jbe@121: #include <lua.h>
jbe@121: #include <lauxlib.h>
jbe@122: #include <stdlib.h>
jbe@121: #include <string.h>
jbe@121: 
jbe@144: // maximum number of nested JSON values (objects and arrays):
jbe@142: #define JSON_MAXDEPTH 100
jbe@142: 
jbe@144: // macros for usage of Lua registry:
jbe@144: #define JSON_REGENT char
jbe@145: #define JSON_REGPOINTER void *
jbe@145: #define json_pushlightref(L, x) (lua_pushlightuserdata((L), &json_reference.x))
jbe@145: #define json_regpointer(x) (&json_registry.x)
jbe@145: #define json_regfetchpointer(L, x) (lua_pushlightuserdata((L), (x)), lua_rawget((L), LUA_REGISTRYINDEX))
jbe@145: #define json_regfetch(L, x) (json_regfetchpointer(L, json_regpointer(x)))
jbe@145: #define json_regstore(L, x) (lua_pushlightuserdata(L, json_regpointer(x)), lua_pushvalue(L, -2), lua_rawset(L, LUA_REGISTRYINDEX));
jbe@145: 
jbe@146: // generate dummy memory addresses that represent non-modifiable lightuserdata (dummy) objects:
jbe@145: static struct {
jbe@146:   JSON_REGENT nullmark;  // magic value to indicate JSON null value in shadow table
jbe@145: } json_reference;
jbe@145: 
jbe@138: 
jbe@144: // generate dummy memory addresses that represent Lua objects
jbe@145: // via lightuserdata keys and LUA_REGISTRYINDEX:
jbe@144: static struct {
jbe@145:   JSON_REGENT shadowtbl;  // ephemeron table that maps tables to their corresponding shadow table
jbe@145:   JSON_REGENT unknownmt;  // metatable for tables that may be either JSON objects or JSON arrays
jbe@145:   JSON_REGENT objectmt;   // metatable for JSON objects
jbe@145:   JSON_REGENT arraymt;    // metatable for JSON arrays
jbe@144: } json_registry;
jbe@138: 
jbe@145: // marks a Lua table as JSON object or JSON array:
jbe@136: // (returns its modified argument or a new table if argument is nil)
jbe@145: static int json_mark(lua_State *L, JSON_REGPOINTER mt) {
jbe@145:   // check if argument is nil
jbe@136:   if (lua_isnoneornil(L, 1)) {
jbe@145:     // create new table at stack position 1:
jbe@136:     lua_settop(L, 0);
jbe@136:     lua_newtable(L);
jbe@145:     // create shadow table (leaving previously created table on stack position 1):
jbe@144:     json_regfetch(L, shadowtbl);
jbe@136:     lua_pushvalue(L, 1);
jbe@136:     lua_newtable(L);
jbe@143:     lua_rawset(L, -3);
jbe@143:   } else {
jbe@145:     // push shadow table on top of stack:
jbe@144:     json_regfetch(L, shadowtbl);
jbe@143:     lua_pushvalue(L, 1);
jbe@143:     lua_rawget(L, -2);
jbe@145:     // if shadow table does not exist:
jbe@143:     if (lua_isnil(L, -1)) {
jbe@145:       // create shadow table and leave it on top of stack:
jbe@143:       lua_newtable(L);
jbe@143:       lua_pushvalue(L, 1);
jbe@143:       lua_pushvalue(L, -2);
jbe@143:       lua_rawset(L, -5);
jbe@143:     }
jbe@145:     // move elements from original table to shadow table (that's expected on top of stack):
jbe@143:     for(lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
jbe@143:       lua_pushvalue(L, -2);
jbe@143:       lua_pushnil(L);
jbe@143:       lua_rawset(L, 1);
jbe@143:       lua_pushvalue(L, -2);
jbe@143:       lua_pushvalue(L, -2);
jbe@143:       lua_rawset(L, -5);
jbe@143:     }
jbe@136:   }
jbe@138:   // discard everything but table to return:
jbe@138:   lua_settop(L, 1);
jbe@136:   // set metatable:
jbe@145:   json_regfetchpointer(L, mt);
jbe@136:   lua_setmetatable(L, 1);
jbe@138:   // return table:
jbe@136:   return 1;
jbe@136: }
jbe@136: 
jbe@136: // marks a table as JSON object:
jbe@136: // (returns its modified argument or a new table if argument is nil)
jbe@136: static int json_object(lua_State *L) {
jbe@145:   return json_mark(L, json_regpointer(objectmt));
jbe@136: }
jbe@136: 
jbe@136: // marks a table as JSON array:
jbe@136: // (returns its modified argument or a new table if argument is nil)
jbe@136: static int json_array(lua_State *L) {
jbe@145:   return json_mark(L, json_regpointer(arraymt));
