# write-stream: like write, but write streams rather than strings

== code
# instruction                     effective address                                                   operand     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

# main:
  # manual test
#?   # write-stream(stdout, _test-stream2)
#?   68/push  _test-stream2/imm32
#?   68/push  1/imm32/stdout
#?   e8/call write-stream/disp32
  # automatic test
#?   e8/call test-write-stream-appends/disp32
  e8/call  run-tests/disp32  # 'run-tests' is a function created automatically by SubX. It calls all functions that start with 'test-'.
  # syscall(exit, Num-test-failures)
  8b/copy                         0/mod/indirect  5/rm32/.disp32            .             .           3/r32/EBX   Num-test-failures/disp32          # copy *Num-test-failures to EBX
  b8/copy-to-EAX  1/imm32
  cd/syscall  0x80/imm8

write-stream:  # f : fd or (address stream), s : (address stream) -> <void>
  # prolog
  55/push-EBP
  89/copy                         3/mod/direct    5/rm32/EBP    .           .             .           4/r32/ESP   .               .                 # copy ESP to EBP
  # if (f < 0x08000000) _write-stream(f, s), return  # f can't be a user-mode address, so treat it as a kernel file descriptor
  81          7/subop/compare     1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none  .           .           8/disp8         0x08000000/imm32  # compare *(EBP+8)
  7d/jump-if-greater-or-equal  $write-stream:fake/disp8
    # push args
  ff          6/subop/push        1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none  .           .           0xc/disp8       .                 # push *(EBP+12)
  ff          6/subop/push        1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none  .           .           8/disp8         .                 # push *(EBP+8)
    # call
  e8/call  _write-stream/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
  eb/jump  $write-stream:end/disp8
$write-stream:fake:
  # otherwise, treat 'f' as a stream to append to
  # save registers
  50/push-EAX
  56/push-ESI
  57/push-EDI
  # ESI = f
  8b/copy                         1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none              6/r32/ESI   8/disp8         .                 # copy *(EBP+8) to ESI
  # EDI = s
  8b/copy                         1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none              7/r32/EDI   0xc/disp8       .                 # copy *(EBP+12) to EDI
  # EAX = _append-4(&f->data[f->write], &f->data[f->length], &s->data[s->read], &s->data[s->write])
    # push &s->data[s->write]
  8b/copy                         0/mod/indirect  7/rm32/EDI    .           .             .           0/r32/EAX   .               .                 # copy *EDI to EAX
  8d/copy-address                 1/mod/*+disp8   4/rm32/sib    7/base/EDI  0/index/EAX   .           0/r32/EAX   0xc/disp8       .                 # copy EDI+EAX+12 to EAX
  50/push-EAX
    # push &s->data[s->read]
  8b/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           0/r32/EAX   4/disp8         .                 # copy *(EDI+4) to EAX
  8d/copy-address                 1/mod/*+disp8   4/rm32/sib    7/base/EDI  0/index/EAX   .           0/r32/EAX   0xc/disp8       .                 # copy EDI+EAX+12 to EAX
  50/push-EAX
    # push &f->data[f->length]
  8b/copy                         1/mod/*+disp8   6/rm32/ESI    .           .             .           0/r32/EAX   8/disp8         .                 # copy *(ESI+8) to EAX
  8d/copy-address                 1/mod/*+disp8   4/rm32/sib    6/base/ESI  0/index/EAX   .           0/r32/EAX   0xc/disp8       .                 # copy ESI+EAX+12 to EAX
  50/push-EAX
    # push &f->data[f->write]
  8b/copy                         0/mod/indirect  6/rm32/ESI    .           .             .           0/r32/EAX   .               .                 # copy *ESI to EAX
  8d/copy-address                 1/mod/*+disp8   4/rm32/sib    6/base/ESI  0/index/EAX   .           0/r32/EAX   0xc/disp8       .                 # copy ESI+EAX+12 to EAX
  50/push-EAX
    # call
  e8/call  _append-4/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0x10/imm32        # add to ESP
  # f->write += EAX
  01/add                          0/mod/indirect  6/rm32/ESI    .           .             .           0/r32/EAX   .               .                 # add EAX to *ESI
  # s->read += EAX
  01/add                          1/mod/*+disp8   7/rm32/EDI    .           .             .           0/r32/EAX   4/disp8         .                 # add EAX to *(EDI+4)
  # restore registers
  5f/pop-to-EDI
  5e/pop-to-ESI
  58/pop-to-EAX
$write-stream:end:
  # epilog
  89/copy                         3/mod/direct    4/rm32/ESP    .           .             .           5/r32/EBP   .               .                 # copy EBP to ESP
  5d/pop-to-EBP
  c3/return

