Streams are used to read or write data in a sequential manner.
BlitzMax supports many kinds of streams, including standard file streams (for reading and writing to files), bank streams (for reading and writing to banks) and endian streams (for swapping the byte order of stream data).
Streams are usually created using OpenStream, ReadStream or WriteStream. However, some kinds of streams provide their own methods for creating streams. For example, banks streams are created with the CreateBankStream command.
OpenStream, ReadStream and WriteStream all require a url parameter, which is used to 'locate' the stream. A url is usually a string value.
If the url contains the string "::", then a stream protocol is being specified. If not, then the url is assumed to be a simple filename.
External modules can add their own stream protocols to the system, allowing you to use streams for a wide variety of purposes. For example, the "incbin::" protocol allows you to read data from a binary file that has been embedded in an application using the Incbin command.
Other protocols include "http::" for reading and writing data over a network, and "littleendian::" and "bigendian::" for swapping the byte order of streams.
To write to a stream, use one of the 'Write' style commands, such as WriteByte.
To read from a stream, use one of the 'Read' style commands, such as ReadByte.
Some kinds of streams (for example, file streams and bank streams) support random access. This means that you can modify where in the stream the next read or write is to occur using the SeekStream command. You can also tell where you are in such streams using the StreamPos command.
When you are finished with a stream, you should always close it using CloseStream. Failure to do so may result in a resource leak, or prevent the stream from successfully opening in future.
Types
editTStreamException
editBase exception type thrown by streams
TStreamReadException
editException type thrown by streams in the event of read errors
TStreamReadException is usually thrown when a stream operation failed to read enough bytes. For example, if the stream ReadInt method fails to read 4 bytes, it will throw a TStreamReadException.
TStreamWriteException
editException type thrown by streams in the event of write errors
TStreamWriteException is usually thrown when a stream operation failed to write enough bytes. For example, if the stream WriteInt method fails to write 4 bytes, it will throw a TStreamWriteException.
TIO
editBase input/output type
To create your own stream types, you should extend TStream and implement at least these methods.
You should also make sure your stream can handle multiple calls to the Close method.
- Eof
- Pos
- Size
- Seek
- Flush
- Close
- Read
- Write
TIO: Methods
editMethod Eof()
Description: Get stream end of file status
Returns: True for end of file reached, otherwise False
Information: For seekable streams such as file streams, Eof generally returns True if the file position equals the file size. This means that no more bytes can be read from the stream. However, it may still be possible to write bytes, in which case the file will 'grow'.
For communication type streams such as socket streams, Eof returns True if the stream has been shut down for some reason - either locally or by the remote host. In this case, no more bytes can be read from or written to the stream.
Method Pos()
Description: Get position of seekable stream
Returns: Stream position as a byte offset, or -1 if stream is not seekable
Method Size()
Description: Get size of seekable stream
Returns: Size, in bytes, of seekable stream, or 0 if stream is not seekable
Method Seek( pos )
Description: Seek to position in seekable stream
Returns: New stream position, or -1 if stream is not seekable
Method Flush()
Description: Flush stream
Information: Flushes any internal stream buffers.
Method Close()
Description: Close stream
Information: Closes the stream after flushing any internal stream buffers.
Method Read( buf:Byte Ptr,count )
Description: Read at least 1 byte from a stream
Returns: Number of bytes successfully read
Information: This method may 'block' if it is not possible to read at least one byte due to IO buffering.
If this method returns 0, the stream has reached end of file.
Method Write( buf:Byte Ptr,count )
Description: Write at least 1 byte to a stream
Returns: Number of bytes successfully written
Information: This method may 'block' if it is not possible to write at least one byte due to IO buffering.
If this method returns 0, the stream has reached end of file.
TStream
editData stream type
TStream extends TIO to provide methods for reading and writing various types of values to and from a stream.
Note that methods dealing with strings - ReadLine, WriteLine, ReadString and WriteString - assume that strings are represented by bytes in the stream. In future, a more powerful TextStream type will be added capable of decoding text streams in multiple formats.
- ReadBytes
- WriteBytes
- SkipBytes
- ReadByte
- WriteByte
- ReadShort
- WriteShort
- ReadInt
- WriteInt
- ReadLong
- WriteLong
- ReadFloat
- WriteFloat
- ReadDouble
- WriteDouble
- ReadLine
- WriteLine
- ReadString
- WriteString
TStream: Methods
editMethod ReadBytes( buf:Byte Ptr,count )
Description: Reads bytes from a stream
Information: ReadBytes reads count bytes from the stream into the memory block specified by buf.
