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Tcl_DictObj(3tcl) Tcl Library Procedures Tcl_DictObj(3tcl)
 


NAME

Tcl_NewDictObj, Tcl_DictObjPut, Tcl_DictObjGet, Tcl_DictObjRemove,
  Tcl_DictObjSize, Tcl_DictObjFirst, Tcl_DictObjNext, Tcl_DictObjDone,
  Tcl_DictObjPutKeyList, Tcl_DictObjRemoveKeyList - manipulate Tcl objects as
  dictionaries

SYNOPSIS


#include <tcl.h>


Tcl_Obj *
Tcl_NewDictObj()


int
Tcl_DictObjGet(interp, dictPtr, keyPtr, valuePtrPtr)


int
Tcl_DictObjPut(interp, dictPtr, keyPtr, valuePtr)


int
Tcl_DictObjRemove(interp, dictPtr, keyPtr)


int
Tcl_DictObjSize(interp, dictPtr, sizePtr)


int
Tcl_DictObjFirst(interp, dictPtr, searchPtr,
                 keyPtrPtr, valuePtrPtr, donePtr)


void
Tcl_DictObjNext(searchPtr, keyPtrPtr, valuePtrPtr, donePtr)


void
Tcl_DictObjDone(searchPtr)


int
Tcl_DictObjPutKeyList(interp, dictPtr, keyc, keyv, valuePtr)


int
Tcl_DictObjRemoveKeyList(interp, dictPtr, keyc, keyv)



ARGUMENTS



  
Tcl_Interp *interp (in)

  
If an error occurs while converting an object to be a dictionary object,
      an error message is left in the interpreter's result object unless
      interp is NULL.





  
Tcl_Obj *dictPtr (in/out)

  
Points to the dictionary object to be manipulated. If dictPtr does
      not already point to a dictionary object, an attempt will be made to
      convert it to one.





  
Tcl_Obj *keyPtr (in)

  
Points to the key for the key/value pair being manipulated within the
      dictionary object.





  
Tcl_Obj **keyPtrPtr (out)

  
Points to a variable that will have the key from a key/value pair placed
      within it. May be NULL to indicate that the caller is not interested in
      the key.





  
Tcl_Obj *valuePtr (in)

  
Points to the value for the key/value pair being manipulate within the
      dictionary object (or sub-object, in the case of
      Tcl_DictObjPutKeyList.)





  
Tcl_Obj **valuePtrPtr (out)

  
Points to a variable that will have the value from a key/value pair placed
      within it. For Tcl_DictObjFirst and Tcl_DictObjNext, this
      may be NULL to indicate that the caller is not interested in the
    value.





  
int *sizePtr (out)

  
Points to a variable that will have the number of key/value pairs
      contained within the dictionary placed within it.





  
Tcl_DictSearch *searchPtr (in/out)

  
Pointer to record to use to keep track of progress in enumerating all
      key/value pairs in a dictionary. The contents of the record will be
      initialized by the call to Tcl_DictObjFirst. If the enumerating is
      to be terminated before all values in the dictionary have been returned,
      the search record must be passed to Tcl_DictObjDone to
      enable the internal locks to be released.





  
int *donePtr (out)

  
Points to a variable that will have a non-zero value written into it when
      the enumeration of the key/value pairs in a dictionary has completed, and
      a zero otherwise.





  
int keyc (in)

  
Indicates the number of keys that will be supplied in the keyv
      array.





  
Tcl_Obj *const *keyv (in)

  
Array of keyc pointers to objects that Tcl_DictObjPutKeyList
      and Tcl_DictObjRemoveKeyList will use to locate the key/value pair
      to manipulate within the sub-dictionaries of the main dictionary object
      passed to them.
    
    

    
 

    

  




DESCRIPTION

Tcl dictionary objects have an internal representation that supports efficient
  mapping from keys to values and which guarantees that the particular ordering
  of keys within the dictionary remains the same modulo any keys being deleted
  (which removes them from the order) or added (which adds them to the end of
  the order). If reinterpreted as a list, the values at the even-valued indices
  in the list will be the keys of the dictionary, and each will be followed (in
  the odd-valued index) by the value associated with that key.


The procedures described in this man page are used to create, modify, index, and
  iterate over dictionary objects from C code.


Tcl_NewDictObj creates a new, empty dictionary object. The string
  representation of the object will be invalid, and the reference count of the
  object will be zero.


Tcl_DictObjGet looks up the given key within the given dictionary and
  writes a pointer to the value associated with that key into the variable
  pointed to by valuePtrPtr, or a NULL if the key has no mapping within
  the dictionary. The result of this procedure is TCL_OK, or
  TCL_ERROR if the dictPtr cannot be converted to a dictionary.


Tcl_DictObjPut updates the given dictionary so that the given key maps to
  the given value; any key may exist at most once in any particular dictionary.
  The dictionary must not be shared, but the key and value may be. This
  procedure may increase the reference count of both key and value if it proves
  necessary to store them. Neither key nor value should be NULL. The result of
  this procedure is TCL_OK, or TCL_ERROR if the dictPtr
  cannot be converted to a dictionary.


