php json_encode application analysis

static PHP_FUNCTION(json_encode)
{
 zval *parameter;
 smart_str buf = {0};
 long options = 0;

 if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "z|l", ¶meter, &options) == FAILURE) {
 return;
 }

 JSON_G(error_code) = PHP_JSON_ERROR_NONE;

 php_json_encode(&buf, parameter, options TSRMLS_CC);

 ZVAL_STRINGL(return_value, buf.c, buf. len, 1);

 smart_str_free(&buf);
 }

JSON_G(error_code) = PHP_JSON_ERROR_NONE; It is a defined json error. This error can be obtained through the json_last_error function. Have you used it? I haven't used it anyway. php_json_encode is the main operation

PHP_JSON_API void php_json_encode(smart_str *buf, zval *val, int options TSRMLS_DC) /* {{{ */
 {
 switch (Z_TYPE_P(val))
 {
 case IS_NULL:
 smart_str_append l(buf, "null", 4); //Output NULL
 break;

 case IS_BOOL:
 if (Z_BVAL_P(val)) {
 smart_str_appendl(buf, "true", 4); //Output true
 } else {
 smart_str_appendl (buf, "false", 5);//Output false
 }
 break;

 case IS_LONG:
 smart_str_append_long(buf, Z_LVAL_P(val));//Output the value of long integer
 break;

 case IS_DOUBLE:
 {
 char *d = NULL;
 int len;
 double dbl = Z_DVAL_P(val);

 if (!zend_isinf(dbl) && !zend_isnan(dbl)) {//Non-infinite
 len = spprintf(&d , 0, "%.*k", (int) EG(precision), dbl);
 smart_str_appendl(buf, d, len);
 efree(d);
 } else {
 php_error_docref(NULL TSRMLS_CC, E_WARNING, " double %.9g does not conform to the JSON spec, encoded as 0", dbl);
 smart_str_appendc(buf, '0');
 }
 }
 break;

 case IS_STRING://string
 json_escape_string(buf , Z_STRVAL_P(val), Z_STRLEN_P(val), options TSRMLS_CC);
 break;

 case IS_ARRAY://Arrays and objects
 case IS_OBJECT:
 json_encode_array(buf, &val, options TSRMLS_CC);
 break;

 default:
 php_error_docref(NULL TSRMLS_CC, E_WARNING, "type is unsupported, encoded as null");
 smart_str_appendl(buf, "null", 4);
 break;
 }

 return;
 }

Obviously, there will be corresponding cases according to different types. The most complex types are string, array, and object. Arrays and objects are the same operation. Let’s take a look at the string first. It’s very long and the comments are written directly in the code.

//options should be supported only after version 5.3, a binary mask composed of the following constants: JSON_HEX_QUOT, JSON_HEX_TAG, JSON_HEX_AMP, JSON_HEX_APOS, JSON_NUMERIC_CHECK, JSON_PRETTY_PRINT, JSON_UNESCAPED_SLASHES, JSON_FORCE_ OBJECT, JSON_UNESCAPED_UNICODE. Although I have not used it. . .
 static void json_escape_string(smart_str *buf, char *s, int len, int options TSRMLS_DC) /* {{{ */
 {
 int pos = 0;
 unsigned short us;
 unsigned short *utf16;

 if ( len == 0) {//If the length is 0, directly return double quotes ""
 smart_str_appendl(buf, """", 2);
 return;
 }

 if (options & PHP_JSON_NUMERIC_CHECK) {//Detection Is it a number from 0 to 9? If it is a number, the data will be returned directly as a long or double type.
 double d;
 int type;
 long p;

 if ((type = is_numeric_string(s, len, &p, &d, 0)) != 0) {
 if (type == IS_LONG) {
 smart_str_append_long(buf , p);
 } else if (type == IS_DOUBLE) {
 if (!zend_isinf(d) && !zend_isnan(d)) {
 char *tmp;
 int l = spprintf(&tmp, 0, "%.* k", (int) EG(precision), d);
 smart_str_appendl(buf, tmp, l);
 efree(tmp);
 } else {
 php_error_docref(NULL TSRMLS_CC, E_WARNING, "double %.9g does not conform to the JSON spec, encoded as 0", d);
 smart_str_appendc(buf, '0');
 }
 }
 return;
 }

 }

 utf16 = (unsigned short *) safe_emalloc(len, sizeof( unsigned short), 0);
 len = utf8_to_utf16(utf16, s, len); //The value you input will be processed once and converted into the corresponding Dec code. For example, 1 is 49 and a is 97. Save it to in utf16.
 if (len <= 0) {//If len is less than 0, an error has occurred. If you use json_encode to process GBK encoding, it will hang up here.
 if (utf16) {
 efree(utf16);
 }
 if (len < 0) {
 JSON_G(error_code) = PHP_JSON_ERROR_UTF8;
 if (!PG(display_errors)) {
 php_error_docref(NULL TSRMLS_CC, E_WARNING, " Invalid UTF-8 sequence in argument");
 }
 smart_str_appendl(buf, "null", 4);
 } else {
 smart_str_appendl(buf, """", 2);
 }
 return;
 }

 smart_str_appendc(buf, '"'); //Enter "

