swift : fix concatenation method to avoid invalid UTF8 stringfication (…

…ggerganov#4325)

examples/llama.swiftui/llama.cpp.swift/LibLlama.swift

@@ -11,6 +11,8 @@ actor LlamaContext {
  private var context: OpaquePointer
  private var batch: llama_batch
  private var tokens_list: [llama_token]
+ /// This variable is used to store temporarily invalid cchars
+ private var temporary_invalid_cchars: [CChar]
 
  var n_len: Int32 = 512
  var n_cur: Int32 = 0
@@ -21,6 +23,7 @@ actor LlamaContext {
  self.context = context
  self.tokens_list = []
  self.batch = llama_batch_init(512, 0, 1)
+ self.temporary_invalid_cchars = []
  }
 
  deinit {
@@ -61,6 +64,7 @@ actor LlamaContext {
  print("attempting to complete \"\(text)\"")
 
  tokens_list = tokenize(text: text, add_bos: true)
+ temporary_invalid_cchars = []
 
  let n_ctx = llama_n_ctx(context)
  let n_kv_req = tokens_list.count + (Int(n_len) - tokens_list.count)
@@ -72,7 +76,7 @@ actor LlamaContext {
  }
 
  for id in tokens_list {
- print(token_to_piece(token: id))
+ print(String(cString: token_to_piece(token: id) + [0]))
  }
 
  // batch = llama_batch_init(512, 0) // done in init()
@@ -115,10 +119,25 @@ actor LlamaContext {
 
  if new_token_id == llama_token_eos(context) || n_cur == n_len {
  print("\n")
- return ""
+ let new_token_str = String(cString: temporary_invalid_cchars + [0])
+ temporary_invalid_cchars.removeAll()
+ return new_token_str
  }
 
- let new_token_str = token_to_piece(token: new_token_id)
+ let new_token_cchars = token_to_piece(token: new_token_id)
+ temporary_invalid_cchars.append(contentsOf: new_token_cchars)
+ let new_token_str: String
+ if let string = String(validatingUTF8: temporary_invalid_cchars + [0]) {
+ temporary_invalid_cchars.removeAll()
+ new_token_str = string
+ } else if (0 ..< temporary_invalid_cchars.count).contains(where: {$0 != 0 && String(validatingUTF8: Array(temporary_invalid_cchars.suffix($0)) + [0]) != nil}) {
+ // in this case, at least the suffix of the temporary_invalid_cchars can be interpreted as UTF8 string
+ let string = String(cString: temporary_invalid_cchars + [0])
+ temporary_invalid_cchars.removeAll()
+ new_token_str = string
+ } else {
+ new_token_str = ""
+ }
  print(new_token_str)
  // tokens_list.append(new_token_id)
 
@@ -144,6 +163,7 @@ actor LlamaContext {
 
  func clear() {
  tokens_list.removeAll()
+ temporary_invalid_cchars.removeAll()
  }
 
  private func tokenize(text: String, add_bos: Bool) -> [llama_token] {
@@ -162,7 +182,8 @@ actor LlamaContext {
  return swiftTokens
  }
 
- private func token_to_piece(token: llama_token) -> String {
+ /// - note: The result does not contain null-terminator
+ private func token_to_piece(token: llama_token) -> [CChar] {
  let result = UnsafeMutablePointer<Int8>.allocate(capacity: 8)
  result.initialize(repeating: Int8(0), count: 8)
  defer {
@@ -176,10 +197,12 @@ actor LlamaContext {
  defer {
  newResult.deallocate()
  }
- _ = llama_token_to_piece(model, token, newResult, -nTokens)
- return String(cString: newResult)
+ let nNewTokens = llama_token_to_piece(model, token, newResult, -nTokens)
+ let bufferPointer = UnsafeBufferPointer(start: newResult, count: Int(nNewTokens))
+ return Array(bufferPointer)
  } else {
- return String(cString: result)
+ let bufferPointer = UnsafeBufferPointer(start: result, count: Int(nTokens))
+ return Array(bufferPointer)
  }
  }
 }