1 # some utilities for converting numbers from hex
  2 # lowercase letters only for now
  3 
  4 == code
  5 #   instruction                     effective address                                                   register    displacement    immediate
  6 # . op          subop               mod             rm32          base        index         scale       r32
  7 # . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
  8 
  9 is-hex-int?:  # in: (addr slice) -> result/eax: boolean
 10     # . prologue
 11     55/push-ebp
 12     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
 13     # . save registers
 14     51/push-ecx
 15     52/push-edx
 16     53/push-ebx
 17     # ecx = s
 18     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .             .           1/r32/ecx   8/disp8         .                 # copy *(ebp+8) to ecx
 19     # edx = s->end
 20     8b/copy                         1/mod/*+disp8   1/rm32/ecx    .           .             .           2/r32/edx   4/disp8         .                 # copy *(ecx+4) to edx
 21     # var curr/ecx: (addr byte) = s->start
 22     8b/copy                         0/mod/indirect  1/rm32/ecx    .           .             .           1/r32/ecx   .               .                 # copy *ecx to ecx
 23     # if s is empty return false
 24     b8/copy-to-eax  0/imm32/false
 25     39/compare                      3/mod/direct    1/rm32/ecx    .           .             .           2/r32/edx   .               .                 # compare ecx with edx
 26     73/jump-if-addr>=  $is-hex-int?:end/disp8
 27     # skip past leading '-'
 28     # . if (*curr == '-') ++curr
 29     31/xor                          3/mod/direct    3/rm32/ebx    .           .             .           3/r32/ebx   .               .                 # clear ebx
 30     8a/copy-byte                    0/mod/indirect  1/rm32/ecx    .           .             .           3/r32/BL    .               .                 # copy byte at *ecx to BL
 31     81          7/subop/compare     3/mod/direct    3/rm32/ebx    .           .             .           .           .               0x2d/imm32/-      # compare ebx
 32     75/jump-if-!=  $is-hex-int?:initial-0/disp8
 33     # . ++curr
 34     41/increment-ecx
 35     # skip past leading '0x'
 36 $is-hex-int?:initial-0:
 37     # . if (*curr != '0') jump to loop
 38     31/xor                          3/mod/direct    3/rm32/ebx    .           .             .           3/r32/ebx   .               .                 # clear ebx
 39     8a/copy-byte                    0/mod/indirect  1/rm32/ecx    .           .             .           3/r32/BL    .               .                 # copy byte at *ecx to BL
 40     81          7/subop/compare     3/mod/direct    3/rm32/ebx    .           .             .           .           .               0x30/imm32/0      # compare ebx
 41     75/jump-if-!=  $is-hex-int?:loop/disp8
 42     # . ++curr
 43     41/increment-ecx
 44 $is-hex-int?:initial-0x:
 45     # . if (curr >= in->end) return true
 46     39/compare                      3/mod/direct    1/rm32/ecx    .           .             .           2/r32/edx   .               .                 # compare ecx with edx
 47     73/jump-if-addr>=  $is-hex-int?:true/disp8
 48     # . if (*curr != 'x') jump to loop  # the previous '0' is still valid so doesn't need to be checked again
 49     31/xor                          3/mod/direct    3/rm32/ebx    .           .             .           3/r32/ebx   .               .                 # clear ebx
 50     8a/copy-byte                    0/mod/indirect  1/rm32/ecx    .           .             .           3/r32/BL    .               .                 # copy byte at *ecx to BL
 51     81          7/subop/compare     3/mod/direct    3/rm32/ebx    .           .             .           .           .               0x78/imm32/x      # compare ebx
 52     75/jump-if-!=  $is-hex-int?:loop/disp8
 53     # . ++curr
 54     41/increment-ecx
 55 $is-hex-int?:loop:
 56     # if (curr >= in->end) return true
 57     39/compare                      3/mod/direct    1/rm32/ecx    .           .             .           2/r32/edx   .               .                 # compare ecx with edx
 58     73/jump-if-addr>=  $is-hex-int?:true/disp8
 59     # var eax: boolean = is-hex-digit?(*curr)
 60     # . . push args
 61     8a/copy-byte                    0/mod/indirect  1/rm32/ecx    .           .             .           0/r32/AL    .               .                 # copy byte at *ecx to AL
 62     50/push-eax
 63     # . . call
 64     e8/call  is-hex-digit?/disp32
 65     # . . discard args
 66     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
 67     # if (eax == false) return false
 68     3d/compare-eax-and  0/imm32/false
 69     74/jump-if-=  $is-hex-int?:end/disp8