If count bytes were not successfully read, a TStreamReadException is thrown. This typically occurs due to end of file.
Method WriteBytes( buf:Byte Ptr,count )
Description: Writes bytes to a stream
Information: WriteBytes writes count bytes from the memory block specified by buf to the stream.
If count bytes were not successfully written, a TStreamWriteException is thrown. This typically occurs due to end of file.
Method SkipBytes( count )
Description: Skip bytes in a stream
Information: SkipBytes read count bytes from the stream and throws them away.
If count bytes were not successfully read, a TStreamReadException is thrown. This typically occurs due to end of file.
Method ReadByte()
Description: Read a byte from the stream
Returns: The read value
Information: If a value could not be read (possibly due to end of file), a TStreamReadException is thrown.
Method WriteByte( n )
Description: Write a byte to the stream
Information: If the value could not be written (possibly due to end of file), a TStreamWriteException is thrown.
Method ReadShort()
Description: Read a short (two bytes) from the stream
Returns: The read value
Information: If a value could not be read (possibly due to end of file), a TStreamReadException is thrown.
Method WriteShort( n )
Description: Write a short (two bytes) to the stream
Information: If the value could not be written (possibly due to end of file), a TStreamWriteException is thrown.
Method ReadInt()
Description: Read an int (four bytes) from the stream
Returns: The read value
Information: If a value could not be read (possibly due to end of file), a TStreamReadException is thrown.
Method WriteInt( n )
Description: Write an int (four bytes) to the stream
Information: If the value could not be written (possibly due to end of file), a TStreamWriteException is thrown.
Method ReadLong:Long()
Description: Read a long (eight bytes) from the stream
Returns: The read value
Information: If a value could not be read (possibly due to end of file), a TStreamReadException is thrown.
Method WriteLong( n:Long )
Description: Write a long (eight bytes) to the stream
Information: If the value could not be written (possibly due to end of file), a TStreamWriteException is thrown.
Method ReadFloat#()
Description: Read a float (four bytes) from the stream
Returns: The read value
Information: If a value could not be read (possibly due to end of file), a TStreamReadException is thrown.
Method WriteFloat( n# )
Description: Write a float (four bytes) to the stream
Information: If the value could not be written (possibly due to end of file), a TStreamWriteException is thrown.
Method ReadDouble!()
Description: Read a double (eight bytes) from the stream
Returns: The read value
Information: If a value could not be read (possibly due to end of file), a TStreamReadException is thrown.
Method WriteDouble( n! )
Description: Write a double (eight bytes) to the stream
Information: If the value could not be written (possibly due to end of file), a TStreamWriteException is thrown.
Method ReadLine$()
Description: Read a line of text from the stream
Information: Bytes are read from the stream until a newline character (ascii code 10) or null character (ascii code 0) is read, or end of file is detected.
Carriage return characters (ascii code 13) are silently ignored.
The bytes read are returned in the form of a string, excluding any terminating newline or null character.
Method WriteLine( str$ )
Description: Write a line of text to the stream
Returns: True if line successfully written, else False
Information: A sequence of bytes is written to the stream (one for each character in str) followed by the line terminating sequence "~r~n".
Method ReadString$( length )
Description: Read characters from the stream
Returns: A string composed of length bytes read from the stream
Information: A TStreamReadException is thrown if not all bytes could be read.
Method WriteString( str$ )
Description: Write characters to the stream
Information: A TStreamWriteException is thrown if not all bytes could be written.
TStreamWrapper
editUtility stream wrapper type
TStreamWrapper 'wraps' an existing stream, redirecting all TIO method calls to the wrapped stream.
This can be useful for writing stream 'filters' that modify the behaviour of existing streams.
Note that the Close method causes the underlying stream to be closed, which may not always be desirable. If necessary, you should override Close with a NOP version.
- SetStream
TStreamWrapper: Methods
editMethod SetStream( stream:TStream )
Description: Set underlying stream
Information: Sets the stream to be 'wrapped'. All calls to TIO methods of this stream will be redirected to stream.
TCStream
editStandard C file stream type
- OpenFile
- CreateWithCStream
TCStream: Functions
editFunction OpenFile:TCStream( path$,readable,writeable )
Description: Create a TCStream from a 'C' filename
Function CreateWithCStream:TCStream( cstream,mode )
Description: Create a TCStream from a 'C' stream handle
TStreamFactory
editBase stream factory type
Stream factories are used by the OpenStream, ReadStream and WriteStream functions to create streams based on a 'url object'.
