JSDoc: Module: Layout

Support for translating between Buffer instances and JavaScript native types.

Layout is the basis of a class hierarchy that associates property names with sequences of encoded bytes.

Layouts are supported for these scalar (numeric) types:

Unsigned integers in little-endian format with 8-bit, 16-bit, 24-bit, 32-bit, 40-bit, and 48-bit representation ranges;
Unsigned integers in big-endian format with 16-bit, 24-bit, 32-bit, 40-bit, and 48-bit representation ranges;
Signed integers in little-endian format with 8-bit, 16-bit, 24-bit, 32-bit, 40-bit, and 48-bit representation ranges;
Signed integers in big-endian format with 16-bit, 24-bit, 32-bit, 40-bit, and 48-bit representation ranges;
64-bit integral values that decode to an exact (if magnitude is less than 2^53) or nearby integral Number in unsigned little-endian, unsigned big-endian, signed little-endian, and unsigned big-endian encodings;
32-bit floating point values with little-endian and big-endian representations;
64-bit floating point values with little-endian and big-endian representations;
Constants that take no space in the encoded expression.

and for these aggregate types:

Sequences of instances of a Layout, with JavaScript representation as an Array and constant or data-dependent length;
Structures that aggregate a heterogeneous sequence of Layout instances, with JavaScript representation as an Object;
Unions that support multiple variant layouts over a fixed (padded) or variable (not padded) span of bytes, using an unsigned integer at the start of the data or a separate layout element to determine which layout to use when interpreting the buffer contents;
BitStructures that contain a sequence of individual BitFields packed into an 8, 16, 24, or 32-bit unsigned integer starting at the least- or most-significant bit;
C strings of varying length;
Blobs of fixed- or variable-length raw data.

All Layout instances are immutable after construction, to prevent internal state from becoming inconsistent.

Author:

Peter A. Bigot

License:

Source:

Layout.js, line 24

See:

buffer-layout on GitHub

Classes

BitField
BitStructure
Blob
Constant
CString
Double
DoubleBE
ExternalLayout
Float
FloatBE
GreedyCount
Int
IntBE
Layout
NearInt64
NearInt64BE
NearUInt64
NearUInt64BE
OffsetLayout
Sequence
Structure
UInt
UIntBE
Union
UnionDiscriminator
UnionLayoutDiscriminator
UTF8
VariantLayout

Methods

(static) bits()

Factory for BitStructure values.

Source:

Layout.js, line 2700

(static) blob()

Factory for Blob values.

Source:

Layout.js, line 2712

(static) const()

Factory for Constant values.

Source:

Layout.js, line 2721

(static) cstr()

Factory for CString values.

Source:

Layout.js, line 2715

(static) f32()

Factory for little-endian 32-bit floating point values.

Source:

Layout.js, line 2685

(static) f32be()

Factory for big-endian 32-bit floating point values.

Source:

Layout.js, line 2688

(static) f64()

Factory for little-endian 64-bit floating point values.

Source:

Layout.js, line 2691

(static) f64be()

Factory for big-endian 64-bit floating point values.

Source:

Layout.js, line 2694

(static) greedy()

Factory for GreedyCount.

Source:

Layout.js, line 2575

(static) ns64()

Factory for little-endian signed int layouts interpreted as Numbers.

Source:

Layout.js, line 2658

(static) ns64be()

Factory for big-endian signed int layouts interpreted as Numbers.

Source:

Layout.js, line 2682

(static) nu64()

Factory for little-endian unsigned int layouts interpreted as Numbers.

Source:

Layout.js, line 2606

(static) nu64be()

Factory for big-endian unsigned int layouts interpreted as Numbers.

Source:

Layout.js, line 2630

(static) offset()

Factory for OffsetLayout.

Source:

Layout.js, line 2578

(static) s8()

Factory for signed int layouts spanning one byte.

Source:

Layout.js, line 2634

(static) s16()

Factory for little-endian signed int layouts spanning two bytes.