jbe@136: }
jbe@136: 
jbe@145: // internal states of JSON parser:
jbe@124: #define JSON_STATE_VALUE 0
jbe@124: #define JSON_STATE_OBJECT_KEY 1
jbe@124: #define JSON_STATE_OBJECT_KEY_TERMINATOR 2
jbe@124: #define JSON_STATE_OBJECT_VALUE 3
jbe@124: #define JSON_STATE_OBJECT_SEPARATOR 4
jbe@124: #define JSON_STATE_ARRAY_VALUE 5
jbe@124: #define JSON_STATE_ARRAY_SEPARATOR 6
jbe@124: #define JSON_STATE_END 7
jbe@121: 
jbe@145: // special Lua stack indicies for json_import function:
jbe@138: #define json_import_objectmt_idx 2
jbe@138: #define json_import_arraymt_idx 3
jbe@138: #define json_import_shadowtbl_idx 4
jbe@138: #define json_import_nullmark_idx 5
jbe@138: 
jbe@136: // decodes a JSON document:
jbe@121: static int json_import(lua_State *L) {
jbe@136:   const char *str;   // string to parse
jbe@136:   size_t total;      // total length of string to parse
jbe@136:   size_t pos = 0;    // current position in string to parse
jbe@136:   size_t level = 0;  // nested levels of objects/arrays currently being processed
jbe@145:   int mode = JSON_STATE_VALUE;  // state of parser (i.e. "what's expected next?")
jbe@136:   char c;              // variable to store a single character to be processed
jbe@145:   luaL_Buffer luabuf;  // Lua buffer to decode JSON string values
jbe@145:   char *cbuf;          // C buffer to decode JSON string values
jbe@136:   size_t writepos;     // write position of decoded strings in C buffer
jbe@145:   // stack shall only contain one function argument:
jbe@138:   lua_settop(L, 1);
jbe@145:   // push objectmt on stack position 2:
jbe@144:   json_regfetch(L, objectmt);
jbe@145:   // push arraymt on stack position 3:
jbe@144:   json_regfetch(L, arraymt);
jbe@145:   // push shadowtbl on stack position 4:
jbe@144:   json_regfetch(L, shadowtbl);
jbe@145:   // push nullmark on stack position 5:
jbe@145:   json_pushlightref(L, nullmark);
jbe@136:   // require string as first argument:
jbe@136:   str = luaL_checklstring(L, 1, &total);
jbe@136:   // if string contains a NULL byte, this is a syntax error
jbe@136:   if (strlen(str) != total) goto json_import_syntax_error;
jbe@136:   // main loop of parser:
jbe@136:   json_import_loop:
jbe@136:   // skip whitespace and store next character in variable 'c':
jbe@146:   while (c = str[pos],
jbe@146:     c == ' ' ||
jbe@146:     c == '\f' ||
jbe@146:     c == '\n' ||
jbe@146:     c == '\r' ||
jbe@146:     c == '\t' ||
jbe@146:     c == '\v'
jbe@146:   ) pos++;
jbe@136:   // switch statement to handle certain (single) characters:
jbe@121:   switch (c) {
jbe@136:   // handle end of JSON document:
jbe@121:   case 0:
jbe@136:     // if end of JSON document was expected, then return top element of stack as result:
jbe@124:     if (mode == JSON_STATE_END) return 1;
jbe@136:     // otherwise, the JSON document was malformed:
jbe@121:     json_import_unexpected_eof:
jbe@121:     lua_pushnil(L);
jbe@121:     if (level == 0) lua_pushliteral(L, "Empty string");
jbe@121:     else lua_pushliteral(L, "Unexpected end of JSON document");
jbe@121:     return 2;
jbe@136:   // new JSON object:
jbe@121:   case '{':
jbe@136:     // if a JSON object is not expected here, then return an error:
jbe@146:     if (
jbe@146:       mode != JSON_STATE_VALUE &&
jbe@146:       mode != JSON_STATE_OBJECT_VALUE &&
jbe@146:       mode != JSON_STATE_ARRAY_VALUE
jbe@146:     ) goto json_import_syntax_error;
jbe@136:     // create JSON object on stack:
jbe@136:     lua_newtable(L);
jbe@136:     // set metatable of JSON object:
jbe@138:     lua_pushvalue(L, json_import_objectmt_idx);
jbe@125:     lua_setmetatable(L, -2);
jbe@136:     // create internal shadow table on stack:
jbe@136:     lua_newtable(L);
jbe@146:     // register internal shadow table:
jbe@123:     lua_pushvalue(L, -2);
jbe@123:     lua_pushvalue(L, -2);
jbe@138:     lua_rawset(L, json_import_shadowtbl_idx);
jbe@146:     // expect object key (or end of object) to follow:
