Add helper functions to deal with data of a device.

1 files changed, 130 insertions, 0 deletions

diff --git a/libjaylink/buffer.c b/libjaylink/buffer.c
new file mode 100644
index 0000000..49103ca
--- /dev/null
+++ b/libjaylink/buffer.c
@@ -0,0 +1,130 @@
+/*
+ * This file is part of the libjaylink project.
+ *
+ * Copyright (C) 2014 Marc Schink <jaylink-dev@marcschink.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "config.h"
+
+/**
+ * Write a 16-bit unsigned integer value to a buffer.
+ *
+ * The value is stored in the buffer in device byte order.
+ *
+ * @param buffer Buffer to write the value into.
+ * @param value Value to write into the buffer in host byte order.
+ * @param offset Offset of the value within the buffer in bytes.
+ */
+void buffer_set_u16(uint8_t *buffer, uint16_t value, size_t offset)
+{
+	/*
+	 * Store the value in the buffer and swap byte order depending on the
+	 * host byte order.
+	 */
+#ifdef WORDS_BIGENDIAN
+	buffer[offset + 0] = value;
+	buffer[offset + 1] = value >> 8;
+#else
+	memcpy(buffer + offset, &value, sizeof(value));
+#endif
+}
+
+/**
+ * Read a 16-bit unsigned integer value from a buffer.
+ *
+ * The value in the buffer is expected to be stored in device byte order.
+ *
+ * @param buffer Buffer to read the value from.
+ * @param offset Offset of the value within the buffer in bytes.
+ *
+ * @return The value read from the buffer in host byte order.
+ */
+uint16_t buffer_get_u16(const uint8_t *buffer, size_t offset)
+{
+	uint16_t value;
+
+	/*
+	 * Read the value from the buffer and swap byte order depending on the
+	 * host byte order.
+	 */
+#ifdef WORDS_BIGENDIAN
+	value = (((uint16_t)buffer[offset + 1])) | \
+		(((uint16_t)buffer[offset + 0]) << 8);
+#else
+	memcpy(&value, buffer + offset, sizeof(value));
+#endif
+
+	return value;
+}
+
+/**
+ * Write a 32-bit unsigned integer value to a buffer.
+ *
+ * The value is stored in the buffer in device byte order.
+ *
+ * @param buffer Buffer to write the value into.
+ * @param value Value to write into the buffer in host byte order.
+ * @param offset Offset of the value within the buffer in bytes.
+ */
+void buffer_set_u32(uint8_t *buffer, uint32_t value, size_t offset)
+{
+	/*
+	 * Store the value in the buffer and swap byte order depending on the
+	 * host byte order.
+	 */
+#ifdef WORDS_BIGENDIAN
+	buffer[offset + 0] = value;
+	buffer[offset + 1] = value >> 8;
+	buffer[offset + 2] = value >> 16;
+	buffer[offset + 3] = value >> 24;
+#else
+	memcpy(buffer + offset, &value, sizeof(value));
+#endif
+}
+
+/**
+ * Read a 32-bit unsigned integer value from a buffer.
+ *
+ * The value in the buffer is expected to be stored in device byte order.
+ *
+ * @param buffer Buffer to read the value from.
+ * @param offset Offset of the value within the buffer in bytes.
+ *
+ * @return The value read from the buffer in host byte order.
+ */
+uint32_t buffer_get_u32(const uint8_t *buffer, size_t offset)
+{
+	uint32_t value;
+
+	/*
+	 * Read the value from the buffer and swap byte order depending on the
+	 * host byte order.
+	 */
+#ifdef WORDS_BIGENDIAN
+	value = (((uint32_t)buffer[offset + 3])) | \
+		(((uint32_t)buffer[offset + 2]) << 8) | \
+		(((uint32_t)buffer[offset + 1]) << 16) | \
+		(((uint32_t)buffer[offset + 0]) << 24);
+#else
+	memcpy(&value, buffer + offset, sizeof(value));
+#endif
+
+	return value;
+}