added integer ==> f32 conversion routines, issue #29

conversion/i16tof32.z80

@@ -0,0 +1,55 @@
+#ifndef included_i16tof32
+#define included_i16tof32
+
+i16tof32:
+;Inputs:
+;   HL holds a 16-bit signed integer, (-32768 to 32767)
+;   BC points to where to write the float
+;Outputs:
+;   Converts A to an f32 float at BC
+;
+  call pushpop
+
+  xor a
+  ld (bc),a
+  inc bc
+
+  ld a,l
+  or h
+  ld d,a
+  jr z,i16tof32_finish
+
+  ld a,h
+  or a
+  jp p,$+10
+  xor a
+  sub l
+  ld l,a
+  sbc a,a
+  sub h
+  ld h,a
+  scf
+
+  rla         ; save the sign
+  ld d,$7F+16 ;Initial exponent
+
+  dec d
+  add hl,hl
+  jr nc,$-2
+
+  rra   ; shift out the sign
+  rr d  ; shift the exponent down, shifting in the sign
+  rr h  ; shift the lsb of the exponent into the significand
+  rr l
+
+  ld a,l
+i16tof32_finish:
+  ld (bc),a
+  inc bc
+  ld a,h
+  ld (bc),a
+  inc bc
+  ld a,d
+  ld (bc),a
+  ret
+#endif

conversion/i8tof32.z80

@@ -0,0 +1,64 @@
+#ifndef included_i8tof32
+#define included_i8tof32
+
+i8tof32:
+;Inputs:
+;   A holds a 8-bit signed integer, (-128 to 127)
+;   BC points to where to write the float
+;Outputs:
+;   Converts A to an f32 float at BC
+;
+  push hl
+  push af
+
+  or a
+  jp p,$+6
+  neg
+  scf
+
+; #ifndef included_u8tof32
+; ##define included_u8tof32
+;   .db $21   ; start of `ld hl,*` to skip the next byte
+; u8tof32:
+;   push hl
+;   push af
+; #else
+; .echo "Hint: it looks like you are using u8tof32 as well as i8tof32. i8tof32 already has code for u8tof32, so you can save bytes by including it first."
+; #endif
+;
+  ; Begin writing the float
+  ld h,b
+  ld l,c
+  ld (hl),0
+  inc hl
+  ld (hl),0
+  inc hl
+
+  jr nz,$+8
+  ld (hl),a
+  inc hl
+  ld (hl),a
+  pop af
+  pop hl
+  ret
+
+  push bc
+  rl c        ; save the sign
+  ld b,$7F+8  ;Initial exponent
+
+  dec b
+  add a,a
+  jr nc,$-2
+
+  rr c  ; shift in a 1 and shift out the sign
+  rr b  ; shift the exponent down, shifting in the sign
+  rra   ; shift the lsb of the exponent into the significand
+  ld (hl),a
+  inc hl
+  ld (hl),b
+
+  pop bc
+  pop af
+  pop hl
+  ret
+#endif

conversion/u16tof32.z80

@@ -0,0 +1,42 @@
+#ifndef included_u16tof32
+#define included_u16tof32
+
+u16tof32:
+;Inputs:
+;   HL holds a 16-bit unsigned integer, (0 to 65535)
+;   BC points to where to write the float
+;Outputs:
+;   Converts HL (unsigned) to an f32 float at BC
+;
+  call pushpop
+
+  xor a
+  ld (bc),a
+  inc bc
+
+  ld a,l
+  or h
+  ld d,a
+  jr z,u16tof32_finish
+
+  ld d,$7F+16 ;Initial exponent
+
+  dec d
+  add hl,hl
+  jr nc,$-2
+
+  srl d ; shift the exponent down, shifting in the sign
+  rr h  ; shift the lsb of the exponent into the significand
+  rr l
+
+  ld a,l
+u16tof32_finish:
+  ld (bc),a
+  inc bc
+  ld a,h
+  ld (bc),a
+  inc bc
+  ld a,d
+  ld (bc),a
+  ret
+#endif

conversion/u8tof32.z80

@@ -0,0 +1,50 @@
+#ifndef included_u8tof32
+#define included_u8tof32
+
+u8tof32:
+;Inputs:
+;   A holds a 8-bit unsigned integer, (0 to 255)
+;   BC points to where to write the float
+;Outputs:
+;   Converts A to an f32 float at BC
+;
+  push hl
+  push af
+
+  ; Begin writing the float
+  ld h,b
+  ld l,c
+  ld (hl),0
+  inc hl
+  ld (hl),0
+  inc hl
+
+  or a
+  jr nz,$+8
+  ld (hl),a
+  inc hl
+  ld (hl),a
+  pop af
+  pop hl
+  ret
+
+  push bc
+  rl c        ; save the sign
+  ld b,$7F+8  ;Initial exponent
+
+  dec b
+  add a,a
+  jr nc,$-2
+
+  rr c  ; shift in a 1 and shift out the sign
+  rr b  ; shift the exponent down, shifting in the sign
+  rra   ; shift the lsb of the exponent into the significand
+  ld (hl),a
+  inc hl
+  ld (hl),b
+
+  pop bc
+  pop af
+  pop hl
+  ret
+#endif