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path: root/065write-buffered.subx
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# write-buffered: like 'write', but for a buffered-file

== 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

write-buffered:  # f: (addr buffered-file), msg: (addr array byte)
    # pseudocode:
    #   in = msg->data
    #   inend = &msg->data[msg->size]
    #   while (in < inend)
    #     if f->write >= f->size
    #       flush(f)
    #       clear-stream(f)
    #     c = *in
    #     f->data[f->write] = c
    #     ++f->write
    #     ++in
    #
    # registers:
    #   in: esi
    #   inend: ecx
    #   f: edi
    #   f->size: edx
    #   f->write: ebx (cached; need to keep in sync)
    #   c: eax
    #
    # . 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
    53/push-ebx
    56/push-esi
    57/push-edi
    # eax = msg
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         0/r32/eax   0xc/disp8       .                 # copy *(ebp+12) to eax
    # var in/esi: (addr byte) = msg->data
    8d/copy-address                 1/mod/*+disp8   0/rm32/eax    .           .             .           6/r32/esi   4/disp8         .                 # copy eax+4 to esi
    # var inend/ecx: (addr byte) = &msg->data[msg->size]
    8b/copy                         0/mod/indirect  0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # copy *eax to ecx
    8d/copy-address                 0/mod/indirect  4/rm32/sib    6/base/esi  1/index/ecx   .           1/r32/ecx   .               .                 # copy esi+ecx to ecx
    # edi = f
    8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         7/r32/edi   8/disp8         .                 # copy *(ebp+8) to edi
    # edx = f->size
    8b/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           2/r32/edx   0xc/disp8       .                 # copy *(edi+12) to edx
    # ebx = f->write
    8b/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           3/r32/ebx   4/disp8         .                 # copy *(edi+4) to ebx
$write-buffered:loop:
    # if (in >= inend) break
    39/compare                      3/mod/direct    6/rm32/esi    .           .             .           1/r32/ecx   .               .                 # compare esi with ecx
    73/jump-if-addr>=  $write-buffered:loop-end/disp8
    # if (f->write >= f->size) flush and clear f's stream
    39/compare                      3/mod/direct    3/rm32/ebx    .           .             .           2/r32/edx   .               .                 # compare ebx with edx
    7c/jump-if-<  $write-buffered:to-stream/disp8
    # . persist f->write
    89/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           3/r32/ebx   4/disp8         .                 # copy ebx to *(edi+4)
    # . flush(f)
    # . . push args
    57/push-edi
    # . . call
    e8/call  flush/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # . clear-stream(stream = f+4)
    # . . push args
    8d/copy-address                 1/mod/*+disp8   7/rm32/edi    .           .             .           0/r32/eax   4/disp8         .                 # copy edi+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->write must now be 0; update its cache at ebx
    31/xor                          3/mod/direct    3/rm32/ebx    .           .             .           3/r32/ebx   .               .                 # clear ebx
$write-buffered:to-stream:
    # write to stream
    # f->data[f->write] = *in
    # . AL = *in
    31/xor                          3/mod/direct    0/rm32/eax    .           .             .           0/r32/eax   .               .                 # clear eax
    8a/copy-byte                    0/mod/indirect  6/rm32/esi    .           .             .           0/r32/AL    .               .                 # copy byte at *esi to AL
    # . f->data[f->write] = AL
    88/copy-byte                    1/mod/*+disp8   4/rm32/sib    7/base/edi  3/index/ebx   .           0/r32/AL    0x10/disp8      .                 # copy AL to *(edi+ebx+16)
    # ++f->write
    43/increment-ebx
    # ++in
    46/increment-esi
    eb/jump  $write-buffered:loop/disp8
$write-buffered:loop-end:
    # persist necessary variables from registers
    89/copy                         1/mod/*+disp8   7/rm32/edi    .           .             .           3/r32/ebx   4/disp8         .                 # copy ebx to *(edi+4)
$write-buffered:end:
    # . 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
    # . epilogue
    89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
    5d/pop-to-ebp
    c3/return

test-write-buffered:
    # - check that write-buffered writes to the file
    # 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
    # write-buffered(_test-buffered-file, "Abc")
    # . . push args
    68/push  "Abc"/imm32
    68/push  _test-buffered-file/imm32
    # . . call
    e8/call  write-buffered/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # flush(_test-buffered-file)
    # . . push args
    68/push  _test-buffered-file/imm32
    # . . call
    e8/call  flush/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # add to esp
    # check-stream-equal(_test-stream, "Abc", msg)
    # . . push args
    68/push  "F - test-write-buffered-single"/imm32
    68/push  "Abc"/imm32
    68/push  _test-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

