#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; } /* * Move read position forward without returning the data * (buffer, number) -> boolean */ int rb_discard(lua_State *L) { ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt"); size_t r = luaL_checkinteger(L, 2); if(r > b->blen) { lua_pushboolean(L, 0); return 1; } b->blen -= r; b->rpos += r; modpos(b); lua_pushboolean(L, 1); return 1; } /* * 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 occurrence 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_discard); lua_setfield(L, -2, "discard"); 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; }