jbe@136:     mode = JSON_STATE_OBJECT_KEY;
jbe@146:     // jump to common code for opening JSON object and JSON array:
jbe@142:     goto json_import_open;
jbe@136:   // new JSON array:
jbe@121:   case '[':
jbe@136:     // if a JSON array is not expected here, then return an error:
jbe@146:     if (
jbe@146:       mode != JSON_STATE_VALUE &&
jbe@146:       mode != JSON_STATE_OBJECT_VALUE &&
jbe@146:       mode != JSON_STATE_ARRAY_VALUE
jbe@146:     ) goto json_import_syntax_error;
jbe@136:     // create JSON array on stack:
jbe@136:     lua_newtable(L);
jbe@136:     // set metatable of JSON array:
jbe@138:     lua_pushvalue(L, json_import_arraymt_idx);
jbe@125:     lua_setmetatable(L, -2);
jbe@136:     // create internal shadow table on stack:
jbe@136:     lua_newtable(L);
jbe@146:     // register internal shadow table:
jbe@123:     lua_pushvalue(L, -2);
jbe@123:     lua_pushvalue(L, -2);
jbe@138:     lua_rawset(L, json_import_shadowtbl_idx);
jbe@140:     // add nil as key (needed to keep stack balance) and as magic to detect arrays:
jbe@140:     lua_pushnil(L);
jbe@146:     // expect array value (or end of array) to follow:
jbe@142:     mode = JSON_STATE_ARRAY_VALUE;
jbe@142:     // continue with common code for opening JSON object and JSON array:
jbe@146:   // common code for opening JSON object or JSON array:
jbe@142:   json_import_open:
jbe@142:     // limit nested levels:
jbe@142:     if (level >= JSON_MAXDEPTH) {
jbe@142:       lua_pushnil(L);
jbe@142:       lua_pushliteral(L, "Too many nested JSON levels");
jbe@142:       return 2;
jbe@142:     }
jbe@142:     // additional buffer overflow protection:
jbe@142:     if (!lua_checkstack(L, LUA_MINSTACK))
jbe@142:       return luaL_error(L, "Caught stack overflow in JSON import function (too many nested levels and stack size too small)");
jbe@136:     // increment level:
jbe@121:     level++;
jbe@142:     // consume input character:
jbe@142:     pos++;
jbe@121:     goto json_import_loop;
jbe@136:   // end of JSON object:
jbe@121:   case '}':
jbe@136:     // if end of JSON object is not expected here, then return an error:
jbe@146:     if (
jbe@146:       mode != JSON_STATE_OBJECT_KEY &&
jbe@146:       mode != JSON_STATE_OBJECT_SEPARATOR
jbe@146:     ) goto json_import_syntax_error;
jbe@136:     // jump to common code for end of JSON object and JSON array:
jbe@121:     goto json_import_close;
jbe@136:   // end of JSON array:
jbe@121:   case ']':
jbe@136:     // if end of JSON array is not expected here, then return an error:
jbe@146:     if (
jbe@146:       mode != JSON_STATE_ARRAY_VALUE &&
jbe@146:       mode != JSON_STATE_ARRAY_SEPARATOR
jbe@146:     ) goto json_import_syntax_error;
jbe@146:     // pop nil key/magic (that was needed to keep stack balance):
jbe@140:     lua_pop(L, 1);
jbe@136:     // continue with common code for end of JSON object and JSON array:
jbe@136:   // common code for end of JSON object or JSON array:
jbe@121:   json_import_close:
jbe@136:     // consume input character:
jbe@121:     pos++;
jbe@136:     // pop shadow table:
jbe@136:     lua_pop(L, 1);
jbe@136:     // check if nested:
jbe@121:     if (--level) {
jbe@146:       // if nested,
jbe@146:       // check if outer(!) structure is an array or object:
jbe@140:       if (lua_isnil(L, -2)) {
jbe@136:         // select array value processing:
jbe@124:         mode = JSON_STATE_ARRAY_VALUE;
jbe@121:       } else {
jbe@136:         // select object value processing:
jbe@124:         mode = JSON_STATE_OBJECT_VALUE;
jbe@121:       }
jbe@136:       // store value in outer structure:
jbe@121:       goto json_import_process_value;
jbe@121:     }
jbe@136:     // if not nested, then expect end of JSON document and continue with loop:
jbe@136:     mode = JSON_STATE_END;
jbe@121:     goto json_import_loop;
jbe@136:   // key terminator:
jbe@121:   case ':':
