Add ReadBenchmark example

examples/ReadBenchmark/ReadBenchmark.ino

+#include <SerialFlash.h>
+#include <SPI.h>
+
+const int FlashChipSelect = 6; // digital pin for flash chip CS pin
+//const int FlashChipSelect = 21; // Arduino 101 built-in SPI Flash
+
+void setup() {
+  //uncomment these if using Teensy audio shield
+  //SPI.setSCK(14);  // Audio shield has SCK on pin 14
+  //SPI.setMOSI(7);  // Audio shield has MOSI on pin 7
+
+  //uncomment these if you have other SPI chips connected
+  //to keep them disabled while using only SerialFlash
+  //pinMode(4, INPUT_PULLUP);
+  //pinMode(10, INPUT_PULLUP);
+
+  Serial.begin(9600);
+
+  // wait for Arduino Serial Monitor
+  while (!Serial) ;
+  delay(100);
+  Serial.println("All Files on SPI Flash chip:");
+
+  if (!SerialFlash.begin(FlashChipSelect)) {
+    while (1) {
+      Serial.println("Unable to access SPI Flash chip");
+      delay(2500);
+    }
+  }
+
+  SerialFlash.opendir();
+  int filecount = 0;
+  while (1) {
+    char filename[64];
+    uint32_t filesize;
+
+    if (SerialFlash.readdir(filename, sizeof(filename), filesize)) {
+      Serial.print("  ");
+      Serial.print(filename);
+      Serial.print(", ");
+      Serial.print(filesize);
+      Serial.print(" bytes");
+      SerialFlashFile file = SerialFlash.open(filename);
+      if (file) {
+        unsigned long usbegin = micros();
+        unsigned long n = filesize;
+        char buffer[256];
+        while (n > 0) {
+          unsigned long rd = n;
+          if (rd > sizeof(buffer)) rd = sizeof(buffer);
+          file.read(buffer, rd);
+          n = n - rd;
+        }
+        unsigned long usend = micros();
+        Serial.print(", read in ");
+        Serial.print(usend - usbegin);
+        Serial.print(" us, speed = ");
+        Serial.print((float)filesize * 1000.0 / (float)(usend - usbegin));
+        Serial.println(" kbytes/sec");
+        file.close();
+      } else {
+        Serial.println(" error reading this file!");
+      }
+      filecount = filecount + 1;
+    } else {
+      if (filecount == 0) {
+        Serial.println("No files found in SerialFlash memory.");
+      }
+      break; // no more files
+    }
+  }
+}
+
+void loop() {
+}
+