Fix crash in server example caused by oob due to no show words scanning

- Replaced scanning code by lookahead based strategy

examples/server/server.cpp

@@ -1,5 +1,5 @@
-#include <httplib.h>
-#include <json.hpp>
+#include "httplib.h"
+#include "json.hpp"
 #include "common.h"
 #include "llama.h"
 
@@ -27,7 +27,8 @@ struct llama_server_context
   std::vector<llama_token> llama_token_newline;
   std::vector<llama_token> embd_inp;
   std::vector<std::vector<llama_token>> no_show_words;
-  std::vector<llama_token> tokens_predicted;
+  std::deque<llama_token> tokens_predicted;
+  std::vector<llama_token>::size_type n_read_ahead = 0;
 
   llama_context *ctx;
   gpt_params params;
@@ -294,64 +295,54 @@ struct llama_server_context
     return result;
   }
 
-  std::string doCompletion()
-  {
-    llama_token token = nextToken();
-    if (token == -1) {
-      return "";
-    }
-    tokens_predicted.clear();
-    tokens_predicted.push_back(token);
-
-    // Avoid add the no show words to the response
-    for (std::vector<llama_token> word_tokens : no_show_words)
-    {
-      size_t match_token = 1;
-      if (tokens_predicted.front() == word_tokens.front())
-      {
-        bool execute_matching = true;
-        if (tokens_predicted.size() > 1) { // if previus tokens had been tested
-          for (size_t i = 1; i < word_tokens.size(); i++)
-          {
-            if (i >= tokens_predicted.size()) {
-              match_token = i;
-              break;
-            }
-            if (tokens_predicted[i] == word_tokens[i])
-            {
-              continue;
-            }
-            else
-            {
-              execute_matching = false;
-              break;
-            }
-          }
-        }
-        while (execute_matching) {
-          if (match_token == word_tokens.size()) {
-            return "";
-          }
-          token = nextToken();
-          tokens_predicted.push_back(token);
-          if (token == word_tokens[match_token])
-          { // the token follow the sequence
-            match_token++;
-          }
-          else if (match_token < word_tokens.size())
-          { // no complete all word sequence
-            break;
-          }
-        }
-      }
-    }
-    if(as_loop) {
+  std::string doCompletion() {
+    if (as_loop) {
       generated_text = "";
     }
-    for (llama_token tkn : tokens_predicted)
-    {
+
+    // Avoid add the no show words to the response
+    bool removed_no_show_words;
+    bool past_end_of_tokens = false;
+    do {
+      removed_no_show_words = false;
+
+      // Fill predicted tokens to `read_ahead` tokens if possible
+      while (tokens_predicted.size() < n_read_ahead) {
+        llama_token token = nextToken();
+        if (token == -1) {
+          past_end_of_tokens = true;
+          break;
+        }
+        tokens_predicted.push_back(token);
+      }
+
+      // Remove sequences of no_show_words in `predicted_tokens`
+      for (const auto &no_show : no_show_words) {
+
+        const auto &occurrence =
+            std::search(tokens_predicted.begin(), tokens_predicted.end(),
+                        no_show.begin(), no_show.end());
+
+        if (occurrence != tokens_predicted.end()) {
+          tokens_predicted.erase(occurrence, occurrence + no_show.size());
+          removed_no_show_words = true;
+        }
+      }
+
+      // Continue until end of tokens or as long as sequences have been removed
+    } while (removed_no_show_words && !past_end_of_tokens);
+
+    if (past_end_of_tokens) {
+      // If end of tokens, return all and clear
+      for (llama_token tkn : tokens_predicted) {
         generated_text += llama_token_to_str(ctx, tkn);
       }
+      tokens_predicted.clear();
+    } else {
+      // Else just pick the 1st token and add it
+      generated_text += llama_token_to_str(ctx, tokens_predicted[0]);
+      tokens_predicted.pop_front();
+    }
     return generated_text;
   }
 
@@ -476,6 +467,15 @@ bool server_params_parse(int argc, char **argv, server_params &sparams, gpt_para
     {
       params.embedding = true;
     }
+    else if (arg == "--keep")
+    {
+      if (++i >= argc)
+      {
+        invalid_param = true;
+        break;
+      }
+      params.n_keep = std::stoi(argv[i]);
+    }
     else if (arg == "-h" || arg == "--help")
     {
       server_print_usage(argc, argv, default_params);
@@ -622,18 +622,22 @@ bool parse_options_completion(json body, llama_server_context& llama, Response &
   if (!body["stop"].is_null())
   {
     std::vector<std::string> stop_words = body["stop"].get<std::vector<std::string>>();
-    for (std::string stop_word : stop_words)
+    for (const std::string& stop_word : stop_words)
     {
       llama.params.antiprompt.push_back(stop_word);
-      llama.no_show_words.push_back(::llama_tokenize(llama.ctx, stop_word, false));
+      auto tokens = ::llama_tokenize(llama.ctx, stop_word, false);
+      llama.n_read_ahead = std::max(llama.n_read_ahead, tokens.size());
+      llama.no_show_words.push_back(tokens);
     }
   }
   if (!body["exclude"].is_null())
   {
     std::vector<std::string> no_show_words = body["exclude"].get<std::vector<std::string>>();
-    for (std::string no_show : no_show_words)
+    for (const std::string& no_show : no_show_words)
     {
-      llama.no_show_words.push_back(::llama_tokenize(llama.ctx, no_show, false));
+      auto tokens = ::llama_tokenize(llama.ctx, no_show, false);
+      llama.n_read_ahead = std::max(llama.n_read_ahead, tokens.size());
+      llama.no_show_words.push_back(tokens);
     }
   }
   return true;