test-write-buffered-with-intermediate-flush:
    # - check that write-buffered flushes in the middle if its buffer fills up
    # 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
    # _test-stream can hold 8 bytes, but _test-buffered-file can hold only 6.
    # Try to write 7 bytes.
    # . write-buffered(_test-buffered-file, "Abcdefg")
    # . . push args
    68/push  "Abcdefg"/imm32
    68/push  _test-buffered-file/imm32
    # . . call
    e8/call  write-buffered/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               8/imm32           # add to esp
    # don't flush
    # 6 bytes should still have gotten to _test-stream
    # . check-ints-equal(*_test-stream->write, 6, msg)
    # . . push args
    68/push  "F - test-write-buffered-with-intermediate-flush: flushed data"/imm32
    68/push  6/imm32
    # . . push *_test-stream->write
    b8/copy-to-eax  _test-stream/imm32
    ff          6/subop/push        0/mod/indirect  0/rm32/eax    .           .             .           .           .               .                 # push *eax
    # . . call
    e8/call  check-ints-equal/disp32
    # . . discard args
    81          0/subop/add         3/mod/direct    4/rm32/esp    .           .             .           .           .               0xc/imm32         # add to esp
    # and 1 byte should still be in _test-buffered-file
    # . check-ints-equal(*_test-buffered-file->write, 1, msg)
    # . . push args
    68/push  "F - test-write-buffered-with-intermediate-flush: unflushed bytes"/imm32
    68/push  1/imm32
    # . . push *_test-buffered-file->write
    b8/copy-to-eax  _test-buffered-file/imm32
    ff          6/subop/push        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         .                 # push *(eax+4)
    # . . 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

# The buffered file for standard error.
Stderr:  # buffered-file
    # file descriptor or (addr stream byte)
    2/imm32  # standard error
$Stderr->buffer:
    # inlined fields for a stream
    #   current write index
    0/imm32
    #   current read index
    0/imm32
    #   size
    8/imm32
    #   data
    00 00 00 00 00 00 00 00  # 8 bytes

# TODO: 8 bytes is too small. We'll need to grow the buffer for efficiency. But
# I don't want to type in 1024 bytes here.

# . . vim:nowrap:textwidth=0
#n75'>75 76 77 78
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//:: Some helpers for debugging.

//: Load the 'map' file generated during 'bootstrap --debug translate' when running
//: 'bootstrap --trace run'.
//: (It'll only affect the trace.)

:(before "End Globals")
map</*address*/uint32_t, string> Symbol_name;  // used only by 'bootstrap run'
map</*address*/uint32_t, string> Source_line;  // used only by 'bootstrap run'
:(before "End --trace Settings")
load_labels();
load_source_lines();
:(code)
void load_labels() {
  ifstream fin("labels");
  if (fin.fail()) return;
  fin >> std::hex;
  while (has_data(fin)) {
    uint32_t addr = 0;
    fin >> addr;
    string name;
    fin >> name;
    put(Symbol_name, addr, name);
  }
}

void load_source_lines() {
  ifstream fin("source_lines");
  if (fin.fail()) return;
  fin >> std::hex;
  while (has_data(fin)) {
    uint32_t addr = 0;
    fin >> addr;
    string line;
    getline(fin, line);
    put(Source_line, addr, hacky_squeeze_out_whitespace(line));
  }
}

:(after "Run One Instruction")
if (contains_key(Symbol_name, EIP))
  trace(Callstack_depth, "run") << "== label " << get(Symbol_name, EIP) << end();
if (contains_key(Source_line, EIP))
  trace(Callstack_depth, "run") << "inst: " << get(Source_line, EIP) << end();
else
  // no source line info; do what you can
  trace(Callstack_depth, "run") << "inst: " << debug_info(EIP) << end();

:(code)
string debug_info(uint32_t inst_address) {
  uint8_t op = read_mem_u8(inst_address);
  if (op != 0xe8) {
    ostringstream out;
    out << HEXBYTE << NUM(op);
    return out.str();
  }
  int32_t offset = read_mem_i32(inst_address+/*skip op*/1);
  uint32_t next_eip = inst_address+/*inst length*/5+offset;
  if (contains_key(Symbol_name, next_eip))
    return "e8/call "+get(Symbol_name, next_eip);
  ostringstream out;
  out << "e8/call 0x" << HEXWORD << next_eip;
  return out.str();
}

//: If a label starts with '$watch-', make a note of the effective address
//: computed by the next instruction. Start dumping out its contents to the
//: trace after every subsequent instruction.

