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                     35: .\"
                     36: .\" Author: Archie Cobbs <archie@freebsd.org>
                     37: .\"
                     38: .\" $Id: string_fp.3,v 1.8 2004/06/02 17:24:37 archie Exp $
                     39: .\"
                     40: .Dd April 22, 2002
                     41: .Dt STRING_FP 3
                     42: .Os
                     43: .Sh NAME
                     44: .Nm string_buf_input ,
                     45: .Nm string_buf_output ,
                     46: .Nm string_buf_content ,
                     47: .Nm string_buf_length
                     48: .Nd string buffer streams
                     49: .Sh LIBRARY
                     50: PDEL Library (libpdel, \-lpdel)
                     51: .Sh SYNOPSIS
                     52: .In sys/types.h
                     53: .In stdio.h
                     54: .In pdel/io/string_fp.h
                     55: .Ft "FILE *"
                     56: .Fn string_buf_input "const void *buf" " size_t len" "int copy"
                     57: .Ft "FILE *"
                     58: .Fn string_buf_output "const void *mtype"
                     59: .Ft "char *"
                     60: .Fn string_buf_content "FILE *fp" "int reset"
                     61: .Ft "int"
                     62: .Fn string_buf_length "FILE *fp"
                     63: .Sh DESCRIPTION
                     64: These functions allow string buffers to be read and written as streams.
                     65: .Pp
                     66: .Fn string_buf_input
                     67: creates a read-only stream that reads from the buffer pointed to by
                     68: .Fa buf
                     69: having length
                     70: .Fa len .
                     71: If
                     72: .Fa copy
                     73: is non-zero, the contents of the buffer are copied and therefore
                     74: .Fa buf
                     75: doesn't need to remain valid while the stream is open.
                     76: Otherwise, the data pointed to by
                     77: .Fa buf
                     78: is not copied and must remain valid while the stream is open.
                     79: .Xr fclose 3
                     80: should be used to close the stream.
                     81: .Pp
                     82: .Fn string_buf_output
                     83: creates a write-only stream that writes into an internal buffer that
                     84: grows dynamically.
                     85: .Xr fclose 3
                     86: should be used to close the stream; this also frees the internal buffer.
                     87: The current buffer length is returned by
                     88: .Fn string_buf_length .
                     89: .Pp
                     90: .Fn string_buf_content
                     91: returns the contents of the internal buffer.
                     92: As with
                     93: .Fn string_buf_length ,
                     94: the
                     95: .Fa fp
                     96: argument must be a stream created by
                     97: .Fn string_buf_output .
                     98: If
                     99: .Fa reset
                    100: is zero, then the internal buffer remains valid and the returned pointer
                    101: should be treated as read-only and not be freed; it also becomes invalid
                    102: with the next operation on the stream.
                    103: If
                    104: .Fa reset
                    105: is non-zero, the current buffer contents are "detached" and returned by
                    106: .Fn string_buf_content ,
                    107: and a new, empty internal buffer is created; in this case, the caller is
                    108: responsible for eventually freeing the returned buffer,
                    109: which is allocated with
                    110: .Xr typed_mem 3
                    111: type
                    112: .Fa mtype ,
                    113: and its contents remain valid until then.
                    114: .Pp
                    115: In either case, the data returned by
                    116: .Fn string_buf_content
                    117: is guaranteed to have one additional '\\0' byte appended.
                    118: Therefore, it is always safe to treat this pointer as a normal C string.
                    119: However, any '\\0' bytes previously written to the stream will cause
                    120: this string to appear truncated.
                    121: .Sh RETURN VALUES
                    122: .Fn string_buf_input ,
                    123: .Fn string_buf_output ,
                    124: and
                    125: .Fn string_buf_content
                    126: return
                    127: .Dv NULL
                    128: to indicate an error, with
                    129: .Va errno
                    130: set appropriately.
                    131: .Pp
                    132: Even if 
                    133: .Fn string_buf_content
                    134: returns
                    135: .Dv NULL ,
                    136: the stream will still need to be closed.
                    137: .Sh IMPLEMENTATION NOTES
                    138: .Fn string_buf_content
                    139: and
                    140: .Fn string_buf_length
                    141: attempt to verify that the supplied stream was indeed created by
                    142: .Fn string_buf_output .
                    143: If they detect otherwise, an immediate assertion failure is generated.
                    144: .Sh SEE ALSO
                    145: .Xr base64 3 ,
                    146: .Xr filter 3 ,
                    147: .Xr fopen 3 ,
                    148: .Xr libpdel 3 ,
                    149: .Xr typed_mem 3
                    150: .Sh HISTORY
                    151: The PDEL library was developed at Packet Design, LLC.
                    152: .Dv "http://www.packetdesign.com/"
                    153: .Sh AUTHORS
                    154: .An Archie Cobbs Aq archie@freebsd.org