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/*
* Lua JSON routines
*
* CAVEATS:
* - JSON "null" handling:
* - Decoding a "null" in an array will leave a "nil" placeholder in Lua, but will not show up at the end of the array.
* - Decoding a "null" in an object will ensure that particular key is deleted in the Lua table.
*/
#include <string.h>
#include <math.h>
#include <lua.h>
#include <lauxlib.h>
#include <json/json.h>
#include "lua_json.h"
#include "utils.h"
#include "str.h"
/* FIXME:
* - Don't just pushnil on error and return?
* - Review all strbuf usage for NULL termination
*/
/* JSON escape a character if required, or return NULL */
static inline char *json_escape_char(int c)
{
switch(c) {
case 0:
return "\\u0000";
case '\\':
return "\\\\";
case '"':
return "\\\"";
case '\b':
return "\\b";
case '\t':
return "\\t";
case '\n':
return "\\n";
case '\f':
return "\\f";
case '\r':
return "\\r";
}
return NULL;
}
/* FIXME:
* - Use lua_checklstring() instead of lua_tolstring() ?*
*/
/* FIXME:
* - Option to encode non-printable characters? Only \" \\ are required
* - Unicode?
* - Improve performance?
*/
static void json_append_string(lua_State *l, struct str *json, int index)
{
char *p;
int i;
const char *str;
size_t len;
str = lua_tolstring(l, index, &len);
strbuf_append_char(json, '\"');
for (i = 0; i < len; i++) {
p = json_escape_char(str[i]);
if (p)
strbuf_append_mem(json, p, strlen(p));
else
strbuf_append_char(json, str[i]);
}
strbuf_append_char(json, '\"');
}
/* Find the size of the array on the top of the Lua stack
* -1 object
* >=0 elements in array
*/
static int lua_array_length(lua_State *l)
{
double k;
int max;
max = 0;
lua_pushnil(l);
/* table, startkey */
while (lua_next(l, -2) != 0) {
/* table, key, value */
if ((k = lua_tonumber(l, -2))) {
/* Integer >= 1 ? */
if (floor(k) == k && k >= 1) {
if (k > max)
max = k;
lua_pop(l, 1);
continue;
}
}
/* Must not be an array (non integer key) */
lua_pop(l, 2);
return -1;
}
return max;
}
static void json_append_data(lua_State *l, struct str *s);
static void json_append_array(lua_State *l, struct str *s, int size)
{
int comma, i;
strbuf_append_mem(s, "[ ", 2);
comma = 0;
for (i = 1; i <= size; i++) {
if (comma)
strbuf_append_mem(s, ", ", 2);
else
comma = 1;
lua_rawgeti(l, -1, i);
json_append_data(l, s);
lua_pop(l, 1);
}
strbuf_append_mem(s, " ]", 2);
}
static void json_append_object(lua_State *l, struct str *s)
{
int comma, keytype;
/* Object */
strbuf_append_mem(s, "{ ", 2);
lua_pushnil(l);
/* table, startkey */
comma = 0;
while (lua_next(l, -2) != 0) {
if (comma)
strbuf_append_mem(s, ", ", 2);
else
comma = 1;
/* table, key, value */
keytype = lua_type(l, -2);
if (keytype == LUA_TNUMBER) {
strbuf_append(s, "\"" LUA_NUMBER_FMT "\": ", lua_tonumber(l, -2));
} else if (keytype == LUA_TSTRING) {
json_append_string(l, s, -2);
strbuf_append_mem(s, ": ", 2);
} else {
die("Cannot serialise table key %s", lua_typename(l, lua_type(l, -2)));
}
/* table, key, value */
json_append_data(l, s);
lua_pop(l, 1);
/* table, key */
}
strbuf_append_mem(s, " }", 2);
}
/* Serialise Lua data into JSON string.
*
* FIXME:
* - Error handling when cannot serialise key or value (return to script)
*/
static void json_append_data(lua_State *l, struct str *s)
{
int len;
switch (lua_type(l, -1)) {
case LUA_TSTRING:
json_append_string(l, s, -1);
break;
case LUA_TNUMBER:
strbuf_append(s, "%lf", lua_tonumber(l, -1));
break;
case LUA_TBOOLEAN:
if (lua_toboolean(l, -1))
strbuf_append_mem(s, "true", 4);
else
strbuf_append_mem(s, "false", 5);
break;
case LUA_TTABLE:
len = lua_array_length(l);
if (len >= 0)
json_append_array(l, s, len);
else
json_append_object(l, s);
break;
case LUA_TNIL:
strbuf_append_mem(s, "null", 4);
break;
default:
/* Remaining types (LUA_TFUNCTION, LUA_TUSERDATA, LUA_TTHREAD, and LUA_TLIGHTUSERDATA)
* cannot be serialised */
/* FIXME: return error */
die("Cannot serialise %s", lua_typename(l, lua_type(l, -1)));
}
}
char *lua_to_json(lua_State *l, int *len)
{
struct str *s;
char *data;
s = strbuf_new();
strbuf_set_increment(s, 256);
json_append_data(l, s);
data = strbuf_to_char(s, len);
return data;
}
int lua_json_encode(lua_State *l)
{
char *json;
int len;
json = lua_to_json(l, &len);
lua_pushlstring(l, json, len);
free(json);
return 1;
}
void lua_json_init(lua_State *l)
{
luaL_Reg reg[] = {
{ "encode", lua_json_encode },
{ "decode", lua_json_decode },
{ NULL, NULL }
};
/* Create "db" table.
* Added functions as table entries
*/
luaL_register(l, "json", reg);
/* FIXME: Debugging */
json_init_lookup_tables();
}
/* vi:ai et sw=4 ts=4:
*/
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