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⌂ ∞ Elite on the BBC Micro and NES

Charts: HME2

[NES version, Bank 0]

       Name: HME2                                                    [Show more]
       Type: Subroutine
   Category: Charts
    Summary: Search the galaxy for a system

    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * TT102 calls HME2




.HME2

 JSR CLYNS              ; Clear the bottom two text rows of the upper screen,
                        ; and move the text cursor to column 1 on row 21, i.e.
                        ; the start of the top row of the two bottom rows

 LDA #14                ; Print extended token 14 ("{clear bottom of screen}
 JSR DETOK_b2           ; PLANET NAME?{fetch line input from keyboard}"). The
                        ; last token calls MT26, which puts the entered search
                        ; term in INWK+5 and the term length in Y

 LDY #9                 ; We start by setting the default name to all A's in the
                        ; buffer at INWK+5, which is where the InputName routine
                        ; expects to find the default name to show, so set a
                        ; counter in Y for ten characters

 STY inputNameSize      ; Set inputNameSize = 9 so we fetch a system name with a
                        ; maximum size of 10 characters in the call to InputName
                        ; below

 LDA #'A'               ; Set A to ASCII "A" so we can fill the name buffer with
                        ; "A" characters

.sear1

 STA INWK+5,Y           ; Set the Y-th character of the name at INWK+5 with "A"

 DEY                    ; Decrement the loop counter

 BPL sear1              ; Loop back until we have filled all ten characters
                        ; of the name

 JSR InputName_b6       ; Get a system name from the controller into INWK+5,
                        ; where the name will be terminated by ASCII 13

 LDA INWK+5             ; If the first character of the entered name is ASCII 13
 CMP #13                ; then no name was entered, so jump to sear2 to return
 BEQ sear2              ; from the subroutine

 JSR TT81               ; Set the seeds in QQ15 (the selected system) to those
                        ; of system 0 in the current galaxy (i.e. copy the seeds
                        ; from QQ21 to QQ15)

 LDA #0                 ; We now loop through the galaxy's systems in order,
 STA XX20               ; until we find a match, so set XX20 to act as a system
                        ; counter, starting with system 0

.HME3

 SETUP_PPU_FOR_ICON_BAR ; If the PPU has started drawing the icon bar, configure
                        ; the PPU to use nametable 0 and pattern table 0

 LDA #%10000000         ; Set the DTW4 flag to %10000000 (justify text, print
 STA DTW4               ; the contents of the buffer whenever a carriage return
                        ; appears in the token)

 ASL A                  ; Set DTW5 = 0, which sets the size of the justified
 STA DTW5               ; text buffer at BUF to zero

 JSR cpl                ; Print the selected system name into the justified text
                        ; buffer

 LDX DTW5               ; Fetch DTW5 into X, so X is now equal to the length of
                        ; the selected system name

 LDA INWK+5,X           ; Fetch the X-th character from the entered search term

 CMP #13                ; If the X-th character is not a carriage return, then
 BNE HME6               ; the selected system name and the entered search term
                        ; are different lengths, so jump to HME6 to move on to
                        ; the next system

.HME4

 DEX                    ; Decrement X so it points to the last letter of the
                        ; selected system name (and, when we loop back here, it
                        ; points to the next letter to the left)

 LDA INWK+5,X           ; Set A to the X-th character of the entered search term

 ORA #%00100000         ; Set bit 5 of the character to make it lower case

 CMP BUF,X              ; If the character in A matches the X-th character of
 BEQ HME4               ; the selected system name in BUF, loop back to HME4 to
                        ; check the next letter to the left

 TXA                    ; The last comparison didn't match, so copy the letter
 BMI HME5               ; number into A, and if it's negative, that means we
                        ; managed to go past the first letters of each term
                        ; before we failed to get a match, so the terms are the
                        ; same, so jump to HME5 to process a successful search

.HME6

                        ; If we get here then the selected system name and the
                        ; entered search term did not match

 JSR DisableJustifyText ; Turn off justified text

 JSR TT20               ; We want to move on to the next system, so call TT20
                        ; to twist the three 16-bit seeds in QQ15

 INC XX20               ; Increment the system counter in XX20

 BNE HME3               ; If we haven't yet checked all 256 systems in the
                        ; current galaxy, loop back to HME3 to check the next
                        ; system

                        ; If we get here then the entered search term did not
                        ; match any systems in the current galaxy

 JSR TT111              ; Select the system closest to galactic coordinates
                        ; (QQ9, QQ10), so we can put the crosshairs back where
                        ; they were before the search

 JSR BOOP               ; Call the BOOP routine to make a low, long beep to
                        ; indicate a failed search

 LDA #215               ; Print extended token 215 ("{left align} UNKNOWN
 JSR DETOK_b2           ; PLANET"), which will print on-screen as the left align
                        ; code disables justified text

 JMP DrawScreenInNMI    ; Configure the NMI handler to draw the screen,
                        ; returning from the subroutine using a tail call

.HME5

                        ; If we get here then we have found a match for the
                        ; entered search

 JSR DisableJustifyText ; Turn off justified text

 JSR CLYNS              ; Clear the bottom two text rows of the upper screen,
                        ; and move the text cursor to column 1 on row 21, i.e.
                        ; the start of the top row of the two bottom rows

 LDA #%00000000         ; Set DTW8 = %00000000 (capitalise the next letter)
 STA DTW8

 LDA QQ15+3             ; The x-coordinate of the system described by the seeds
 STA QQ9                ; in QQ15 is in QQ15+3 (s1_hi), so we copy this to QQ9
                        ; as the x-coordinate of the search result

 LDA QQ15+1             ; The y-coordinate of the system described by the seeds
 STA QQ10               ; in QQ15 is in QQ15+1 (s0_hi), so we copy this to QQ10
                        ; as the y-coordinate of the search result

 JMP ReturnFromSearch   ; Jump back into TT102 to select the found system and
                        ; return from the subroutine using a tail call

.sear2

 JSR CLYNS              ; Clear the bottom two text rows of the upper screen,
                        ; and move the text cursor to column 1 on row 21, i.e.
                        ; the start of the top row of the two bottom rows

 JMP DrawScreenInNMI    ; Configure the NMI handler to draw the screen,
                        ; returning from the subroutine using a tail call