Tcl_ByteArrayObj(3) Tcl Library Procedures Tcl_ByteArrayObj(3)

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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

Tcl 8.1 Tcl_ByteArrayObj(3)