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package llm
import "iter"
type TokenBuffer struct {
tokenizer Tokenizer
window int
stride int
buffer []int64
document int
position int
includeTail bool
config TokenBufferConfig
}
type TokenBufferConfig struct {
Window int
Stride int
PadLeft bool
PadRight bool
PadTokenID int64
}
type TokenWindow struct {
Document int
Tokens []int64
Seen int
PaddingLeft int
PaddingRight int
}
func NewTokenBuffer(tokenizer Tokenizer, cfg TokenBufferConfig) *TokenBuffer {
if cfg.Stride > cfg.Window {
panic("stride exceeds window")
}
if cfg.PadLeft && cfg.PadRight {
panic("either pad left or right")
}
return &TokenBuffer{
tokenizer: tokenizer,
window: cfg.Window,
stride: cfg.Stride,
buffer: make([]int64, 0, 2*cfg.Window),
document: -1,
position: 0,
includeTail: true,
config: cfg,
}
}
func (tb *TokenBuffer) IncludeTail() bool {
return tb.includeTail
}
func (tb *TokenBuffer) SetIncludeTail(includeTail bool) {
tb.includeTail = includeTail
}
func (tb *TokenBuffer) Position() int {
return tb.position
}
func (tb *TokenBuffer) Push(document int, text string) iter.Seq[TokenWindow] {
return func(yield func(window TokenWindow) bool) {
if tb.document != -1 && document != tb.document {
w, ok := tb.Tail()
if ok && !yield(w) {
return
}
}
tb.document = document
if text == "" {
return
}
ids := toInt64(tb.tokenizer.Tokenize(text))
tb.buffer = append(tb.buffer, ids...)
for len(tb.buffer) >= tb.window {
w := TokenWindow{
Document: tb.document,
Tokens: make([]int64, tb.window),
Seen: min(tb.Position(), tb.window-tb.stride),
}
copy(w.Tokens, tb.buffer[:tb.window])
if !yield(w) {
return
}
tb.position += tb.stride
tb.buffer = append(tb.buffer[:0], tb.buffer[tb.stride:]...)
}
}
}
func (tb *TokenBuffer) Tail() (TokenWindow, bool) {
seen := min(tb.Position(), min(len(tb.buffer), tb.window-tb.stride))
w := TokenWindow{
Document: tb.document,
Seen: seen,
}
tb.document = -1
tb.position = 0
if !tb.includeTail || len(tb.buffer) == 0 {
tb.buffer = tb.buffer[:0]
return w, false
}
w.Tokens = make([]int64, len(tb.buffer))
copy(w.Tokens, tb.buffer)
if tb.config.PadLeft || tb.config.PadRight {
padding := make([]int64, tb.window-len(w.Tokens))
for i := range padding {
padding[i] = tb.config.PadTokenID
}
if tb.config.PadLeft {
w.Tokens = append(padding, w.Tokens...)
w.PaddingLeft = len(padding)
} else {
w.Tokens = append(w.Tokens, padding...)
w.PaddingRight = len(padding)
}
}
tb.buffer = tb.buffer[:0]
return w, true
}
func (tb *TokenBuffer) Stream(docs iter.Seq2[int, string]) iter.Seq[TokenWindow] {
return func(yield func(window TokenWindow) bool) {
for n, d := range docs {
for w := range tb.Push(n, d) {
if !yield(w) {
return
}
}
if w, ok := tb.Tail(); ok && !yield(w) {
return
}
}
}
}
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