jbe@136:     // if key terminator is not expected here, then return an error:
jbe@124:     if (mode != JSON_STATE_OBJECT_KEY_TERMINATOR)
jbe@121:       goto json_import_syntax_error;
jbe@136:     // consume input character:
jbe@121:     pos++;
jbe@146:     // expect object value to follow:
jbe@124:     mode = JSON_STATE_OBJECT_VALUE;
jbe@146:     // continue with loop:
jbe@121:     goto json_import_loop;
jbe@136:   // value terminator (NOTE: trailing comma at end of value or key-value list is tolerated by this parser)
jbe@121:   case ',':
jbe@146:     // branch according to parser state:
jbe@124:     if (mode == JSON_STATE_OBJECT_SEPARATOR) {
jbe@146:       // expect an object key to follow:
jbe@124:       mode = JSON_STATE_OBJECT_KEY;
jbe@124:     } else if (mode == JSON_STATE_ARRAY_SEPARATOR) {
jbe@146:       // expect an array value to follow:
jbe@124:       mode = JSON_STATE_ARRAY_VALUE;
jbe@121:     } else {
jbe@136:        // if value terminator is not expected here, then return an error:
jbe@136:        goto json_import_syntax_error;
jbe@121:     }
jbe@136:     // consume input character:
jbe@121:     pos++;
jbe@136:     // continue with loop:
jbe@121:     goto json_import_loop;
jbe@136:   // string literal:
jbe@121:   case '"':
jbe@146:     // consume quote character:
jbe@146:     pos++;
jbe@136:     // prepare buffer to decode string (with maximum possible length) and set write position to zero:
jbe@121:     cbuf = luaL_buffinitsize(L, &luabuf, total-pos);
jbe@121:     writepos = 0;
jbe@146:     // loop through the characters until encountering end quote:
jbe@121:     while ((c = str[pos++]) != '"') {
jbe@121:       if (c == 0) {
jbe@146:         // handle unexpected end of JSON document:
jbe@121:         goto json_import_unexpected_eof;
jbe@121:       } else if (c < 32 || c == 127) {
jbe@136:         // do not allow ASCII control characters:
jbe@136:         // NOTE: illegal UTF-8 sequences and extended control characters are not sanitized
jbe@136:         //       by this parser to allow different encodings than Unicode
jbe@121:         lua_pushnil(L);
jbe@121:         lua_pushliteral(L, "Unexpected control character in JSON string");
jbe@121:         return 2;
jbe@121:       } else if (c == '\\') {
jbe@136:         // read next char after backslash escape:
jbe@121:         c = str[pos++];
jbe@121:         switch (c) {
jbe@136:         // unexpected end-of-string:
jbe@121:         case 0:
jbe@121:           goto json_import_unexpected_eof;
jbe@136:         // unescaping of quotation mark, slash, and backslash:
jbe@121:         case '"':
jbe@121:         case '/':
jbe@121:         case '\\':
jbe@121:           cbuf[writepos++] = c;
jbe@121:           break;
jbe@136:         // unescaping of backspace:
jbe@146:         case 'b': cbuf[writepos++] = '\b'; break;
jbe@136:         // unescaping of form-feed:
jbe@146:         case 'f': cbuf[writepos++] = '\f'; break;
jbe@136:         // unescaping of new-line:
jbe@146:         case 'n': cbuf[writepos++] = '\n'; break;
jbe@136:         // unescaping of carriage-return:
jbe@146:         case 'r': cbuf[writepos++] = '\r'; break;
jbe@136:         // unescaping of tabulator:
jbe@146:         case 't': cbuf[writepos++] = '\t'; break;
jbe@136:         // unescaping of UTF-16 characters
jbe@121:         case 'u':
jbe@121:           lua_pushnil(L);
jbe@121:           lua_pushliteral(L, "JSON unicode escape sequences are not implemented yet");  // TODO
jbe@121:           return 2;
jbe@136:         // unexpected escape sequence:
jbe@121:         default:
jbe@121:           lua_pushnil(L);
jbe@121:           lua_pushliteral(L, "Unexpected string escape sequence in JSON document");
jbe@121:           return 2;
jbe@121:         }
jbe@121:       } else {
jbe@136:         // normal character:
jbe@121:         cbuf[writepos++] = c;
jbe@121:       }
jbe@121:     }
jbe@136:     // process buffer to Lua string:
