Particles: StoreParticleData

       Name: StoreParticleData                                       [Show more]
       Type: Subroutine
   Category: Particles
    Summary: Store the data for a new particle in the particle data buffer
  Deep dive: Particles and particle clouds
    Context: See this subroutine in context in the source code
 References: This subroutine is called as follows:
             * AddBulletParticleToBuffer calls StoreParticleData


 Arguments:

   (R0, R1, R2)                     Particle coordinate

   (R3, R4, R5)                     Particle velocity

   R6                               Particle lifespan counter (i.e. how many
                                    iterations around the main loop before the
                                    particle expires)

   R7                               Particle flags

   Stack                            Contains a value to restore into R8 at the
                                    end, and the return address


.StoreParticleData

 LDR     R8, [R11, #particleCount]  \ Set R8 to the number of particles that are
                                    \ already on-screen

 CMP     R8, #MAX_PARTICLES         \ If R8 >= MAX_PARTICLES then we already
 LDMHSFD R13!, {R8, PC}             \ have the maximum number of particles
                                    \ on-screen, so restore the value of R8 from
                                    \ the stack and return from the subroutine

 ADD     R8, R8, #1                 \ Increment the particle counter to record
 STR     R8, [R11, #particleCount]  \ that we have added a new particle

 LDR     R8, [R11, #particleEnd]    \ Set R8 to the address of the end of the
                                    \ particle data buffer, which is where we
                                    \ can store the new batch of data

 STMIA   R8!, {R0-R7}               \ Store the eight words of particle data in
                                    \ the buffer, updating R8 as we go

 STR     R8, [R11, #particleEnd]    \ Update particleEnd with the new address of
                                    \ the end of the buffer

 MOV     R9, #0                     \ Zero the last word of the next particle's
 STR     R9, [R8, #7*4]             \ data after the one we just wrote, so this
                                    \ acts as a null terminator

 LDMFD   R13!, {R8, PC}             \ Restore the value of R8 from the stack and
                                    \ return from the subroutine