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getBit endian

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This commit is contained in:
Ryan Oldenburg 2022-05-25 22:09:07 -05:00
parent 11bd83b495
commit 7b1cd09cd3
1 changed files with 4 additions and 5 deletions
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9
src/pixie/fileformats/jpeg.nim
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@ -529,10 +529,9 @@ proc getBit(state: var DecoderState): int =
## Get a single bit. ## Get a single bit.
if state.bitsBuffered < 1: if state.bitsBuffered < 1:
state.fillBitBuffer() state.fillBitBuffer()
let k = state.bitBuffer result = ((state.bitBuffer and cast[uint32](0x80000000)) shr 31).int
state.bitBuffer = state.bitBuffer shl 1 state.bitBuffer = state.bitBuffer shl 1
dec state.bitsBuffered dec state.bitsBuffered
return (k.int and 0x80000000.int)
proc getBitsAsSignedInt(state: var DecoderState, n: int): int = proc getBitsAsSignedInt(state: var DecoderState, n: int): int =
## Get n number of bits as a signed integer. ## Get n number of bits as a signed integer.
@ -616,7 +615,7 @@ proc decodeProgressiveBlock(
state.components[component].dcPred = dc state.components[component].dcPred = dc
data[0] = cast[int16](dc * (1 shl state.successiveApproxLow)) data[0] = cast[int16](dc * (1 shl state.successiveApproxLow))
else: else:
if getBit(state) != 0: if state.getBit() != 0:
data[0] = cast[int16](data[0] + (1 shl state.successiveApproxLow)) data[0] = cast[int16](data[0] + (1 shl state.successiveApproxLow))
proc decodeProgressiveContinuationBlock( proc decodeProgressiveContinuationBlock(
@ -689,7 +688,7 @@ proc decodeProgressiveContinuationBlock(
else: else:
if s != 1: if s != 1:
failInvalid("bad huffman code") failInvalid("bad huffman code")
if getBit(state) != 0: if state.getBit() != 0:
s = bit.int s = bit.int
else: else:
s = -bit.int s = -bit.int
@ -698,7 +697,7 @@ proc decodeProgressiveContinuationBlock(
let zig = deZigZag[k] let zig = deZigZag[k]
inc k inc k
if data[zig] != 0: if data[zig] != 0:
if getBit(state) != 0: if state.getBit() != 0:
if (data[zig] and bit) == 0: if (data[zig] and bit) == 0:
if data[zig] > 0: if data[zig] > 0:
data[zig] = cast[int16](data[zig] + bit) data[zig] = cast[int16](data[zig] + bit)