34 lines
1.9 KiB
Plaintext
34 lines
1.9 KiB
Plaintext
# TODO: read-byte-buffered
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# Return next byte value in eax, with top 3 bytes cleared.
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# Abort on reaching end of stream.
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read-byte: # s: (addr stream byte) -> result/eax: byte
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# . prologue
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55/push-ebp
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89/copy 3/mod/direct 5/rm32/ebp . . . 4/r32/esp . . # copy esp to ebp
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# . save registers
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51/push-ecx
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56/push-esi
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# esi = s
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8b/copy 1/mod/*+disp8 5/rm32/ebp . . . 6/r32/esi 8/disp8 . # copy *(ebp+8) to esi
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# ecx = s->read
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8b/copy 1/mod/*+disp8 6/rm32/esi . . . 1/r32/ecx 4/disp8 . # copy *(esi+4) to ecx
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# if (f->read >= f->write) abort
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3b/compare 0/mod/indirect 6/rm32/esi . . . 1/r32/ecx . . # compare ecx with *esi
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0f 8d/jump-if->= $read-byte:end/disp32 # TODO: abort
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# result = f->data[f->read]
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31/xor 3/mod/direct 0/rm32/eax . . . 0/r32/eax . . # clear eax
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8a/copy-byte 1/mod/*+disp8 4/rm32/sib 6/base/esi 1/index/ecx . 0/r32/AL 0xc/disp8 . # copy byte at *(esi+ecx+12) to AL
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# ++f->read
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ff 0/subop/increment 1/mod/*+disp8 6/rm32/esi . . . . 4/disp8 . # increment *(esi+4)
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$read-byte:end:
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# . restore registers
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5e/pop-to-esi
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59/pop-to-ecx
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# . epilogue
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89/copy 3/mod/direct 4/rm32/esp . . . 5/r32/ebp . . # copy ebp to esp
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5d/pop-to-ebp
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c3/return
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# . . vim:nowrap:textwidth=0
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