# streams: data structure for operating on arrays in a stateful manner
#
# A stream looks like this:
# write : int # index at which writes go
# read : int # index that we've read until
# data : (array byte) # prefixed by length as usual
#
# some primitives for operating on streams:
# - clear-stream (clears everything but the data length)
# - rewind-stream (resets read pointer)
== 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
clear-stream: # f : (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
# EAX = f
8b/copy 1/mod/*+disp8 5/rm32/EBP . . 0/r32/EAX 8/disp8 . # copy *(EBP+8) to EAX
# ECX = f->length
8b/copy 1/mod/*+disp8 0/rm32/EAX . . . 1/r32/ECX 8/disp8 . # copy *(EAX+8) to ECX
# ECX = &f->data[f->length]
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
# f->write = 0
c7 0/subop/copy 0/mod/direct 0/rm32/EAX . . . . . 0/imm32 # copy to *EAX
# f->read = 0
c7 0/subop/copy 1/mod/*+disp8 0/rm32/EAX . . . . 4/disp8 0/imm32 # copy to *(EAX+4)
# EAX = f->data
81 0/subop/add 3/mod/direct 0/rm32/EAX . . . . . 0xc/imm32 # add to EAX
# while (true)
$clear-stream:loop:
# if (EAX >= ECX) break
39/compare 3/mod/direct 0/rm32/EAX . . . 1/r32/ECX . . # compare EAX with ECX
73/jump-if-greater-or-equal-unsigned $clear-stream:end/disp8
# *EAX = 0
c6 0/subop/copy 0/mod/direct 0/rm32/EAX . . . . . 0/imm8 # copy byte to *EAX
# ++EAX
40/increment-EAX
eb/jump $clear-stream:loop/disp8
$clear-stream:end:
# . restore registers
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
rewind-stream: # f : (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
# EAX = f
8b/copy 1/mod/*+disp8 5/rm32/EBP . . 0/r32/EAX 8/disp8 . # copy *(EBP+8) to EAX
# f->read = 0
c7 0/subop/copy 1/mod/*+disp8 0/rm32/EAX . . . . 4/disp8 0/imm32 # copy to *(EAX+4)
$rewind-stream:end:
# . restore registers
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
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