Source:

Layout.js, line 2638

(static) s16be()

Factory for big-endian signed int layouts spanning two bytes.

Source:

Layout.js, line 2662

(static) s24()

Factory for little-endian signed int layouts spanning three bytes.

Source:

Layout.js, line 2642

(static) s24be()

Factory for big-endian signed int layouts spanning three bytes.

Source:

Layout.js, line 2666

(static) s32()

Factory for little-endian signed int layouts spanning four bytes.

Source:

Layout.js, line 2646

(static) s32be()

Factory for big-endian signed int layouts spanning four bytes.

Source:

Layout.js, line 2670

(static) s40()

Factory for little-endian signed int layouts spanning five bytes.

Source:

Layout.js, line 2650

(static) s40be()

Factory for big-endian signed int layouts spanning five bytes.

Source:

Layout.js, line 2674

(static) s48()

Factory for little-endian signed int layouts spanning six bytes.

Source:

Layout.js, line 2654

(static) s48be()

Factory for big-endian signed int layouts spanning six bytes.

Source:

Layout.js, line 2678

(static) seq()

Factory for Sequence values.

Source:

Layout.js, line 2703

(static) struct()

Factory for Structure values.

Source:

Layout.js, line 2697

(static) u8()

Factory for unsigned int layouts spanning one byte.

Source:

Layout.js, line 2582

(static) u16()

Factory for little-endian unsigned int layouts spanning two bytes.

Source:

Layout.js, line 2586

(static) u16be()

Factory for big-endian unsigned int layouts spanning two bytes.

Source:

Layout.js, line 2610

(static) u24()

Factory for little-endian unsigned int layouts spanning three bytes.

Source:

Layout.js, line 2590

(static) u24be()

Factory for big-endian unsigned int layouts spanning three bytes.

Source:

Layout.js, line 2614

(static) u32()

Factory for little-endian unsigned int layouts spanning four bytes.

Source:

Layout.js, line 2594

(static) u32be()

Factory for big-endian unsigned int layouts spanning four bytes.

Source:

Layout.js, line 2618

(static) u40()

Factory for little-endian unsigned int layouts spanning five bytes.

Source:

Layout.js, line 2598

(static) u40be()

Factory for big-endian unsigned int layouts spanning five bytes.

Source:

Layout.js, line 2622

(static) u48()

Factory for little-endian unsigned int layouts spanning six bytes.

Source:

Layout.js, line 2602

(static) u48be()

Factory for big-endian unsigned int layouts spanning six bytes.

Source:

Layout.js, line 2626

(static) union()

Factory for Union values.

Source:

Layout.js, line 2706

(static) unionLayoutDiscriminator()

Factory for UnionLayoutDiscriminator values.

Source:

Layout.js, line 2709

(static) utf8()

Factory for UTF8 values.

Source:

Layout.js, line 2718

(inner) bindConstructorLayout(Class, layout)

Augment a class so that instances can be encoded/decoded using a given layout.

Calling this function couples Class with layout in several ways:

Class.layout_ becomes a static member property equal to layout;
layout.boundConstructor_ becomes a static member property equal to Class;
The makeDestinationObject() property of layout is set to a function that returns a new Class();
Class.decode(b, offset) becomes a static member function that delegates to layout.decode. The synthesized function may be captured and extended.
Class.prototype.encode(b, offset) provides an instance member function that delegates to layout.encode with src set to this. The synthesized function may be captured and extended, but when the extension is invoked this must be explicitly bound to the instance.

Parameters:

Name	Type	Description
`Class`	class	a JavaScript class with a nullary constructor.
`layout`	module:Layout~Layout	the Layout instance used to encode instances of `Class`.

Source:

Layout.js, line 354

(inner) fixBitwiseResult()

JavaScript chose to define bitwise operations as operating on signed 32-bit values in 2's complement form, meaning any integer with bit 31 set is going to look negative. For right shifts that's not a problem, because >>> is a logical shift, but for every other bitwise operator we have to compensate for possible negative results.

Source:

Layout.js, line 1939