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Tcl_StringObj(3)            Tcl Library Procedures            Tcl_StringObj(3)

______________________________________________________________________________


NAME

       Tcl_NewStringObj, Tcl_NewUnicodeObj, Tcl_SetStringObj,
       Tcl_SetUnicodeObj, Tcl_GetStringFromObj, Tcl_GetString,
       Tcl_GetUnicodeFromObj, Tcl_GetUnicode, Tcl_GetUniChar,
       Tcl_GetCharLength, Tcl_GetRange, Tcl_AppendToObj,
       Tcl_AppendUnicodeToObj, Tcl_AppendObjToObj, Tcl_AppendStringsToObj,
       Tcl_AppendStringsToObjVA, Tcl_AppendLimitedToObj, Tcl_Format,
       Tcl_AppendFormatToObj, Tcl_ObjPrintf, Tcl_AppendPrintfToObj,
       Tcl_SetObjLength, Tcl_AttemptSetObjLength, Tcl_ConcatObj - manipulate
       Tcl values as strings


SYNOPSIS

       #include <tcl.h>

       Tcl_Obj *
       Tcl_NewStringObj(bytes, length)

       Tcl_Obj *
       Tcl_NewUnicodeObj(unicode, numChars)

       void
       Tcl_SetStringObj(objPtr, bytes, length)

       void
       Tcl_SetUnicodeObj(objPtr, unicode, numChars)

       char *
       Tcl_GetStringFromObj(objPtr, lengthPtr)

       char *
       Tcl_GetString(objPtr)

       Tcl_UniChar *
       Tcl_GetUnicodeFromObj(objPtr, lengthPtr)

       Tcl_UniChar *
       Tcl_GetUnicode(objPtr)

       Tcl_UniChar
       Tcl_GetUniChar(objPtr, index)

       int
       Tcl_GetCharLength(objPtr)

       Tcl_Obj *
       Tcl_GetRange(objPtr, first, last)

       void
       Tcl_AppendToObj(objPtr, bytes, length)

       void
       Tcl_AppendUnicodeToObj(objPtr, unicode, numChars)

       void
       Tcl_AppendObjToObj(objPtr, appendObjPtr)

       void
       Tcl_AppendStringsToObj(objPtr, string, string, ... (char *)NULL)

       void
       Tcl_AppendStringsToObjVA(objPtr, argList)

       void
       Tcl_AppendLimitedToObj(objPtr, bytes, length, limit, ellipsis)

       Tcl_Obj *
       Tcl_Format(interp, format, objc, objv)

       int
       Tcl_AppendFormatToObj(interp, objPtr, format, objc, objv)

       Tcl_Obj *
       Tcl_ObjPrintf(format, ...)

       void
       Tcl_AppendPrintfToObj(objPtr, format, ...)

       void
       Tcl_SetObjLength(objPtr, newLength)

       int
       Tcl_AttemptSetObjLength(objPtr, newLength)

       Tcl_Obj *
       Tcl_ConcatObj(objc, objv)


ARGUMENTS

       const char *bytes (in)                        Points to the first byte
                                                     of an array of
                                                     UTF-8-encoded bytes used
                                                     to set or append to a
                                                     string value.  This byte
                                                     array may contain
                                                     embedded null characters
                                                     unless numChars is
                                                     negative.  (Applications
                                                     needing null bytes should
                                                     represent them as the
                                                     two-byte sequence
                                                     \300\200, use
                                                     Tcl_ExternalToUtf to
                                                     convert, or
                                                     Tcl_NewByteArrayObj if
                                                     the string is a
                                                     collection of
                                                     uninterpreted bytes.)

       int length (in)                               The number of bytes to
                                                     copy from bytes when
                                                     initializing, setting, or
                                                     appending to a string
                                                     value.  If negative, all
                                                     bytes up to the first
                                                     null are used.

       const Tcl_UniChar *unicode (in)               Points to the first byte
                                                     of an array of Unicode
                                                     characters used to set or
                                                     append to a string value.
                                                     This byte array may
                                                     contain embedded null
                                                     characters unless
                                                     numChars is negative.

       int numChars (in)                             The number of Unicode
                                                     characters to copy from
                                                     unicode when
                                                     initializing, setting, or
                                                     appending to a string
                                                     value.  If negative, all
                                                     characters up to the
                                                     first null character are
                                                     used.

       int index (in)                                The index of the Unicode
                                                     character to return.

       int first (in)                                The index of the first
                                                     Unicode character in the
                                                     Unicode range to be
                                                     returned as a new value.

       int last (in)                                 The index of the last
                                                     Unicode character in the
                                                     Unicode range to be
                                                     returned as a new value.

