NAME

       Tcl_NewByteArrayObj,  Tcl_SetByteArrayObj, Tcl_GetByteArrayFromObj, Tcl_SetByteArrayLength
       - manipulate Tcl values as a arrays of bytes

SYNOPSIS

       #include <tcl.h>

       Tcl_Obj *
       Tcl_NewByteArrayObj(bytes, length)

       void
       Tcl_SetByteArrayObj(objPtr, bytes, length)

       unsigned char *
       Tcl_GetByteArrayFromObj(objPtr, lengthPtr)

       unsigned char *
       Tcl_SetByteArrayLength(objPtr, length)

ARGUMENTS

       const unsigned char *bytes (in)              The array of bytes used to initialize or  set
                                                    a  byte-array  value.  May  be  NULL  even if
                                                    length is non-zero.

       int length (in)                              The length of the array of bytes.  It must be
                                                    >= 0.

       Tcl_Obj *objPtr (in/out)                     For  Tcl_SetByteArrayObj,  this points to the
                                                    value to be  converted  to  byte-array  type.
                                                    For        Tcl_GetByteArrayFromObj        and
                                                    Tcl_SetByteArrayLength, this  points  to  the
                                                    value from which to get the byte-array value;
                                                    if objPtr does not already point to  a  byte-
                                                    array value, it will be converted to one.

       int *lengthPtr (out)                         If  non-NULL,  filled  with the length of the
                                                    array of bytes in the value.
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DESCRIPTION

       These procedures are used to create, modify, and read Tcl byte-array values from  C  code.
       Byte-array  values  are typically used to hold the results of binary IO operations or data
       structures created with the binary command.  In Tcl, an array of bytes is  not  equivalent
       to a string.  Conceptually, a string is an array of Unicode characters, while a byte-array
       is an array of 8-bit quantities with no implicit meaning.  Accessor functions are provided
       to  get  the  string  representation of a byte-array or to convert an arbitrary value to a
       byte-array.  Obtaining the  string  representation  of  a  byte-array  value  (by  calling
       Tcl_GetStringFromObj)  produces a properly formed UTF-8 sequence with a one-to-one mapping
       between the bytes in the internal representation and the UTF-8 characters  in  the  string
       representation.

       Tcl_NewByteArrayObj  and Tcl_SetByteArrayObj will create a new value of byte-array type or
       modify an existing value to have a byte-array type.  Both  of  these  procedures  set  the
       value's type to be byte-array and set the value's internal representation to a copy of the
       array of bytes given by bytes. Tcl_NewByteArrayObj returns a pointer to a newly  allocated
       value  with  a  reference  count  of zero.  Tcl_SetByteArrayObj invalidates any old string
       representation and, if the value is not already a byte-array value, frees any old internal
       representation. If bytes is NULL then the new byte array contains arbitrary values.

       Tcl_GetByteArrayFromObj  converts  a Tcl value to byte-array type and returns a pointer to
       the value's new internal representation as an array of bytes.  The length of this array is
       stored in lengthPtr if lengthPtr is non-NULL.  The storage for the array of bytes is owned
       by the value and should not be freed.  The contents of the array may be  modified  by  the
       caller   only  if  the  value  is  not  shared  and  the  caller  invalidates  the  string
       representation.

       Tcl_SetByteArrayLength converts the Tcl value to byte-array type and changes the length of
       the  value's  internal representation as an array of bytes.  If length is greater than the
       space currently allocated for the array, the array is reallocated to the new  length;  the
       newly  allocated  bytes  at the end of the array have arbitrary values.  If length is less
       than the space currently allocated for the array, the length of array is  reduced  to  the
       new length.  The return value is a pointer to the value's new array of bytes.

SEE ALSO

       Tcl_GetStringFromObj, Tcl_NewObj, Tcl_IncrRefCount, Tcl_DecrRefCount

KEYWORDS

       value, binary data, byte array, utf, unicode, internationalization