util-src/ringbuffer.c

   1
   2 #include <stdlib.h>
   3 #include <unistd.h>
   4 #include <string.h>
   5 #include <stdio.h>
   6
   7 #include <lua.h>
   8 #include <lauxlib.h>
   9
  10 typedef struct {
  11         size_t rpos; /* read position */
  12         size_t wpos; /* write position */
  13         size_t alen; /* allocated size */
  14         size_t blen; /* current content size */
  15         char buffer[];
  16 } ringbuffer;
  17
  18 char readchar(ringbuffer *b) {
  19         b->blen--;
  20         return b->buffer[(b->rpos++) % b->alen];
  21 }
  22
  23 void writechar(ringbuffer *b, char c) {
  24         b->blen++;
  25         b->buffer[(b->wpos++) % b->alen] = c;
  26 }
  27
  28 /* make sure position counters stay within the allocation */
  29 void modpos(ringbuffer *b) {
  30         b->rpos = b->rpos % b->alen;
  31         b->wpos = b->wpos % b->alen;
  32 }
  33
  34 int find(ringbuffer *b, const char *s, size_t l) {
  35         size_t i, j;
  36         int m;
  37
  38         if(b->rpos == b->wpos) { /* empty */
  39                 return 0;
  40         }
  41
  42         /* look for a matching first byte */
  43         for(i = 0; i <= b->blen - l; i++) {
  44                 if(b->buffer[(b->rpos + i) % b->alen] == *s) {
  45                         m = 1;
  46
  47                         /* check if the following byte also match */
  48                         for(j = 1; j < l; j++)
  49                                 if(b->buffer[(b->rpos + i + j) % b->alen] != s[j]) {
  50                                         m = 0;
  51                                         break;
  52                                 }
  53
  54                         if(m) {
  55                                 return i + l;
  56                         }
  57                 }
  58         }
  59
  60         return 0;
  61 }
  62
  63 /*
  64  * Find first position of a substring in buffer
  65  * (buffer, string) -> number
  66  */
  67 int rb_find(lua_State *L) {
  68         size_t l, m;
  69         ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
  70         const char *s = luaL_checklstring(L, 2, &l);
  71         m = find(b, s, l);
  72
  73         if(m > 0) {
  74                 lua_pushinteger(L, m);
  75                 return 1;
  76         }
  77
  78         return 0;
  79 }
  80
  81 /*
  82  * Move read position forward without returning the data
  83  * (buffer, number) -> boolean
  84  */
  85 int rb_discard(lua_State *L) {
  86         ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
  87         size_t r = luaL_checkinteger(L, 2);
  88
  89         if(r > b->blen) {
  90                 lua_pushboolean(L, 0);
  91                 return 1;
  92         }
  93
  94         b->blen -= r;
  95         b->rpos += r;
  96         modpos(b);
  97
  98         lua_pushboolean(L, 1);
  99         return 1;
 100 }
 101
 102 /*
 103  * Read bytes from buffer
 104  * (buffer, number, boolean?) -> string
 105  */
 106 int rb_read(lua_State *L) {
 107         ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
 108         size_t r = luaL_checkinteger(L, 2);
 109         int peek = lua_toboolean(L, 3);
 110
 111         if(r > b->blen) {
 112                 lua_pushnil(L);
 113                 return 1;
 114         }
 115
 116         if((b->rpos + r) > b->alen) {
 117                 /* Substring wraps around to the beginning of the buffer */
 118                 lua_pushlstring(L, &b->buffer[b->rpos], b->alen - b->rpos);
 119                 lua_pushlstring(L, b->buffer, r - (b->alen - b->rpos));
 120                 lua_concat(L, 2);
 121         } else {
 122                 lua_pushlstring(L, &b->buffer[b->rpos], r);
 123         }
 124
 125         if(!peek) {
 126                 b->blen -= r;
 127                 b->rpos += r;
 128                 modpos(b);
 129         }
 130
 131         return 1;
 132 }
 133
 134 /*
 135  * Read buffer until first occurrence of a substring
 136  * (buffer, string) -> string
