Module: Buffers¶

Support for buffers - regions of memory without a particular interpretation.

This module provides bytes and buffer types which can be used to manage memory regions.

A bytes is a contiguous memory region - really a data structure containing a pointer, length, and also the information necessary to free the memory region when it is no longer used.

A buffer consists of a sequence views into bytes objects. A bytes object might be shared by several buffer objects.

These types should be safe to use in a multi-locale context. These types should free their memory after the last user of that memory goes out of scope. They are currently reference counted but that may not always be the case.

record bytes¶

This type represents a contiguous sequence of bytes. This sequence of bytes is represented with a C pointer and length and is currently reference counted. Note that this record contains private fields in addition to the home field.

var home: locale¶

The home locale storing the data

proc bytes.bytes()¶

Construct an empty bytes object

proc bytes.bytes(len: int(64), out error: syserr)

Construct a bytes object by allocating zero-filled memory.

Arguments:	len – the number of bytes to allocate error – (optional) capture an error that was encountered instead of halting on error

proc bytes.len: int(64)¶

Returns:	the number of bytes stored in a bytes object

record buffer_iterator¶

This type represents a particular location with a buffer. Use buffer methods like buffer.start and buffer.advance to create and manipulate buffer_iterator s. Note that this record contains private fields in addition to the home field.

var home: locale¶

The home locale storing the data

record buffer_range¶

A region within a buffer (indicated by two buffer_iterator s )

var start: buffer_iterator¶

var end: buffer_iterator¶

proc buffer_range.len: int(64)¶

Returns:	the number of bytes stored in a buffer_range

record buffer¶

A buffer which can contain multiple memory regions (that is, multiple regions of bytes objects). Note that this record contains private fields in addition to the home field.

var home: locale¶

The home locale storing the data

proc buffer.buffer(out error: syserr)¶

Create an empty buffer.

Arguments:	error – (optional) capture an error that was encountered instead of halting on error

proc buffer.flatten(range: buffer_range, out error: syserr)¶

Flatten a buffer. Create a new bytes object and copy the buffer into it. This function should work even if buffer is remote.

Arguments:	range – the region of the buffer to copy, for example buffer.all() error – (optional) capture an error that was encountered instead of halting on error
Returns:	a newly constructed bytes object on the current locale

proc buffer.len¶

Returns:	the number of bytes stored in a buffer object

proc buffer.append(b: bytes, skip_bytes: int(64) = 0, len_bytes: int(64) = b.len, out error: syserr)¶

Append a bytes object to a buffer. This function might store the passed bytes object by reference instead of copying it. The current implementation will always do so and will always increase the reference count of the bytes object. The version of this function called without the error argument will halt if an error is encountered.

Arguments:	b – the bytes object to append skip_bytes – how many bytes at the front of b to skip len_bytes – how many bytes to append to the buffer error – (optional) capture an error that was encountered instead of halting on error

proc buffer.append(buf: buffer, part: buffer_range = AppendExpr.Call08, out error: syserr)

Append a buffer object to a buffer. This function might store a pointers to the bytes objects contained in buf instead of copying them. If that happens, the current implementation will increase their reference counts. The version of this function called without the error argument will halt if an error is encountered.

Arguments:	buf – the buffer object to append part – a buffer_range indicating which section of the buffer to copy. Defaults to all of the buffer. error – (optional) capture an error that was encountered instead of halting on error

proc buffer.prepend(b: bytes, skip_bytes: int(64) = 0, len_bytes: int(64) = b.len, out error: syserr)¶

Prepend a bytes object to a buffer. This function might store the passed bytes object by reference instead of copying it. The current implementation will always do so and will always increase the reference count of the bytes object. The version of this function called without the error argument will halt if an error is encountered.

Arguments:	b – the bytes object to prepend skip_bytes – how many bytes at the front of b to skip len_bytes – how many bytes to append to the buffer error – (optional) capture an error that was encountered instead of halting on error

proc buffer.start(): buffer_iterator¶

Returns:	a buffer_iterator to the start of a buffer

proc buffer.end(): buffer_iterator¶

Returns:	a buffer_iterator to the end of a buffer

proc buffer.all(): buffer_range¶

Returns:	a buffer_range for the entirety of a buffer

proc buffer.next_part(ref it: buffer_iterator)¶

Advance a buffer_iterator to the next contigous memory region stored therein

Arguments:	it – the buffer iterator to advance

proc buffer.prev_part(ref it: buffer_iterator)¶

Advance a buffer_iterator to the previous contigous memory region stored therein

Arguments:	it – the buffer iterator to advance

proc buffer.advance(ref it: buffer_iterator, amount: int(64))¶

Advance a buffer_iterator by a particular number of bytes.

Arguments:	it – the buffer iterator to advance amount – the number of bytes to advance

proc buffer.copyout(it: buffer_iterator, out value, out error: syserr): buffer_iterator¶

Read a basic type from a buffer. This method reads the value by copying from memory - so it reads a binary value in native endianness.

Arguments:	it – a buffer_iterator where reading will start value – a basic type (integral or floating point value) error – (optional) capture an error that was encountered instead of halting on error
Returns:	a buffer iterator storing the position immediately after the read value.

proc buffer.copyin(it: buffer_iterator, value, out error: syserr): buffer_iterator¶

Write a basic type to a buffer. This method writes the value by copying to memory - so it reads a binary value in native endianness.

Arguments:	it – a buffer_iterator where reading will start value – a basic type (integral or floating point value) error – (optional) capture an error that was encountered instead of halting on error
Returns:	a buffer iterator storing the position immediately after the written value.