From 60fb31cfdd625ea3bc4a12a8440715c8ff0c9242 Mon Sep 17 00:00:00 2001 From: Mark Pulford Date: Sun, 1 May 2011 02:11:10 +0930 Subject: Create "cjson" Lua module, support UCS-2 escapes - Convert lua_json_init() into luaopen_cjson() to support dynamic .so loading. - Rename "json" to "cjson" to reduce conflicts with other JSON modules. - Remove unnecessary *_pcall_* API. Lua calls are fast enough, even through C. - Encode empty tables as objects - Add support for decoding all UCS-2 escape codes. --- lua_cjson.c | 780 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 780 insertions(+) create mode 100644 lua_cjson.c (limited to 'lua_cjson.c') diff --git a/lua_cjson.c b/lua_cjson.c new file mode 100644 index 0000000..203b3b8 --- /dev/null +++ b/lua_cjson.c @@ -0,0 +1,780 @@ +/* Lua JSON routines + */ + +/* Caveats: + * - Assumes strings are valid UTF-8 and mostly treats them as opaque + * binary data. Will not throw an exception on bad data. + * - Will decode \uXXXX escapes, but leaves high codepoints as UTF-8 + * when encoding. + * - JSON "null" values are represented as lightuserdata. Compare with + * json.null. + * - Parsing comments is not supported. According to json.org, this isn't + * part of the spec. + * - Parser accepts number formats beyond the JSON spec. + * + * Note: lua_json_decode() probably spends significant time rehashing + * tables since it is difficult to know their size ahead of time. + * Earlier JSON libaries didn't have this problem but the intermediate + * storage (and their implementations) were much slower anyway.. + */ + +/* FIXME: + * - Option to encode non-printable characters? Only \" \\ are required + * - Protect against cycles when encoding JSON from a data structure + * - Max depth? Notice cycles? + * - Handle huge sparse arrays? + */ + +#include +#include +#include + +#include + +#include +#include + +#include "strbuf.h" + +/* ===== ENCODING ===== */ + +static void json_encode_exception(lua_State *l, strbuf_t *json, + char *location, int lindex) + +{ + strbuf_free(json); + + luaL_error(l, "Cannot serialise %s: %s", location, + lua_typename(l, lua_type(l, lindex))); +} + +/* 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; +} + +/* json_append_string args: + * - lua_State + * - JSON strbuf + * - String (Lua stack index) + * + * Returns nothing. Doesn't remove string from Lua stack */ +static void json_append_string(lua_State *l, strbuf_t *json, int lindex) +{ + char *p; + int i; + const char *str; + size_t len; + + str = lua_tolstring(l, lindex, &len); + + /* Worst case is len * 6 (all unicode escapes). + * This buffer is reused constantly for small strings + * If there are any excess pages, they won't be hit anyway. + * This gains ~5% speedup. */ + strbuf_ensure_empty_length(json, len * 6); + + strbuf_append_char(json, '\"'); + for (i = 0; i < len; i++) { + p = json_escape_char(str[i]); + if (p) + strbuf_append_string(json, p); + else + strbuf_append_char_unsafe(json, str[i]); + } + strbuf_append_char(json, '\"'); +} + +/* Find the size of the array on the top of the Lua stack + * -1 object (not a pure array) + * >=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 (lua_isnumber(l, -2) && + (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, strbuf_t *json); + +/* json_append_array args: + * - lua_State + * - JSON strbuf + * - Size of passwd Lua array (top of stack) */ +static void json_append_array(lua_State *l, strbuf_t *json, int array_length) +{ + int comma, i; + + strbuf_append_string(json, "[ "); + + comma = 0; + for (i = 1; i <= array_length; i++) { + if (comma) + strbuf_append_string(json, ", "); + else + comma = 1; + + lua_rawgeti(l, -1, i); + json_append_data(l, json); + lua_pop(l, 1); + } + + strbuf_append_string(json, " ]"); +} + +static void json_append_object(lua_State *l, strbuf_t *json) +{ + int comma, keytype; + + /* Object */ + strbuf_append_string(json, "{ "); + + lua_pushnil(l); + /* table, startkey */ + comma = 0; + while (lua_next(l, -2) != 0) { + if (comma) + strbuf_append_string(json, ", "); + else + comma = 1; + + /* table, key, value */ + keytype = lua_type(l, -2); + if (keytype == LUA_TNUMBER) { + strbuf_append_fmt(json, "\"" LUA_NUMBER_FMT "\": ", + lua_tonumber(l, -2)); + } else if (keytype == LUA_TSTRING) { + json_append_string(l, json, -2); + strbuf_append_string(json, ": "); + } else { + json_encode_exception(l, json, "table key", -2); + /* never returns */ + } + + /* table, key, value */ + json_append_data(l, json); + lua_pop(l, 1); + /* table, key */ + } + + strbuf_append_string(json, " }"); +} + +/* Serialise Lua data into JSON string. */ +static void json_append_data(lua_State *l, strbuf_t *json) +{ + int len; + + switch (lua_type(l, -1)) { + case LUA_TSTRING: + json_append_string(l, json, -1); + break; + case LUA_TNUMBER: + strbuf_append_fmt(json, "%lf", lua_tonumber(l, -1)); + break; + case LUA_TBOOLEAN: + if (lua_toboolean(l, -1)) + strbuf_append_string(json, "true"); + else + strbuf_append_string(json, "false"); + break; + case LUA_TTABLE: + len = lua_array_length(l); + if (len > 0) + json_append_array(l, json, len); + else + json_append_object(l, json); + break; + case LUA_TNIL: + strbuf_append_string(json, "null"); + break; + case LUA_TLIGHTUSERDATA: + if (lua_touserdata(l, -1) == NULL) { + strbuf_append_string(json, "null"); + break; + } + default: + /* Remaining types (LUA_TFUNCTION, LUA_TUSERDATA, LUA_TTHREAD, + * and LUA_TLIGHTUSERDATA) cannot be serialised */ + json_encode_exception(l, json, "value", -1); + /* never returns */ + } +} + +static int json_encode(lua_State *l) +{ + strbuf_t buf; + char *json; + int len; + + luaL_argcheck(l, lua_gettop(l) == 1, 1, "expected 1 argument"); + + strbuf_init(&buf, 0); + json_append_data(l, &buf); + json = strbuf_free_to_string(&buf, &len); + + lua_pushlstring(l, json, len); + free(json); + + return 1; +} + +/* ===== DECODING ===== */ + +typedef struct { + const char *data; + int index; + strbuf_t *tmp; /* Temporary storage for strings */ +} json_parse_t; + +typedef enum { + T_OBJ_BEGIN, + T_OBJ_END, + T_ARR_BEGIN, + T_ARR_END, + T_STRING, + T_NUMBER, + T_BOOLEAN, + T_NULL, + T_COLON, + T_COMMA, + T_END, + T_WHITESPACE, + T_ERROR, + T_UNKNOWN +} json_token_type_t; + +static const char *json_token_type_name[] = { + "T_OBJ_BEGIN", + "T_OBJ_END", + "T_ARR_BEGIN", + "T_ARR_END", + "T_STRING", + "T_NUMBER", + "T_BOOLEAN", + "T_NULL", + "T_COLON", + "T_COMMA", + "T_END", + "T_WHITESPACE", + "T_ERROR", + "T_UNKNOWN", + NULL +}; + +typedef struct { + json_token_type_t type; + int index; + union { + char *string; + double number; + int boolean; + } value; + int length; /* FIXME: Merge into union? Won't save memory, but more logical */ +} json_token_t; + +static void json_process_value(lua_State *l, json_parse_t *json, json_token_t *token); + +static json_token_type_t json_ch2token[256]; +static char json_ch2escape[256]; + +static void json_global_init() +{ + int i; + + /* Tag all characters as an error */ + for (i = 0; i < 256; i++) + json_ch2token[i] = T_ERROR; + + /* Set tokens that require no further processing */ + json_ch2token['{'] = T_OBJ_BEGIN; + json_ch2token['}'] = T_OBJ_END; + json_ch2token['['] = T_ARR_BEGIN; + json_ch2token[']'] = T_ARR_END; + json_ch2token[','] = T_COMMA; + json_ch2token[':'] = T_COLON; + json_ch2token['\0'] = T_END; + json_ch2token[' '] = T_WHITESPACE; + json_ch2token['\t'] = T_WHITESPACE; + json_ch2token['\n'] = T_WHITESPACE; + json_ch2token['\r'] = T_WHITESPACE; + + /* Update characters that require further processing */ + json_ch2token['n'] = T_UNKNOWN; + json_ch2token['t'] = T_UNKNOWN; + json_ch2token['f'] = T_UNKNOWN; + json_ch2token['"'] = T_UNKNOWN; + json_ch2token['-'] = T_UNKNOWN; + for (i = 0; i < 10; i++) + json_ch2token['0' + i] = T_UNKNOWN; + + for (i = 0; i < 256; i++) + json_ch2escape[i] = 0; /* String error */ + + json_ch2escape['"'] = '"'; + json_ch2escape['\\'] = '\\'; + json_ch2escape['/'] = '/'; + json_ch2escape['b'] = '\b'; + json_ch2escape['t'] = '\t'; + json_ch2escape['n'] = '\n'; + json_ch2escape['f'] = '\f'; + json_ch2escape['r'] = '\r'; + json_ch2escape['u'] = 'u'; /* This needs to be parsed as unicode */ +} + +static inline int hexdigit2int(char hex) +{ + if ('0' <= hex && hex <= '9') + return hex - '0'; + + /* Force lowercase */ + hex |= 0x20; + if ('a' <= hex && hex <= 'f') + return 10 + hex - 'a'; + + return -1; +} + +static int decode_hex4(const char *hex) +{ + int digit[4]; + int i; + + /* Convert ASCII hex digit to numeric digit + * Note: this returns an error for invalid hex digits, including + * NULL */ + for (i = 0; i < 4; i++) { + digit[i] = hexdigit2int(hex[i]); + if (digit[i] < 0) { + return -1; + } + } + + return (digit[0] << 12) + + (digit[1] << 8) + + (digit[2] << 4) + + digit[3]; +} + +static int codepoint_to_utf8(char *utf8, int codepoint) +{ + if (codepoint <= 0x7F) { + utf8[0] = codepoint; + return 1; + } + + if (codepoint <= 0x7FF) { + utf8[0] = (codepoint >> 6) | 0xC0; + utf8[1] = (codepoint & 0x3F) | 0x80; + return 2; + } + + if (codepoint <= 0xFFFF) { + utf8[0] = (codepoint >> 12) | 0xE0; + utf8[1] = ((codepoint >> 6) & 0x3F) | 0x80; + utf8[2] = (codepoint & 0x3F) | 0x80; + return 3; + } + + return 0; +} + + +/* Called when index pointing to beginning of UCS-2 hex code: uXXXX + * Translate to UTF-8 and append to temporary token string. + * Must advance index to the next character to be processed. + * Returns: 0 success + * -1 error + */ +static int json_append_unicode_escape(json_parse_t *json) +{ + char utf8[4]; /* 3 bytes of UTF-8 can handle UCS-2 */ + int codepoint; + int len; + + /* Skip 'u' */ + json->index++; + + /* Fetch UCS-2 codepoint */ + codepoint = decode_hex4(&json->data[json->index]); + if (codepoint < 0) { + return -1; + } + + /* Convert to UTF-8 */ + len = codepoint_to_utf8(utf8, codepoint); + if (!len) { + return -1; + } + + /* Append bytes and advance counter */ + strbuf_append_mem(json->tmp, utf8, len); + json->index += 4; + + return 0; +} + +static void json_next_string_token(json_parse_t *json, json_token_t *token) +{ + char ch; + + /* Caller must ensure a string is next */ + assert(json->data[json->index] == '"'); + + /* Skip " */ + json->index++; + + /* json->tmp is the temporary strbuf used to accumulate the + * decoded string value. */ + json->tmp->length = 0; + while ((ch = json->data[json->index]) != '"') { + if (!ch) { + /* Premature end of the string */ + token->type = T_ERROR; + return; + } + + /* Handle escapes */ + if (ch == '\\') { + /* Skip \ and fetch escape character */ + json->index++; + ch = json->data[json->index]; + + /* Translate escape code and append to tmp string */ + ch = json_ch2escape[(unsigned char)ch]; + if (ch == 'u') { + if (json_append_unicode_escape(json) < 0) + continue; + + token->type = T_ERROR; + return; + } + if (!ch) { + /* Invalid escape code */ + token->type = T_ERROR; + return; + } + } + /* Append normal character or translated single character + * Unicode escapes are handled above */ + strbuf_append_char(json->tmp, ch); + json->index++; + } + json->index++; /* Eat final quote (") */ + + strbuf_ensure_null(json->tmp); + + token->type = T_STRING; + token->value.string = strbuf_string(json->tmp, NULL); + token->length = json->tmp->length; +} + +static void json_next_number_token(json_parse_t *json, json_token_t *token) +{ + const char *startptr; + char *endptr; + + /* FIXME: + * Verify that the number takes the following form: + * -?(0|[1-9]|[1-9][0-9]+)(.[0-9]+)?([eE][-+]?[0-9]+)? + * strtod() below allows other forms (Hex, infinity, NaN,..) */ + /* i = json->index; + if (json->data[i] == '-') + i++; + j = i; + while ('0' <= json->data[i] && json->data[i] <= '9') + i++; + if (i == j) + return T_ERROR; */ + + token->type = T_NUMBER; + startptr = &json->data[json->index]; + token->value.number = strtod(&json->data[json->index], &endptr); + if (startptr == endptr) + token->type = T_ERROR; + else + json->index += endptr - startptr; /* Skip the processed number */ + + return; +} + +/* Fills in the token struct. + * T_STRING will return a pointer to the json_parse_t temporary string + * T_ERROR will leave the json->index pointer at the error. + */ +static void json_next_token(json_parse_t *json, json_token_t *token) +{ + int ch; + + /* Eat whitespace. FIXME: UGLY */ + token->type = json_ch2token[(unsigned char)json->data[json->index]]; + while (token->type == T_WHITESPACE) + token->type = json_ch2token[(unsigned char)json->data[++json->index]]; + + token->index = json->index; + + /* Don't advance the pointer for an error or the end */ + if (token->type == T_ERROR || token->type == T_END) + return; + + /* Found a known token, advance index and return */ + if (token->type != T_UNKNOWN) { + json->index++; + return; + } + + /* Process characters which triggered T_UNKNOWN */ + ch = json->data[json->index]; + + if (ch == '"') { + json_next_string_token(json, token); + return; + } else if (ch == '-' || ('0' <= ch && ch <= '9')) { + json_next_number_token(json, token); + return; + } else if (!strncmp(&json->data[json->index], "true", 4)) { + token->type = T_BOOLEAN; + token->value.boolean = 1; + json->index += 4; + return; + } else if (!strncmp(&json->data[json->index], "false", 5)) { + token->type = T_BOOLEAN; + token->value.boolean = 0; + json->index += 5; + return; + } else if (!strncmp(&json->data[json->index], "null", 4)) { + token->type = T_NULL; + json->index += 4; + return; + } + + token->type = T_ERROR; +} + +/* This function does not return. + * DO NOT CALL WITH DYNAMIC MEMORY ALLOCATED. + * The only supported exception is the temporary parser string + * json->tmp struct. + * json and token should exist on the stack somewhere. + * luaL_error() will long_jmp and release the stack */ +static void json_throw_parse_error(lua_State *l, json_parse_t *json, + const char *exp, json_token_t *token) +{ + strbuf_free(json->tmp); + luaL_error(l, "Expected %s but found type <%s> at character %d", + exp, json_token_type_name[token->type], token->index); +} + +static void json_parse_object_context(lua_State *l, json_parse_t *json) +{ + json_token_t token; + + /* 3 slots required: + * .., table, key, value */ + luaL_checkstack(l, 3, "too many nested data structures"); + + lua_newtable(l); + + json_next_token(json, &token); + + /* Handle empty objects */ + if (token.type == T_OBJ_END) + return; + + while (1) { + if (token.type != T_STRING) + json_throw_parse_error(l, json, "object key", &token); + + lua_pushlstring(l, token.value.string, token.length); /* Push key */ + + json_next_token(json, &token); + if (token.type != T_COLON) + json_throw_parse_error(l, json, "colon", &token); + + json_next_token(json, &token); + json_process_value(l, json, &token); + lua_rawset(l, -3); /* Set key = value */ + + json_next_token(json, &token); + + if (token.type == T_OBJ_END) + return; + + if (token.type != T_COMMA) + json_throw_parse_error(l, json, "comma or object end", &token); + + json_next_token(json, &token); + } +} + +/* Handle the array context */ +static void json_parse_array_context(lua_State *l, json_parse_t *json) +{ + json_token_t token; + int i; + + /* 2 slots required: + * .., table, value */ + luaL_checkstack(l, 2, "too many nested data structures"); + + lua_newtable(l); + + json_next_token(json, &token); + + /* Handle empty arrays */ + if (token.type == T_ARR_END) + return; + + i = 1; + while (1) { + json_process_value(l, json, &token); + lua_rawseti(l, -2, i); /* arr[i] = value */ + + json_next_token(json, &token); + + if (token.type == T_ARR_END) + return; + + if (token.type != T_COMMA) + json_throw_parse_error(l, json, "comma or array end", &token); + + json_next_token(json, &token); + i++; + } +} + +/* Handle the "value" context */ +static void json_process_value(lua_State *l, json_parse_t *json, json_token_t *token) +{ + switch (token->type) { + case T_STRING: + lua_pushlstring(l, token->value.string, token->length); + break;; + case T_NUMBER: + lua_pushnumber(l, token->value.number); + break;; + case T_BOOLEAN: + lua_pushboolean(l, token->value.boolean); + break;; + case T_OBJ_BEGIN: + json_parse_object_context(l, json); + break;; + case T_ARR_BEGIN: + json_parse_array_context(l, json); + break;; + case T_NULL: + /* In Lua, setting "t[k] = nil" will delete k from the table. + * Hence a NULL pointer lightuserdata object is used instead */ + lua_pushlightuserdata(l, NULL); + break;; + default: + json_throw_parse_error(l, json, "value", token); + } +} + +/* json_text must be null terminated string */ +static void lua_json_decode(lua_State *l, const char *json_text) +{ + json_parse_t json; + json_token_t token; + + json.data = json_text; + json.index = 0; + json.tmp = strbuf_new(0); + + json_next_token(&json, &token); + json_process_value(l, &json, &token); + + /* Ensure there is no more input left */ + json_next_token(&json, &token); + + if (token.type != T_END) + json_throw_parse_error(l, &json, "the end", &token); + + strbuf_free(json.tmp); +} + +static int json_decode(lua_State *l) +{ + const char *json; + + luaL_argcheck(l, lua_gettop(l) <= 1, 2, "found too many arguments"); + json = luaL_checkstring(l, 1); + + lua_json_decode(l, json); + + return 1; +} + +/* ===== INITIALISATION ===== */ + +/* FIXME: Rewrite to keep lookup tables within Lua (userdata?) + * Remove pthread dependency */ +static pthread_once_t json_global_init_once = PTHREAD_ONCE_INIT; + +int luaopen_cjson(lua_State *l) +{ + luaL_Reg reg[] = { + { "encode", json_encode }, + { "decode", json_decode }, + { NULL, NULL } + }; + + luaL_register(l, "cjson", reg); + + /* Set cjson.null */ + lua_pushlightuserdata(l, NULL); + lua_setfield(l, -2, "null"); + + pthread_once(&json_global_init_once, json_global_init); + + /* Return cjson table */ + return 1; +} + +/* vi:ai et sw=4 ts=4: + */ -- cgit v1.2.3-55-g6feb