jbe@121: #include <lua.h>
jbe@121: #include <lauxlib.h>
jbe@122: #include <stdlib.h>
jbe@121: #include <string.h>
jbe@154: #include <math.h>
jbe@121: 
jbe@144: // maximum number of nested JSON values (objects and arrays):
jbe@150: // NOTE: The Lua reference states that the stack may typically contain at least
jbe@150: //       "a few thousand elements". Since every nested level consumes
jbe@150: //       3 elements on the Lua stack (the object/array, its shadow table,
jbe@150: //       a string key or a placeholder), we limit the number of nested levels
jbe@150: //       to 500. If a stack overflow would still happen in the import function,
jbe@150: //       this is detected nevertheless and an error is thrown (instead of
jbe@150: //       returning nil and an error string).
jbe@150: #define JSON_MAXDEPTH 500
jbe@142: 
jbe@155: // generate dummy memory addresses that represents null values:
jbe@155: char json_nullmark;
jbe@155: #define json_isnullmark(L, i) (lua_touserdata((L), (i)) == &json_nullmark)
jbe@155: #define json_pushnullmark(L) lua_pushlightuserdata((L), &json_nullmark)
jbe@155: 
jbe@144: // macros for usage of Lua registry:
jbe@144: #define JSON_REGENT char
jbe@145: #define JSON_REGPOINTER void *
jbe@145: #define json_regpointer(x) (&json_registry.x)
jbe@151: #define json_regfetchpointer(L, x) lua_rawgetp((L), LUA_REGISTRYINDEX, (x))
jbe@151: #define json_regfetch(L, x) json_regfetchpointer(L, json_regpointer(x))
jbe@151: #define json_regstore(L, x) lua_rawsetp(L, LUA_REGISTRYINDEX, json_regpointer(x))
jbe@145: 
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 objectmt;   // metatable for JSON objects
jbe@145:   JSON_REGENT arraymt;    // metatable for JSON arrays
jbe@144: } json_registry;
jbe@138: 
jbe@157: // returns the string "<JSON null marker>":
jbe@157: static int json_nullmark_tostring(lua_State *L) {
jbe@157:   lua_pushliteral(L, "<JSON null marker>");
jbe@157:   return 1;
jbe@157: }
jbe@157: 
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: 
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@152:   size_t arraylen;     // variable to temporarily store the array length
jbe@147:   // stack shall contain one function argument:
jbe@138:   lua_settop(L, 1);
jbe@147:   // push objectmt onto stack position 2:
jbe@144:   json_regfetch(L, objectmt);
jbe@147:   // push arraymt onto stack position 3:
jbe@144:   json_regfetch(L, arraymt);
jbe@147:   // push shadowtbl onto stack position 4:
jbe@144:   json_regfetch(L, shadowtbl);
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@147:     // put Lua true value onto 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@147:     // put Lua false value onto 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@153:     // different behavor for top-level and sub-levels:
jbe@153:     if (level) {
jbe@153:       // if sub-level,
jbe@153:       // push special null-marker onto stack:
jbe@155:       json_pushnullmark(L);
jbe@153:     } else {
jbe@153:       // if top-level,
jbe@153:       // push nil onto stack:
jbe@153:       lua_pushnil(L);
jbe@153:     }
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@152:     // get current array length:
jbe@152:     arraylen = lua_rawlen(L, -3);
jbe@152:     // throw error if array would exceed INT_MAX elements:
jbe@152:     // TODO: Lua 5.3 may support more elements
jbe@152:     if (arraylen >= INT_MAX) {
jbe@152:       lua_pushnil(L);
jbe@152:       lua_pushfstring(L, "Array exceeded length of %d elements", INT_MAX);
jbe@152:     }
