mdw@git.distorted.org.uk Git - ssr/blob - StraySrc/Libraries/BAS/src/s/insert

   1 ;
   2 ; insert.s
   3 ;
   4 ; Insert zero-filled chunks of data
   5 ;
   6 ; © 1994-1998 Straylight
   7 ;
   8
   9 ;----- Licensing note -------------------------------------------------------
  10 ;
  11 ; This file is part of Straylight's BASIC Assembler Supplement.
  12 ;
  13 ; BAS is free software; you can redistribute it and/or modify
  14 ; it under the terms of the GNU General Public License as published by
  15 ; the Free Software Foundation; either version 2, or (at your option)
  16 ; any later version.
  17 ;
  18 ; BAS is distributed in the hope that it will be useful,
  19 ; but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 ; GNU General Public License for more details.
  22 ;
  23 ; You should have received a copy of the GNU General Public License
  24 ; along with BAS.  If not, write to the Free Software Foundation,
  25 ; 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  26
  27 ;----- Standard header ------------------------------------------------------
  28
  29                 GET     libs:header
  30                 GET     libs:swis
  31
  32                 GET     libs:stream
  33
  34 ;----- External dependencies ------------------------------------------------
  35
  36                 GET     sh.bas
  37                 GET     sh.workspace
  38
  39 ;----- Main code ------------------------------------------------------------
  40
  41                 AREA    |BAS$$Code|,CODE,READONLY
  42
  43 ; --- insert_align ---
  44 ;
  45 ; On entry:     --
  46 ;
  47 ; On exit:      --
  48 ;
  49 ; Use:          Inserts `0' bytes to align O% and P% to the next word
  50 ;               boundary.
  51
  52                 EXPORT  insert_align
  53 insert_align    ROUT
  54
  55                 STMFD   R13!,{R0,R14}           ;Save some registers
  56                 LDR     R14,[R7,#:INDEX:be__percents]
  57                 LDR     R0,[R14,#('P'-'A')*4]   ;Load current loc counter
  58                 ANDS    R0,R0,#3                ;Get non-word-alignedness
  59                 RSBNE   R0,R0,#4                ;Work out bytes to insert
  60                 BLNE    insert_reserve          ;Reserve so many bytes
  61                 LDMFD   R13!,{R0,PC}^           ;And return to caller
  62
  63                 LTORG
  64
  65 ; --- insert_reserve ---
  66 ;
  67 ; On entry:     R0 == amount of memory to reserve
  68 ;
  69 ; On exit:      --
  70 ;
  71 ; Use:          Reserves R0 bytes of memory at the current position.  The
  72 ;               memory is filled with 0s.
  73
  74                 EXPORT  insert_reserve
  75 insert_reserve  ROUT
  76
  77                 STMFD   R13!,{R0-R9,R12,R14}    ;Save some registers
  78                 MOV     R12,R7                  ;Get workspace in R12
  79
  80                 LDR     R14,be__percents        ;Load the % variable address
  81                 ADD     R14,R14,#('O'-'A')*4    ;Find O% and P%
  82                 LDMIA   R14,{R1,R3}             ;Load them out nicely
  83                 ADD     R2,R1,R0                ;Bump along O%
  84                 ADD     R3,R3,R0                ;And bump along P%
  85                 STMIA   R14,{R2,R3}             ;Save them back again
  86
  87                 CMP     R0,#0                   ;Insert no bytes?
  88                 BEQ     %90insert_reserve       ;Yup -- do nothing then
  89                 MOV     R2,#0                   ;A zero word
  90
  91                 TST     R1,#3                   ;Is destination word-aligned?
  92                 BEQ     %10insert_reserve       ;Yes -- skip onwards then
  93 00              STRB    R2,[R1],#1              ;Zero a single byte
  94                 SUBS    R0,R0,#1                ;Decrement counter
  95                 BEQ     %90insert_reserve       ;Done it all -- return
  96                 TST     R1,#3                   ;Is destination word-aligned?
  97                 BNE     %00insert_reserve       ;No -- go round again
  98
  99                 ; --- Now blast 0s out AQAP ---
 100
 101 10              MOV     R3,#0
 102                 MOV     R4,#0
 103                 MOV     R5,#0
 104                 MOV     R6,#0
 105                 MOV     R7,#0
 106                 MOV     R8,#0
 107                 MOV     R9,#0
 108
 109                 SUBS    R0,R0,#16               ;4 or more words to do?
 110                 BLT     %03insert_reserve
 111                 SUBS    R0,R0,#16               ;8 or more words to do?
 112                 BLT     %02insert_reserve
 113
 114 01              STMIA   R1!,{R2-R9}             ;Blank out 8 words
 115                 SUBS    R0,R0,#32               ;Decrement counter
 116                 BGE     %01insert_reserve       ;And keep going round
 117
 118                 CMP     R0,#-32                 ;Are we finished?
 119                 BEQ     %90insert_reserve       ;Yes -- return then
 120
 121 02              ADDS    R0,R0,#16               ;4 whole words to do?
 122                 BLT     %03insert_reserve
 123                 STMIA   R1!,{R2-R5}             ;Blank out 4 words
 124                 BEQ     %90insert_reserve       ;Done -- return then
 125                 SUB     R0,R0,#16
 126
 127 03              ADDS    R0,R0,#8                ;2 whole words to do?
 128                 BLT     %04insert_reserve
 129                 STMIA   R1!,{R2,R3}             ;Blank out 2 words
 130                 BEQ     %90insert_reserve       ;Done -- return then
 131                 SUB     R0,R0,#8
 132
 133 04              ADDS    R0,R0,#4                ;1 word to do?
 134                 BLT     %05insert_reserve
 135                 STR     R2,[R1],#4              ;Blank out 1 word
 136                 BEQ     %90insert_reserve       ;Done -- return then
 137                 SUB     R0,R0,#4
 138
 139 05              ADDS    R0,R0,#4
 140                 BEQ     %90insert_reserve       ;Done -- return then
 141
 142 06              STRB    R2,[R1],#1              ;Save 1 byte
 143                 SUBS    R2,R2,#1
 144                 BGT     %06insert_reserve
 145
 146 90              LDMFD   R13!,{R0-R9,R12,PC}^    ;And return to caller
 147
 148                 LTORG
 149
 150 ;----- That's all, folks ----------------------------------------------------
 151
 152                 END