diff --git a/src/input/InputStream.cxx b/src/input/InputStream.cxx
index 419c4f07f..bf6fd198e 100644
--- a/src/input/InputStream.cxx
+++ b/src/input/InputStream.cxx
@@ -132,10 +132,39 @@ InputStream::LockRead(void *ptr, size_t _size, Error &error)
 	return Read(ptr, _size, error);
 }
 
+bool
+InputStream::ReadFull(void *_ptr, size_t _size, Error &error)
+{
+	uint8_t *ptr = (uint8_t *)_ptr;
+
+	size_t nbytes_total = 0;
+	while (_size > 0) {
+		size_t nbytes = Read(ptr + nbytes_total, _size, error);
+		if (nbytes == 0)
+			return false;
+
+		nbytes_total += nbytes;
+		_size -= nbytes;
+	}
+	return true;
+}
+
+bool
+InputStream::LockReadFull(void *ptr, size_t _size, Error &error)
+{
+#if !CLANG_CHECK_VERSION(3,6)
+	/* disabled on clang due to -Wtautological-pointer-compare */
+	assert(ptr != nullptr);
+#endif
+	assert(_size > 0);
+
+	const ScopeLock protect(mutex);
+	return ReadFull(ptr, _size, error);
+}
+
 bool
 InputStream::LockIsEOF()
 {
 	const ScopeLock protect(mutex);
 	return IsEOF();
 }
-
diff --git a/src/input/InputStream.hxx b/src/input/InputStream.hxx
index 84b4f3fae..3733b20a5 100644
--- a/src/input/InputStream.hxx
+++ b/src/input/InputStream.hxx
@@ -363,6 +363,25 @@ public:
 	 */
 	gcc_nonnull_all
 	size_t LockRead(void *ptr, size_t size, Error &error);
+
+	/**
+	 * Reads the whole data from the stream into the caller-supplied buffer.
+	 *
+	 * The caller must lock the mutex.
+	 *
+	 * @param ptr the buffer to read into
+	 * @param size the number of bytes to read
+	 * @return true if the whole data was read, false otherwise.
+	 */
+	gcc_nonnull_all
+	bool ReadFull(void *ptr, size_t size, Error &error);
+
+	/**
+	 * Wrapper for ReadFull() which locks and unlocks the mutex;
+	 * the caller must not be holding it already.
+	 */
+	gcc_nonnull_all
+	bool LockReadFull(void *ptr, size_t size, Error &error);
 };
 
 #endif