62 lines
3.5 KiB
Plaintext
62 lines
3.5 KiB
Plaintext
# streams: data structure for operating on arrays in a stateful manner
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#
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# A stream looks like this:
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# read : int # index that we've read until
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# write : int # index at which writes go
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# data : (array byte) # prefixed by length as usual
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#
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# primitives for operating on streams:
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# - clear-stream (clears everything but the data length)
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# - stream-equal? (compares stream data with a string; ignores read pointer)
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# - rewind-reads (resets read pointer; not yet implemented)
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== code
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# instruction effective address register displacement immediate
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# . op subop mod rm32 base index scale r32
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# . 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
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# main:
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e8/call run-tests/disp32 # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.
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# syscall(exit, Num-test-failures)
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8b/copy 0/mod/indirect 5/rm32/.disp32 . . 3/r32/EBX Num-test-failures/disp32 # copy *Num-test-failures to EBX
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b8/copy-to-EAX 1/imm32/exit
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cd/syscall 0x80/imm8
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clear-stream: # f : (address stream) -> <void>
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# . prolog
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55/push-EBP
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89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP
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# . save registers
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50/push-EAX
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51/push-ECX
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# EAX = f
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8b/copy 1/mod/*+disp8 5/rm32/EBP . . 0/r32/EAX 8/disp8 . # copy *(EBP+8) to EAX
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# ECX = f->length
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8b/copy 1/mod/*+disp8 0/rm32/EAX . . . 1/r32/ECX 8/disp8 . # copy *(EAX+8) to ECX
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# ECX = &f->data[f->length]
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8d/copy-address 1/mod/*+disp8 4/rm32/sib 0/base/EAX 1/index/ECX . 1/r32/ECX 0xc/disp8 . # copy EAX+ECX+12 to ECX
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# f->write = 0
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c7 0/subop/copy 0/mod/direct 0/rm32/EAX . . . . . 0/imm32 # copy to *EAX
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# f->read = 0
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c7 0/subop/copy 1/mod/*+disp8 0/rm32/EAX . . . . 4/disp8 0/imm32 # copy to *(EAX+4)
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# EAX = f->data
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81 0/subop/add 3/mod/direct 0/rm32/EAX . . . . . 0xc/imm32 # add to EAX
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# while (true)
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$clear-stream:loop:
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# if EAX >= ECX break
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39/compare 3/mod/direct 0/rm32/EAX . . . 1/r32/ECX . . # compare EAX with ECX
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7d/jump-if-greater-or-equal $clear-stream:end/disp8
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# *EAX = 0
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c6 0/subop/copy 0/mod/direct 0/rm32/EAX . . . . . 0/imm8 # copy byte to *EAX
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# ++EAX
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40/increment-EAX
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eb/jump $clear-stream:loop/disp8
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$clear-stream:end:
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# . restore registers
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59/pop-to-ECX
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58/pop-to-EAX
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# . epilog
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89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP
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5d/pop-to-EBP
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c3/return
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