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1 | /* |
2 | * Copyright (c) 1988 Regents of the University of California. | |
3 | * All rights reserved. | |
4 | * | |
5 | * Redistribution and use in source and binary forms are permitted | |
6 | * provided that this notice is preserved and that due credit is given | |
7 | * to the University of California at Berkeley. The name of the University | |
8 | * may not be used to endorse or promote products derived from this | |
9 | * software without specific prior written permission. This software | |
10 | * is provided ``as is'' without express or implied warranty. | |
11 | */ | |
12 | ||
13 | #ifndef lint | |
14 | static char sccsid[] = "@(#)ring.c 1.8 (Berkeley) %G%"; | |
15 | #endif /* not lint */ | |
16 | ||
cde671b6 | 17 | /* |
8b6750f5 | 18 | * This defines a structure for a ring buffer. |
cde671b6 | 19 | * |
8b6750f5 | 20 | * The circular buffer has two parts: |
cde671b6 | 21 | *((( |
8b6750f5 GM |
22 | * full: [consume, supply) |
23 | * empty: [supply, consume) | |
cde671b6 GM |
24 | *]]] |
25 | * | |
cde671b6 GM |
26 | */ |
27 | ||
28 | #include <stdio.h> | |
29 | #include <errno.h> | |
30 | ||
31 | #ifdef size_t | |
32 | #undef size_t | |
33 | #endif | |
34 | ||
35 | #include <sys/types.h> | |
36 | #include <sys/ioctl.h> | |
37 | #include <sys/socket.h> | |
38 | ||
39 | #include "ring.h" | |
40 | #include "general.h" | |
41 | ||
42 | /* Internal macros */ | |
43 | ||
115a5494 GM |
44 | #if !defined(MIN) |
45 | #define MIN(a,b) (((a)<(b))? (a):(b)) | |
46 | #endif /* !defined(MIN) */ | |
cde671b6 | 47 | |
115a5494 GM |
48 | #define ring_subtract(d,a,b) ((((int)(a))-((int)(b)) >= 0)? \ |
49 | (a)-(b): (((a)-(b))+(d)->size)) | |
cde671b6 GM |
50 | |
51 | #define ring_increment(d,a,c) (((a)+(c) < (d)->top)? \ | |
52 | (a)+(c) : (((a)+(c))-(d)->size)) | |
53 | ||
218b1a4c GM |
54 | #define ring_decrement(d,a,c) (((a)-(c) >= (d)->bottom)? \ |
55 | (a)-(c) : (((a)-(c))-(d)->size)) | |
56 | ||
cde671b6 GM |
57 | |
58 | /* | |
59 | * The following is a clock, used to determine full, empty, etc. | |
60 | * | |
61 | * There is some trickiness here. Since the ring buffers are initialized | |
62 | * to ZERO on allocation, we need to make sure, when interpreting the | |
8b6750f5 | 63 | * clock, that when the times are EQUAL, then the buffer is FULL. |
cde671b6 GM |
64 | */ |
65 | static u_long ring_clock = 0; | |
66 | ||
67 | ||
8b6750f5 GM |
68 | #define ring_empty(d) (((d)->consume == (d)->supply) && \ |
69 | ((d)->consumetime >= (d)->supplytime)) | |
70 | #define ring_full(d) (((d)->supply == (d)->consume) && \ | |
71 | ((d)->supplytime > (d)->consumetime)) | |
cde671b6 GM |
72 | |
73 | ||
74 | ||
75 | ||
76 | ||
77 | /* Buffer state transition routines */ | |
78 | ||
115a5494 GM |
79 | ring_init(ring, buffer, count) |
80 | Ring *ring; | |
81 | char *buffer; | |
82 | int count; | |
83 | { | |
84 | memset((char *)ring, 0, sizeof *ring); | |
85 | ||
86 | ring->size = count; | |
87 | ||
8b6750f5 | 88 | ring->supply = ring->consume = ring->bottom = buffer; |