Tcl_DictObjRemove updates the given dictionary so that the given key has
  no mapping to any value. The dictionary must not be shared, but the key may
  be. The key actually stored in the dictionary will have its reference count
  decremented if it was present. It is not an error if the key did not
  previously exist. The result of this procedure is TCL_OK, or
  TCL_ERROR if the dictPtr cannot be converted to a dictionary.


Tcl_DictObjSize updates the given variable with the number of key/value
  pairs currently in the given dictionary. The result of this procedure is
  TCL_OK, or TCL_ERROR if the dictPtr cannot be converted
  to a dictionary.


Tcl_DictObjFirst commences an iteration across all the key/value pairs in
  the given dictionary, placing the key and value in the variables pointed to by
  the keyPtrPtr and valuePtrPtr arguments (which may be NULL to
  indicate that the caller is uninterested in they key or variable
  respectively.) The next key/value pair in the dictionary may be retrieved with
  Tcl_DictObjNext. Concurrent updates of the dictionary's internal
  representation will not modify the iteration processing unless the dictionary
  is unshared, when this will trigger premature termination of the iteration
  instead (which Tcl scripts cannot trigger via the dict command.) The
  searchPtr argument points to a piece of context that is used to
  identify which particular iteration is being performed, and is initialized by
  the call to Tcl_DictObjFirst. The donePtr argument points to a
  variable that is updated to be zero of there are further key/value pairs to be
  iterated over, or non-zero if the iteration is complete. The order of
  iteration is implementation-defined. If the dictPtr argument cannot be
  converted to a dictionary, Tcl_DictObjFirst returns TCL_ERROR
  and the iteration is not commenced, and otherwise it returns TCL_OK.


When Tcl_DictObjFirst is called upon a dictionary, a lock is placed on
  the dictionary to enable that dictionary to be iterated over safely without
  regard for whether the dictionary is modified during the iteration. Because of
  this, once the iteration over a dictionary's keys has finished (whether
  because all values have been iterated over as indicated by the variable
  indicated by the donePtr argument being set to one, or because no
  further values are required) the Tcl_DictObjDone function must be
  called with the same searchPtr as was passed to Tcl_DictObjFirst
  so that the internal locks can be released. Once a particular searchPtr
  is passed to Tcl_DictObjDone, passing it to Tcl_DictObjNext
  (without first initializing it with Tcl_DictObjFirst) will result in no
  values being produced and the variable pointed to by donePtr being set
  to one. It is safe to call Tcl_DictObjDone multiple times on the same
  searchPtr for each call to Tcl_DictObjFirst.


The procedures Tcl_DictObjPutKeyList and Tcl_DictObjRemoveKeyList
  are the close analogues of Tcl_DictObjPut and Tcl_DictObjRemove
  respectively, except that instead of working with a single dictionary, they
  are designed to operate on a nested tree of dictionaries, with inner
  dictionaries stored as values inside outer dictionaries. The keyc and
  keyv arguments specify a list of keys (with outermost keys first) that
  acts as a path to the key/value pair to be affected. Note that there is no
  corresponding operation for reading a value for a path as this is easy to
  construct from repeated use of Tcl_DictObjGet. With
  Tcl_DictObjPutKeyList, nested dictionaries are created for non-terminal
  keys where they do not already exist. With Tcl_DictObjRemoveKeyList,
  all non-terminal keys must exist and have dictionaries as their values.

EXAMPLE

Using the dictionary iteration interface to search determine if there is a key
  that maps to itself:





Tcl_DictSearch search;
Tcl_Obj *key, *value;
int done;


/*
 * Assume interp and objPtr are parameters.  This is the
 * idiomatic way to start an iteration over the dictionary; it
 * sets a lock on the internal representation that ensures that
 * there are no concurrent modification issues when normal
 * reference count management is also used.  The lock is
 * released automatically when the loop is finished, but must
 * be released manually when an exceptional exit from the loop
 * is performed. However it is safe to try to release the lock
 * even if we've finished iterating over the loop.
 */
if ( Tcl_DictObjFirst(interp, objPtr, &search,
        &key, &value, &done) != TCL_OK) {
    return TCL_ERROR;
}
for (; !done ;  Tcl_DictObjNext(&search, &key, &value, &done)) {
    /*
     * Note that strcmp() is not a good way of comparing
     * objects and is just used here for demonstration
     * purposes.
     */
    if (!strcmp(Tcl_GetString(key), Tcl_GetString(value))) {
        break;
    }
}
Tcl_DictObjDone(&search);
Tcl_SetObjResult(interp, Tcl_NewBooleanObj(!done));
return TCL_OK;





SEE ALSO

Tcl_NewObj, Tcl_DecrRefCount, Tcl_IncrRefCount, Tcl_InitObjHashTable

KEYWORDS

dict, dict object, dictionary, dictionary object, hash table, iteration,
  object



  

    8.5
    Tcl