func testWritePostClose(obs kanzi.OutputBitStream) {
defer func() {
if r := recover(); r != nil {
fmt.Printf("Error: %v\n", r.(error).Error())
}
}()
fmt.Printf("\nTrying to write to closed stream\n")
obs.WriteBit(1)
}
// alphabet must be sorted in increasing order
func EncodeAlphabet(obs kanzi.OutputBitStream, alphabet []byte) int {
alphabetSize := len(alphabet)
// First, push alphabet encoding mode
if alphabetSize == 256 {
// Full alphabet
obs.WriteBit(FULL_ALPHABET)
obs.WriteBit(EIGHT_BIT_ALPHABET)
return 256
}
if alphabetSize == 128 {
flag := true
for i := byte(0); i < 128; i++ {
if alphabet[i] != i {
flag = false
break
}
}
if flag == true {
obs.WriteBit(FULL_ALPHABET)
obs.WriteBit(SEVEN_BIT_ALPHABET)
return 128
}
}
obs.WriteBit(PARTIAL_ALPHABET)
diffs := make([]int, 32)
maxSymbolDiff := 1
if (alphabetSize != 0) && ((alphabetSize < 32) || (alphabetSize > 224)) {
obs.WriteBit(DELTA_ENCODED_ALPHABET)
if alphabetSize >= 224 {
// Big alphabet, encode all missing symbols
alphabetSize = 256 - alphabetSize
obs.WriteBits(uint64(alphabetSize), 5)
obs.WriteBit(ABSENT_SYMBOLS_MASK)
symbol := uint8(0)
previous := uint8(0)
for i, n := 0, 0; n < alphabetSize; {
if symbol == alphabet[i] {
if i < len(alphabet)-1 {
i++
}
symbol++
continue
}
diffs[n] = int(symbol) - int(previous)
symbol++
previous = symbol
if diffs[n] > maxSymbolDiff {
maxSymbolDiff = diffs[n]
}
n++
}
} else {
// Small alphabet, encode all present symbols
obs.WriteBits(uint64(alphabetSize), 5)
obs.WriteBit(PRESENT_SYMBOLS_MASK)
previous := uint8(0)
for i := 0; i < alphabetSize; i++ {
diffs[i] = int(alphabet[i]) - int(previous)
previous = alphabet[i] + 1
if diffs[i] > maxSymbolDiff {
maxSymbolDiff = diffs[i]
}
}
}
// Write log(max(diff)) to bitstream
log := uint(1)
for 1<<log <= maxSymbolDiff {
log++
}
obs.WriteBits(uint64(log-1), 3) // delta size
// Write all symbols with delta encoding
for i := 0; i < alphabetSize; i++ {
obs.WriteBits(uint64(diffs[i]), log)
}
} else {
// Regular (or empty) alphabet
obs.WriteBit(BIT_ENCODED_ALPHABET)
masks := make([]uint64, 4)
for i := 0; i < alphabetSize; i++ {
masks[alphabet[i]>>6] |= (1 << uint(alphabet[i]&63))
}
for i := range masks {
obs.WriteBits(masks[i], 64)
}
}
return alphabetSize
}
