58 lines
1.5 KiB
JavaScript
58 lines
1.5 KiB
JavaScript
var assert = require('assert')
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var Reader = module.exports = function(options) {
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//TODO - remove for version 1.0
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if(typeof options == 'number') {
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options = { headerSize: options }
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}
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options = options || {}
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this.offset = 0
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this.lastChunk = false
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this.chunk = null
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this.headerSize = options.headerSize || 0
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this.lengthPadding = options.lengthPadding || 0
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this.header = null
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assert(this.headerSize < 2, 'pre-length header of more than 1 byte length not currently supported')
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}
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Reader.prototype.addChunk = function(chunk) {
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this.offset = 0
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this.chunk = chunk
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if(this.lastChunk) {
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this.chunk = Buffer.concat([this.lastChunk, this.chunk])
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this.lastChunk = false
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}
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}
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Reader.prototype._save = function() {
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//save any unread chunks for next read
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if(this.offset < this.chunk.length) {
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this.lastChunk = this.chunk.slice(this.offset)
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}
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return false
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}
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Reader.prototype.read = function() {
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if(this.chunk.length < (this.headerSize + 4 + this.offset)) {
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return this._save()
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}
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if(this.headerSize) {
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this.header = this.chunk[this.offset]
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}
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//read length of next item
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var length = this.chunk.readUInt32BE(this.offset + this.headerSize) + this.lengthPadding
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//next item spans more chunks than we have
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var remaining = this.chunk.length - (this.offset + 4 + this.headerSize)
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if(length > remaining) {
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return this._save()
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}
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this.offset += (this.headerSize + 4)
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var result = this.chunk.slice(this.offset, this.offset + length)
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this.offset += length
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return result
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}
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