Add util.ringbuffer, a ringbuffer with a file handle like interface

2 files changed, 234 insertions, 2 deletions

diff --git a/util-src/Makefile b/util-src/Makefile
index 5f35b81b..85b190b9 100644
--- a/util-src/Makefile
+++ b/util-src/Makefile
@@ -1,12 +1,12 @@
 
 include ../config.unix
 
-CFLAGS+=-ggdb -I$(LUA_INCDIR)
+CFLAGS+=-ggdb -Wall -pedantic -I$(LUA_INCDIR)
 
 INSTALL_DATA=install -m644
 TARGET?=../util/
 
-ALL=encodings.so hashes.so net.so pposix.so signal.so table.so
+ALL=encodings.so hashes.so net.so pposix.so signal.so table.so ringbuffer.so
 
 .PHONY: all install clean
 .SUFFIXES: .c .o .so
diff --git a/util-src/ringbuffer.c b/util-src/ringbuffer.c
new file mode 100644
index 00000000..f5fa136b
--- /dev/null
+++ b/util-src/ringbuffer.c
@@ -0,0 +1,232 @@
+
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdio.h>
+
+#include <lua.h>
+#include <lauxlib.h>
+
+#define MIN(a, b) ((a)>(b)?(b):(a))
+#define MAX(a, b) ((a)>(b)?(a):(b))
+
+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, int l) {
+	size_t i, j;
+	int m;
+
+	if(b->rpos == b->wpos) { /* empty */
+		return 0;
+	}
+
+	for(i = 0; i <= b->blen - l; i++) {
+		if(b->buffer[(b->rpos + i) % b->alen] == *s) {
+			m = 1;
+
+			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;
+}
+
+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;
+}
+
+
+int rb_read(lua_State* L) {
+	ringbuffer* b = luaL_checkudata(L, 1, "ringbuffer_mt");
+	int 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) {
+		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;
+}
+
+
+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;
+}
+
+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->%p %d/%d", b, b->buffer, 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));
+	b->rpos = 0;
+	b->wpos = 0;
+	b->alen = size;
+	b->blen = 0;
+	b->buffer = malloc(size);
+
+	if(b->buffer == NULL) {
+		return 0;
+	}
+
+	luaL_getmetatable(L, "ringbuffer_mt");
+	lua_setmetatable(L, -2);
+
+	return 1;
+}
+
+int rb_gc(lua_State* L) {
+	ringbuffer* b = luaL_checkudata(L, 1, "ringbuffer_mt");
+
+	if(b->buffer != NULL) {
+		free(b->buffer);
+	}
+
+	return 0;
+}
+
+int luaopen_util_ringbuffer(lua_State* L) {
+	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_pushcfunction(L, rb_gc);
+		lua_setfield(L, -2, "__gc");
+
+		lua_newtable(L); /* __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_newtable(L);
+	lua_pushcfunction(L, rb_new);
+	lua_setfield(L, -2, "new");
+	return 1;
+}