ISC DHCP  4.4.3
A reference DHCPv4 and DHCPv6 implementation
buffer.h
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1 /* buffer.h
2 
3  Definitions for the object management API protocol buffering... */
4 
5 /*
6  * Copyright (C) 2004-2022 Internet Systems Consortium, Inc. ("ISC")
7  * Copyright (c) 1996-2003 by Internet Software Consortium
8  *
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10  * License, v. 2.0. If a copy of the MPL was not distributed with this
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27  */
28 
29 /* OMAPI buffers are ring buffers, which means that the beginning of the
30  buffer and the end of the buffer chase each other around. As long as
31  the tail never catches up to the head, there's room in the buffer for
32  data.
33 
34  - If the tail and the head are equal, the buffer is empty.
35 
36  - If the tail is less than the head, the contents of the buffer
37  are the bytes from the head to the end of buffer, and in addition,
38  the bytes between the beginning of the buffer and the tail, not
39  including the byte addressed by the tail.
40 
41  - If the tail is greater than the head, then the buffer contains
42  valid bytes starting with the byte addressed by the head, and
43  ending with the byte before the byte addressed by the tail.
44 
45  There will always be at least one byte of waste, because the tail can't
46  increase so that it's equal to the head (that would represent an empty
47  buffer. */
48 #define OMAPI_BUF_SIZE 4048
49 typedef struct _omapi_buffer {
50  struct _omapi_buffer *next; /* Buffers can be chained. */
51  u_int32_t refcnt; /* Buffers are reference counted. */
52  u_int16_t head, tail; /* Buffers are organized in a ring. */
53  char buf [OMAPI_BUF_SIZE]; /* The actual buffer is included in
54  the buffer data structure. */
56 
57 #define BUFFER_BYTES_FREE(x) \
58  ((x) -> tail > (x) -> head \
59  ? sizeof ((x) -> buf) - ((x) -> tail - (x) -> head) \
60  : (x) -> head - (x) -> tail)
61 
62 #define BYTES_IN_BUFFER(x) \
63  ((x) -> tail > (x) -> head \
64  ? (x) -> tail - (x) -> head - 1 \
65  : sizeof ((x) -> buf) - ((x) -> head - (x) -> tail) - 1)
66 
67 isc_result_t omapi_connection_require (omapi_object_t *, unsigned);
68 isc_result_t omapi_connection_copyout (unsigned char *,
69  omapi_object_t *, unsigned);
71  const unsigned char *, unsigned);
73 isc_result_t omapi_connection_get_uint32 (omapi_object_t *, u_int32_t *);
74 isc_result_t omapi_connection_put_uint32 (omapi_object_t *, u_int32_t);
75 isc_result_t omapi_connection_get_uint16 (omapi_object_t *, u_int16_t *);
76 isc_result_t omapi_connection_put_uint16 (omapi_object_t *, u_int32_t);
isc_result_t omapi_connection_get_uint16(omapi_object_t *, u_int16_t *)
Definition: buffer.c:606
isc_result_t omapi_connection_put_uint32(omapi_object_t *, u_int32_t)
Definition: buffer.c:595
struct _omapi_buffer omapi_buffer_t
isc_result_t omapi_connection_copyout(unsigned char *, omapi_object_t *, unsigned)
Definition: buffer.c:359
isc_result_t omapi_connection_put_uint16(omapi_object_t *, u_int32_t)
Definition: buffer.c:621
isc_result_t omapi_connection_copyin(omapi_object_t *, const unsigned char *, unsigned)
Definition: buffer.c:265
isc_result_t omapi_connection_require(omapi_object_t *, unsigned)
Definition: connection.c:563
isc_result_t omapi_connection_get_uint32(omapi_object_t *, u_int32_t *)
Definition: buffer.c:580
isc_result_t omapi_connection_flush(omapi_object_t *)
#define OMAPI_BUF_SIZE
Definition: buffer.h:48
u_int16_t tail
Definition: buffer.h:52
char buf[OMAPI_BUF_SIZE]
Definition: buffer.h:53
u_int16_t head
Definition: buffer.h:52
struct _omapi_buffer * next
Definition: buffer.h:50
u_int32_t refcnt
Definition: buffer.h:51