From 3350c34a74844e21ea69077e01efff3bae64bdcd Mon Sep 17 00:00:00 2001 From: Kartik Agaram Date: Tue, 23 Mar 2021 17:31:08 -0700 Subject: . --- html/linux/106stream.subx.html | 137 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 137 insertions(+) create mode 100644 html/linux/106stream.subx.html (limited to 'html/linux/106stream.subx.html') diff --git a/html/linux/106stream.subx.html b/html/linux/106stream.subx.html new file mode 100644 index 00000000..e5d97176 --- /dev/null +++ b/html/linux/106stream.subx.html @@ -0,0 +1,137 @@ + + + + +Mu - linux/106stream.subx + + + + + + + + + + +https://github.com/akkartik/mu/blob/main/linux/106stream.subx +
+ 1 # streams: data structure for operating on arrays in a stateful manner
+ 2 #
+ 3 # A stream looks like this:
+ 4 #   write: int  # index at which writes go
+ 5 #   read: int  # index that we've read until
+ 6 #   data: (array byte)  # prefixed by size as usual
+ 7 #
+ 8 # some primitives for operating on streams:
+ 9 #   - clear-stream (clears everything but the data size)
+10 #   - rewind-stream (resets read pointer)
+11 
+12 == code
+13 #   instruction                     effective address                                                   register    displacement    immediate
+14 # . op          subop               mod             rm32          base        index         scale       r32
+15 # . 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
+16 
+17 clear-stream:  # f: (addr stream byte)
+18     # . prologue
+19     55/push-ebp
+20     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+21     # . save registers
+22     50/push-eax
+23     51/push-ecx
+24     # eax = f
+25     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         0/r32/eax   8/disp8         .                 # copy *(ebp+8) to eax
+26     # var count/ecx: int = f->size
+27     8b/copy                         1/mod/*+disp8   0/rm32/eax    .           .             .           1/r32/ecx   8/disp8         .                 # copy *(eax+8) to ecx
+28     # var max/ecx: (addr byte) = &f->data[f->size]
+29     8d/copy-address                 1/mod/*+disp8   4/rm32/sib    0/base/eax  1/index/ecx   .           1/r32/ecx   0xc/disp8       .                 # copy eax+ecx+12 to ecx
+30     # f->write = 0
+31     c7          0/subop/copy        0/mod/direct    0/rm32/eax    .           .             .           .           .               0/imm32           # copy to *eax
+32     # f->read = 0
+33     c7          0/subop/copy        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         0/imm32           # copy to *(eax+4)
+34     # - clear all stream data
+35     # - this isn't strictly necessary, and it can slow things down *a lot*, but better safe than sorry.
+36     # var curr/eax: (addr byte) = f->data
+37     81          0/subop/add         3/mod/direct    0/rm32/eax    .           .             .           .           .               0xc/imm32         # add to eax
+38 $clear-stream:loop:
+39     # if (curr >= max) break
+40     39/compare                      3/mod/direct    0/rm32/eax    .           .             .           1/r32/ecx   .               .                 # compare eax with ecx
+41     73/jump-if-addr>=  $clear-stream:end/disp8
+42     # *curr = 0
+43     c6          0/subop/copy-byte   0/mod/direct    0/rm32/eax    .           .             .           .           .               0/imm8            # copy byte to *eax
+44     # ++curr
+45     40/increment-eax
+46     eb/jump  $clear-stream:loop/disp8
+47 $clear-stream:end:
+48     # . restore registers
+49     59/pop-to-ecx
+50     58/pop-to-eax
+51     # . epilogue
+52     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
+53     5d/pop-to-ebp
+54     c3/return
+55 
+56 rewind-stream:  # f: (addr stream byte)
+57     # . prologue
+58     55/push-ebp
+59     89/copy                         3/mod/direct    5/rm32/ebp    .           .             .           4/r32/esp   .               .                 # copy esp to ebp
+60     # . save registers
+61     50/push-eax
+62     # eax = f
+63     8b/copy                         1/mod/*+disp8   5/rm32/ebp    .           .                         0/r32/eax   8/disp8         .                 # copy *(ebp+8) to eax
+64     # f->read = 0
+65     c7          0/subop/copy        1/mod/*+disp8   0/rm32/eax    .           .             .           .           4/disp8         0/imm32           # copy to *(eax+4)
+66 $rewind-stream:end:
+67     # . restore registers
+68     58/pop-to-eax
+69     # . epilogue
+70     89/copy                         3/mod/direct    4/rm32/esp    .           .             .           5/r32/ebp   .               .                 # copy ebp to esp
+71     5d/pop-to-ebp
+72     c3/return
+73 
+74 # . . vim:nowrap:textwidth=0
+
+ + + -- cgit 1.4.1-2-gfad0