jbe@121:     luaL_pushresultsize(&luabuf, writepos);
jbe@136:     // continue with processing of decoded string:
jbe@121:     goto json_import_process_value;
jbe@121:   }
jbe@136:   // process values whose type is is not deducible from a single character:
jbe@136:   if ((c >= '0' && c <= '9') || c == '-' || c == '+') {
jbe@146:     // for numbers,
jbe@146:     // use strtod() call to parse a (double precision) floating point number:
jbe@122:     char *endptr;
jbe@122:     double numval;
jbe@122:     numval = strtod(str+pos, &endptr);
jbe@146:     // catch parsing errors:
jbe@122:     if (endptr == str+pos) goto json_import_syntax_error;
jbe@146:     // consume characters that were parsed:
jbe@122:     pos += endptr - (str+pos);
jbe@146:     // push parsed (double precision) floating point number on Lua stack:
jbe@122:     lua_pushnumber(L, numval);
jbe@122:   } else if (!strncmp(str+pos, "true", 4)) {
jbe@136:     // consume 4 input characters for "true":
jbe@121:     pos += 4;
jbe@136:     // put Lua true value on stack:
jbe@136:     lua_pushboolean(L, 1);
jbe@121:   } else if (!strncmp(str+pos, "false", 5)) {
jbe@136:     // consume 5 input characters for "false":
jbe@121:     pos += 5;
jbe@136:     // put Lua false value on stack:
jbe@136:     lua_pushboolean(L, 0);
jbe@121:   } else if (!strncmp(str+pos, "null", 4)) {
jbe@136:     // consume 4 input characters for "null":
jbe@136:     pos += 4;
jbe@136:     // put special null-marker on stack:
jbe@138:     lua_pushvalue(L, json_import_nullmark_idx);
jbe@121:   } else {
jbe@136:     // all other cases are a syntax error:
jbe@121:     goto json_import_syntax_error;
jbe@121:   }
jbe@136:   // process a decoded value or key value pair (expected on top of Lua stack):
jbe@136:   json_import_process_value:
jbe@121:   switch (mode) {
jbe@136:   // an object key has been read:
jbe@124:   case JSON_STATE_OBJECT_KEY:
jbe@136:     // if an object key is not a string, then this is a syntax error:
jbe@121:     if (lua_type(L, -1) != LUA_TSTRING) goto json_import_syntax_error;
jbe@146:     // expect key terminator to follow:
jbe@124:     mode = JSON_STATE_OBJECT_KEY_TERMINATOR;
jbe@146:     // continue with loop:
jbe@121:     goto json_import_loop;
jbe@136:   // a key value pair has been read:
jbe@124:   case JSON_STATE_OBJECT_VALUE:
jbe@136:     // store key value pair in outer shadow table:
jbe@130:     lua_rawset(L, -3);
jbe@146:     // expect value terminator (or end of object) to follow:
jbe@124:     mode = JSON_STATE_OBJECT_SEPARATOR;
jbe@146:     // continue with loop:
jbe@121:     goto json_import_loop;
jbe@136:   // an array value has been read:
jbe@124:   case JSON_STATE_ARRAY_VALUE:
jbe@136:     // store value in outer shadow table:
jbe@140:     lua_rawseti(L, -3, lua_rawlen(L, -3) + 1);
jbe@146:     // expect value terminator (or end of object) to follow:
jbe@124:     mode = JSON_STATE_ARRAY_SEPARATOR;
jbe@146:     // continue with loop
jbe@121:     goto json_import_loop;
jbe@136:   // a single value has been read:
jbe@124:   case JSON_STATE_VALUE:
jbe@136:     // leave value on top of stack, expect end of JSON document, and continue with loop:
jbe@124:     mode = JSON_STATE_END;
jbe@121:     goto json_import_loop;
jbe@121:   }
jbe@146:   // syntax error handling (reachable by goto statement):
jbe@136:   json_import_syntax_error:
jbe@121:   lua_pushnil(L);
jbe@121:   lua_pushliteral(L, "Syntax error in JSON document");
jbe@121:   return 2;
jbe@121: }
jbe@121: 
jbe@146: // special Lua stack indicies for json_path function:
jbe@138: #define json_path_shadowtbl_idx 1
jbe@138: #define json_path_nullmark_idx 2
jbe@146: 
jbe@146: // stack offset of arguments to json_path function:
jbe@138: #define json_path_idxshift 2
jbe@138: 
jbe@146: // gets a value or its type from a JSON document (passed as first argument)
jbe@146: // optionally using a path (passed as variable number of keys after first argument):
