'\"
'\" Copyright (c) 1997 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH Tcl_ByteArrayObj 3tcl 8.1 Tcl "Tcl Library Procedures"
.\" The -*- nroff -*- definitions below are for supplemental macros used
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\h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
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.SH NAME
Tcl_NewByteArrayObj, Tcl_SetByteArrayObj, Tcl_GetByteArrayFromObj, Tcl_SetByteArrayLength \- manipulate Tcl values as a arrays of bytes
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
Tcl_Obj *
\fBTcl_NewByteArrayObj\fR(\fIbytes, length\fR)
.sp
void
\fBTcl_SetByteArrayObj\fR(\fIobjPtr, bytes, length\fR)
.sp
unsigned char *
\fBTcl_GetByteArrayFromObj\fR(\fIobjPtr, lengthPtr\fR)
.sp
unsigned char *
\fBTcl_SetByteArrayLength\fR(\fIobjPtr, length\fR)
.SH ARGUMENTS
.AS "const unsigned char" *lengthPtr in/out
.AP "const unsigned char" *bytes in
The array of bytes used to initialize or set a byte-array value. May be NULL
even if \fIlength\fR is non-zero.
.AP int length in
The length of the array of bytes.  It must be >= 0.
.AP Tcl_Obj *objPtr in/out
For \fBTcl_SetByteArrayObj\fR, this points to the value to be converted to
byte-array type.  For \fBTcl_GetByteArrayFromObj\fR and
\fBTcl_SetByteArrayLength\fR, this points to the value from which to get
the byte-array value; if \fIobjPtr\fR does not already point to a byte-array
value, it will be converted to one.
.AP size_t | int *lengthPtr out
Filled with the length of the array of bytes in the value.
May be (int *)NULL when not used.
.BE

.SH DESCRIPTION
.PP
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
\fBbinary\fR 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
\fBTcl_GetStringFromObj\fR) 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.
.PP
\fBTcl_NewByteArrayObj\fR and \fBTcl_SetByteArrayObj\fR 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 \fIbytes\fR. \fBTcl_NewByteArrayObj\fR returns a
pointer to a newly allocated value with a reference count of zero.
\fBTcl_SetByteArrayObj\fR invalidates any old string representation and, if
the value is not already a byte-array value, frees any old internal
representation. If \fIbytes\fR is NULL then the new byte array contains
arbitrary values.
.PP
\fBTcl_GetByteArrayFromObj\fR 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 \fIlengthPtr\fR if
\fIlengthPtr\fR 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.
.PP
\fBTcl_SetByteArrayLength\fR converts the Tcl value to byte-array type
and changes the length of the value's internal representation as an
array of bytes.  If \fIlength\fR 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
\fIlength\fR 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.

.SH "REFERENCE COUNT MANAGEMENT"
.PP
\fBTcl_NewByteArrayObj\fR always returns a zero-reference object, much
like \fBTcl_NewObj\fR.
.PP
\fBTcl_SetByteArrayObj\fR and \fBTcl_SetByteArrayLength\fR do not modify the
reference count of their \fIobjPtr\fR arguments, but do require that the
object be unshared.
.PP
\fBTcl_GetByteArrayFromObj\fR does not modify the reference count of its
\fIobjPtr\fR argument; it only reads.

.SH "SEE ALSO"
Tcl_GetStringFromObj, Tcl_NewObj, Tcl_IncrRefCount, Tcl_DecrRefCount

.SH KEYWORDS
value, binary data, byte array, utf, unicode, internationalization