       Tcl_Obj *objPtr (in/out)                      Points to a value to
                                                     manipulate.

       Tcl_Obj *appendObjPtr (in)                    The value to append to
                                                     objPtr in
                                                     Tcl_AppendObjToObj.

       int *lengthPtr (out)                          If non-NULL, the location
                                                     where
                                                     Tcl_GetStringFromObj will
                                                     store the length of a
                                                     value's string
                                                     representation.

       const char *string (in)                       Null-terminated string
                                                     value to append to
                                                     objPtr.

       va_list argList (in)                          An argument list which
                                                     must have been
                                                     initialized using
                                                     va_start, and cleared
                                                     using va_end.

       int limit (in)                                Maximum number of bytes
                                                     to be appended.

       const char *ellipsis (in)                     Suffix to append when the
                                                     limit leads to string
                                                     truncation.  If NULL is
                                                     passed then the suffix
                                                     "..." is used.

       const char *format (in)                       Format control string
                                                     including % conversion
                                                     specifiers.

       int objc (in)                                 The number of elements to
                                                     format or concatenate.

       Tcl_Obj *objv[] (in)                          The array of values to
                                                     format or concatenate.

       int newLength (in)                            New length for the string
                                                     value of objPtr, not
                                                     including the final null
                                                     character.
______________________________________________________________________________


DESCRIPTION

       The procedures described in this manual entry allow Tcl values to be
       manipulated as string values.  They use the internal representation of
       the value to store additional information to make the string
       manipulations more efficient.  In particular, they make a series of
       append operations efficient by allocating extra storage space for the
       string so that it does not have to be copied for each append.  Also,
       indexing and length computations are optimized because the Unicode
       string representation is calculated and cached as needed.  When using
       the Tcl_Append* family of functions where the interpreter's result is
       the value being appended to, it is important to call Tcl_ResetResult
       first to ensure you are not unintentionally appending to existing data
       in the result value.

       Tcl_NewStringObj and Tcl_SetStringObj create a new value or modify an
       existing value to hold a copy of the string given by bytes and length.
       Tcl_NewUnicodeObj and Tcl_SetUnicodeObj create a new value or modify an
       existing value to hold a copy of the Unicode string given by unicode
       and numChars.  Tcl_NewStringObj and Tcl_NewUnicodeObj return a pointer
       to a newly created value with reference count zero.  All four
       procedures set the value to hold a copy of the specified string.
       Tcl_SetStringObj and Tcl_SetUnicodeObj free any old string
       representation as well as any old internal representation of the value.

       Tcl_GetStringFromObj and Tcl_GetString return a value's string
       representation.  This is given by the returned byte pointer and (for
       Tcl_GetStringFromObj) length, which is stored in lengthPtr if it is
       non-NULL.  If the value's UTF string representation is invalid (its
       byte pointer is NULL), the string representation is regenerated from
       the value's internal representation.  The storage referenced by the
       returned byte pointer is owned by the value manager.  It is passed back
       as a writable pointer so that extension author creating their own
       Tcl_ObjType will be able to modify the string representation within the
       Tcl_UpdateStringProc of their Tcl_ObjType.  Except for that limited
       purpose, the pointer returned by Tcl_GetStringFromObj or Tcl_GetString
       should be treated as read-only.  It is recommended that this pointer be
       assigned to a (const char *) variable.  Even in the limited situations
       where writing to this pointer is acceptable, one should take care to
       respect the copy-on-write semantics required by Tcl_Obj's, with
       appropriate calls to Tcl_IsShared and Tcl_DuplicateObj prior to any in-
       place modification of the string representation.  The procedure
       Tcl_GetString is used in the common case where the caller does not need
       the length of the string representation.

