string_table_parser.go

package yasha

import (
	"math"

	"github.com/davecgh/go-spew/spew"
)

const (
	MaxNameLength  = 0x400
	KeyHistorySize = 32
)

type CSTObject interface {
	GetStringData() []byte
	GetNumEntries() int32
	GetMaxEntries() int32
	GetUserDataFixedSize() bool
	GetUserDataSizeBits() int32
}

type USTObject interface {
	GetStringData() []byte
	GetNumChangedEntries() int32
}

func ParseCST(obj CSTObject) map[int]*StringTableItem {
	return Parse(
		obj.GetStringData(),
		int(obj.GetNumEntries()),
		int(obj.GetMaxEntries()),
		int(obj.GetUserDataSizeBits()),
		obj.GetUserDataFixedSize(),
	)
}

func ParseUST(obj USTObject, meta *CacheItem) map[int]*StringTableItem {
	return Parse(
		obj.GetStringData(),
		int(obj.GetNumChangedEntries()),
		meta.MaxEntries,
		meta.Bits,
		meta.IsFixedSize,
	)
}

func Parse(data []byte, numEntries, maxEntries, dataSizeBits int, dataFixedSize bool) map[int]*StringTableItem {
	br := NewBitReader(data)

	bitsPerIndex := int(math.Log(float64(maxEntries)) / math.Log(2))
	keyHistory := make([]string, 0, KeyHistorySize)
	result := map[int]*StringTableItem{}
	mysteryFlag := br.ReadBoolean()
	index := -1
	nameBuf := ""

	for len(result) < numEntries {
		if br.ReadBoolean() {
			index++
		} else {
			index = int(br.ReadUBits(bitsPerIndex))
		}
		nameBuf = ""
		if br.ReadBoolean() {
			if mysteryFlag && br.ReadBoolean() {
				panic("mysteryFlag assertion failed!")
			}
			if br.ReadBoolean() {
				basis := br.ReadUBits(5)
				length := br.ReadUBits(5)
				if int(basis) >= len(keyHistory) {
					// spew.Dump("Ignoring invalid history index...", keyHistory, basis, length)
					nameBuf += br.ReadStringN(MaxNameLength)
				} else {
					s := keyHistory[basis]
					if int(length) > len(s) {
						spew.Dump(s, length)
						nameBuf += s + br.ReadStringN(int(MaxNameLength))
					} else {
						nameBuf += s[0:length] + br.ReadStringN(int(MaxNameLength-length))
					}
				}
			} else {
				nameBuf += br.ReadStringN(MaxNameLength)
			}
			if len(keyHistory) >= KeyHistorySize {
				copy(keyHistory[0:], keyHistory[1:])
				keyHistory[len(keyHistory)-1] = "" // or the zero value of T
				keyHistory = keyHistory[:len(keyHistory)-1]
			}
			keyHistory = append(keyHistory, nameBuf)
		}
		value := []byte{}
		if br.ReadBoolean() {
			bitLength := 0
			if dataFixedSize {
				bitLength = dataSizeBits
			} else {
				bitLength = int(br.ReadUBits(14) * 8)
			}
			value = append(value, br.ReadBitsAsBytes(bitLength)...)
		}
		result[index] = &StringTableItem{Str: nameBuf, Data: value}
	}

	return result
}