== 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: (addr buffered-file), s: (addr stream byte) # pseudocode: # while true # if (s->write >= s->size) 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 # . prologue 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->size) abort 3b/compare 1/mod/*+disp8 7/rm32/edi . . . 2/r32/edx 8/disp8 . # compare edx with *(edi+8) 7d/jump-if->= $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-< $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-= $slurp:end/disp8 $slurp:from-stream: # var c/eax: byte = 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] = c 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 # . epilogue 89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp 5d/pop-to-ebp c3/return $slurp:abort: # . _write(2/stderr, error) # . . push args 68/push "slurp: destination too small\n"/imm32 68/push 2/imm32/stderr # . . call e8/call _write/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 8/imm32 # add to esp # . syscall_exit(1) bb/copy-to-ebx 1/imm32 e8/call syscall_exit/disp32 # never gets here test-slurp: # setup # . clear-stream(_test-stream) # . . push args 68/push _test-stream/imm32 # . . call e8/call clear-stream/disp32 # . . discard args 81 0/subop/add 3/mod/direct 4/rm32/esp . . . . . 4/imm32 # add to esp # . clear-stream($_test-buffered-file->buffer) # . . push args 68/push $_test-buffered-file->buffer/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-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