A brief discussion of PHP source code 1: explode and implode functions

This article mainly introduces a brief discussion of PHP source code 1: explode and implode functions, which has a certain reference value. Now I share it with you. Friends in need can refer to it.

1. explode and implode Function
array explode (string separator, string string [, int limit])
This function returns an array composed of strings. Each element is a substring of string. They are used as boundary points by string separator. Split it out. If the limit parameter is set, the returned array contains up to limit elements, and the last element will contain the remainder of the string.

The time complexity of this function should be O(strlen(separator) * strlen(string))
The implementation process is basically to traverse the string string and compare it with the separator. If they are the same, then Write to the hash table, and move the string pointer to a new position (that is, the right side of each separator);

In addition, there is special processing for the case where the limit is less than 0
The implementation of this function is mainly dependent on For the php_memnstr function, we can see its definition in the php.h file,
#define php_memnstr zend_memnstr
The real function is zend_memnstr, you can see it in line 217 of the Zend/zend_operators.h file The definition, its implementation is mainly a while loop and two C language functions memchr and memcmp

string implode (string glue, array pieces)
This function returns an array of pieces connected with glue string The string of each element.
This function can take an array as a parameter, an array and a string as parameters, and the order of the string and array can be changed. There are special treatments for each situation in the program, as follows Code:

if (argc == 1) {
                            if (Z_TYPE_PP(arg1) != IS_ARRAY) {                            //              只有一个参数并且还不是数组
                                          php_error_docref(NULL TSRMLS_CC, E_WARNING, "Argument must be an array");
                                          return;
                            } 
                            MAKE_STD_ZVAL(delim);#define _IMPL_EMPTY ""
                            ZVAL_STRINGL(delim, _IMPL_EMPTY, sizeof(_IMPL_EMPTY) - 1, 0); 
                            SEPARATE_ZVAL(arg1);
                            arr = *arg1;
              } else {              //              两个参数
                            if (Z_TYPE_PP(arg1) == IS_ARRAY) {              //              如果每一个参数是数组
                                          arr = *arg1;
                                          convert_to_string_ex(arg2);
                                          delim = *arg2;
                            } else if (Z_TYPE_PP(arg2) == IS_ARRAY) {              //              如果第二个参数是数组
                                          arr = *arg2;
                                          convert_to_string_ex(arg1);
                                          delim = *arg1;
                            } else {
                                          php_error_docref(NULL TSRMLS_CC, E_WARNING, "Invalid arguments passed");
                                          return;
                            }
              }

In the end, the array will be assigned to arr, the delimited string will be assigned to delim, and the missing string will be set to ""

is a process of traversing the array and concatenating the strings. It’s just that smart_str related functions are used in this process (please click here for more information), and different connection operations are performed for different types (if it is a number, the number needs to be converted into a string, these are processed by related functions in smart_str )

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