 137  */
 138 int rb_readuntil(lua_State *L) {
 139         size_t l, m;
 140         ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
 141         const char *s = luaL_checklstring(L, 2, &l);
 142         m = find(b, s, l);
 143
 144         if(m > 0) {
 145                 lua_settop(L, 1);
 146                 lua_pushinteger(L, m);
 147                 return rb_read(L);
 148         }
 149
 150         return 0;
 151 }
 152
 153 /*
 154  * Write bytes into the buffer
 155  * (buffer, string) -> integer
 156  */
 157 int rb_write(lua_State *L) {
 158         size_t l, w = 0;
 159         ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
 160         const char *s = luaL_checklstring(L, 2, &l);
 161
 162         /* Does `l` bytes fit? */
 163         if((l + b->blen) > b->alen) {
 164                 lua_pushnil(L);
 165                 return 1;
 166         }
 167
 168         while(l-- > 0) {
 169                 writechar(b, *s++);
 170                 w++;
 171         }
 172
 173         modpos(b);
 174
 175         lua_pushinteger(L, w);
 176
 177         return 1;
 178 }
 179
 180 int rb_tostring(lua_State *L) {
 181         ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
 182         lua_pushfstring(L, "ringbuffer: %p %d/%d", b, b->blen, b->alen);
 183         return 1;
 184 }
 185
 186 int rb_length(lua_State *L) {
 187         ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
 188         lua_pushinteger(L, b->blen);
 189         return 1;
 190 }
 191
 192 int rb_size(lua_State *L) {
 193         ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
 194         lua_pushinteger(L, b->alen);
 195         return 1;
 196 }
 197
 198 int rb_free(lua_State *L) {
 199         ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
 200         lua_pushinteger(L, b->alen - b->blen);
 201         return 1;
 202 }
 203
 204 int rb_new(lua_State *L) {
 205         size_t size = luaL_optinteger(L, 1, sysconf(_SC_PAGESIZE));
 206         ringbuffer *b = lua_newuserdata(L, sizeof(ringbuffer) + size);
 207
 208         b->rpos = 0;
 209         b->wpos = 0;
 210         b->alen = size;
 211         b->blen = 0;
 212
 213         luaL_getmetatable(L, "ringbuffer_mt");
 214         lua_setmetatable(L, -2);
 215
 216         return 1;
 217 }
 218
 219 int luaopen_util_ringbuffer(lua_State *L) {
 220 #if (LUA_VERSION_NUM > 501)
 221         luaL_checkversion(L);
 222 #endif
 223
 224         if(luaL_newmetatable(L, "ringbuffer_mt")) {
 225                 lua_pushcfunction(L, rb_tostring);
 226                 lua_setfield(L, -2, "__tostring");
 227                 lua_pushcfunction(L, rb_length);
 228                 lua_setfield(L, -2, "__len");
 229
 230                 lua_createtable(L, 0, 7); /* __index */
 231                 {
 232                         lua_pushcfunction(L, rb_find);
 233                         lua_setfield(L, -2, "find");
 234                         lua_pushcfunction(L, rb_discard);
 235                         lua_setfield(L, -2, "discard");
 236                         lua_pushcfunction(L, rb_read);
 237                         lua_setfield(L, -2, "read");
 238                         lua_pushcfunction(L, rb_readuntil);
 239                         lua_setfield(L, -2, "readuntil");
 240                         lua_pushcfunction(L, rb_write);
 241                         lua_setfield(L, -2, "write");
 242                         lua_pushcfunction(L, rb_size);
 243                         lua_setfield(L, -2, "size");
 244                         lua_pushcfunction(L, rb_length);
 245                         lua_setfield(L, -2, "length");
 246                         lua_pushcfunction(L, rb_free);
 247                         lua_setfield(L, -2, "free");
 248                 }
 249                 lua_setfield(L, -2, "__index");
 250         }
 251
 252         lua_createtable(L, 0, 1);
 253         lua_pushcfunction(L, rb_new);
 254         lua_setfield(L, -2, "new");
 255         return 1;
 256 }