159 lines
7.8 KiB
Plaintext
159 lines
7.8 KiB
Plaintext
== 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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# read all bytes from 'f' and store them into 's'
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# abort if 's' is too small
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slurp: # f: (addr buffered-file), s: (addr stream byte)
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# pseudocode:
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# while true
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# if (s->write >= s->size) abort
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# if (f->read >= f->write) populate stream from file
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# if (f->write == 0) break
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# AL = f->data[f->read]
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# s->data[s->write] = AL
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# ++f->read
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# ++s->write
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# . prologue
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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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52/push-edx
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56/push-esi
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57/push-edi
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# esi = f
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8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 8/disp8 . # copy *(ebp+8) to esi
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# ecx = f->read
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8b/copy 1/mod/*+disp8 6/rm32/esi . . . 1/r32/ecx 8/disp8 . # copy *(esi+8) to ecx
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# edi = s
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8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 7/r32/edi 0xc/disp8 . # copy *(ebp+12) to edi
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# edx = s->write
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8b/copy 0/mod/indirect 7/rm32/edi . . . 2/r32/edx . . # copy *edi to edx
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$slurp:loop:
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# if (s->write >= s->size) abort
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3b/compare 1/mod/*+disp8 7/rm32/edi . . . 2/r32/edx 8/disp8 . # compare edx with *(edi+8)
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7d/jump-if->= $slurp:abort/disp8
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# if (f->read >= f->write) populate stream from file
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3b/compare 1/mod/*+disp8 6/rm32/esi . . . 1/r32/ecx 4/disp8 . # compare ecx with *(esi+4)
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7c/jump-if-< $slurp:from-stream/disp8
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# . clear-stream(stream = f+4)
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# . . push args
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8d/copy-address 1/mod/*+disp8 6/rm32/esi . . . 0/r32/eax 4/disp8 . # copy esi+4 to eax
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50/push-eax
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# . . call
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e8/call clear-stream/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp
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# . f->read must now be 0; update its cache at ecx
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31/xor 3/mod/direct 1/rm32/ecx . . . 1/r32/ecx . . # clear ecx
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# . eax = read(f->fd, stream = f+4)
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# . . push args
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50/push-eax
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ff 6/subop/push 0/mod/indirect 6/rm32/esi . . . . . . # push *esi
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# . . call
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e8/call read/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# if (f->write == 0) break
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# since f->read was initially 0, eax is the same as f->write
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# . if (eax == 0) return true
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3d/compare-eax-and 0/imm32
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74/jump-if-= $slurp:end/disp8
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$slurp:from-stream:
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# var c/eax: byte = f->data[f->read]
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31/xor 3/mod/direct 0/rm32/eax . . . 0/r32/eax . . # clear eax
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8a/copy-byte 1/mod/*+disp8 4/rm32/sib 6/base/esi 1/index/ecx . 0/r32/AL 0x10/disp8 . # copy byte at *(esi+ecx+16) to AL
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# s->data[s->write] = c
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88/copy-byte 1/mod/*+disp8 4/rm32/sib 7/base/edi 2/index/edx . 0/r32/AL 0xc/disp8 . # copy AL to *(edi+edx+12)
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# ++f->read
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41/increment-ecx
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# ++s->write
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42/increment-edx
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eb/jump $slurp:loop/disp8
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$slurp:end:
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# save f->read
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89/copy 1/mod/*+disp8 6/rm32/esi . . . 1/r32/ecx 8/disp8 . # copy ecx to *(esi+8)
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# save s->write
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89/copy 0/mod/indirect 7/rm32/edi . . . 2/r32/edx . . # copy edx to *edi
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# . restore registers
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5f/pop-to-edi
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5e/pop-to-esi
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5a/pop-to-edx
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59/pop-to-ecx
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58/pop-to-eax
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# . epilogue
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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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$slurp:abort:
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# . _write(2/stderr, error)
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# . . push args
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68/push "slurp: destination too small\n"/imm32
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68/push 2/imm32/stderr
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# . . call
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e8/call _write/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# . syscall_exit(1)
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bb/copy-to-ebx 1/imm32
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e8/call syscall_exit/disp32
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# never gets here
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test-slurp:
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# setup
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# . clear-stream(_test-stream)
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# . . push args
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68/push _test-stream/imm32
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# . . call
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e8/call clear-stream/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp
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# . clear-stream($_test-buffered-file->buffer)
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# . . push args
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68/push $_test-buffered-file->buffer/imm32
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# . . call
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e8/call clear-stream/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp
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# . clear-stream(_test-tmp-stream)
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# . . push args
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68/push _test-tmp-stream/imm32
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# . . call
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e8/call clear-stream/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp
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# write(_test-stream, "ab\ncd")
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# . . push args
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68/push "ab\ncd"/imm32
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68/push _test-stream/imm32
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# . . call
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e8/call write/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# read a line from _test-stream (buffered by _test-buffered-file) into _test-tmp-stream
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# . eax = slurp(_test-buffered-file, _test-tmp-stream)
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# . . push args
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68/push _test-tmp-stream/imm32
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68/push _test-buffered-file/imm32
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# . . call
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e8/call slurp/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp
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# check-stream-equal(_test-tmp-stream, "ab\ncd", msg)
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# . . push args
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68/push "F - test-slurp"/imm32
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68/push "ab\ncd"/imm32
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68/push _test-tmp-stream/imm32
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# . . call
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e8/call check-stream-equal/disp32
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# . . discard args
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81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 0xc/imm32 # add to esp
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# end
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c3/return
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# . . vim:nowrap:textwidth=0
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