DString

Tcl_DString(3)               Tcl Library Procedures               Tcl_DString(3)



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NAME
       Tcl_DStringInit, Tcl_DStringAppend, Tcl_DStringAppendElement,
       Tcl_DStringStartSublist, Tcl_DStringEndSublist, Tcl_DStringLength,
       Tcl_DStringValue, Tcl_DStringSetLength, Tcl_DStringTrunc,
       Tcl_DStringFree, Tcl_DStringResult, Tcl_DStringGetResult - manipulate
       dynamic strings

SYNOPSIS
       #include <tcl.h>

       Tcl_DStringInit(dsPtr)

       char *
       Tcl_DStringAppend(dsPtr, bytes, length)

       char *
       Tcl_DStringAppendElement(dsPtr, element)

       Tcl_DStringStartSublist(dsPtr)

       Tcl_DStringEndSublist(dsPtr)

       int
       Tcl_DStringLength(dsPtr)

       char *
       Tcl_DStringValue(dsPtr)

       Tcl_DStringSetLength(dsPtr, newLength)

       Tcl_DStringTrunc(dsPtr, newLength)

       Tcl_DStringFree(dsPtr)

       Tcl_DStringResult(interp, dsPtr)

       Tcl_DStringGetResult(interp, dsPtr)

ARGUMENTS
       Tcl_DString *dsPtr (in/out)         Pointer to structure that is used to
                                           manage a dynamic string.

       const char *bytes (in)              Pointer to characters to append to
                                           dynamic string.

       const char *element (in)            Pointer to characters to append as
                                           list element to dynamic string.

       int length (in)                     Number of bytes from bytes to add to
                                           dynamic string.  If -1, add all
                                           characters up to null terminating
                                           character.

       int newLength (in)                  New length for dynamic string, not
                                           including null terminating character.

       Tcl_Interp *interp (in/out)         Interpreter whose result is to be set
                                           from or moved to the dynamic string.
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DESCRIPTION
       Dynamic strings provide a mechanism for building up arbitrarily long
       strings by gradually appending information.  If the dynamic string is
       short then there will be no memory allocation overhead;  as the string
       gets larger, additional space will be allocated as needed.

       Tcl_DStringInit initializes a dynamic string to zero length.  The
       Tcl_DString structure must have been allocated by the caller.  No
       assumptions are made about the current state of the structure; anything
       already in it is discarded.  If the structure has been used previously,
       Tcl_DStringFree should be called first to free up any memory allocated
       for the old string.

       Tcl_DStringAppend adds new information to a dynamic string, allocating
       more memory for the string if needed.  If length is less than zero then
       everything in bytes is appended to the dynamic string;  otherwise length
       specifies the number of bytes to append.  Tcl_DStringAppend returns a
       pointer to the characters of the new string.  The string can also be
       retrieved from the string field of the Tcl_DString structure.

       Tcl_DStringAppendElement is similar to Tcl_DStringAppend except that it
       does not take a length argument (it appends all of element) and it
       converts the string to a proper list element before appending.
       Tcl_DStringAppendElement adds a separator space before the new list
       element unless the new list element is the first in a list or sub-list
       (i.e. either the current string is empty, or it contains the single
       character “{”, or the last two characters of the current string are “
       {”).  Tcl_DStringAppendElement returns a pointer to the characters of the
       new string.

       Tcl_DStringStartSublist and Tcl_DStringEndSublist can be used to create
       nested lists.  To append a list element that is itself a sublist, first
       call Tcl_DStringStartSublist, then call Tcl_DStringAppendElement for each
       of the elements in the sublist, then call Tcl_DStringEndSublist to end
       the sublist.  Tcl_DStringStartSublist appends a space character if
       needed, followed by an open brace;  Tcl_DStringEndSublist appends a close
       brace.  Lists can be nested to any depth.

       Tcl_DStringLength is a macro that returns the current length of a dynamic
       string (not including the terminating null character).  Tcl_DStringValue
       is a  macro that returns a pointer to the current contents of a dynamic
       string.

       Tcl_DStringSetLength changes the length of a dynamic string.  If
       newLength is less than the string's current length, then the string is
       truncated.  If newLength is greater than the string's current length,
       then the string will become longer and new space will be allocated for
       the string if needed.  However, Tcl_DStringSetLength will not initialize
       the new space except to provide a terminating null character;  it is up
       to the caller to fill in the new space.  Tcl_DStringSetLength does not
       free up the string's storage space even if the string is truncated to
       zero length, so Tcl_DStringFree will still need to be called.

       Tcl_DStringTrunc changes the length of a dynamic string.  This procedure
       is now deprecated.  Tcl_DStringSetLength  should be used instead.

       Tcl_DStringFree should be called when you are finished using the string.
       It frees up any memory that was allocated for the string and
       reinitializes the string's value to an empty string.

       Tcl_DStringResult sets the result of interp to the value of the dynamic
       string given by dsPtr.  It does this by moving a pointer from dsPtr to
       the interpreter's result.  This saves the cost of allocating new memory
       and copying the string.  Tcl_DStringResult also reinitializes the dynamic
       string to an empty string.

       Tcl_DStringGetResult does the opposite of Tcl_DStringResult.  It sets the
       value of dsPtr to the result of interp and it clears interp's result.  If
       possible it does this by moving a pointer rather than by copying the
       string.


KEYWORDS
       append, dynamic string, free, result



Tcl                                    7.4                        Tcl_DString(3)