bfile *b; mbuf *key, *val;

          bdelete(b, key) bfile *b; mbuf key;

          bwrite(b, key, val) bfile *b; mbuf key, val;

          These functions manipulate files of key/value records.  Such
          files are created by cbt(1). To load the functions use ld(1)
          option -lcbt.

          The records occur sorted by their keys, which must be dis-
          tinct.  Both keys and values are arrays of characters
          accessed through the data type `mbuf':

               typedef struct {
                    char *mdata;   /* pointer to the data */
                    short mlen;    /* number of bytes in the data */
               } mbuf;

          Bopen attempts to open a named B-tree, and if successful
          establishes a read pointer pointing to the beginning of the
          file and returns a pointer to be used in calling the other
          routines.  Typ is 0 for read-only or 2 for read-write.
          Bopen returns a descriptor that identifies the file to the
          other functions.

          Bclose closes a B-tree.

          Bseek positions the read pointer of the file to the record
          whose key is the first not less than key. The routine

     CBT(3X)                                                   CBT(3X)

          returns 1 if key is in the file, EOF if key is greater than
          any key in the file, and 0 otherwise.

          Bfirst sets the read pointer to the beginning of the file.
          It has the same error return as bseek.

          Bkey returns the current key.  The element mdata of the
          returned structure is 0 on errors, otherwise it points to a
          critical static buffer.

          Breclen returns the length of the value part of the current

          Bread reads the value at the read pointer into the space
          pointed to by val->mdata, places its length in val->mlen,
          and advances the read pointer to the record with the next
          greater key.  If key is not 0 the key of the record is read
          into the space pointed to by key->mdata and its length is
          placed in key->mlen. Bread returns 0 if successful.

          Bdelete removes the record with the given key, returning 1
          if the record was found, -1 if there was an error, and 0
          otherwise, The read pointer is left undefined.

          Bwrite writes the given value with the given key, returning
          0 if there was no error.  An existing record with that key
          will be replaced.  The read pointer is left undefined.

          The btree name is stored in files name.T and name.F.

          cbt(1), dbm(3)

          Routines which return pointers return 0 on errors, routines
          which return integers return -1.

          The lengths of keys and values are limited.