jbe@136:     // store value in outer shadow table:
jbe@152:     lua_rawseti(L, -3, arraylen + 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@146: 
jbe@146: // stack offset of arguments to json_path function:
jbe@155: #define json_path_idxshift 1
jbe@138: 
jbe@146: // gets a value or its type from a JSON document (passed as first argument)
jbe@147: // 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@148:   // insert shadowtbl into stack at position 1 (shifting the arguments):
jbe@144:   json_regfetch(L, shadowtbl);
jbe@138:   lua_insert(L, 1);
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@155:     if (json_isnullmark(L, -1)) lua_pushnil(L);
jbe@137:   } else {
jbe@137:     // if the type was requested,
jbe@137:     // check if value is the null-marker:
jbe@155:     if (json_isnullmark(L, -1)) {
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@147: // gets a value from a JSON document (passed as first argument)
jbe@147: // using a path (passed as 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@147: // gets a value's type from a JSON document (passed as first argument)
jbe@147: // 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@147: // returns the length of a JSON array (or zero for a table without numeric keys):
jbe@130: static int json_len(lua_State *L) {
jbe@147:   // stack shall contain one function argument:
jbe@130:   lua_settop(L, 1);
jbe@148:   // try to get corresponding shadow table for first argument:
jbe@144:   json_regfetch(L, shadowtbl);
jbe@130:   lua_pushvalue(L, 1);
jbe@138:   lua_rawget(L, -2);
jbe@147:   // if shadow table does not exist, return length of argument, else length of shadow table:
jbe@147:   lua_pushnumber(L, lua_rawlen(L, lua_isnil(L, -1) ? 1 : -1));
jbe@123:   return 1;
jbe@123: }
jbe@123: 
jbe@130: static int json_index(lua_State *L) {
jbe@148:   // stack shall contain two function arguments:
jbe@130:   lua_settop(L, 2);
jbe@155:   // get corresponding shadow table for first argument:
jbe@144:   json_regfetch(L, shadowtbl);
jbe@130:   lua_pushvalue(L, 1);
jbe@155:   lua_rawget(L, -2);
jbe@148:   // throw error if no shadow table was found:
jbe@139:   if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148:   // use key passed as second argument to lookup value in shadow table:
jbe@130:   lua_pushvalue(L, 2);
jbe@130:   lua_rawget(L, -2);
jbe@148:   // if value is null-marker, then push nil onto stack:
jbe@155:   if (json_isnullmark(L, -1)) lua_pushnil(L);
jbe@148:   // return either looked up value, or nil
jbe@127:   return 1;
jbe@127: }
jbe@127: 
jbe@130: static int json_newindex(lua_State *L) {
jbe@148:   // stack shall contain three function arguments:
jbe@130:   lua_settop(L, 3);
jbe@148:   // get corresponding shadow table for first argument:
jbe@144:   json_regfetch(L, shadowtbl);
jbe@123:   lua_pushvalue(L, 1);
jbe@143:   lua_rawget(L, -2);
jbe@148:   // throw error if no shadow table was found:
jbe@130:   if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@148:   // replace first argument with shadow table:
jbe@130:   lua_replace(L, 1);
jbe@148:   // reset stack and use second and third argument to write to shadow table:
jbe@139:   lua_settop(L, 3);
jbe@130:   lua_rawset(L, 1);
jbe@148:   // return nothing:
jbe@148:   return 0;
jbe@121: }
jbe@121: 
jbe@135: static int json_pairs_iterfunc(lua_State *L) {
jbe@149:   // stack shall contain two function arguments:
jbe@135:   lua_settop(L, 2);
jbe@155:   // get corresponding shadow table for first argument:
jbe@144:   json_regfetch(L, shadowtbl);