jbe@137: static int json_path(lua_State *L, int type_mode) {
jbe@146:   int stacktop;                      // stack index of top of stack (after shifting)
jbe@146:   int idx = 2 + json_path_idxshift;  // stack index of current argument to process
jbe@146:   // insert json_shadowtbl on stack at position 1 (shifting the arguments):
jbe@144:   json_regfetch(L, shadowtbl);
jbe@138:   lua_insert(L, 1);
jbe@146:   // insert json_nullmark on stack at position 2 (shifting the arguments):
jbe@145:   json_pushlightref(L, nullmark);
jbe@138:   lua_insert(L, 2);
jbe@146:   // store stack index of top of stack:
jbe@138:   stacktop = lua_gettop(L);
jbe@146:   // use first argument as "current value" (stored on top of stack):
jbe@138:   lua_pushvalue(L, 1 + json_path_idxshift);
jbe@146:   // process each "path key" (2nd argument and following arguments):
jbe@138:   while (idx <= stacktop) {
jbe@146:     // if "current value" (on top of stack) is nil, then the path cannot be walked and nil is returned:
jbe@137:     if (lua_isnil(L, -1)) return 1;
jbe@137:     // try to get shadow table of "current value":
jbe@130:     lua_pushvalue(L, -1);
jbe@138:     lua_rawget(L, json_path_shadowtbl_idx);
jbe@126:     if (lua_isnil(L, -1)) {
jbe@137:       // if no shadow table is found,
jbe@130:       if (lua_type(L, -1) == LUA_TTABLE) {
jbe@146:         // and if "current value" is a table,
jbe@146:         // drop nil from stack:
jbe@146:         lua_pop(L, 1);
jbe@137:         // get "next value" using the "path key":
jbe@130:         lua_pushvalue(L, idx++);
jbe@130:         lua_gettable(L, -2);
jbe@130:       } else {
jbe@137:         // if "current value" is not a table,
jbe@146:         // then the path cannot be walked and nil (already on top of stack) is returned:
jbe@137:         return 1;
jbe@130:       }
jbe@130:     } else {
jbe@137:       // if a shadow table is found,
jbe@137:       // set "current value" to its shadow table:
jbe@130:       lua_replace(L, -2);
jbe@137:       // get "next value" using the "path key":
jbe@130:       lua_pushvalue(L, idx++);
jbe@130:       lua_rawget(L, -2);
jbe@126:     }
jbe@137:     // the "next value" replaces the "current value":
jbe@130:     lua_replace(L, -2);
jbe@126:   }
jbe@137:   if (!type_mode) {
jbe@137:     // if a value (and not its type) was requested,
jbe@137:     // check if value is the null-marker, and store nil on top of Lua stack in that case:
jbe@138:     if (lua_rawequal(L, -1, json_path_nullmark_idx)) lua_pushnil(L);
jbe@137:   } else {
jbe@137:     // if the type was requested,
jbe@137:     // check if value is the null-marker:
jbe@138:     if (lua_rawequal(L, -1, json_path_nullmark_idx)) {
jbe@137:       // if yes, store string "null" on top of Lua stack:
jbe@130:       lua_pushliteral(L, "null");
jbe@137:     } else {
jbe@137:       // otherwise,
jbe@138:       // check if metatable indicates "object" or "array":
jbe@138:       if (lua_getmetatable(L, -1)) {
jbe@144:         json_regfetch(L, objectmt);
jbe@138:         if (lua_rawequal(L, -2, -1)) {
jbe@146:           // if value has metatable for JSON objects,
jbe@138:           // return string "object":
jbe@138:           lua_pushliteral(L, "object");
jbe@138:           return 1;
jbe@138:         }
jbe@144:         json_regfetch(L, arraymt);
jbe@138:         if (lua_rawequal(L, -3, -1)) {
jbe@146:           // if value has metatable for JSON arrays,
jbe@146:           // return string "object":
jbe@138:           lua_pushliteral(L, "array");
jbe@138:           return 1;
jbe@138:         }
jbe@146:         // remove 3 metatables (one of the value, two for comparison) from stack:
jbe@138:         lua_pop(L, 3);
jbe@138:       }
jbe@138:       // otherwise, get the Lua type:
jbe@138:       lua_pushstring(L, lua_typename(L, lua_type(L, -1)));
jbe@126:     }
jbe@126:   }
jbe@137:   // return the top most value on the Lua stack:
