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CA-VO

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CA-CLIPPER
NETWORKING

USE <file> (exclusive off)

1) open file
2) read file header
3) fill buffer:
  if index:
    a) open index file
    b) lock index file
    c) search index file for 'top' of index
    d) read indicated record into buffer
    e) unlock index file
  if no index:
    a) read first record into buffer

SEEK/FIND

1) if 'hot' flag set, flush buffer
2) lock index file
3) search index file for specified key
  if found:
    a) read record into buffer
  if not found:
    a) set record pointer to lastrec()+1
    b) set end of file flag
    c) store spaces into record buffer
4) unlock index file

SKIP 0

1) if 'hot' flag set, flush buffer

SKIP n

1) if 'hot' flag set, flush buffer
2) lock index file
3) search for next index entry
  if found:
    a) read record into buffer
  if not found:
    a) set record pointer to lastrec()+1
    b) set end of file flag
    c) store spaces into record buffer
4) unlock index file

GOTO n

1) if 'hot' flag set, flush buffer
  if not past eof:
    a) set new record pointer
    b) read record into buffer
  if past eof:
    a) set record pointer to lastrec()+1
    b) store spaces into record buffer

RLOCK()/FLOCK()

1) if 'hot' flag set, flush buffer
2) issue lock request to server
  if successful:
    a) read record into buffer
  if not successful:
    a) exit

APPEND BLANK

1) if 'hot' flag set, flush buffer
2) lock header
3) calculate new record number based on file size
4) issue record lock request to server
  if successful:
    a) set record pointer to lastrec()+1
    b) write out spaces to new record
    c) store spaces into record buffer
    d) set 'hot' buffer flag
5) unlock header

REPLACE

1) search symbol table for field name
2) move data into record buffer
3) set 'hot' buffer flag

GET (to database field)

1) set 'hot' buffer flag if any data key pressed

STORE

1) search symbol table for field name
2) move data from record buffer to memory variable

UNLOCK

1) if 'hot' buffer flag set
    a) lock index file
    b) (re)write index entry
    c) unlock index file
    d) write record buffer
    e) reset 'hot' buffer flag (clear)
2) unlock record

COMMIT

1) if 'hot' buffer flag set
    a) lock index file
    b) (re)write index entry
    c) unlock index file
    d) write record buffer
    e) reset 'hot' buffer flag (clear)
    f) repeat a-e for all select areas
    g) issue DOS function 68h (ignored prior to DOS 3.3)

Memo field STORE

1) lock memo file
2) move to memo record number (from DBF)
3) read (next) 512 byte memo block into a buffer
4) repeat step 3 until ^Z found in buffer
5) reread entire memo field in one block

Memo field REPLACE (new field)

1) lock memo file
2) move to eof
3) write out new entry
4) replace pointer in DBF

Memo field REPLACE

1) lock memo file
  if replacement field length < 512 bytes:
    a) write block back to original field
  if replacement field length => 512 bytes:
    a) write ^Z to start of original (old) entry
    b) move to eof
    c) write out new entry
    d) adjust pointer in DBF
2) unlock memo file

Flushing the buffer

1) lock index file
2) (re)write index entry
3) unlock index file
4) write record buffer
5) reset 'hot' buffer flag (clear)

Summary

The 'hot' buffer flag is set by:

		`replace`
		`append blank`
		`recall`
		`delete`
		`get` (to a database field)

The record buffer is refreshed by:

		`seek/find`
		`goto`
		`skip` (<>0)
		`rlock()/flock()`

The record buffer is flushed by:

		`seek/find`
		`goto`
		`skip` (any)
		`rlock()/flock()`
		`unlock`
		`commit`

The memo buffer is refreshed by:

reference by field name

The memo buffer is flushed by:

replace