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The binio command has three sub commands:
- binio copy inChannel outChannel ?count?
-
Copies from inChannel to outChannel, up to the number of bytes
indicated by the optional count argument or up to end of file
on inChannel. inChannel must have been opened for reading and
outChannel must have been opened for writing. This operation
returns the number of bytes copied, or -1 on error.
- binio pack outChannel format ?data1 data2 ...?
-
Packs binary data onto outChannel, a channel that must have
been opened for writing. The format argument determines how the
optional data1 through datan arguments are interpreted. This
operation returns the number of data items successfully packed
on outChannel or -1 if an error occurred. If an error occurred,
it is possible that some output has already occurred. The
various specifications that can appear in the format string are
explained below. This operation reorders the bytes of each
datum to match the order expected on outChannel if its byte
order is different from that of the architecture on which the
Tcl command is being executed.
- binio unpack inChannel format ?var1 var2 ...?
-
Unpacks binary data from inChannel into the named variables.
The inChannel argument must denote a channel opened for
reading. The format argument determines how the data obtained
from the channel is translated into string representation and
stored in the var1
through varn variables. If any of the variables are not
initialized then the command creates them as local variables.
This operation returns the number of data items successfully
unpacked from inChannel or -1 if an error occurred. If -1 is
returned, it is possible that some input may already have
occurred. The various format specifications that can appear in
the format string are explained below. This operation reorders
the bytes of each datum to match the byte order expected on the
architecture on which the command is executed if it is
different from the byte order that is in effect on inChannel.
And now the table of the format specifiers available to binio.
It includes a comparison to binary format of tcl 8.0 too.
| Format |
Meaning |
Meaning in 8.0 |
| a |
-- |
string, '\0'-padded |
| A |
-- |
string, space-padded |
| b |
-- |
binary digits, low-2-high |
| B |
-- |
binary digits, high-2-low |
| c |
signed int, 8 bit (char) |
see left |
| C |
unsigned int, 8 bit |
-- |
| d |
signed int, 32 bit |
floating number, 64 bit |
| D |
signed int, 16 bit |
-- |
| f |
floating number, 32 bit |
see left |
| F |
floating number, 64 bit |
-- |
| h |
-- |
hex digits, low-2-high |
| H |
-- |
hex digits, high-2-low |
| i |
-- |
signed int, 32 bit, little endian |
| I |
-- |
signed int, 32 bit, big-endian |
| l |
signed int, 64 bit |
-- |
| L |
unsigned int, 64 bit |
-- |
| o |
signed int, 32 bit, octal |
-- |
| O |
signed int, 16 bit, octal |
-- |
| s |
string, '\0'-terminated |
signed int, 16 bit, little-endian |
| S |
-- |
signed int, 16 bit, big-endian |
| u |
unsigned int, 32 bit |
-- |
| U |
unsigned int, 32 bit |
-- |
| x |
signed int, 32 bit, hex |
'\0' |
| X |
signed int, 16 bit, hex |
Set cursor relative |
| @ |
-- |
Set cursor absolute |
There is a more subtle difference too. In contrast to binio,
which uses the channel byteorder to determine the endianness of the
written data binary format requires an explicit
specification. In general binary format is much nearer to
the perl equivalent ((un)pack), despite the names.
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