jbe@135:   lua_pushvalue(L, 1);
jbe@155:   lua_rawget(L, -2);
jbe@149:   // throw error if no shadow table was found:
jbe@135:   if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149:   // get next key value pair from shadow table (using previous key from argument 2)
jbe@149:   // and return nothing if there is no next pair:
jbe@135:   lua_pushvalue(L, 2);
jbe@135:   if (!lua_next(L, -2)) return 0;
jbe@149:   // replace null-marker with nil:
jbe@155:   if (json_isnullmark(L, -1)) {
jbe@135:     lua_pop(L, 1);
jbe@135:     lua_pushnil(L);
jbe@135:   }
jbe@149:   // return key and value (or key and nil, if null-marker was found):
jbe@135:   return 2;
jbe@135: }
jbe@135: 
jbe@149: // returns a triple such that 'for key, value in pairs(obj) do ... end'
jbe@149: // iterates through all key value pairs (including JSON null keys represented as Lua nil):
jbe@135: static int json_pairs(lua_State *L) {
jbe@149:   // return triple of function json_pairs_iterfunc, first argument, and nil:
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@134: static int json_ipairs_iterfunc(lua_State *L) {
jbe@152:   lua_Integer idx;
jbe@149:   // stack shall contain two function arguments:
jbe@134:   lua_settop(L, 2);
jbe@149:   // calculate new index by incrementing second argument:
jbe@134:   idx = lua_tointeger(L, 2) + 1;
jbe@149:   // get corresponding shadow table for first argument:
jbe@155:   json_regfetch(L, shadowtbl);
jbe@134:   lua_pushvalue(L, 1);
jbe@155:   lua_rawget(L, -2);
jbe@149:   // throw error if no shadow table was found:
jbe@134:   if (lua_isnil(L, -1)) return luaL_error(L, "Shadow table not found");
jbe@149:   // do integer lookup in shadow table:
jbe@134:   lua_rawgeti(L, -1, idx);
jbe@149:   // return nothing if there was no value:
jbe@134:   if (lua_isnil(L, -1)) return 0;
jbe@149:   // return new index and
jbe@149:   // either the looked up value if it is not equal to the null-marker
jbe@149:   // or nil instead of null-marker:
jbe@134:   lua_pushinteger(L, idx);
jbe@155:   if (json_isnullmark(L, -2)) lua_pushnil(L);
jbe@134:   else lua_pushvalue(L, -2);
jbe@134:   return 2;
jbe@134: }
jbe@134: 
jbe@149: // returns a triple such that 'for idx, value in ipairs(ary) do ... end'
jbe@149: // iterates through all values (including JSON null represented as Lua nil):
jbe@134: static int json_ipairs(lua_State *L) {
jbe@149:   // return triple of function json_ipairs_iterfunc, first argument, and zero:
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@154: #define JSON_TABLETYPE_UNKNOWN 0
jbe@154: #define JSON_TABLETYPE_OBJECT 1
jbe@154: #define JSON_TABLETYPE_ARRAY 2
jbe@154: 
jbe@154: static int json_export(lua_State *L) {
jbe@154:   lua_Number num;
jbe@154:   const char *str;
jbe@154:   unsigned char c;
jbe@154:   size_t strlen;
jbe@154:   size_t pos = 0;
jbe@154:   luaL_Buffer buf;
jbe@154:   char hexcode[7];  // backslash, character 'u', 4 hex digits, and terminating NULL byte
jbe@154:   int luatype;
jbe@154:   int tabletype = JSON_TABLETYPE_UNKNOWN;
jbe@154:   int needsep = 0;
jbe@154:   lua_Integer idx;
jbe@154:   lua_settop(L, 1);
jbe@157:   if (json_isnullmark(L, 1)) {
jbe@157:     lua_pushnil(L);
jbe@157:     lua_replace(L, 1);
jbe@157:   }
jbe@154:   switch (lua_type(L, 1)) {
jbe@154:   case LUA_TNIL:
jbe@154:     lua_pushliteral(L, "null");
jbe@154:     return 1;
jbe@154:   case LUA_TNUMBER:
jbe@154:     num = lua_tonumber(L, 1);
jbe@154:     if (isnan(num)) return luaL_error(L, "JSON export not possible for NaN value");
