**************************************************
* System Call: F$SLink
*
* Function: System Link
*
* Input:  A = Module type
*         X = Module name string pointer
*         Y = Name string DAT image pointer
*
* Output: A = Module type
*         B = Module revision
*         X = Updated name string pointer
*         Y = Module entry point
*         U = Module pointer
*
* Error:  CC = C bit set; B = error code
*
FSLink   ldy    R$Y,u       get DAT image pointer of name
         bra    L0398       skip ahead


**************************************************
* System Call: F$ELink
*
* Function: Link using module directory entry
*
* Input:  B = Module type
*         X = Pointer to module directory entry
*
* Output: None
*
* Error:  CC = C bit set; B = error code
*
FELink   pshs   u           preserve register stack pointer
         ldb    R$B,u       get module type
         ldx    R$X,u       get pointer to module directory entry
         bra    L03AF       skip ahead


**************************************************
* System Call: F$Link
*
* Function: Link to a memory module
*
* Input:  X = Address of module name
*         A = Type/Language byte
*
* Output: X = Advanced past module name
*         Y = Module entry point address
*         U = Module header address
*         A = Module type/language byte
*         B = Module attributes/revision byte
*
* Error:  CC = C bit set; B = error code
*
FLink    ldx    <D.Proc     get pointer to DAT image
         leay   P$DATImg,x  point to process DAT image
L0398    pshs   u           preserve register stack pointer
         ldx    R$X,u       get pointer to path name
         lda    R$A,u       get module type
         lbsr   L068D       search module directory
         bcs    L041E       not there, exit with error
         leay   ,u          point to module directory entry
         ldu    ,s          get register stack pointer
         stx    R$X,u       save updated module name pointer
         std    R$D,u       save type/language
         leax   ,y          point to directory entry
L03AF    bitb   #ReEnt      is it re-entrant?
         bne    L03BB       yes, skip ahead
         ldd    MD$Link,x   is module busy?
         beq    L03BB       no, go link it
         ldb    #E$ModBsy   return module busy error
         bra    L041E       return
L03BB    ldd    MD$MPtr,x   get module pointer
         pshs   d,x         preserve that & directory pointer
         ldy    MD$MPDAT,x  get module DAT image pointer
         ldd    MD$MBSiz,x  get block size
         addd   #$1FFF      round it up
         tfr    a,b
         lsrb
         lsrb
         lsrb
         lsrb
         lsrb
*         adda   #$02
         lsra
         inca             instead of adda #2, above
         lsra
         lsra
         lsra
         lsra
         pshs   a
         leau   ,y          point to module DAT image
         bsr    L0422       is it already linked in process space?
         bcc    L03EB       yes, skip ahead
         lda    ,s
         lbsr   L0A33       find free low block in process DAT image
         bcc    L03E8       found some, skip ahead
         leas   5,s         purge stack
         bra    L041E       return error

L03E8    lbsr   L0A8C       copy memory blocks into process DAT image
L03EB    ldb    #P$Links   point to memory block link counts
         abx              smaller and faster than leax P$Links,x
         sta    ,s          Save block # on stack
         lsla               account for 2 bytes/entry
         leau   a,x         Point to block # we want
         ldd    ,u          Get link count for that block
         IFNE   H6309
         incd               Bump up by 1
         ELSE
         addd   #$0001
         ENDC
         beq    L03FC       If wraps to 0, leave at $FFFF
         std    ,u          Otherwise, store new link count
L03FC    ldu    $03,s
         ldd    MD$Link,u
         IFNE   H6309
         incd
         ELSE
         addd   #$0001
         ENDC
         beq    L0406
         std    MD$Link,u
L0406    puls   b,x,y,u
         lbsr   CmpLBlk
         stx    R$U,u
         ldx    MD$MPtr,y
         ldy    ,y
         ldd    #M$Exec     get offset to execution address
         lbsr   L0B02       get execution offset
         addd   R$U,u       add it to start of module
         std    R$Y,u       set execution entry point
         clrb               No error & return
         rts   

L041E    orcc   #Carry      Error & return
         puls   u,pc

L0422    ldx    <D.Proc     get pointer to current process
         leay   P$DATImg,x  point to process DAT image
         clra  
         pshs   d,x,y
         subb   #DAT.BlCt
         negb  
         lslb  
         leay   b,y
         IFNE   H6309
L0430    ldw    ,s          Get counter
         ELSE
L0430    ldx    ,s
         ENDC
         pshs   u,y
L0434    ldd    ,y++
         cmpd   ,u++
         bne    L0449
         IFNE   H6309
         decw               Dec counter
         ELSE
         leax   -1,x
         ENDC
         bne    L0434       If not done, keep going
         puls   d,u
         subd   4,s
         lsrb  
         stb    ,s
         clrb  
         puls   d,x,y,pc    Restore regs & return

L0449    puls   u,y
         leay   -2,y
         cmpy   4,s
         bcc    L0430
         puls   d,x,y,pc