[PHP source reading]explode and implode functions, explodeimplode_php tutorial

[PHP source reading]explode and implode functions, Explodeimplode

The explode and implode functions are primarily used as string-array operations, such as taking a parameter to split a string based on a character, or using one word to match the result of an array and outputting it as a string. These two functions are often used in PHP, so it is necessary to understand their rationale.

Explode

Array explode (string $delimiter, String $string, [, $limit])

Returns an array of strings, each of which is a substring of string, separated by the $delimiter as the boundary point.

$limit

If $limit is set and is a positive number, the returned array contains a maximum of $limit elements, and the last element will contain the remainder of the $string.

If $limit is a negative number, all elements except the last-$limit element are returned.

If $limit is 0, it will be treated as 1.

$delimiter

If $delimiter is empty, the function returns FALSE. If delimiter is not in a string and $limit is negative, an empty array is returned.

Core source

    //returns False if Delimiter is an empty string    if(Delim_len = =0) {php_error_docref (NULL tsrmls_cc, e_warning,"Empty delimiter");    Return_false; }    //Initialize the returned arrayArray_init (Return_value); if(Str_len = =0) {          if(Limit >=0) {              //if the string is empty and limit is greater than or equal to 0, an array containing an empty string is returned, noting that sizeof ("") = = 1Add_next_index_stringl (Return_value,"",sizeof("") -1,1); }        return; }    //initializing string variables for zstr and ZdelimZval_stringl (&zstr, str, Str_len,0); Zval_stringl (&zdelim, Delim, Delim_len,0); if(Limit >1) {        //limit greater than 1,limit default is Long_maxPhp_explode (&zdelim, &zstr, Return_value, limit); } Else if(Limit <0) {        //limit is negativePhp_explode_negative_limit (&zdelim, &zstr, Return_value, limit); } Else {        //limit is 0, treated as 1, returns the entire string, and the Add_index_stringl function appends str to the array return_valueAdd_index_stringl (Return_value,0, str, Str_len,1); }

After processing the special case and initializing the variable, call the php_explode/php_explode_negative_limit function to proceed with the next step. Here is the source code for the Php_explode function

Php_explode

ENDP= Z_strval_p (str) +z_strlen_p (str); //P1 point to start of stringP1 =z_strval_p (str); //P2 points to the position of the first separator, the main use of the PHP_MEMNSTR function is to find the separator positionP2 =php_memnstr (z_strval_p (str), z_strval_p (Delim), Z_strlen_p (Delim), ENDP); if(P2 = =NULL) {        //p2 null means no delimiter is found and returns the entire string directlyAdd_next_index_stringl (Return_value, p1, Z_strlen_p (str),1); } Else {         Do {            //add P1 to the Return_value array and move to the next delimiter positionAdd_next_index_stringl (Return_value, p1, P2-p1,1); P1= P2 +z_strlen_p (Delim); }  while((P2 = Php_memnstr (P1, Z_strval_p (Delim), Z_strlen_p (Delim), ENDP))! = NULL &&--limit >1); //append the last value to Return_value        if(P1 <=ENDP) Add_next_index_stringl (Return_value, p1, ENDP-P1,1); }

When implemented, calls the Add_next_index_stringl to add each string to the array return_value . Add_next_index_string is the core function of this function.

int Const Char UINT int duplicate) {    *tmp;    Make_std_zval (TMP);    ZVAL_STRINGL (TMP, str, length, duplicate);     return sizeof (Zval *), NULL);}

The ADD_NEXT_INDEX_STRINGL function calls the Zend_hash_next_index_insert function to insert str into the array. And look at the source code of the Php_explode_negative_limit function

Php_explode_negative_limit

//if delimiter is not in a string, and the limit is negative, nothing is done, and returning an empty ARRAY,P2 is null to indicate that delimiter is not in string    if(P2 = =NULL) {        /*
If limit <=-1, then nothing is done, so if there is only one string, then-1 + (limit) <= 0
Returns an empty array*/    } Else {        intAllocated = Explode_alloc_step, found =0; LongI, To_return; Char**positions = Emalloc (Allocated *sizeof(Char*)); //the position of the first wordpositions[found++] =P1;  Do {            if(Found >=allocated) {Allocated= Found + Explode_alloc_step;/*Make sure there's enough memory space*/positions= Erealloc (positions, allocated*sizeof(Char*)); }            //positions Save the starting position of each wordpositions[found++] = P1 = p2 +z_strlen_p (Delim); }  while((P2 = Php_memnstr (P1, Z_strval_p (Delim), Z_strlen_p (Delim), ENDP))! =NULL); //To_return is the number of return_value, in fact equal to found-|limit|To_return = limit +found; /*limit is at least-1, so no bounds checking is required: I is never less than found*/         for(i =0; i < to_return;i++) {/*This check is to check that To_return is greater than 0*/Add_next_index_stringl (Return_value, Positions[i], (positions[i+1]-Z_strlen_p (Delim))-Positions[i],1                );    } efree (positions); }

Php_explode_negative_limit is a similar operation to Php_implode, and after finding the delimited string, call the Add_next_index_string function to add the limit + found string to the Return_ The value array.