jbe@154:     if (isinf(num)) return luaL_error(L, "JSON export not possible for infinite numbers");
jbe@154:     lua_tostring(L, 1);
jbe@154:     return 1;
jbe@154:   case LUA_TBOOLEAN:
jbe@154:     if (lua_toboolean(L, 1)) lua_pushliteral(L, "true");
jbe@154:     else lua_pushliteral(L, "false");
jbe@154:     return 1;
jbe@154:   case LUA_TSTRING:
jbe@154:     str = lua_tolstring(L, 1, &strlen);
jbe@154:     luaL_buffinit(L, &buf);
jbe@154:     luaL_addchar(&buf, '"');
jbe@154:     while (pos < strlen) {
jbe@154:       c = str[pos++];
jbe@154:       if (c == '"')       luaL_addstring(&buf, "\\\"");
jbe@154:       else if (c == '\\') luaL_addstring(&buf, "\\\\");
jbe@154:       else if (c == 127)  luaL_addstring(&buf, "\\u007F");
jbe@154:       else if (c >= 32)   luaL_addchar(&buf, c);
jbe@154:       else if (c == '\b') luaL_addstring(&buf, "\\b");
jbe@154:       else if (c == '\f') luaL_addstring(&buf, "\\f");
jbe@154:       else if (c == '\n') luaL_addstring(&buf, "\\n");
jbe@154:       else if (c == '\r') luaL_addstring(&buf, "\\r");
jbe@154:       else if (c == '\t') luaL_addstring(&buf, "\\t");
jbe@154:       else if (c == '\v') luaL_addstring(&buf, "\\v");
jbe@154:       else {
jbe@154:         sprintf(hexcode, "\\u%04X", c);
jbe@154:         luaL_addstring(&buf, hexcode);
jbe@154:       }
jbe@154:     }
jbe@154:     luaL_addchar(&buf, '"');
jbe@154:     luaL_pushresult(&buf);
jbe@154:     return 1;
jbe@154:   case LUA_TTABLE:
jbe@154:     if (lua_getmetatable(L, 1)) {
jbe@154:       json_regfetch(L, objectmt);
jbe@154:       if (lua_rawequal(L, -2, -1)) {
jbe@154:         tabletype = JSON_TABLETYPE_OBJECT;
jbe@154:       } else {
jbe@154:         json_regfetch(L, arraymt);
jbe@154:         if (lua_rawequal(L, -3, -1)) tabletype = JSON_TABLETYPE_ARRAY;
jbe@154:       }
jbe@154:     }
jbe@154:     json_regfetch(L, shadowtbl);
jbe@154:     lua_pushvalue(L, 1);
jbe@154:     lua_rawget(L, -2);
jbe@154:     if (!lua_isnil(L, -1)) lua_replace(L, 1);
jbe@154:     lua_settop(L, 1);
jbe@154:     if (tabletype == JSON_TABLETYPE_UNKNOWN) {
jbe@154:       for (lua_pushnil(L); lua_next(L, 1); lua_pop(L, 1)) {
jbe@154:         luatype = lua_type(L, -2);
jbe@154:         if (tabletype == JSON_TABLETYPE_UNKNOWN) {
jbe@154:           if (luatype == LUA_TSTRING) tabletype = JSON_TABLETYPE_OBJECT;
jbe@154:           else if (luatype == LUA_TNUMBER) tabletype = JSON_TABLETYPE_ARRAY;
jbe@154:         } else if (
jbe@154:           (tabletype == JSON_TABLETYPE_OBJECT && luatype == LUA_TNUMBER) ||
jbe@154:           (tabletype == JSON_TABLETYPE_ARRAY && luatype == LUA_TSTRING)
jbe@154:         ) {
jbe@154:           goto json_export_tabletype_error;
jbe@154:         }
jbe@154:       }
jbe@154:     }
jbe@154:     switch (tabletype) {
jbe@154:     case JSON_TABLETYPE_OBJECT:
jbe@154:       lua_settop(L, 3);
jbe@154:       luaL_buffinit(L, &buf);
jbe@154:       luaL_addchar(&buf, '{');
jbe@154:       for (lua_pushnil(L); lua_next(L, 1); ) {
jbe@154:         if (lua_type(L, -2) == LUA_TSTRING) {
jbe@154:           lua_replace(L, 3);
jbe@154:           lua_replace(L, 2);
jbe@154:           if (needsep) luaL_addchar(&buf, ',');
jbe@154:           else needsep = 1;
jbe@154:           lua_pushcfunction(L, json_export);
jbe@154:           lua_pushvalue(L, 2);
jbe@154:           lua_call(L, 1, 1);
jbe@154:           luaL_addvalue(&buf);
jbe@154:           luaL_addchar(&buf, ':');
jbe@155:           if (json_isnullmark(L, 3)) {
jbe@154:             luaL_addstring(&buf, "null");
