lwIP - A Minimal TCP/IP implementation - Wikia

15 API REFERENCE 15.2 Buffer functions
buf = netbuf_new(); /* create a new netbuf */
netbuf_alloc(buf, 100); /* allocate 100 bytes of buffer */
/* do something with the netbuf */
/* [...] */
}
netbuf_delete(buf); /* deallocate netbuf */
15.2.3 netbuf alloc()
Synopsis
void * netbuf alloc(struct netbuf *buf, int size)
Description
Allocates buffer memory with size number of bytes for the netbuf buf. The function returns a
pointer to the allocated memory. Any memory previously allocated to the netbuf buf is deallocated.
The allocated memory can later be deallocated with the netbuf_free() function. Since
protocol headers are expected to precede the data when it should be sent, the function allocates
memory for protocol headers as well as for the actual data.
15.2.4 netbuf free()
Synopsis
int netbuf free(struct netbuf *buf)
Description
Deallocates the buffer memory associated with the netbuf buf. If no buffer memory has been
allocated for the netbuf, this function does nothing.
15.2.5 netbuf ref()
Synopsis
int netbuf ref(struct netbuf *buf, void *data, int size)
Description
Associates the external memory pointer to by the data pointer with the netbuf buf. The size of the
external memory is given by size. Any memory previously allocated to the netbuf is deallocated.
The difference between allocating memory for the netbuf with netbuf_alloc() and allocating
memory using, e.g., malloc() and referencing it with netbuf_ref() is that in the former case,
space for protocol headers is allocated as well which makes processing and sending the buffer
faster.
Example
This example shows a simple use of the netbuf_ref() function.
int
main()
{
struct netbuf *buf;
char string[] = "A string";
/* create a new netbuf */
buf = netbuf_new();
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