       Tcl_GetUnicodeFromObj and Tcl_GetUnicode return a value's value as a
       Unicode string.  This is given by the returned pointer and (for
       Tcl_GetUnicodeFromObj) length, which is stored in lengthPtr if it is
       non-NULL.  The storage referenced by the returned byte pointer is owned
       by the value manager and should not be modified by the caller.  The
       procedure Tcl_GetUnicode is used in the common case where the caller
       does not need the length of the unicode string representation.

       Tcl_GetUniChar returns the index'th character in the value's Unicode
       representation. The index is assumed to be in the appropriate range.

       Tcl_GetRange returns a newly created value comprised of the characters
       between first and last (inclusive) in the value's Unicode
       representation.  If the value's Unicode representation is invalid, the
       Unicode representation is regenerated from the value's string
       representation.  If first < 0, then the returned string starts at the
       beginning of the value. If last < 0, then the returned string ends at
       the end of the value.

       Tcl_GetCharLength returns the number of characters (as opposed to
       bytes) in the string value.

       Tcl_AppendToObj appends the data given by bytes and length to the
       string representation of the value specified by objPtr.  If the value
       has an invalid string representation, then an attempt is made to
       convert bytes to the Unicode format.  If the conversion is successful,
       then the converted form of bytes is appended to the value's Unicode
       representation.  Otherwise, the value's Unicode representation is
       invalidated and converted to the UTF format, and bytes is appended to
       the value's new string representation.  Eventually buffer growth is
       done by large allocations to optimize multiple calls.

       Tcl_AppendUnicodeToObj appends the Unicode string given by unicode and
       numChars to the value specified by objPtr.  If the value has an invalid
       Unicode representation, then unicode is converted to the UTF format and
       appended to the value's string representation.  Appends are optimized
       to handle repeated appends relatively efficiently (it over-allocates
       the string or Unicode space to avoid repeated reallocations and copies
       of value's string value).

       Tcl_AppendObjToObj is similar to Tcl_AppendToObj, but it appends the
       string or Unicode value (whichever exists and is best suited to be
       appended to objPtr) of appendObjPtr to objPtr.

       Tcl_AppendStringsToObj is similar to Tcl_AppendToObj except that it can
       be passed more than one value to append and each value must be a null-
       terminated string (i.e. none of the values may contain internal null
       characters).  Any number of string arguments may be provided, but the
       last argument must be a NULL pointer to indicate the end of the list.

       Tcl_AppendStringsToObjVA is the same as Tcl_AppendStringsToObj except
       that instead of taking a variable number of arguments it takes an
       argument list.

       Tcl_AppendLimitedToObj is similar to Tcl_AppendToObj except that it
       imposes a limit on how many bytes are appended.  This can be handy when
       the string to be appended might be very large, but the value being
       constructed should not be allowed to grow without bound. A common usage
       is when constructing an error message, where the end result should be
       kept short enough to be read.  Bytes from bytes are appended to objPtr,
       but no more than limit bytes total are to be appended. If the limit
       prevents all length bytes that are available from being appended, then
       the appending is done so that the last bytes appended are from the
       string ellipsis. This allows for an indication of the truncation to be
       left in the string.  When length is -1, all bytes up to the first zero
       byte are appended, subject to the limit. When ellipsis is NULL, the
       default string ... is used. When ellipsis is non-NULL, it must point to
       a zero-byte-terminated string in Tcl's internal UTF encoding.  The
       number of bytes appended can be less than the lesser of length and
       limit when appending fewer bytes is necessary to append only whole
       multi-byte characters.

       Tcl_Format is the C-level interface to the engine of the format
       command.  The actual command procedure for format is little more than

              Tcl_Format(interp, Tcl_GetString(objv[1]), objc-2, objv+2);

       The objc Tcl_Obj values in objv are formatted into a string according
       to the conversion specification in format argument, following the
       documentation for the format command.  The resulting formatted string
       is converted to a new Tcl_Obj with refcount of zero and returned.  If
       some error happens during production of the formatted string, NULL is
       returned, and an error message is recorded in interp, if interp is non-
       NULL.

