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#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;
static void writechar(ringbuffer *b, char c) {
b->blen++;
b->buffer[(b->wpos++) % b->alen] = c;
}
/* make sure position counters stay within the allocation */
static void modpos(ringbuffer *b) {
b->rpos = b->rpos % b->alen;
b->wpos = b->wpos % b->alen;
}
static 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
*/
static 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
*/
static 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
*/
static 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
*/
static 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
*/
static 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;
}
static 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;
}
static int rb_length(lua_State *L) {
ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
lua_pushinteger(L, b->blen);
return 1;
}
static int rb_size(lua_State *L) {
ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
lua_pushinteger(L, b->alen);
return 1;
}
static int rb_free(lua_State *L) {
ringbuffer *b = luaL_checkudata(L, 1, "ringbuffer_mt");
lua_pushinteger(L, b->alen - b->blen);
return 1;
}
static 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;
}
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