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* 5852Kartik Agaram2020-01-011-0/+414
generated by cgit-pink 1.4.1-2-gfad0 (git 2.36.2.497.gbbea4dcf42) at 2024-11-30 06:36:04 +0000
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== 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->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
    # . 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->length) 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
    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->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
generated by cgit-pink 1.4.1-2-gfad0 (git 2.36.2.497.gbbea4dcf42) at 2024-11-30 06:36:04 +0000