 //The following code is to escape some special characters such as double quotes, backslashes, etc.
 while (pos < len)
 {
 us = utf16[pos++];

 switch (us)
 {
 case '"':
 if (options & PHP_JSON_HEX_QUOT) {
 smart_str_appendl(buf, "\u0022", 6);
 } else {
 smart_str_appendl(buf, " \"", 2);
 }
 break;

 case '\':
 smart_str_appendl(buf, "\\", 2);
 break;
 case '/':
 smart_str_appendl(buf, "\/" , 2);
 break;

 case 'b':
 smart_str_appendl(buf, "\b", 2);
 break;

 case 'f':
 smart_str_appendl(buf, "\f", 2);
 break;

 case 'n':
 smart_str_appendl(buf, "\n", 2);
 break;

 case 'r':
 smart_str_appendl(buf, "\r", 2);
 break;

 case 't':
 smart_str_appendl(buf, "\t", 2);
 break;

 case '<':
 if (options & PHP_JSON_HEX_TAG) {
 smart_str_appendl(buf, "\u003C", 6) ;
 } else {
 smart_str_appendc(buf, '<');
 }
 break;

 case '>':
 if (options & PHP_JSON_HEX_TAG) {
 smart_str_appendl(buf, "\u003E", 6);
 } else {
 smart_str_appendc(buf, '>');
 }
 break;

 case '&':
 if (options & PHP_JSON_HEX_AMP) {
 smart_str_appendl(buf, "\u0026", 6);
 } else {
 smart_str_appendc(buf, '&');
 }
 break;

 case ''':
 if (options & PHP_JSON_HEX_APOS) {
 smart_str_appendl(buf, "\u0027", 6);
 } else {
 smart_str_appendc(buf, ''');
 }
 break;

 default: //Up to here, the value will be appended to buf without special characters
 if (us >= ' ' && (us & 127) == us) {
 smart_str_appendc(buf, (unsigned char) us);
 }else {
                                            smart_str_appendl(buf, "\u", 2);
                                            us = REVERSE16(us);

                                            smart_str_appendc(buf, digits[us & ((1 << 4) - 1)]);
                                            us >>= 4;
                                            smart_str_appendc(buf, digits[us & ((1 << 4) - 1)]);
                                            us >>= 4;
                                            smart_str_appendc(buf, digits[us & ((1 << 4) - 1)]);
                                            us >>= 4;
                                            smart_str_appendc(buf, digits[us & ((1 << 4) - 1)]);
                                    }
                                    break;
                    }
            }
            smart_str_appendc(buf, '"'); //结束 双引号。
            efree(utf16);
    }

Let’s take a look at arrays and objects. It’s also very simple.

static void json_encode_array(smart_str *buf, zval **val, int options TSRMLS_DC) /* {{{ */
{
            int i, r;
            HashTable *myht;

            if (Z_TYPE_PP(val) == IS_ARRAY) {
                    myht = HASH_OF(*val);
                    r = (options & PHP_JSON_FORCE_OBJECT) ? PHP_JSON_OUTPUT_OBJECT : json_determine_array_type(val TSRMLS_CC);
            } else {
                    myht = Z_OBJPROP_PP(val);
                    r = PHP_JSON_OUTPUT_OBJECT;
            }

            if (myht && myht->nApplyCount > 1) {
                    php_error_docref(NULL TSRMLS_CC, E_WARNING, "recursion detected");
                    smart_str_appendl(buf, "null", 4);
                    return;
            }
    //开始标签
            if (r == PHP_JSON_OUTPUT_ARRAY) {
                    smart_str_appendc(buf, '[');
            } else {
                    smart_str_appendc(buf, '{');
            }

            i = myht ? zend_hash_num_elements(myht) : 0;

            if (i > 0)
            {
                    char *key;
                    zval **data;
                    ulong index;
                    uint key_len;
                    HashPosition pos;
                    HashTable *tmp_ht;
                    int need_comma = 0;

                    zend_hash_internal_pointer_reset_ex(myht, &pos);
    //便利哈希表
                    for (;; zend_hash_move_forward_ex(myht, &pos)) {
                            i = zend_hash_get_current_key_ex(myht, &key, &key_len, &index, 0, &pos);
                            if (i == HASH_KEY_NON_EXISTANT)
                                    break;

                            if (zend_hash_get_current_data_ex(myht, (void **) &data, &pos) == SUCCESS) {
                                    tmp_ht = HASH_OF(*data);
                                    if (tmp_ht) {
                                            tmp_ht->nApplyCount++;
                                    }

                                    if (r == PHP_JSON_OUTPUT_ARRAY) {
                                            if (need_comma) {
                                                    smart_str_appendc(buf, ',');
                                            } else {
                                                    need_comma = 1;
                                            }
    //将值append到 buf中
                                            php_json_encode(buf, *data, options TSRMLS_CC);
                                    } else if (r == PHP_JSON_OUTPUT_OBJECT) {
                                            if (i == HASH_KEY_IS_STRING) {
                                                    if (key[0] == '