jbe@137:   return 1;
jbe@130: }
jbe@130: 
jbe@137: // gets a value from a JSON document (first argument)
jbe@137: // optionally using a path (variable number of keys after first argument):
jbe@130: static int json_get(lua_State *L) {
jbe@137:   return json_path(L, 0);
jbe@130: }
jbe@130: 
jbe@137: // gets a value's type from a JSON document (first argument)
jbe@137: // optionally using a path (variable number of keys after first argument):
jbe@130: static int json_type(lua_State *L) {
jbe@137:   return json_path(L, 1);
jbe@130: }
jbe@130: 
jbe@137: // checks if a value in a JSON document (first argument) is null:
jbe@130: static int json_isnull(lua_State *L) {
jbe@137:   const char *jsontype;
jbe@138:   lua_pushcfunction(L, json_type);
jbe@137:   lua_insert(L, 1);
jbe@137:   lua_call(L, lua_gettop(L) - 1, 1);
jbe@137:   jsontype = lua_tostring(L, -1);
jbe@137:   if (jsontype && !strcmp(jsontype, "null")) lua_pushboolean(L, 1);
jbe@137:   else lua_pushboolean(L, 0);
jbe@137:   return 1;
jbe@130: }
jbe@130: 
jbe@146: // special Lua stack indicies for json_setnull function:
jbe@138: #define json_setnull_unknownmt_idx 3
jbe@138: #define json_setnull_objectmt_idx 4
jbe@138: #define json_setnull_arraymt_idx 5
jbe@138: #define json_setnull_shadowtbl_idx 6
jbe@138: 
jbe@131: static int json_setnull(lua_State *L) {
jbe@138:   // truncate stack to two elements:
jbe@131:   lua_settop(L, 2);
jbe@138:   // push json_unknownmt to stack position 3:
jbe@144:   json_regfetch(L, unknownmt);
jbe@138:   // push json_objectmt to stack position 4:
jbe@144:   json_regfetch(L, objectmt);
jbe@138:   // push json_arraymt to stack position 5:
jbe@144:   json_regfetch(L, arraymt);
jbe@138:   // push json_shadowtbl to stack position 6:
jbe@144:   json_regfetch(L, shadowtbl);
jbe@138:   //
jbe@138:   lua_getmetatable(L, 1);
jbe@138:   if (
jbe@138:     !lua_rawequal(L, -1, json_setnull_unknownmt_idx) &&
jbe@138:     !lua_rawequal(L, -1, json_setnull_objectmt_idx) &&
jbe@138:     !lua_rawequal(L, -1, json_setnull_arraymt_idx)
jbe@138:   ) {
jbe@138:     lua_pushvalue(L, json_setnull_unknownmt_idx);
jbe@138:     lua_setmetatable(L, 1);
jbe@138:   }
jbe@131:   lua_pushvalue(L, 1);
jbe@138:   lua_rawget(L, json_setnull_shadowtbl_idx);
jbe@131:   if (lua_isnil(L, -1)) {
jbe@131:     lua_newtable(L);
jbe@131:     lua_pushvalue(L, 1);
jbe@131:     lua_pushvalue(L, -2);
jbe@138:     lua_rawset(L, json_setnull_shadowtbl_idx);
jbe@131:   }
jbe@131:   lua_pushvalue(L, 2);
jbe@145:   json_pushlightref(L, nullmark);
jbe@131:   lua_rawset(L, -3);
jbe@131:   return 0;
jbe@131: }
jbe@131: 
jbe@130: static int json_len(lua_State *L) {
jbe@130:   lua_settop(L, 1);
jbe@144:   json_regfetch(L, shadowtbl);
jbe@130:   lua_pushvalue(L, 1);
jbe@138:   lua_rawget(L, -2);
jbe@138:   lua_pushinteger(L, lua_rawlen(L, lua_isnil(L, -1) ? 1 : -1));
jbe@123:   return 1;
jbe@123: }
jbe@123: 
jbe@146: // special Lua stack indicies for json_index function:
jbe@141: #define json_index_nullmark_idx 3
jbe@141: #define json_index_shadowtbl_idx 4
jbe@141: 
jbe@130: static int json_index(lua_State *L) {
jbe@130:   lua_settop(L, 2);
jbe@145:   json_pushlightref(L, nullmark);  // on stack position 3
jbe@144:   json_regfetch(L, shadowtbl);
jbe@130:   lua_pushvalue(L, 1);
jbe@141:   lua_rawget(L, json_index_shadowtbl_idx);
jbe@139:   if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@130:   lua_pushvalue(L, 2);
jbe@130:   lua_rawget(L, -2);
jbe@141:   if (lua_rawequal(L, -1, json_index_nullmark_idx)) lua_pushnil(L);
jbe@127:   return 1;
jbe@127: }
jbe@127: 
jbe@130: static int json_newindex(lua_State *L) {
jbe@130:   lua_settop(L, 3);
jbe@144:   json_regfetch(L, shadowtbl);
jbe@123:   lua_pushvalue(L, 1);
jbe@143:   lua_rawget(L, -2);
jbe@130:   if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@130:   lua_replace(L, 1);
jbe@139:   lua_settop(L, 3);
jbe@130:   lua_rawset(L, 1);
jbe@121:   return 1;
