aboutsummaryrefslogtreecommitdiffstats
path: root/util-src/ringbuffer.c
blob: 233b9058e0958e2ddb1a1e50fb17dba418159cb1 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233

#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>

#include <lua.h>
#include <lauxlib.h>

typedef struct {
	size_t rpos; /* read position */
	size_t wpos; /* write position */
	size_t alen; /* allocated size */
	size_t blen; /* current content size */
	char buffer[];
} ringbuffer;

char readchar(ringbuffer *b) {
	b->blen--;
	return b->buffer[(b->rpos++) % b->alen];
}

void writechar(ringbuffer *b, char c) {
	b->blen++;
	b->buffer[(b->wpos++) % b->alen] = c;
}

/* make sure position counters stay within the allocation */
void modpos(ringbuffer *b) {
	b->rpos = b->rpos % b->alen;
	b->wpos = b->wpos % b->alen;
}

int find(ringbuffer *b, const char *s, size_t l) {
	size_t i, j;
	int m;

	if(b->rpos == b->wpos) { /* empty */
		return 0;
	}

	/* look for a matching first byte */
	for(i = 0; i <= b->blen - l; i++) {
		if(b->buffer[(b->rpos + i) % b->alen] == *s) {
			m = 1;

			/* check if the following byte also match */
			for(j = 1; j < l; j++)
				if(b->buffer[(b->rpos + i + j) % b->alen] != s[j]) {
					m = 0;
					break;
				}

			if(m) {
				return i + l;
			}
		}
	}

	return 0;
}

/*
 * Find first position of a substring in buffer
 * (buffer, string) -> number
 */
int rb_find(lua_State *L) {
	size_t l, m;
	ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
	const char *s = luaL_checklstring(L, 2, &l);
	m = find(b, s, l);

	if(m > 0) {
		lua_pushinteger(L, m);
		return 1;
	}

	return 0;
}

/*
 * Read bytes from buffer
 * (buffer, number, boolean?) -> string
 */
int rb_read(lua_State *L) {
	ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
	size_t r = luaL_checkinteger(L, 2);
	int peek = lua_toboolean(L, 3);

	if(r > b->blen) {
		lua_pushnil(L);
		return 1;
	}

	if((b->rpos + r) > b->alen) {
		/* Substring wraps around to the beginning of the buffer */
		lua_pushlstring(L, &b->buffer[b->rpos], b->alen - b->rpos);
		lua_pushlstring(L, b->buffer, r - (b->alen - b->rpos));
		lua_concat(L, 2);
	} else {
		lua_pushlstring(L, &b->buffer[b->rpos], r);
	}

	if(!peek) {
		b->blen -= r;
		b->rpos += r;
		modpos(b);
	}

	return 1;
}

/*
 * Read buffer until first occurence of a substring
 * (buffer, string) -> string
 */
int rb_readuntil(lua_State *L) {
	size_t l, m;
	ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
	const char *s = luaL_checklstring(L, 2, &l);
	m = find(b, s, l);

	if(m > 0) {
		lua_settop(L, 1);
		lua_pushinteger(L, m);
		return rb_read(L);
	}

	return 0;
}

/*
 * Write bytes into the buffer
 * (buffer, string) -> integer
 */
int rb_write(lua_State *L) {
	size_t l, w = 0;
	ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
	const char *s = luaL_checklstring(L, 2, &l);

	/* Does `l` bytes fit? */
	if((l + b->blen) > b->alen) {
		lua_pushnil(L);
		return 1;
	}

	while(l-- > 0) {
		writechar(b, *s++);
		w++;
	}

	modpos(b);

	lua_pushinteger(L, w);

	return 1;
}

int rb_tostring(lua_State *L) {
	ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
	lua_pushfstring(L, "ringbuffer: %p %d/%d", b, b->blen, b->alen);
	return 1;
}

int rb_length(lua_State *L) {
	ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
	lua_pushinteger(L, b->blen);
	return 1;
}

int rb_size(lua_State *L) {
	ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
	lua_pushinteger(L, b->alen);
	return 1;
}

int rb_free(lua_State *L) {
	ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
	lua_pushinteger(L, b->alen - b->blen);
	return 1;
}

int rb_new(lua_State *L) {
	size_t size = luaL_optinteger(L, 1, sysconf(_SC_PAGESIZE));
	ringbuffer *b = lua_newuserdata(L, sizeof(ringbuffer) + size);

	b->rpos = 0;
	b->wpos = 0;
	b->alen = size;
	b->blen = 0;

	luaL_getmetatable(L, "ringbuffer_mt");
	lua_setmetatable(L, -2);

	return 1;
}

int luaopen_util_ringbuffer(lua_State *L) {
#if (LUA_VERSION_NUM > 501)
	luaL_checkversion(L);
#endif

	if(luaL_newmetatable(L, "ringbuffer_mt")) {
		lua_pushcfunction(L, rb_tostring);
		lua_setfield(L, -2, "__tostring");
		lua_pushcfunction(L, rb_length);
		lua_setfield(L, -2, "__len");

		lua_createtable(L, 0, 7); /* __index */
		{
			lua_pushcfunction(L, rb_find);
			lua_setfield(L, -2, "find");
			lua_pushcfunction(L, rb_read);
			lua_setfield(L, -2, "read");
			lua_pushcfunction(L, rb_readuntil);
			lua_setfield(L, -2, "readuntil");
			lua_pushcfunction(L, rb_write);
			lua_setfield(L, -2, "write");
			lua_pushcfunction(L, rb_size);
			lua_setfield(L, -2, "size");
			lua_pushcfunction(L, rb_length);
			lua_setfield(L, -2, "length");
			lua_pushcfunction(L, rb_free);
			lua_setfield(L, -2, "free");
		}
		lua_setfield(L, -2, "__index");
	}

	lua_createtable(L, 0, 1);
	lua_pushcfunction(L, rb_new);
	lua_setfield(L, -2, "new");
	return 1;
}