Tcl_ByteArrayObj(3) Tcl Library Procedures Tcl_ByteArrayObj(3)______________________________________________________________________________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_Get‐
ByteArrayFromObj 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 con‐
verted to one.
int *lengthPtr (out) If non-NULL, filled with
the length of the array of
bytes in the value.
_________________________________________________________________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 representa‐
tion 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 allo‐
cated value with a reference count of zero. Tcl_SetByteArrayObj inval‐
idates 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 allo‐
cated 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
Tcl 8.1 Tcl_ByteArrayObj(3)
