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