115a5494 GM |
89 | |
90 | ring->top = ring->bottom+ring->size; | |
91 | ||
92 | return 1; | |
93 | } | |
cde671b6 | 94 | |
218b1a4c GM |
95 | /* Mark routines */ |
96 | ||
97 | /* | |
98 | * Mark the most recently supplied byte. | |
99 | */ | |
100 | ||
101 | void | |
102 | ring_mark(ring) | |
103 | Ring *ring; | |
104 | { | |
105 | ring->mark = ring_decrement(ring, ring->supply, 1); | |
106 | } | |
107 | ||
108 | /* | |
109 | * Is the ring pointing to the mark? | |
110 | */ | |
111 | ||
112 | int | |
113 | ring_at_mark(ring) | |
114 | Ring *ring; | |
115 | { | |
116 | if (ring->mark == ring->consume) { | |
117 | return 1; | |
118 | } else { | |
119 | return 0; | |
120 | } | |
121 | } | |
122 | ||
123 | /* | |
124 | * Clear any mark set on the ring. | |
125 | */ | |
126 | ||
127 | void | |
128 | ring_clear_mark(ring) | |
129 | Ring *ring; | |
130 | { | |
131 | ring->mark = 0; | |
132 | } | |
133 | ||
cde671b6 GM |
134 | /* |
135 | * Add characters from current segment to ring buffer. | |
136 | */ | |
137 | void | |
8b6750f5 | 138 | ring_supplied(ring, count) |
cde671b6 GM |
139 | Ring *ring; |
140 | int count; | |
141 | { | |
8b6750f5 GM |
142 | ring->supply = ring_increment(ring, ring->supply, count); |
143 | ring->supplytime = ++ring_clock; | |
cde671b6 GM |
144 | } |
145 | ||
146 | /* | |
8b6750f5 | 147 | * We have just consumed "c" bytes. |
cde671b6 GM |
148 | */ |
149 | void | |
8b6750f5 | 150 | ring_consumed(ring, count) |
cde671b6 GM |
151 | Ring *ring; |
152 | int count; | |
153 | { | |
ad1c581e GM |
154 | if (count == 0) /* don't update anything */ |
155 | return; | |
156 | ||
218b1a4c GM |
157 | if (ring->mark && |
158 | (ring_subtract(ring, ring->mark, ring->consume) < count)) { | |
159 | ring->mark = 0; | |
160 | } | |
8b6750f5 GM |
161 | ring->consume = ring_increment(ring, ring->consume, count); |
162 | ring->consumetime = ++ring_clock; | |
8166d918 GM |
163 | /* |
164 | * Try to encourage "ring_empty_consecutive()" to be large. | |
165 | */ | |
166 | if (ring_empty(ring)) { | |
167 | ring->consume = ring->supply = ring->bottom; | |
168 | } | |
cde671b6 GM |
169 | } |
170 | ||
e8507c1e | 171 | |
cde671b6 GM |
172 | |
173 | /* Buffer state query routines */ | |
174 | ||
175 | ||
8b6750f5 | 176 | /* Number of bytes that may be supplied */ |
cde671b6 GM |
177 | int |
178 | ring_empty_count(ring) | |
179 | Ring *ring; | |
180 | { | |
8b6750f5 | 181 | if (ring_empty(ring)) { /* if empty */ |
cde671b6 GM |
182 | return ring->size; |
183 | } else { | |
8b6750f5 | 184 | return ring_subtract(ring, ring->consume, ring->supply); |
cde671b6 GM |
185 | } |
186 | } | |
187 | ||
8b6750f5 | 188 | /* number of CONSECUTIVE bytes that may be supplied */ |
cde671b6 GM |
189 | int |
190 | ring_empty_consecutive(ring) | |
191 | Ring *ring; | |
192 | { | |
8b6750f5 GM |
193 | if ((ring->consume < ring->supply) || ring_empty(ring)) { |
194 | /* | |
195 | * if consume is "below" supply, or empty, then | |
196 | * return distance to the top | |
197 | */ | |
