Imager::IO - Imager's io_layer object. |
Imager::IO - Imager's io_layer object.
# Imager supplies Imager::IO objects to various callbacks my $IO = ...;
my $count = $IO->write($data); my $count = $IO->read($buffer, $max_count); my $position = $IO->seek($offset, $whence); my $status = $IO->close;
Imager uses an abstraction when dealing with image files to allow the same code to work with disk files, in memory data and callbacks.
If you're writing an Imager file handler your code will be passed an Imager::IO object to write to or read from.
Note that Imager::IO can only work with collections of bytes - if you need to read UTF-8 data you will need to read the bytes and decode them. If you want to write UTF-8 data you will need to encode your characters to bytes and write the bytes.
new_fd($fd)
my $io = Imager::IO->new(fileno($fh));
new_buffer($data)
Buffer I/O layers are read only.
$data
can either a simple octet string, or a reference to an octet
string. If $data
contains characters with a code point above
0xFF
an exception will be thrown.
new_fh($fh)
new_bufchain()
bufchain
based I/O layer. This accumulates the file
data as a chain of buffers starting from an empty stream.
Use the slurp() method to retrieve the accumulated content into a perl string.
These methods use buffered I/O to improve performance unless you call
set_buffered()
to disable buffering.
Prior to Imager 0.86 the write and read methods performed raw I/O.
write($data)
If you supply a UTF-8 flagged string it will be converted to a byte string, which may have a performance impact.
Returns -1 on error, though in most cases if the result of the write isn't the number of bytes supplied you'll want to treat it as an error anyway.
my $buffer; my $count = $io->read($buffer, $max_bytes);
Reads up to $max_bytes bytes from the current position in the file and stores them in $buffer. Returns the number of bytes read on success or an empty list on failure. Note that a read of zero bytes is not a failure, this indicates end of file.
read2($size)
my $buffer = $io->read2($max_bytes);
An alternative interface to read, that might be simpler to use in some cases.
Returns the data read or an empty list. At end of file the data read will be an empty string.
my $new_position = $io->seek($offset, $whence);
Seek to a new position in the file. Possible values for $whence are:
SEEK_SET
- $offset is the new position in the file.
SEEK_CUR
- $offset is the offset from the current position in
the file.
SEEK_END
- $offset is the offset relative to the end of the
file.
Note that seeking past the end of the file may or may not result in an error.
Any buffered output will be flushed, if flushing fails, seek()
will
return -1.
Returns the new position in the file, or -1 on error.
getc()
Returns the ordinal of the byte or -1 on error or end of file.
while ((my $c = $io->getc) != -1) { print chr($c); }
gets()
gets($max_size)
end_of_line
.
The default max_size
is 8192.
The default end_of_line
is ord "\n"
.
Returns nothing if the stream is in error or at end of file.
Returns the line as a string, including the line terminator (if one was found) on success.
while (defined(my $line = $io->gets)) { # do something with $line }
peekc()
For an unbuffered stream a buffer will be setup and loaded with a single character.
Returns the ordinal of the byte or -1 on error or end of file.
my $c = $io->peekc;
peekn($size)
size
bytes from the file as a string.
Only up to the stream buffer size bytes (currently 8192) can be peeked.
This method ignores the buffering state of the stream.
Returns nothing on EOF.
my $s = $io->peekn(4); if ($s =~ /^(II|MM)\*\0/) { print "TIFF image"; }
putc($code)
Returns code
on success, or -1 on failure.
close()
my $result = $io->close;
Call when you're done with the file. If the IO object is connected to a file this won't close the file handle, but buffers may be flushed (if any).
Returns 0 on success, -1 on failure.
eof()
$io->eof
Test if the stream is at end of file. No further read requests will be passed to your read callback until you seek().
error()
my $data = $io->read2(100); $io->error and die "Failed";
When the stream has the error flag set no further read or write requests will be passed to your callbacks until you seek.
flush()
$io->flush or die "Flush error";
Flush any buffered output. This will not call lower write layers when the stream has it's error flag set.
Returns a true value on success.
is_buffered()
Returns a true value if the stream is buffered.
set_buffered($enabled)
$enabled
is a non-zero integer, enable buffering, other disable
it.
Disabling buffering will flush any buffered output, but any buffered input will be retained and consumed by input methods.
Returns true if any buffered output was flushed successfully, false if there was an error flushing output.
These call the underlying I/O abstraction directly.
raw_write()
If you supply a UTF-8 flagged string it will be converted to a byte string, which may have a performance impact.
Returns -1 on error, though in most cases if the result of the write isn't the number of bytes supplied you'll want to treat it as an error anyway.
raw_read()
my $buffer; my $count = $io->raw_read($buffer, $max_bytes);
Reads up to $max_bytes bytes from the current position in the file and stores them in $buffer. Returns the number of bytes read on success or an empty list on failure. Note that a read of zero bytes is not a failure, this indicates end of file.
raw_read2()
my $buffer = $io->raw_read2($max_bytes);
An alternative interface to raw_read, that might be simpler to use in some cases.
Returns the data read or an empty list.
raw_seek()
my $new_position = $io->raw_seek($offset, $whence);
Seek to a new position in the file. Possible values for $whence are:
SEEK_SET
- $offset is the new position in the file.
SEEK_CUR
- $offset is the offset from the current position in
the file.
SEEK_END
- $offset is the offset relative to the end of the
file.
Note that seeking past the end of the file may or may not result in an error.
Returns the new position in the file, or -1 on error.
raw_close()
my $result = $io->raw_close;
Call when you're done with the file. If the IO object is connected to a file this won't close the file handle.
Returns 0 on success, -1 on failure.
slurp()
new_bufchain()
method.
my $data = $io->slurp;
dump()
stderr
.
$io->dump();
Tony Cook <tonyc@cpan.org>
Imager, Imager::Files
Imager::IO - Imager's io_layer object. |