net: buf: Add net_buf_pull_mem() API

This is the same as net_buf_pull(), except that instead of returning
the new buf->data it returns the old buf->data. This was recently
discussed in github issue zephyrproject-rtos#12562.

Signed-off-by: Johan Hedberg <[email protected]>

Author: Johan Hedberg

include/net/buf.h

@@ -296,6 +296,19 @@ void net_buf_simple_push_u8(struct net_buf_simple *buf, u8_t val);
  */
 void *net_buf_simple_pull(struct net_buf_simple *buf, size_t len);
 
+/**
+ *  @brief Remove data from the beginning of the buffer.
+ *
+ *  Removes data from the beginning of the buffer by modifying the data
+ *  pointer and buffer length.
+ *
+ *  @param buf Buffer to update.
+ *  @param len Number of bytes to remove.
+ *
+ *  @return Pointer to the old location of the buffer data.
+ */
+void *net_buf_simple_pull_mem(struct net_buf_simple *buf, size_t len);
+
 /**
  *  @brief Remove a 8-bit value from the beginning of the buffer
  *
@@ -1147,6 +1160,20 @@ static inline void *net_buf_user_data(const struct net_buf *buf)
  */
 #define net_buf_pull(buf, len) net_buf_simple_pull(&(buf)->b, len)
 
+/**
+ *  @def net_buf_pull_mem
+ *  @brief Remove data from the beginning of the buffer.
+ *
+ *  Removes data from the beginning of the buffer by modifying the data
+ *  pointer and buffer length.
+ *
+ *  @param buf Buffer to update.
+ *  @param len Number of bytes to remove.
+ *
+ *  @return Pointer to the old beginning of the buffer data.
+ */
+#define net_buf_pull_mem(buf, len) net_buf_simple_pull_mem(&(buf)->b, len)
+
 /**
  *  @def net_buf_pull_u8
  *  @brief Remove a 8-bit value from the beginning of the buffer

subsys/net/buf.c

@@ -868,6 +868,20 @@ void *net_buf_simple_pull(struct net_buf_simple *buf, size_t len)
 	return buf->data += len;
 }
 
+void *net_buf_simple_pull_mem(struct net_buf_simple *buf, size_t len)
+{
+	void *data = buf->data;
+
+	NET_BUF_SIMPLE_DBG("buf %p len %zu", buf, len);
+
+	NET_BUF_SIMPLE_ASSERT(buf->len >= len);
+
+	buf->len -= len;
+	buf->data += len;
+
+	return data;
+}
+
 u8_t net_buf_simple_pull_u8(struct net_buf_simple *buf)
 {
 	u8_t val;