:(after "Run One Instruction")
dump_watch_points();
:(before "End Globals")
map<string, uint32_t> Watch_points;
:(before "End Reset")
Watch_points.clear();
:(code)
void dump_watch_points() {
  if (Watch_points.empty()) return;
  trace(Callstack_depth, "dbg") << "watch points:" << end();
  for (map<string, uint32_t>::iterator p = Watch_points.begin();  p != Watch_points.end();  ++p)
    trace(Callstack_depth, "dbg") << "  " << p->first << ": " << HEXWORD << p->second << " -> " << HEXWORD << read_mem_u32(p->second) << end();
}

:(before "End Globals")
string Watch_this_effective_address;
:(after "Run One Instruction")
Watch_this_effective_address = "";
if (contains_key(Symbol_name, EIP) && starts_with(get(Symbol_name, EIP), "$watch-"))
  Watch_this_effective_address = get(Symbol_name, EIP);
:(after "Found effective_address(addr)")
if (!Watch_this_effective_address.empty()) {
  dbg << "now watching " << HEXWORD << addr << " for " << Watch_this_effective_address << end();
  put(Watch_points, Watch_this_effective_address, addr);
}

//: If a label starts with '$dump-stack', dump out to the trace n bytes on
//: either side of ESP.

:(after "Run One Instruction")
if (contains_key(Symbol_name, EIP) && starts_with(get(Symbol_name, EIP), "$dump-stack")) {
  dump_stack(64);
}
:(code)
void dump_stack(int n) {
  uint32_t stack_pointer = Reg[ESP].u;
  uint32_t start = ((stack_pointer-n)&0xfffffff0);
  dbg << "stack:" << end();
  for (uint32_t addr = start;  addr < start+n*2;  addr+=16) {
    if (addr >= AFTER_STACK) break;
    ostringstream out;
    out << HEXWORD << addr << ":";
    for (int i = 0;  i < 16;  i+=4) {
      out << ' ';
      out << ((addr+i == stack_pointer) ? '[' : ' ');
      out << HEXWORD << read_mem_u32(addr+i);
      out << ((addr+i == stack_pointer) ? ']' : ' ');
    }
    dbg << out.str() << end();
  }
}

//: Special label that dumps regions of memory.
//: Not a general mechanism; by the time you get here you're willing to hack
//: on the emulator.
:(after "Run One Instruction")
if (contains_key(Symbol_name, EIP) && get(Symbol_name, EIP) == "$dump-stream-at-EAX")
  dump_stream_at(Reg[EAX].u);
:(code)
void dump_stream_at(uint32_t stream_start) {
  int32_t stream_length = read_mem_i32(stream_start + 8);
  dbg << "stream length: " << std::dec << stream_length << end();
  for (int i = 0;  i < stream_length + 12;  ++i)
    dbg << "0x" << HEXWORD << (stream_start+i) << ": " << HEXBYTE << NUM(read_mem_u8(stream_start+i)) << end();
}

//: helpers

:(code)
string hacky_squeeze_out_whitespace(const string& s) {
  // strip whitespace at start
  string::const_iterator first = s.begin();
  while (first != s.end() && isspace(*first))
    ++first;
  if (first == s.end()) return "";

  // strip whitespace at end
  string::const_iterator last = --s.end();
  while (last != s.begin() && isspace(*last))
    --last;
  ++last;

  // replace runs of spaces/dots with single space until comment or string
  // TODO:
  //   leave alone dots not surrounded by whitespace
  //   leave alone '#' within word
  //   leave alone '"' within word
  //   squeeze spaces after end of string
  ostringstream out;
  bool previous_was_space = false;
  bool in_comment_or_string = false;
  for (string::const_iterator curr = first;  curr != last;  ++curr) {
    if (in_comment_or_string)
      out << *curr;
    else if (isspace(*curr) || *curr == '.')
      previous_was_space = true;
    else {
      if (previous_was_space)
        out << ' ';
      out << *curr;
      previous_was_space = false;
      if (*curr == '#' || *curr == '"') in_comment_or_string = true;
    }
  }
  return out.str();
}