       Tcl_AppendFormatToObj is an appending alternative form of Tcl_Format
       with functionality equivalent to:

              Tcl_Obj *newPtr = Tcl_Format(interp, format, objc, objv);
              if (newPtr == NULL) return TCL_ERROR;
              Tcl_AppendObjToObj(objPtr, newPtr);
              Tcl_DecrRefCount(newPtr);
              return TCL_OK;

       but with greater convenience and efficiency when the appending
       functionality is needed.

       Tcl_ObjPrintf serves as a replacement for the common sequence

              char buf[SOME_SUITABLE_LENGTH];
              sprintf(buf, format, ...);
              Tcl_NewStringObj(buf, -1);

       but with greater convenience and no need to determine
       SOME_SUITABLE_LENGTH. The formatting is done with the same core
       formatting engine used by Tcl_Format.  This means the set of supported
       conversion specifiers is that of the format command but the behavior is
       as similar as possible to sprintf. Format specifiers which were added
       by C99 (like "hh", "ll", "j", "z", "t", "L") are not supported.  When a
       conversion specifier passed to Tcl_ObjPrintf includes a precision, the
       value is taken as a number of bytes, as sprintf does, and not as a
       number of characters, as format does.  This is done on the assumption
       that C code is more likely to know how many bytes it is passing around
       than the number of encoded characters those bytes happen to represent.
       The variable number of arguments passed in should be of the types that
       would be suitable for passing to sprintf.  Note in this example usage,
       x is of type int.

              int x = 5;
              Tcl_Obj *objPtr = Tcl_ObjPrintf("Value is %d", x);

       If the value of format contains internal inconsistencies or invalid
       specifier formats, the formatted string result produced by
       Tcl_ObjPrintf will be an error message describing the error.  It is
       impossible however to provide runtime protection against mismatches
       between the format and any subsequent arguments.  Compile-time
       protection may be provided by some compilers.

       Tcl_AppendPrintfToObj is an appending alternative form of Tcl_ObjPrintf
       with functionality equivalent to

              Tcl_Obj *newPtr = Tcl_ObjPrintf(format, ...);
              Tcl_AppendObjToObj(objPtr, newPtr);
              Tcl_DecrRefCount(newPtr);

       but with greater convenience and efficiency when the appending
       functionality is needed.

       The Tcl_SetObjLength procedure changes the length of the string value
       of its objPtr argument.  If the newLength argument is greater than the
       space allocated for the value's string, then the string space is
       reallocated and the old value is copied to the new space; the bytes
       between the old length of the string and the new length may have
       arbitrary values.  If the newLength argument is less than the current
       length of the value's string, with objPtr->length is reduced without
       reallocating the string space; the original allocated size for the
       string is recorded in the value, so that the string length can be
       enlarged in a subsequent call to Tcl_SetObjLength without reallocating
       storage.  In all cases Tcl_SetObjLength leaves a null character at
       objPtr->bytes[newLength].

       Tcl_AttemptSetObjLength is identical in function to Tcl_SetObjLength
       except that if sufficient memory to satisfy the request cannot be
       allocated, it does not cause the Tcl interpreter to panic.  Thus, if
       newLength is greater than the space allocated for the value's string,
       and there is not enough memory available to satisfy the request,
       Tcl_AttemptSetObjLength will take no action and return 0 to indicate
       failure.  If there is enough memory to satisfy the request,
       Tcl_AttemptSetObjLength behaves just like Tcl_SetObjLength and returns
       1 to indicate success.

       The Tcl_ConcatObj function returns a new string value whose value is
       the space-separated concatenation of the string representations of all
       of the values in the objv array. Tcl_ConcatObj eliminates leading and
       trailing white space as it copies the string representations of the
       objv array to the result. If an element of the objv array consists of
       nothing but white space, then that value is ignored entirely. This
       white-space removal was added to make the output of the concat command
       cleaner-looking. Tcl_ConcatObj returns a pointer to a newly-created
       value whose ref count is zero.


SEE ALSO

       Tcl_NewObj(3), Tcl_IncrRefCount(3), Tcl_DecrRefCount(3), format(n),
       sprintf(3)


KEYWORDS

       append, internal representation, value, value type, string value,
       string type, string representation, concat, concatenate, unicode

Tcl                                   8.1                     Tcl_StringObj(3)

tcl 8.6.14 - Generated Sun Mar 3 16:21:09 CST 2024
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