Implode

String implode (string $glue, array $pieces)
String implode (array $pieces)

Converts the value of a one-dimensional array to a string

The implode function can receive two parameter sequences.

Core code

if(Arg2 = =NULL) {        //The second parameter is empty, and the first argument must be an array        if(Z_TYPE_PP (arg1)! =Is_array) {Php_error_docref (NULL tsrmls_cc, e_warning,"Argument must is an array"); return; } make_std_zval (Delim);#define_impl_empty ""//By default, use the ConnectZval_stringl (Delim, _impl_empty,sizeof(_impl_empty)-1,0);        Separate_zval (ARG1); Arr= *arg1; } Else {        //set the value of a parameter based on the parameter type        if(Z_TYPE_PP (arg1) = =Is_array) {arr= *arg1;            CONVERT_TO_STRING_EX (ARG2); Delim= *arg2; } Else if(Z_TYPE_PP (arg2) = =Is_array) {arr= *arg2;            CONVERT_TO_STRING_EX (ARG1); Delim= *arg1; } Else{php_error_docref (NULL tsrmls_cc, e_warning,"Invalid arguments passed"); return; }    }    //Call the Php_implode function to convertPhp_implode (Delim, arr, Return_value tsrmls_cc);

In the underlying implementation, the IMPLODE function processes the parameters and calls the Php_implode function for conversion.

Php_implode

//iterate through each element of the array, determine its type, and then call the Smart_str_appendl function to append the value to the string     while(ZEND_HASH_GET_CURRENT_DATA_EX (Z_arrval_p (arr), (void* *) &tmp, &pos) = =SUCCESS) {        Switch((*TMP)type) {             CaseIs_string:smart_str_appendl (&implstr, Z_STRVAL_PP (TMP), Z_STRLEN_PP (TMP));  Break;  CaseIs_long: {CharStmp[max_length_of_long +1]; Str_len= slprintf (Stmp,sizeof(STMP),"%ld", Z_LVAL_PP (TMP)); Smart_str_appendl (&implstr, Stmp, Str_len); }                 Break;  CaseIs_bool:if(Z_LVAL_PP (tmp) = =1) {Smart_str_appendl (&IMPLSTR,"1",sizeof("1")-1); }                 Break;  CaseIs_null: Break;  Caseis_double: {Char*stmp; Str_len= spprintf (&stmp,0,"%.*g", (int) EG (precision), Z_DVAL_PP (TMP)); Smart_str_appendl (&implstr, Stmp, Str_len);            Efree (STMP); }                 Break;  CaseIs_object: {intcopy;                Zval expr; Zend_make_printable_zval (*tmp, &expr, &copy); Smart_str_appendl (&implstr, Z_strval (expr), Z_strlen (expr)); if(copy) {Zval_dtor (&expr); }            }                 Break; default: Tmp_val= **tmp; Zval_copy_ctor (&tmp_val); Convert_to_string (&tmp_val); Smart_str_appendl (&Implstr, Z_strval (Tmp_val), Z_strlen (Tmp_val)); Zval_dtor (&tmp_val);  Break; }        //Add glue characters        if(++i! =Numelems) {Smart_str_appendl (&Implstr, Z_strval_p (Delim), Z_strlen_p (Delim)); } zend_hash_move_forward_ex (Z_arrval_p (arr),&POS); }    //Add a character 0 at the tailSmart_str_0 (&IMPLSTR);

As you can see, the Php_implode function iterates through each element of the array, determines its type, makes the necessary type conversions, and then calls the Smart_str_appendl function to append the value to the string. Smart_str_appendl is the core function in the implode implementation code.

Smart_str_appendl

#define Smart_str_appendl (dest, SRC, len) \    0)#define smart_str_ APPENDL_EX (dest, SRC, nlen, what) do {            \    register size_t __nl;                                            \    *__dest = (SMART_STR *) (dest);                        \                                                                    \    smart_str_alloc4 (__dest, (Nlen), (what), __nl);                    \    memcpy (__dest->c + __dest->len, (SRC), (nlen));                    \    __dest->len = __nl;                                                  while (0)

SMART_STR_APPENDL_EX primarily calls the memcpy function for string copying.

Original article, writing Limited, Caishuxueqian, if there is not in the text, million hope to inform.

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