198 | return ring_subtract(ring, ring->top, ring->supply); | |
cde671b6 GM |
199 | } else { |
200 | /* | |
201 | * else, return what we may. | |
202 | */ | |
8b6750f5 | 203 | return ring_subtract(ring, ring->consume, ring->supply); |
cde671b6 GM |
204 | } |
205 | } | |
206 | ||
218b1a4c GM |
207 | /* Return the number of bytes that are available for consuming |
208 | * (but don't give more than enough to get to cross over set mark) | |
209 | */ | |
210 | ||
cde671b6 | 211 | int |
8b6750f5 | 212 | ring_full_count(ring) |
cde671b6 GM |
213 | Ring *ring; |
214 | { | |
218b1a4c GM |
215 | if ((ring->mark == 0) || (ring->mark == ring->consume)) { |
216 | if (ring_full(ring)) { | |
217 | return ring->size; /* nothing consumed, but full */ | |
218 | } else { | |
219 | return ring_subtract(ring, ring->supply, ring->consume); | |
220 | } | |
cde671b6 | 221 | } else { |
218b1a4c | 222 | return ring_subtract(ring, ring->mark, ring->consume); |
cde671b6 GM |
223 | } |
224 | } | |
225 | ||
218b1a4c GM |
226 | /* |
227 | * Return the number of CONSECUTIVE bytes available for consuming. | |
228 | * However, don't return more than enough to cross over set mark. | |
229 | */ | |
cde671b6 | 230 | int |
8b6750f5 | 231 | ring_full_consecutive(ring) |
cde671b6 GM |
232 | Ring *ring; |
233 | { | |
218b1a4c GM |
234 | if ((ring->mark == 0) || (ring->mark == ring->consume)) { |
235 | if ((ring->supply < ring->consume) || ring_full(ring)) { | |
236 | return ring_subtract(ring, ring->top, ring->consume); | |
237 | } else { | |
238 | return ring_subtract(ring, ring->supply, ring->consume); | |
239 | } | |
cde671b6 | 240 | } else { |
218b1a4c GM |
241 | if (ring->mark < ring->consume) { |
242 | return ring_subtract(ring, ring->top, ring->consume); | |
243 | } else { /* Else, distance to mark */ | |
244 | return ring_subtract(ring, ring->mark, ring->consume); | |
245 | } | |
cde671b6 GM |
246 | } |
247 | } | |
248 | ||
cde671b6 | 249 | /* |
8b6750f5 | 250 | * Move data into the "supply" portion of of the ring buffer. |
cde671b6 GM |
251 | */ |
252 | void | |
8b6750f5 | 253 | ring_supply_data(ring, buffer, count) |
cde671b6 GM |
254 | Ring *ring; |
255 | char *buffer; | |
256 | int count; | |
257 | { | |
258 | int i; | |
259 | ||
260 | while (count) { | |
115a5494 | 261 | i = MIN(count, ring_empty_consecutive(ring)); |
8b6750f5 GM |
262 | memcpy(ring->supply, buffer, i); |
263 | ring_supplied(ring, i); | |
cde671b6 GM |
264 | count -= i; |
265 | buffer += i; | |
266 | } | |
267 | } | |
268 | ||
269 | ||
270 | /* | |
8b6750f5 | 271 | * Move data from the "consume" portion of the ring buffer |
cde671b6 GM |
272 | */ |
273 | void | |
8b6750f5 | 274 | ring_consume_data(ring, buffer, count) |
cde671b6 GM |
275 | Ring *ring; |
276 | char *buffer; | |
277 | int count; | |
278 | { | |
279 | int i; | |
280 | ||
281 | while (count) { | |
8b6750f5 GM |
282 | i = MIN(count, ring_full_consecutive(ring)); |
283 | memcpy(buffer, ring->consume, i); | |
284 | ring_consumed(ring, i); | |
cde671b6 GM |
285 | count -= i; |
286 | buffer += i; | |
287 | } | |
288 | } |