util/{Const,Writable}Buffer: add operator[]

src/input/TextInputStream.cxx

@@ -63,7 +63,7 @@ bool TextInputStream::ReadLine(std::string &line)
 			   the current line */
 			dest = buffer.Write();
 			assert(!dest.IsEmpty());
-			dest.data[0] = '\n';
+			dest[0] = '\n';
 			buffer.Append(1);
 		}
 	} while (p == nullptr);

src/pcm/FallbackResampler.cxx

@@ -85,7 +85,7 @@ pcm_resample_fallback(PcmBuffer &buffer,
 		while (dest_pos < dest_samples) {
 			unsigned src_pos = dest_pos * src_rate / dest_rate;
 
-			dest_buffer[dest_pos++] = src.data[src_pos];
+			dest_buffer[dest_pos++] = src[src_pos];
 		}
 		break;
 	case 2:
@@ -93,8 +93,8 @@ pcm_resample_fallback(PcmBuffer &buffer,
 			unsigned src_pos = dest_pos * src_rate / dest_rate;
 			src_pos &= ~1;
 
-			dest_buffer[dest_pos++] = src.data[src_pos];
-			dest_buffer[dest_pos++] = src.data[src_pos + 1];
+			dest_buffer[dest_pos++] = src[src_pos];
+			dest_buffer[dest_pos++] = src[src_pos + 1];
 		}
 		break;
 	}

src/util/ConstBuffer.hxx

@@ -143,6 +143,17 @@ struct ConstBuffer {
 	constexpr const_iterator cend() const {
 		return data + size;
 	}
+
+#ifdef NDEBUG
+	constexpr
+#endif
+	const T &operator[](size_type i) const {
+#ifndef NDEBUG
+		assert(i < size);
+#endif
+
+		return data[i];
+	}
 };
 
 #endif

src/util/WritableBuffer.hxx

@@ -145,6 +145,17 @@ struct WritableBuffer {
 	constexpr const_iterator cend() const {
 		return data + size;
 	}
+
+#ifdef NDEBUG
+	constexpr
+#endif
+	T &operator[](size_type i) const {
+#ifndef NDEBUG
+		assert(i < size);
+#endif
+
+		return data[i];
+	}
 };
 
 #endif