== code # instruction effective address register displacement immediate # . op subop mod rm32 base index scale r32 # . 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 # read all bytes from 'f' and store them into 's' # abort if 's' is too small slurp: # f : (address buffered-file), s : (address stream byte) -> # pseudocode: # while true # if (s->write >= s->length) abort # if (f->read >= f->write) populate stream from file # if (f->write == 0) break # AL = f->data[f->read] # s->data[s->write] = AL # ++f->read # ++s->write # . prolog 55/push-EBP 89/copy 3/mod/direct 5/rm32/EBP . . . 4/r32/ESP . . # copy ESP to EBP # . save registers 50/push-EAX 51/push-ECX 52/push-EDX 56/push-ESI 57/push-EDI # ESI = f 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 6/r32/ESI 8/disp8 . # copy *(EBP+8) to ESI # ECX = f->read 8b/copy 1/mod/*+disp8 6/rm32/ESI . . . 1/r32/ECX 8/disp8 . # copy *(ESI+8) to ECX # EDI = s 8b/copy 1/mod/*+disp8 5/rm32/EBP . . . 7/r32/EDI 0xc/disp8 . # copy *(EBP+12) to EDI # EDX = s->write 8b/copy 0/mod/indirect 7/rm32/EDI . . . 2/r32/EDX . . # copy *EDI to EDX $slurp:loop: # if (s->write >= s->length) abort 3b/compare 1/mod/*+disp8 7/rm32/EDI . . . 2/r32/EDX 8/disp8 . # compare EDX with *(EDI+8) 7d/jump-if-greater-or-equal $slurp:abort/disp8 # if (f->read >= f->write) populate stream from file 3b/compare 1/mod/*+disp8 6/rm32/ESI . . . 1/r32/ECX 4/disp8 . # compare ECX with *(ESI+4) 7c/jump-if-lesser $slurp:from-stream/disp8 # . clear-stream(stream = f+4) # . . push args 8d/copy-address 1/mod/*+disp8 6/rm32/ESI . . . 0/r32/EAX 4/disp8 . # copy ESI+4 to EAX 50/push-EAX # . . call e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP # . f->read must now be 0; update its cache at ECX 31/xor 3/mod/direct 1/rm32/ECX . . . 1/r32/ECX . . # clear ECX # . EAX = read(f->fd, stream = f+4) # . . push args 50/push-EAX ff 6/subop/push 0/mod/indirect 6/rm32/ESI . . . . . . # push *ESI # . . call e8/call read/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP # if (f->write == 0) break # since f->read was initially 0, EAX is the same as f->write # . if (EAX == 0) return true 3d/compare-EAX-and 0/imm32 74/jump-if-equal $slurp:end/disp8 $slurp:from-stream: # AL = f->data[f->read] 31/xor 3/mod/direct 0/rm32/EAX . . . 0/r32/EAX . . # clear EAX 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 # s->data[s->write] = AL 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) # ++f->read 41/increment-ECX # ++s->write 42/increment-EDX eb/jump $slurp:loop/disp8 $slurp:end: # save f->read 89/copy 1/mod/*+disp8 6/rm32/ESI . . . 1/r32/ECX 8/disp8 . # copy ECX to *(ESI+8) # save s->write 89/copy 0/mod/indirect 7/rm32/EDI . . . 2/r32/EDX . . # copy EDX to *EDI # . restore registers 5f/pop-to-EDI 5e/pop-to-ESI 5a/pop-to-EDX 59/pop-to-ECX 58/pop-to-EAX # . epilog 89/copy 3/mod/direct 4/rm32/ESP . . . 5/r32/EBP . . # copy EBP to ESP 5d/pop-to-EBP c3/return $slurp:abort: # . _write(2/stderr, error) # . . push args 68/push "slurp: destination too small\n"/imm32 68/push 2/imm32/stderr # . . call e8/call _write/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP # . syscall(exit, 1) bb/copy-to-EBX 1/imm32 b8/copy-to-EAX 1/imm32/exit cd/syscall 0x80/imm8 # never gets here test-slurp: # setup # . clear-stream(_test-stream) # . . push args 68/push _test-stream/imm32 # . . call e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP # . clear-stream(_test-buffered-file+4) # . . push args b8/copy-to-EAX _test-buffered-file/imm32 05/add-to-EAX 4/imm32 50/push-EAX # . . call e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP # . clear-stream(_test-tmp-stream) # . . push args 68/push _test-tmp-stream/imm32 # . . call e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 4/imm32 # add to ESP # write(_test-stream, "ab\ncd") # . . push args 68/push "ab\ncd"/imm32 68/push _test-stream/imm32 # . . call e8/call write/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP # read a line from _test-stream (buffered by _test-buffered-file) into _test-tmp-stream # . EAX = slurp(_test-buffered-file, _test-tmp-stream) # . . push args 68/push _test-tmp-stream/imm32 68/push _test-buffered-file/imm32 # . . call e8/call slurp/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 8/imm32 # add to ESP # check-stream-equal(_test-tmp-stream, "ab\ncd", msg) # . . push args 68/push "F - test-slurp"/imm32 68/push "ab\ncd"/imm32 68/push _test-tmp-stream/imm32 # . . call e8/call check-stream-equal/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/ESP . . . . . 0xc/imm32 # add to ESP # end c3/return # . . vim:nowrap:textwidth=0