VENTI-PACKET(2) VENTI-PACKET(2)
NAME
Packet, packetalloc, packetappend, packetasize, packetcmp,
packetconcat, packetconsume, packetcopy, packetdup,
packetforeign, packetfragments, packetfree, packetheader,
packetpeek, packetprefix, packetsha1, packetsize,
packetsplit, packetstats, packettrailer, packettrim - zero-
copy network buffers
SYNOPSIS
#include <u.h>
#include <libc.h>
#include <venti.h>
Packet* packetalloc(void);
void packetappend(Packet *p, uchar *buf, int n)
uint packetasize(Packet *p)
int packetcmp(Packet *p, Packet *q)
void packetconcat(Packet *p, Packet *q)
int packetconsume(Packet *p, uchar *buf, int n)
int packetcopy(Packet *p, uchar *buf, int offset, int n)
Packet* packetdup(Packet *p, int offset, int n)
Packet* packetforeign(uchar *buf, int n,
void (*free)(void *a), void *a)
int packetfragments(Packet *p, IOchunk *io, int nio,
int offset)
void packetfree(Packet *p)
uchar* packetheader(Packet *p, int n)
uchar* packetpeek(Packet *p, uchar *buf, int offset, int n)
void packetprefix(Packet *p, uchar *buf, int n)
void packetsha1(Packet *p, uchar sha1[20])
uint packetsize(Packet *p)
Packet* packetsplit(Packet *p, int n)
void packetstats(void)
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VENTI-PACKET(2) VENTI-PACKET(2)
uchar* packettrailer(Packet *p, int n)
int packettrim(Packet *p, int offset, int n)
DESCRIPTION
A Packet is a chain of blocks of data. Each block, called a
fragment, is contiguous in memory, but the entire packet may
not be. This representation helps avoid unnecessary memory
copies.
Packetalloc allocates an empty packet.
Packetappend appends the n bytes at buf to the end of p.
Packetasize returns the number of data bytes allocated to p.
This may be larger than the number of bytes stored in p
because fragments may not be filled completely.
Packetcmp compares the data sections of two packets as
memcmp (see memory(2)) would.
Packetconcat removes all data from q, appending it to p.
Packetconsume removes n bytes from the beginning of p, stor-
ing them into buf.
Packetcopy copies n bytes at offset in p to buf.
Packetdup creates a new packet initialized with n bytes from
offset in p.
Packetforeign allocates a packet containing `foreign' data:
the n bytes pointed to by buf. Once the bytes are no longer
needed, they are freed by calling free(a).
Packetfragments initializes up to nio of the io structures
with pointers to the data in p, starting at offset. It
returns the total number of bytes represented by the
returned structures. Packetfragments initializes any unused
io structures with nil pointer and zero length.
Packetfree frees the packet p.
Packetheader returns a pointer to the first n bytes of p,
making them contiguous in memory if necessary.
Packetpeek returns a pointer to the n bytes at offset in p.
If the requested bytes are already stored contiguously in
memory, the returned pointer points at the internal data
storage for p. Otherwise, the bytes are copied into buf, and
packetpeek returns buf.
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VENTI-PACKET(2) VENTI-PACKET(2)
Packetprefix inserts a copy of the n bytes at buf at the
beginning of p.
Packetsha1 computes the SHA1 hash of the data contained in
p.
Packetsize returns the length, in bytes, of the data con-
tained in p.
Packetsplit returns a new packet initialized with n bytes
removed from the beginning of p.
Packetstats prints run-time statistics to standard output.
Packettrailer returns a pointer to the last n bytes of p,
making them contiguous in memory if necessary.
Packettrim deletes all bytes from the packet p except the n
bytes at offset offset.
SOURCE
/sys/src/libventi
SEE ALSO
venti(2)
DIAGNOSTICS
These functions return errors only when passed invalid
inputs, e.g., requests for data at negative offsets or
beyond the end of a packet.
Functions returning pointers return nil on error; functions
returning integers return -1 on error. Most functions
returning integers return 0 on success. The exceptions are
packetfragments and packetcmp, whose return values are
described above.
When these functions run out of memory, they print error
messages and call sysfatal.
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