add basic working example

2026-09-11 00:59:31 +00:00 · 2025-01-27 18:41:44 -06:00
commit 56af3f8159
5 changed files with 207 additions and 0 deletions
@@ -0,0 +1,120 @@
+package bmip10
+
+type Config struct {
+	SampleStates       uint32
+	CodedStates        uint32
+	LossyCodeWidth     uint32
+	LossyRounding      uint32
+	LosslessCodes      uint32
+	LossyCodes         uint32
+	CodeTables         uint32
+	DefaultTable       uint32
+	LowestTableThresh  uint32
+	HighestTableThresh uint32
+	LossyFlag          uint32
+}
+
+func SetupBMIP10(sampleBits uint32, codedBits uint32) *Config {
+	config := Config{}
+	config.SampleStates = 1 << sampleBits
+	config.CodedStates = 1 << codedBits
+	config.LossyCodeWidth = (1 << (sampleBits - codedBits + 1)) - 1
+	config.LossyRounding = config.LossyCodeWidth / 2
+	config.LosslessCodes = config.CodedStates / 2
+	config.LossyCodes = config.CodedStates / 2
+	config.CodeTables = 1 + config.CodedStates/2
+	config.DefaultTable = config.CodeTables / 2
+	config.LowestTableThresh = config.LosslessCodes / 2
+	config.HighestTableThresh = config.SampleStates - (config.LosslessCodes / 2)
+	config.LossyFlag = (1 << codedBits) / 2
+
+	return &config
+}
+
+// Use the decoded sample to select the next table to use
+func NextTable(config *Config, sample int32) int32 {
+	if sample < int32(config.LowestTableThresh) {
+		return 0
+	} else if sample >= int32(config.HighestTableThresh) {
+		return int32(config.LossyCodes)
+	} else {
+		return (sample - int32(config.LowestTableThresh) + int32(config.LossyRounding)) / int32(config.LossyCodeWidth)
+	}
+}
+
+// For a given sample and code table calculate the code word
+func EncodeSample(config *Config, table int32, sample int32) int32 {
+	lossless_low := table * int32(config.LossyCodeWidth)
+	lossless_high := lossless_low + int32(config.LosslessCodes)
+
+	if sample >= lossless_low && sample < lossless_high {
+		return sample - lossless_low
+	} else if sample < lossless_low {
+
+		return int32(config.LossyFlag) | (sample / int32(config.LossyCodeWidth))
+	} else {
+		return int32(config.LossyFlag) | ((sample-lossless_high)/int32(config.LossyCodeWidth) + table)
+	}
+}
+
+// For a given code word and code table decode the sample
+func DecodeSample(config *Config, table int32, code_word int32) int32 {
+	index := code_word & ^int32(config.LossyFlag)
+	if (code_word & int32(config.LossyFlag)) != 0 {
+		if index < table {
+			return index*int32(config.LossyCodeWidth) + int32(config.LossyRounding)
+		} else {
+			return index*int32(config.LossyCodeWidth) + int32(config.LossyRounding) + int32(config.LosslessCodes)
+		}
+	} else {
+
+		return table*int32(config.LossyCodeWidth) + index
+	}
+}
+
+type Encoder struct {
+	Config *Config
+	Table  int32
+}
+
+func NewEncoder(sampleBits uint32, codedBits uint32) *Encoder {
+	config := SetupBMIP10(sampleBits, codedBits)
+	return &Encoder{
+		Config: config,
+		Table:  int32(config.DefaultTable),
+	}
+}
+
+func (e *Encoder) Encode(sample int32) int32 {
+	code_word := EncodeSample(e.Config, e.Table, sample)
+	decoded := DecodeSample(e.Config, e.Table, code_word)
+	e.Table = NextTable(e.Config, decoded)
+	return code_word
+}
+
+func (e *Encoder) Reset(sample int32) {
+	e.Table = int32(e.Config.DefaultTable)
+}
+
+type Decoder struct {
+	Config *Config
+	Table  int32
+}
+
+func NewDecoder(sampleBits uint32, codedBits uint32) *Decoder {
+	config := SetupBMIP10(sampleBits, codedBits)
+	return &Decoder{
+		Config: config,
+		Table:  int32(config.DefaultTable),
+	}
+}
+
+func (d *Decoder) Decode(code_word int32) int32 {
+	decoded := DecodeSample(d.Config, d.Table, code_word)
+	d.Table = NextTable(d.Config, decoded)
+	return decoded
+}
+
+func (d *Decoder) Reset(sample int32) {
+	d.Table = int32(d.Config.DefaultTable)
+}