Url objects are usually strings, in which case the url is divided into 2 parts - a protocol and a path. These are separated by a double colon string - "::".
To create your own stream factories, you should extend the TStreamFactory type and implement the CreateStream method.
To install your stream factory, simply create an instance of it using 'New'.
- CreateStream
TStreamFactory: Methods
editMethod CreateStream:TStream( url:Object,proto$,path$,readable,writeable )
Description: Create a stream based on a url object
Information: Types which extends TStreamFactory must implement this method.
url contains the original url object as supplied to OpenStream, ReadStream or WriteStream.
If url is a string, proto contains the url protocol - for example, the "incbin" part of "incbin::myfile".
If url is a string, path contains the remainder of the url - for example, the "myfile" part of "incbin::myfile".
If url is not a string, both proto and path will be Null.
Functions
editOpenStream
editFunction OpenStream:TStream( url:Object,readable=True,writeable=True )
Description: Open a stream for reading/writing
Returns: A stream object
Information: All streams created by OpenStream, ReadStream or WriteStream should eventually be closed using CloseStream.
ReadStream
editFunction ReadStream:TStream( url:Object )
Description: Open a stream for reading
Returns: A stream object
Information: All streams created by OpenStream, ReadStream or WriteStream should eventually be closed using CloseStream.
Example:
' readstream.bmx
' opens a read stream to the blitzbasic.com website and
' dumps the homepage to the console using readline and print
in=ReadStream("http::blitzbasic.com")
If Not in RuntimeError "Failed to open a ReadStream to file http::www.blitzbasic.com"
While Not Eof(in)
Print ReadLine(in)
Wend
CloseStream in
WriteStream
editFunction WriteStream:TStream( url:Object )
Description: Open a stream for writing
Returns: A stream object
Information: All streams created by OpenStream, ReadStream or WriteStream should eventually be closed using CloseStream.
Example:
' writestream.bmx
' opens a write stream to the file mygame.ini and
' outputs a simple text file using WriteLine
out=WriteStream("mygame.ini")
if not out RuntimeError "Failed to open a WriteStream to file mygame.ini"
WriteLine out,"[display]"
WriteLine out,"width=800"
WriteLine out,"height=600"
WriteLine out,"depth=32"
WriteLine out,""
WriteLine out,"[highscores]"
WriteLine out,"AXE=1000"
WriteLine out,"HAL=950"
WriteLine out,"MAK=920"
CloseStream out
print "File mygame.ini created, bytes="+FileSize("mygame.ini")
Eof
editFunction Eof( stream:TStream )
Description: Get stream end of file status
Returns: True If stream is at end of file
StreamPos
editFunction StreamPos( stream:TStream )
Description: Get current position of seekable stream
Returns: Current stream position, or -1 If stream is not seekable
StreamSize
editFunction StreamSize( stream:TStream )
Description: Get current size of seekable stream
Returns: Current stream size in bytes, or -1 If stream is not seekable
SeekStream
editFunction SeekStream( stream:TStream,pos )
Description: Set stream position of seekable stream
Returns: New stream position, or -1 If stream is not seekable
FlushStream
editFunction FlushStream( stream:TStream )
Description: Flush a stream
Information: FlushStream writes any outstanding buffered data to stream.
CloseStream
editFunction CloseStream( stream:TStream )
Description: Close a stream
Information: All streams should be closed when they are no longer required. Closing a stream also flushes the stream before it closes.
ReadByte
editFunction ReadByte( stream:TStream )
Description: Read a Byte from a stream
Returns: A Byte value
Information: ReadByte reads a single Byte from stream. A TStreamReadException is thrown If there is not enough data available.
ReadShort
editFunction ReadShort( stream:TStream )
Description: Read a Short from a stream
Returns: A Short value
Information: ReadShort reads 2 bytes from stream. A TStreamReadException is thrown If there is not enough data available.
ReadInt
editFunction ReadInt( stream:TStream )
Description: Read an Int from a stream
Returns: An Int value
Information: ReadInt reads 4 bytes from stream. A TStreamReadException is thrown If there is not enough data available.
ReadLong
editFunction ReadLong:Long( stream:TStream )
Description: Read a Long from a stream
Returns: A Long value
Information: ReadLong reads 8 bytes from stream. A TStreamReadException is thrown If there is not enough data available.