jbe@154:           } else {
jbe@154:             lua_pushcfunction(L, json_export);
jbe@154:             lua_pushvalue(L, 3);
jbe@154:             lua_call(L, 1, 1);
jbe@154:             luaL_addvalue(&buf);
jbe@154:           }
jbe@154:           lua_pushvalue(L, 2);
jbe@154:         } else {
jbe@154:           lua_pop(L, 1);
jbe@154:         }
jbe@154:       }
jbe@154:       luaL_addchar(&buf, '}');
jbe@154:       luaL_pushresult(&buf);
jbe@154:       return 1;
jbe@154:     case JSON_TABLETYPE_ARRAY:
jbe@154:       lua_settop(L, 2);
jbe@154:       luaL_buffinit(L, &buf);
jbe@154:       luaL_addchar(&buf, '[');
jbe@154:       for (idx = 1; ; idx++) {
jbe@154:         lua_rawgeti(L, 1, idx);
jbe@154:         if (lua_isnil(L, -1)) {
jbe@154:           lua_pop(L, 1);
jbe@154:           break;
jbe@154:         }
jbe@154:         lua_replace(L, 2);
jbe@154:         if (needsep) luaL_addchar(&buf, ',');
jbe@154:         else needsep = 1;
jbe@154:         lua_pushcfunction(L, json_export);
jbe@154:         lua_pushvalue(L, 2);
jbe@154:         lua_call(L, 1, 1);
jbe@154:         luaL_addvalue(&buf);
jbe@154:       }
jbe@154:       luaL_addchar(&buf, ']');
jbe@154:       luaL_pushresult(&buf);
jbe@154:       return 1;
jbe@154:     }
jbe@154:     json_export_tabletype_error:
jbe@154:     return luaL_error(L, "JSON export not possible for ambiguous table (cannot decide whether it is an object or array)");
jbe@154:   }
jbe@154:   return luaL_error(L, "JSON export not possible for values of type \"%s\"", lua_typename(L, lua_type(L, 1)));
jbe@154: }
jbe@154: 
jbe@149: // functions in library module:
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@154:   {"export", json_export},
jbe@130:   {"get", json_get},
jbe@127:   {"type", json_type},
jbe@121:   {NULL, NULL}
jbe@121: };
jbe@121: 
jbe@149: // metamethods for JSON objects, JSON arrays, and unknown JSON collections (object or array):
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@160:   {"__tostring", json_export},
jbe@126:   {NULL, NULL}
jbe@126: };
jbe@126: 
jbe@157: // metamethods for JSON null marker:
jbe@157: static const struct luaL_Reg json_nullmark_metamethods[] = {
jbe@157:   {"__tostring", json_nullmark_tostring},
jbe@157:   {NULL, NULL}
jbe@157: };
jbe@157: 
jbe@149: // initializes json library:
jbe@121: int luaopen_json(lua_State *L) {
jbe@149:   // empty stack:
jbe@126:   lua_settop(L, 0);
jbe@149:   // push library module onto stack position 1:
jbe@149:   lua_newtable(L);
jbe@149:   // register library functions:
jbe@149:   luaL_setfuncs(L, json_module_functions, 0);
jbe@149:   // create and store objectmt:
jbe@138:   lua_newtable(L);
jbe@138:   luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144:   json_regstore(L, objectmt);
jbe@149:   // create and store arraymt:
jbe@138:   lua_newtable(L);
jbe@138:   luaL_setfuncs(L, json_metatable_functions, 0);
jbe@144:   json_regstore(L, arraymt);
jbe@149:   // create and store ephemeron table to store shadow tables for each JSON object/array
jbe@149:   // to allow NULL values returned as nil
jbe@149:   lua_newtable(L);
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@157:   // set metatable of null marker and make it available through library module:
jbe@157:   json_pushnullmark(L);
jbe@157:   lua_newtable(L);
jbe@157:   luaL_setfuncs(L, json_nullmark_metamethods, 0);
jbe@157:   lua_setmetatable(L, -2);
jbe@157:   lua_setfield(L, 1, "null");
jbe@157:   // return library module (that's expected on top of stack):
jbe@121:   return 1;
jbe@121: }