#include <SD.h>

void readfile() {
  File test3 = SD.open("/testfile.txt", "r");
  while (test3.available()) {
    Serial.write(test3.read());
  }
  test3.close();
}

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("Hello, ESP32-S3!");

  SPI.begin(8, 17, 46, 9);
  SD.begin(9);
  Serial.printf("card size: %d\n", SD.cardSize());

  Serial.println("\ntest1");
  File test1 = SD.open("/testfile.txt","a");
  test1.print("this is test content!\n");
  test1.close();
  readfile();

  Serial.println("\ntest2");
  File test2 = SD.open("/testfile.txt", "a");
  test2.seek(0, SeekEnd);
  test2.write((const uint8_t*)"that", 4);
  test2.close();
  readfile();

  Serial.println("\ntest3");
  FILE* f;
  f = fopen("/sd/testfile.txt", "a");
  const char* newtext = "thus";
  fseek(f, 0, SeekEnd);
  fwrite(newtext, sizeof(char), 4, f);
  fclose(f);
  readfile();
}

void loop() {
  // put your main code here, to run repeatedly:
  delay(10); // this speeds up the simulation
}