ReadFloat
editFunction ReadFloat#( stream:TStream )
Description: Read a Float from a stream
Returns: A Float value
Information: ReadFloat reads 4 bytes from stream. A TStreamReadException is thrown If there is not enough data available.
ReadDouble
editFunction ReadDouble!( stream:TStream )
Description: Read a Double from a stream
Returns: A Double value
Information: ReadDouble reads 8 bytes from stream. A TStreamWriteException is thrown If there is not enough data available.
WriteByte
editFunction WriteByte( stream:TStream,n )
Description: Write a Byte to a stream
Information: WriteByte writes a single Byte to stream. A TStreamWriteException is thrown If the Byte could Not be written
WriteShort
editFunction WriteShort( stream:TStream,n )
Description: Write a Short to a stream
Information: WriteShort writes 2 bytes to stream. A TStreamWriteException is thrown if not all bytes could be written
WriteInt
editFunction WriteInt( stream:TStream,n )
Description: Write an Int to a stream
Information: WriteInt writes 4 bytes to stream. A TStreamWriteException is thrown if not all bytes could be written
WriteLong
editFunction WriteLong( stream:TStream,n:Long )
Description: Write a Long to a stream
Information: WriteLong writes 8 bytes to stream. A TStreamWriteException is thrown if not all bytes could be written
WriteFloat
editFunction WriteFloat( stream:TStream,n# )
Description: Write a Float to a stream
Information: WriteFloat writes 4 bytes to stream. A TStreamWriteException is thrown if not all bytes could be written
WriteDouble
editFunction WriteDouble( stream:TStream,n! )
Description: Write a Double to a stream
Information: WriteDouble writes 8 bytes to stream. A TStreamWriteException is thrown if not all bytes could be written
ReadString
editFunction ReadString$( stream:TStream,length )
Description: Read a String from a stream
Returns: A String of length length
Information: A TStreamReadException is thrown if not all bytes could be read.
WriteString
editFunction WriteString( stream:TStream,str$ )
Description: Write a String to a stream
Information: Each character in str is written to stream.
A TStreamWriteException is thrown if not all bytes could be written.
ReadLine
editFunction ReadLine$( stream:TStream )
Description: Read a line of text from a stream
Returns: A string
Information: Bytes are read from stream until a newline character (ascii code 10) or null character (ascii code 0) is read, or end of file is detected.
Carriage Return characters (ascii code 13) are silently ignored.
The bytes read are returned in the form of a string, excluding any terminating newline or null character.
WriteLine
editFunction WriteLine( stream:TStream,str$ )
Description: Write a line of text to a stream
Returns: True if line successfully written, else False
Information: A sequence of bytes is written to the stream (one for each character in str) followed by the line terminating sequence "~r~n".
LoadString
editFunction LoadString$( url:Object )
Description: Load a String from a stream
Returns: A String
Information: The specified url is opened for reading, and each byte in the resultant stream (until eof of file is reached) is read into a string.
A TStreamReadException is thrown if the stream could not be read.
SaveString
editFunction SaveString( str$,url:Object )
Description: Save a String to a stream
Information: The specified url is opened For writing, and each character of str is written to the resultant stream.
A TStreamWriteException is thrown if not all bytes could be written.
LoadByteArray
editFunction LoadByteArray:Byte[]( url:Object )
Description: Load a Byte array from a stream
Returns: A Byte array
Information: The specified url is opened for reading, and each byte in the resultant stream (until eof of reached) is read into a byte array.
SaveByteArray
editFunction SaveByteArray( byteArray:Byte[],url:Object )
Description: Save a Byte array to a stream
Information: The specified url is opened For writing, and each element of byteArray is written to the resultant stream.
A TStreamWriteException is thrown if not all bytes could be written.
CopyStream
editFunction CopyStream( fromStream:TStream,toStream:TStream,bufSize=4096 )
Description: Copy stream contents to another stream
Information: CopyStream copies bytes from fromStream to toStream Until fromStream reaches end of file.
A TStreamWriteException is thrown if not all bytes could be written.
CopyBytes
editFunction CopyBytes( fromStream:TStream,toStream:TStream,count,bufSize=4096 )
Description: Copy bytes from one stream to another
Information: CopyBytes copies count bytes from fromStream to toStream.
A TStreamReadException is thrown if not all bytes could be read, and a TStreamWriteException is thrown if not all bytes could be written.
CasedFileName
editFunction CasedFileName$(path$)
Description: Returns a case sensitive filename if it exists from a case insensitive file path.