86 lines
2.4 KiB
TypeScript
86 lines
2.4 KiB
TypeScript
//binary data writer tuned for encoding binary specific to the postgres binary protocol
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export class Writer {
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private buffer: Buffer
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private offset: number = 5
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private headerPosition: number = 0
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constructor(private size = 256) {
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this.buffer = Buffer.allocUnsafe(size)
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}
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private ensure(size: number): void {
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var remaining = this.buffer.length - this.offset
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if (remaining < size) {
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var oldBuffer = this.buffer
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// exponential growth factor of around ~ 1.5
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// https://stackoverflow.com/questions/2269063/buffer-growth-strategy
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var newSize = oldBuffer.length + (oldBuffer.length >> 1) + size
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this.buffer = Buffer.allocUnsafe(newSize)
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oldBuffer.copy(this.buffer)
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}
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}
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public addInt32(num: number): Writer {
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this.ensure(4)
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this.buffer[this.offset++] = (num >>> 24) & 0xff
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this.buffer[this.offset++] = (num >>> 16) & 0xff
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this.buffer[this.offset++] = (num >>> 8) & 0xff
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this.buffer[this.offset++] = (num >>> 0) & 0xff
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return this
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}
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public addInt16(num: number): Writer {
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this.ensure(2)
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this.buffer[this.offset++] = (num >>> 8) & 0xff
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this.buffer[this.offset++] = (num >>> 0) & 0xff
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return this
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}
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public addCString(string: string): Writer {
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if (!string) {
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this.ensure(1)
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} else {
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var len = Buffer.byteLength(string)
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this.ensure(len + 1) // +1 for null terminator
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this.buffer.write(string, this.offset, 'utf-8')
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this.offset += len
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}
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this.buffer[this.offset++] = 0 // null terminator
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return this
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}
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public addString(string: string = ''): Writer {
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var len = Buffer.byteLength(string)
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this.ensure(len)
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this.buffer.write(string, this.offset)
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this.offset += len
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return this
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}
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public add(otherBuffer: Buffer): Writer {
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this.ensure(otherBuffer.length)
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otherBuffer.copy(this.buffer, this.offset)
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this.offset += otherBuffer.length
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return this
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}
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private join(code?: number): Buffer {
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if (code) {
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this.buffer[this.headerPosition] = code
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//length is everything in this packet minus the code
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const length = this.offset - (this.headerPosition + 1)
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this.buffer.writeInt32BE(length, this.headerPosition + 1)
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}
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return this.buffer.slice(code ? 0 : 5, this.offset)
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}
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public flush(code?: number): Buffer {
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var result = this.join(code)
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this.offset = 5
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this.headerPosition = 0
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this.buffer = Buffer.allocUnsafe(this.size)
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return result
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}
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}
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