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utils = require './utils'
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class Struct
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constructor: (@fields = {}) ->
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decode: (stream, parent, length = 0) ->
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res = @_setup stream, parent, length
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@_parseFields stream, res, @fields
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@process?.call(res, stream)
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return res
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_setup: (stream, parent, length) ->
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res = {}
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# define hidden properties
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Object.defineProperties res,
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parent: { value: parent }
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_startOffset: { value: stream.pos }
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_currentOffset: { value: 0, writable: true }
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_length: { value: length }
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return res
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_parseFields: (stream, res, fields) ->
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for key, type of fields
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if typeof type is 'function'
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val = type.call(res, res)
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else
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val = type.decode(stream, res)
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unless val is undefined
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if val instanceof utils.PropertyDescriptor
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Object.defineProperty res, key, val
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else
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res[key] = val
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res._currentOffset = stream.pos - res._startOffset
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return
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size: (val = {}, parent, includePointers = true) ->
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ctx =
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parent: parent
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val: val
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pointerSize: 0
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size = 0
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for key, type of @fields when type.size?
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size += type.size(val[key], ctx)
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if includePointers
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size += ctx.pointerSize
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return size
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encode: (stream, val, parent) ->
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@preEncode?.call(val, stream)
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ctx =
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pointers: []
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startOffset: stream.pos
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parent: parent
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val: val
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pointerSize: 0
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ctx.pointerOffset = stream.pos + @size(val, ctx, false)
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for key, type of @fields when type.encode?
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type.encode(stream, val[key], ctx)
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i = 0
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while i < ctx.pointers.length
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ptr = ctx.pointers[i++]
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ptr.type.encode(stream, ptr.val, ptr.parent)
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return
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module.exports = Struct
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