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This commit is contained in:
Ryan Oldenburg 2022-05-12 22:51:33 -05:00
parent f03b2e2ef3
commit 6cfb98553c
1 changed files with 37 additions and 37 deletions
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74
src/pixie/fileformats/jpeg.nim
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@ -64,8 +64,8 @@ type
DecoderState = object DecoderState = object
buffer: string buffer: string
pos, bitCount: int pos, bitsBuffered: int
bits: uint32 bitBuffer: uint32
hitEnd: bool hitEnd: bool
imageHeight, imageWidth: int imageHeight, imageWidth: int
quantizationTables: array[4, array[64, uint8]] quantizationTables: array[4, array[64, uint8]]
@ -306,8 +306,8 @@ proc decodeSOF2(state: var DecoderState) =
proc reset(state: var DecoderState) = proc reset(state: var DecoderState) =
## Rests the decoder state need for reset markers. ## Rests the decoder state need for reset markers.
state.bits = 0 state.bitBuffer = 0
state.bitCount = 0 state.bitsBuffered = 0
for component in 0 ..< state.components.len: for component in 0 ..< state.components.len:
state.components[component].dcPred = 0 state.components[component].dcPred = 0
state.hitEnd = false state.hitEnd = false
@ -381,7 +381,7 @@ proc decodeSOS(state: var DecoderState) =
if len != 0: if len != 0:
failInvalid() failInvalid()
proc fillBits(state: var DecoderState) = proc fillBitBuffer(state: var DecoderState) =
## When we are low on bits, we need to call this to populate some more. ## When we are low on bits, we need to call this to populate some more.
while true: while true:
let b = if state.hitEnd: let b = if state.hitEnd:
@ -396,45 +396,45 @@ proc fillBits(state: var DecoderState) =
dec state.pos dec state.pos
state.hitEnd = true state.hitEnd = true
return return
state.bits = state.bits or (b shl (24 - state.bitCount)) state.bitBuffer = state.bitBuffer or (b shl (24 - state.bitsBuffered))
state.bitCount += 8 state.bitsBuffered += 8
if not(state.bitCount <= 24): if not(state.bitsBuffered <= 24):
break break
proc huffmanDecode(state: var DecoderState, tableCurrent, table: int): uint8 = proc huffmanDecode(state: var DecoderState, tableCurrent, table: int): uint8 =
## Decode a uint8 from the huffman table. ## Decode a uint8 from the huffman table.
if state.bitCount < 16: if state.bitsBuffered < 16:
state.fillBits() state.fillBitBuffer()
var huffman {.byaddr.} = state.huffmanTables[tableCurrent][table] var huffman {.byaddr.} = state.huffmanTables[tableCurrent][table]
let let
fastId = (state.bits shr (32 - fastBits)) and ((1 shl fastBits) - 1) fastId = (state.bitBuffer shr (32 - fastBits)) and ((1 shl fastBits) - 1)
fast = huffman.fast[fastId] fast = huffman.fast[fastId]
if fast < 255: if fast < 255:
let size = huffman.sizes[fast].int let size = huffman.sizes[fast].int
if size > state.bitCount: if size > state.bitsBuffered:
failInvalid() failInvalid()
state.bits = state.bits shl size state.bitBuffer = state.bitBuffer shl size
state.bitCount -= size state.bitsBuffered -= size
return huffman.symbols[fast] return huffman.symbols[fast]
var var
tmp = (state.bits shr 16).int tmp = (state.bitBuffer shr 16).int
i = fastBits + 1 i = fastBits + 1
while i < huffman.maxCodes.len: while i < huffman.maxCodes.len:
if tmp < huffman.maxCodes[i]: if tmp < huffman.maxCodes[i]:
break break
inc i inc i
if i == 17 or i > state.bitCount: if i == 17 or i > state.bitsBuffered:
failInvalid() failInvalid()
let symbolId = (state.bits shr (32 - i)).int + huffman.deltas[i] let symbolId = (state.bitBuffer shr (32 - i)).int + huffman.deltas[i]
state.bits = state.bits shl i state.bitBuffer = state.bitBuffer shl i
state.bitCount -= i state.bitsBuffered -= i
huffman.symbols[symbolId] huffman.symbols[symbolId]
template lrot(value: uint32, shift: int): uint32 = template lrot(value: uint32, shift: int): uint32 =
@ -443,36 +443,36 @@ template lrot(value: uint32, shift: int): uint32 =
proc getBit(state: var DecoderState): int = proc getBit(state: var DecoderState): int =
## Get a single bit. ## Get a single bit.
if state.bitCount < 1: if state.bitsBuffered < 1:
state.fillBits() state.fillBitBuffer()
let k = state.bits let k = state.bitBuffer
state.bits = state.bits shl 1 state.bitBuffer = state.bitBuffer shl 1
dec state.bitCount dec state.bitsBuffered
return (k.int and 0x80000000.int) 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.
if n notin 0 .. 16: if n notin 0 .. 16:
failInvalid() failInvalid()
if state.bitCount < n: if state.bitsBuffered < n:
state.fillBits() state.fillBitBuffer()
let sign = cast[int32](state.bits) shr 31 let sign = cast[int32](state.bitBuffer) shr 31
var k = lrot(state.bits, n) var k = lrot(state.bitBuffer, n)
state.bits = k and (not bitMasks[n]) state.bitBuffer = k and (not bitMasks[n])
k = k and bitMasks[n] k = k and bitMasks[n]
state.bitCount -= n state.bitsBuffered -= n
result = k.int + (biases[n] and (not sign)) result = k.int + (biases[n] and (not sign))
proc getBitsAsUnsignedInt(state: var DecoderState, n: int): int = proc getBitsAsUnsignedInt(state: var DecoderState, n: int): int =
## Get n number of bits as a unsigned integer. ## Get n number of bits as a unsigned integer.
if n notin 0 .. 16: if n notin 0 .. 16:
failInvalid() failInvalid()
if state.bitCount < n: if state.bitsBuffered < n:
state.fillBits() state.fillBitBuffer()
var k = lrot(state.bits, n) var k = lrot(state.bitBuffer, n)
state.bits = k and (not bitMasks[n]) state.bitBuffer = k and (not bitMasks[n])
k = k and bitMasks[n] k = k and bitMasks[n]
state.bitCount -= n state.bitsBuffered -= n
return k.int return k.int
proc decodeRegularBlock( proc decodeRegularBlock(
@ -775,8 +775,8 @@ proc checkReset(state: var DecoderState) =
## Check if we might have run into a reset marker, then deal with it. ## Check if we might have run into a reset marker, then deal with it.
dec state.todo dec state.todo
if state.todo <= 0: if state.todo <= 0:
if state.bitCount < 24: if state.bitsBuffered < 24:
state.fillBits() state.fillBitBuffer()
if state.buffer[state.pos] == 0xFF.char: if state.buffer[state.pos] == 0xFF.char:
if state.buffer[state.pos+1] in {0xD0.char .. 0xD7.char}: if state.buffer[state.pos+1] in {0xD0.char .. 0xD7.char}: