php json_encode应用分析 -tutorial php-php.cn

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);
}

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JSON_G(error_code) = PHP_JSON_ERROR_NONE; 是定义的json错误，该错误可以通过json_last_error函数获取，你用过吗？反正我没用过。 php_json_encode是主要的操作

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_appendl(buf, "null", 4); //输出NULL
break;
case IS_BOOL:
if (Z_BVAL_P(val)) {
smart_str_appendl(buf, "true", 4);//输出true
} else {
smart_str_appendl(buf, "false", 5);//输出false
}
break;
case IS_LONG:
smart_str_append_long(buf, Z_LVAL_P(val));//输出长整形的值
break;
case IS_DOUBLE:
{
char *d = NULL;
int len;
double dbl = Z_DVAL_P(val);
if (!zend_isinf(dbl) && !zend_isnan(dbl)) {//非无穷尽
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://字符串
json_escape_string(buf, Z_STRVAL_P(val), Z_STRLEN_P(val), options TSRMLS_CC);
break;
case IS_ARRAY://数组和对象
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;
}

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很明显，根据不同的类型，会有相应的case。最复杂的是字符串、数组、对象这三种类型，数组和对象是同一种操作。先看看字符串吧，很长，注释直接写在代码里。

//options应该是5.3版本之后才支持的，由以下常量组成的二进制掩码： 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.虽然我没用过。。。
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) {//如果长度为0，则直接返回双引号 ""
smart_str_appendl(buf, "\"\"", 2);
return;
}
if (options & PHP_JSON_NUMERIC_CHECK) {//检测是否为0-9的数字，如果是数字，那么就会直接把数据作为long或double类型返回。
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); //这里会对你输入的值一次处理转成对应的Dec码，比如1是49，a是97这样的，保存到utf16中。
if (len if (utf16) {
efree(utf16);
}
if (len 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, '"'); //输入 \"
//下面这一段代码就是将一些特殊字符转义如双引号，反斜线等等
while (pos {
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: //一直到这里，没有特殊字符就会把值append到buf中
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 us >>= 4;
smart_str_appendc(buf, digits[us & ((1 us >>= 4;
smart_str_appendc(buf, digits[us & ((1 us >>= 4;
smart_str_appendc(buf, digits[us & ((1 }
break;
}
}
smart_str_appendc(buf, '"'); //结束双引号。
efree(utf16);
}

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再来看看数组和对象，也很简单，

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] == '\0' && Z_TYPE_PP(val) == IS_OBJECT) {
/* Skip protected and private members. */
if (tmp_ht) {
tmp_ht->nApplyCount--;
}
continue;
}
if (need_comma) {
smart_str_appendc(buf, ',');
} else {
need_comma = 1;
}
json_escape_string(buf, key, key_len - 1, options & ~PHP_JSON_NUMERIC_CHECK TSRMLS_CC);
smart_str_appendc(buf, ':');
php_json_encode(buf, *data, options TSRMLS_CC);
} else {
if (need_comma) {
smart_str_appendc(buf, ',');
} else {
need_comma = 1;
}
smart_str_appendc(buf, '"');
smart_str_append_long(buf, (long) index);
smart_str_appendc(buf, '"');
smart_str_appendc(buf, ':');
php_json_encode(buf, *data, options TSRMLS_CC);
}
}
if (tmp_ht) {
tmp_ht->nApplyCount--;
}
}
}
}
//结束标签
if (r == PHP_JSON_OUTPUT_ARRAY) {
smart_str_appendc(buf, ']');
} else {
smart_str_appendc(buf, '}');
}
}