1 files changed, 125 insertions, 0 deletions
diff --git a/doc/number-guessing-bot/bot.cpp b/doc/number-guessing-bot/bot.cpp
new file mode 100644
index 0000000..f14e917
--- /dev/null
+++ b/doc/number-guessing-bot/bot.cpp
@@ -0,0 +1,125 @@
+// Copyright 2024 Huawei Cloud Computing Technology Co., Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cstring>
+#include <iostream>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+void print_buffer(char *start, char *end) {
+  ++end;
+  while (start != end) {
+    std::cout << *start++;
+  }
+}
+
+bool ends_with(char *end, std::string const &token) {
+  auto it = token.rbegin();
+  while (it != token.rend()) {
+    if (*it++ != *end--) {
+      return false;
+    }
+  }
+  return true;
+}
+
+int main(int argc, char **argv) {
+  int pipefd_a[2]; // pipefd_a[0] reads from pipe
+                   // pipefd_a[1] writes to pipe
+  int pipefd_b[2];
+  if (pipe(pipefd_a) == -1) {
+    perror("pipe error");
+    exit(EXIT_FAILURE);
+  }
+  if (pipe(pipefd_b) == -1) {
+    perror("pipe error");
+    exit(EXIT_FAILURE);
+  }
+
+  auto pid = fork();
+  if (pid == -1) {
+    perror("fork error");
+    exit(EXIT_FAILURE);
+  }
+
+  if (pid == 0) {
+    std::string const s{argv[1]};
+    std::string const token = s.substr(s.rfind('/') + 1);
+    std::cout << "playing: " << s << std::endl;
+
+    // child reads from pipefd_a[0];
+    //       writes to pipefd_b[1];
+    dup2(pipefd_b[1], STDOUT_FILENO);
+    dup2(pipefd_a[0], STDIN_FILENO);
+
+    close(pipefd_a[1]); // close unused write end
+    close(pipefd_b[0]); // close unused read end
+    close(pipefd_b[1]);
+    close(pipefd_a[0]);
+    execl(s.c_str(), token.c_str());
+
+    _exit(0);
+  } else {
+    // master reads from pipefd_b[0]
+    //        writes to pipefd_a[1];
+    close(pipefd_a[0]);
+    close(pipefd_b[1]);
+
+    bool run = true;
+    int a = 1;
+    int b = 101;
+    int trial = 50;
+
+    char buffer[1024];
+    char *p = buffer;
+    std::string s;
+    while (run) {
+      while (read(pipefd_b[0], p, 1)) {
+        if (*p == '\n') {
+          print_buffer(buffer, p);
+          p = buffer;
+          continue;
+        }
+        if (*p == '!') {
+          if (ends_with(p, "win!")) {
+            run = false;
+            print_buffer(buffer, p);
+            std::cout << std::endl;
+            break;
+          }
+          if (ends_with(p, "small!")) {
+            a = trial;
+            trial = (a + b) / 2;
+          }
+          if (ends_with(p, "big!")) {
+            b = trial;
+            trial = (a + b) / 2;
+          }
+          char trial_buf[80];
+          int len = sprintf(trial_buf, "%d\n", trial);
+          write(pipefd_a[1], trial_buf, len);
+        }
+        if (!run) {
+          break;
+        }
+        ++p;
+      }
+    }
+    close(pipefd_b[0]);
+    close(pipefd_a[1]);
+    int status;
+    waitpid(0, &status, 0);
+  }
+}