_write-stream:  # fd : int, s : (address stream) -> <void>
  # 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
  53/push-EBX
  56/push-ESI
  57/push-EDI
  # ESI = s
  8b/copy                         1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none  .           6/r32/ESI   0xc/disp8       .                 # copy *(EBP+12) to ESI
  # EDI = s->read
  8b/copy                         1/mod/*+disp8   6/rm32/ESI    .           .             .           7/r32/EDI   4/disp8         .                 # copy *(ESI+4) to EDI
  # EDX = s->write
  8b/copy                         0/mod/indirect  6/rm32/ESI    .           .             .           2/r32/EDX   .               .                 # copy *ESI to EDX
  # syscall(write, fd, &s->data[s->read], s->write-s->read)
    # fd : EBX
  8b/copy                         1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none  .           3/r32/EBX   8/disp8         .                 # copy *(EBP+8) to EBX
    # data : ECX = &s->data[s->read]
  8d/copy-address                 1/mod/*+disp8   4/rm32/sib    6/base/ESI  7/index/EDI   .           1/r32/ECX   0xc/disp8       .                 # copy ESI+EDI+12 to ECX
    # size : EDX = s->write - s->read
  29/subtract                     3/mod/direct    2/rm32/EDX    .           .             .           7/r32/EDI   .               .                 # subtract EDI from EDX
    # syscall
  b8/copy-to-EAX  4/imm32/write
  cd/syscall  0x80/imm8
  # restore registers
  5f/pop-to-EDI
  5e/pop-to-ESI
  5b/pop-to-EBX
  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

test-write-stream-single:
  # 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-stream2)
    # push args
  68/push  _test-stream2/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-stream2, "Ab")
    # push args
  68/push  "Ab"/imm32
  68/push  _test-stream2/imm32
    # call
  e8/call  write/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
  # write-stream(_test-stream, _test-stream2)
    # push args
  68/push  _test-stream2/imm32
  68/push  _test-stream/imm32
    # call
  e8/call  write-stream/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
  # check-ints-equal(*_test-stream.data, 41/A 62/b 00 00, msg)
    # push args
  68/push  "F - test-write-stream-single"/imm32
  68/push  0x006241/imm32/Ab
    # push *_test-stream.data
  b8/copy-to-EAX  _test-stream/imm32
  ff          6/subop/push        1/mod/*+disp8   0/rm32/EAX    .           .             .           .           0xc/disp8       .                 # push *(EAX+12)
    # call
  e8/call  check-ints-equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
  # end
  c3/return

test-write-stream-appends:
  # 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-stream2)
    # push args
  68/push  _test-stream2/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-stream2, "C")
    # push args
  68/push  "C"/imm32
  68/push  _test-stream2/imm32
    # call
  e8/call  write/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
  # write-stream(_test-stream, _test-stream2)
    # push args
  68/push  _test-stream2/imm32
  68/push  _test-stream/imm32
    # call
  e8/call  write-stream/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
  # write(_test-stream2, "D")
    # push args
  68/push  "D"/imm32
  68/push  _test-stream2/imm32
    # call
  e8/call  write/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
  # write-stream(_test-stream, _test-stream2)
    # push args
  68/push  _test-stream2/imm32
  68/push  _test-stream/imm32
    # call
  e8/call  write-stream/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               8/imm32           # add to ESP
  # check-ints-equal(*_test-stream.data, 43/C 44/D 00 00, msg)
    # push args
  68/push  "F - test-write-stream-appends"/imm32
  68/push  0x00004443/imm32/C-D
    # push *_test-stream.data
  b8/copy-to-EAX  _test-stream/imm32
  ff          6/subop/push        1/mod/*+disp8   0/rm32/EAX    .           .             .           .           0xc/disp8       .                 # push *(EAX+12)
    # call
  e8/call  check-ints-equal/disp32
    # discard args
  81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               0xc/imm32         # add to ESP
  # end
  c3/return

== data

_test-stream2:
  # current write index
  04 00 00 00
  # current read index
  01 00 00 00
  # length (= 8)
  08 00 00 00
  # data
  41 42 43 44 00 00 00 00  # 8 bytes

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