4840

New helper: printing a string to a buffered file.

1 files changed, 220 insertions, 0 deletions

diff --git a/subx/064write-buffered.subx b/subx/064write-buffered.subx
new file mode 100644
index 00000000..7889e255
--- /dev/null
+++ b/subx/064write-buffered.subx
@@ -0,0 +1,220 @@
+# 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
+
+# main:
+#?     e8/call test-write-buffered/disp32
+#?     e8/call test-write-buffered-with-intermediate-flush/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-buffered:  # f : (address buffered-file), msg : (address array byte) -> <void>
+    # pseudocode:
+    #   in = msg->data
+    #   inend = &msg->data[msg->length]
+    #   while in < inend
+    #     if f->write >= f->length
+    #       flush(f)
+    #       clear-stream(f)
+    #     f->data[f->write] = *in
+    #     ++f->write
+    #     ++in
+    #
+    # registers:
+    #   ESI : in
+    #   ECX : inend
+    #   EDI : f
+    #   EDX : f->length
+    #   EBX : f->write (cached copy, need to keep in sync)
+    #   EAX : temp
+    #
+    # . 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
+    # EAX = msg
+    8b/copy                         1/mod/*+disp8   4/rm32/sib    5/base/EBP  4/index/none              0/r32/EAX   0xc/disp8       .                 # copy *(EBP+12) to EAX
+    # in/ESI = msg->data
+    8d/copy-address                 1/mod/*+disp8   0/rm32/EAX    .           .             .           6/r32/ESI   4/disp8         .                 # copy EAX+4 to ESI
+    # inend/ECX = &msg->data[msg->length]
+    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   4/rm32/sib    5/base/EBP  4/index/none              7/r32/EDI   8/disp8         .                 # copy *(EBP+8) to EDI
+    # EDX = f->length
+    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
+    7d/jump-if-greater-or-equal  $write-buffered:loop-end/disp8
+    # if (f->write >= f->length) flush and clear f's stream
+    39/compare                      3/mod/direct    3/rm32/EBX    .           .             .           2/r32/EDX   .               .                 # compare EBX with EDX
+    7c/jump-if-lesser  $write-buffered:to-stream/disp8
+    # . persist f->write
+    89/copy                         1/mod/*+disp8   7/rm32/EDI    .           .             .           3/r32/EBX   4/disp8         .                 # copy EBX to *(EDI+4)
+    # . flush(f)
+    # . . push args
+    57/push-EDI
+    # . . call
+    e8/call  flush/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
+    # . clear-stream(stream = f+4)
+    # . . push args
+    8d/copy-address                 1/mod/*+disp8   7/rm32/EDI    .           .             .           0/r32/EAX   4/disp8         .                 # copy EDI+4 to EAX
+    50/push-EAX
+    # . . call
+    e8/call  clear-stream/disp32
+    # . . discard args
+    81          0/subop/add         3/mod/direct    4/rm32/ESP    .           .             .           .           .               4/imm32           # add to ESP
+    # . clear EBX (cached f->write)
+    31/xor                          3/mod/direct    3/rm32/EBX    .           .             .           3/r32/EBX   .               .                 # clear EBX
+$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
+    # . epilog
+    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+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
+    # 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-ints-equal(*_test-stream->data, "Abc", msg)
+    # . . push args
+    68/push  "F - test-write-buffered-single"/imm32
+    68/push  0x636241/imm32
+    # . . 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-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+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
+    # _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
+
+# . . vim:nowrap:textwidth=0