jbe@121: }
jbe@121: 
jbe@146: // special Lua stack indicies for json_pairs_iterfunc function:
jbe@139: #define json_pairs_iterfunc_nullmark_idx 3
jbe@139: #define json_pairs_iterfunc_shadowtbl_idx 4
jbe@139: 
jbe@135: static int json_pairs_iterfunc(lua_State *L) {
jbe@135:   lua_settop(L, 2);
jbe@145:   json_pushlightref(L, nullmark);  // on stack position 3
jbe@144:   json_regfetch(L, shadowtbl);
jbe@135:   lua_pushvalue(L, 1);
jbe@139:   lua_rawget(L, json_pairs_iterfunc_shadowtbl_idx);
jbe@135:   if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@135:   lua_pushvalue(L, 2);
jbe@135:   if (!lua_next(L, -2)) return 0;
jbe@139:   if (lua_rawequal(L, -1, json_pairs_iterfunc_nullmark_idx)) {
jbe@135:     lua_pop(L, 1);
jbe@135:     lua_pushnil(L);
jbe@135:   }
jbe@135:   return 2;
jbe@135: }
jbe@135: 
jbe@135: static int json_pairs(lua_State *L) {
jbe@139:   lua_pushcfunction(L, json_pairs_iterfunc);
jbe@135:   lua_pushvalue(L, 1);
jbe@135:   lua_pushnil(L);
jbe@135:   return 3;
jbe@135: }
jbe@135: 
jbe@146: // special Lua stack indicies for json_ipairs_iterfunc function:
jbe@139: #define json_ipairs_iterfunc_nullmark_idx 3
jbe@139: #define json_ipairs_iterfunc_shadowtbl_idx 4
jbe@139: 
jbe@134: static int json_ipairs_iterfunc(lua_State *L) {
jbe@134:   int idx;
jbe@134:   lua_settop(L, 2);
jbe@145:   json_pushlightref(L, nullmark);  // on stack position 3
jbe@144:   json_regfetch(L, shadowtbl);
jbe@134:   idx = lua_tointeger(L, 2) + 1;
jbe@134:   lua_pushvalue(L, 1);
jbe@139:   lua_rawget(L, json_ipairs_iterfunc_shadowtbl_idx);
jbe@134:   if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@134:   lua_rawgeti(L, -1, idx);
jbe@134:   if (lua_isnil(L, -1)) return 0;
jbe@134:   lua_pushinteger(L, idx);
jbe@139:   if (lua_rawequal(L, -2, json_ipairs_iterfunc_nullmark_idx)) lua_pushnil(L);
jbe@134:   else lua_pushvalue(L, -2);
jbe@134:   return 2;
jbe@134: }
jbe@134: 
jbe@134: static int json_ipairs(lua_State *L) {
jbe@139:   lua_pushcfunction(L, json_ipairs_iterfunc);
jbe@134:   lua_pushvalue(L, 1);
jbe@134:   lua_pushinteger(L, 0);
jbe@134:   return 3;
jbe@134: }
jbe@134: 
jbe@121: static const struct luaL_Reg json_module_functions[] = {
jbe@133:   {"object", json_object},
jbe@133:   {"array", json_array},
jbe@121:   {"import", json_import},
jbe@130:   {"get", json_get},
jbe@127:   {"type", json_type},
jbe@123:   {"isnull", json_isnull},
jbe@131:   {"setnull", json_setnull},
jbe@121:   {NULL, NULL}
jbe@121: };
jbe@121: 
jbe@126: static const struct luaL_Reg json_metatable_functions[] = {
jbe@130:   {"__len", json_len},
jbe@130:   {"__index", json_index},
jbe@130:   {"__newindex", json_newindex},
jbe@135:   {"__pairs", json_pairs},
jbe@134:   {"__ipairs", json_ipairs},
jbe@126:   {NULL, NULL}
jbe@126: };
jbe@126: 
jbe@121: int luaopen_json(lua_State *L) {
jbe@126:   lua_settop(L, 0);
jbe@138:   lua_newtable(L);  // library
jbe@138:   lua_newtable(L);
jbe@138:   luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144:   json_regstore(L, unknownmt);
jbe@138:   lua_setfield(L, 1, "ambiguous_mt");
jbe@138:   lua_newtable(L);
jbe@138:   luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144:   json_regstore(L, objectmt);
jbe@138:   lua_setfield(L, 1, "object_mt");
jbe@138:   lua_newtable(L);
jbe@138:   luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144:   json_regstore(L, arraymt);
jbe@138:   lua_setfield(L, 1, "array_mt");
jbe@138:   lua_newtable(L);  // ephemeron table to store shadow tables for each JSON object/array to allow NULL values returned as nil
jbe@138:   lua_newtable(L);  // metatable for ephemeron table
jbe@121:   lua_pushliteral(L, "__mode");
jbe@121:   lua_pushliteral(L, "k");
jbe@138:   lua_rawset(L, -3);
jbe@138:   lua_setmetatable(L, -2);
jbe@144:   json_regstore(L, shadowtbl);
jbe@138:   lua_settop(L, 1);
jbe@138:   luaL_setfuncs(L, json_module_functions, 0);
jbe@121:   return 1;
jbe@121: }