From 68a0cb53fd5a550fc8fbac0d90d6205bb177cc60 Mon Sep 17 00:00:00 2001
From: Phil Schatzmann <phil.schatzmann@gmail.com>
Date: Sun, 8 May 2022 16:17:31 +0200
Subject: [PATCH] FileRingBuffer

---
 src/Experiments/FileRingBuffer.h | 142 +++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 src/Experiments/FileRingBuffer.h

diff --git a/src/Experiments/FileRingBuffer.h b/src/Experiments/FileRingBuffer.h
new file mode 100644
index 000000000..b1a08bdaa
--- /dev/null
+++ b/src/Experiments/FileRingBuffer.h
@@ -0,0 +1,142 @@
+#pragma once
+namespace audio_tools {
+
+/**
+ * @brief An SD backed Ring Buffer that we can use to receive
+ * streaming audio. We expect an open file as parameter. The
+ * file must support the stream interface and the seek method.
+ * @author Phil Schatzmann
+ * @copyright GPLv3
+ */
+
+template <class F> class FileRingBuffer : public Stream {
+public:
+  /**
+   * @brief Construct a new Ring Buffer File Stream object
+   *
+   * @param file open file in read / write open
+   * @param size maximum file size
+   */
+  FileRingBuffer(size_t size = 500000, bool autoFlushOnOverflow = true) {
+    this->max_size = size;
+    this->auto_flush = autoFlushOnOverflow;
+  }
+
+  void begin(F file, ) {
+    this->file = file;
+    active = true;
+  }
+
+  /// Write at the end of the ring buffer
+  size write(uint8_t buffer, size_t len) {
+    if (!active)
+      return 0;
+    int write_len = len;
+    int result = 0;
+
+    // limit write len to available space
+    if (write_len > availableForWrite()) {
+      if (auto_flush) {
+        // remove oldest data to make space
+        int to_free = write_len - availableForWrite();
+        read_pos += to_free;
+        available -= to_free;
+        if (read_pos >= max_size) {
+          read_pos -= max_size;
+        }
+        assert(write_len <= availableForWrite())
+      } else {
+        // limit data to write
+        write_len = availableForWrite();
+      }
+    }
+
+    if (write_len > 0) {
+      int part_at_end = write_len;
+      int part_at_start = 0;
+
+      // Check if we would read past the end
+      if (write_pos + write_len > size) {
+        part_at_end = size - write_pos;
+        part_at_start = len - part_at_end;
+        if (part_at_start < read_pos) {
+          LOGE("SDRingBuffer is full");
+          part_at_start = 0;
+        }
+      }
+
+      if (!file.seek(write_pos)) {
+        LOGE("seek: %d", write_pos);
+      }
+      size_t written =
+          file.writeBytes(buffer, part_at_end) if (written == len) {
+        result += part_at_end;
+        write_pos += part_at_start;
+        available += part_at_start;
+      }
+      else {
+        LOGE("write at end failed: %d instead of %d", written, part_at_end);
+      }
+
+      // at overflow we restart to write at the beginning
+      if (part_at_start > 0) {
+        if (!file.seek(0)) {
+          LOGE("seek: %d", 0);
+        }
+        size_t written = file.writeBytes(buffer, part_at_start);
+        if (written == len) {
+          result += part_at_start;
+          write_pos = part_at_start;
+          available += part_at_start;
+        } else {
+          LOGE("write at start failed: %d instead of %d", written,
+               part_at_start);
+        }
+      }
+    } else {
+      LOGE("SDRingBuffer is full");
+    }
+    return result;
+  }
+
+  /// Read from the beginning of the ring buffer
+  size readBytes(uint8_t buffer, size_t len) {
+    if (!active)
+      return 0;
+    int read_len = len;
+    // if we do not have enough data we limit the size
+    if (read_len > available) {
+      read_len = available;
+    }
+    // if we read at end we need to limit the size
+    if (read_pos + read_len > max_size) {
+      read_len = max_size - read_pos;
+    }
+    // read the data
+    if (!file.seek(read_pos){
+      LOGE("seek: %d", read_pos);
+    }
+    if (file.readBytes(buffer, read_len) == read_len) {
+      read_pos += read_len;
+    }
+    // at end we start at the beginning again
+    if (read_pos >= max_size) {
+      read_pos = 0;
+    }
+    return read_len;
+  }
+
+  size available() { return available; }
+  size availableForWrite() { return max_size - available; }
+
+protected:
+  bool active = false;
+  bool auto_flush;
+  size_t max_size;
+  size_t read_pos = 0;
+  size_t write_pos = 0;
+  size_t available = 0;
+  F file;
+};
+
+} // namespace audio_tools
\ No newline at end of file