 70     # ++curr
 71     41/increment-ecx
 72     # loop
 73     eb/jump  $is-hex-int?:loop/disp8
 74 $is-hex-int?:true:
 75     # return true
 76     b8/copy-to-eax  1/imm32/true
 77 $is-hex-int?:end:
 78     # . restore registers
 79     5b/pop-to-ebx
 80     5a/pop-to-edx
 81     59/pop-to-ecx
 82     # . epilogue
 83     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
 84     5d/pop-to-ebp
 85     c3/return
 86 
 87 test-is-hex-int:
 88     # . prologue
 89     55/push-ebp
 90     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
 91     # (eax..ecx) = "34"
 92     b8/copy-to-eax  "34"/imm32
 93     8b/copy                         0/mod/indirect  0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # copy *eax to ecx
 94     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    0/base/eax  1/index/ecx   .           1/r32/ecx   4/disp8         .                 # copy eax+ecx+4 to ecx
 95     05/add-to-eax  4/imm32
 96     # var slice/ecx: slice = {eax, ecx}
 97     51/push-ecx
 98     50/push-eax
 99     89/copy                         3/mod/direct    1/rm32/ecx    .           .             .           4/r32/esp   .               .                 # copy esp to ecx
100     # eax = is-hex-int?(slice)
101     # . . push args
102     51/push-ecx
103     # . . call
104     e8/call  is-hex-int?/disp32
105     # . . discard args
106     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
107     # check-ints-equal(eax, 1, msg)
108     # . . push args
109     68/push  "F - test-is-hex-int"/imm32
110     68/push  1/imm32/true
111     50/push-eax
112     # . . call
113     e8/call  check-ints-equal/disp32
114     # . . discard args
115     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
116     # . epilogue
117     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
118     5d/pop-to-ebp
119     c3/return
120 
121 test-is-hex-int-handles-letters:
122     # . prologue
123     55/push-ebp
124     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
125     # (eax..ecx) = "34a"
126     b8/copy-to-eax  "34a"/imm32
127     8b/copy                         0/mod/indirect  0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # copy *eax to ecx
128     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    0/base/eax  1/index/ecx   .           1/r32/ecx   4/disp8         .                 # copy eax+ecx+4 to ecx
129     05/add-to-eax  4/imm32
130     # var slice/ecx: slice = {eax, ecx}
131     51/push-ecx
132     50/push-eax
133     89/copy                         3/mod/direct    1/rm32/ecx    .           .             .           4/r32/esp   .               .                 # copy esp to ecx
134     # eax = is-hex-int?(slice)
135     # . . push args
136     51/push-ecx
137     # . . call
138     e8/call  is-hex-int?/disp32
139     # . . discard args
140     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
141     # check-ints-equal(eax, 1, msg)
142     # . . push args
143     68/push  "F - test-is-hex-int-handles-letters"/imm32
144     68/push  1/imm32/true
145     50/push-eax
146     # . . call
147     e8/call  check-ints-equal/disp32
148     # . . discard args
149     81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
150     # . epilogue
151     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
152     5d/pop-to-ebp
153     c3/return
154 
155 test-is-hex-int-with-trailing-char:
156     # . prologue
157     55/push-ebp
158     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
159     # (eax..ecx) = "34q"
160     b8/copy-to-eax  "34q"/imm32
161     8b/copy                         0/mod/indirect  0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # copy *eax to ecx
162     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    0/base/eax  1/index/ecx   .           1/r32/ecx   4/disp8         .                 # copy eax+ecx+4 to ecx
163     05/add-to-eax  4/imm32
164     # var slice/ecx: slice = {eax, ecx}
165     51/push-ecx
166     50/push-eax
167     89/copy                         3/mod/direct    1/rm32/ecx    .           .             .           4/r32/esp   .               .                 # copy esp to ecx
168     # eax = is-hex-int?(slice)
169     # . . push args
170     51/push-ecx
171     # . . call
172     e8/call  is-hex-int?/disp32
173     # . . discard args
174     81          0/subop/add         3/mod/direct    4/rm32/esp    x
      tmpx <- shift-left 1
      tmpx <- increment
      add-to err, tmpx
    }
    # loop termination condition
    compare x, 0
    loop-if-<
  }
}

fn draw-disc screen: (addr screen), cx: int, cy: int, radius: int, color: int, border-color: int {
  var r/eax: int <- copy 0
  {
    compare r, radius
    break-if->=
    draw-circle screen, cx cy, r, color
    r <- increment
    loop
  }
  draw-circle screen, cx cy, r, border-color
}