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const Struct = require('./Struct');
const getPath = (object, pathArray) => {
return pathArray.reduce((prevObj, key) => prevObj && prevObj[key], object);
};
class VersionedStruct extends Struct {
constructor(type, versions = {}) {
super();
this.type = type;
this.versions = versions;
if (typeof type === 'string') {
this.versionPath = type.split('.');
}
}
decode(stream, parent, length = 0) {
const res = this._setup(stream, parent, length);
if (typeof this.type === 'string') {
res.version = getPath(parent, this.versionPath);
} else {
res.version = this.type.decode(stream);
}
if (this.versions.header) {
this._parseFields(stream, res, this.versions.header);
}
const fields = this.versions[res.version];
if ((fields == null)) {
throw new Error(`Unknown version ${res.version}`);
}
if (fields instanceof VersionedStruct) {
return fields.decode(stream, parent);
}
this._parseFields(stream, res, fields);
if (this.process != null) {
this.process.call(res, stream);
}
return res;
}
size(val, parent, includePointers = true) {
let key, type;
if (!val) {
throw new Error('Not a fixed size');
}
const ctx = {
parent,
val,
pointerSize: 0
};
let size = 0;
if (typeof this.type !== 'string') {
size += this.type.size(val.version, ctx);
}
if (this.versions.header) {
for (key in this.versions.header) {
type = this.versions.header[key];
if (type.size != null) {
size += type.size(val[key], ctx);
}
}
}
const fields = this.versions[val.version];
if ((fields == null)) {
throw new Error(`Unknown version ${val.version}`);
}
for (key in fields) {
type = fields[key];
if (type.size != null) {
size += type.size(val[key], ctx);
}
}
if (includePointers) {
size += ctx.pointerSize;
}
return size;
}
encode(stream, val, parent) {
let key, type;
if (this.preEncode != null) {
this.preEncode.call(val, stream);
}
const ctx = {
pointers: [],
startOffset: stream.pos,
parent,
val,
pointerSize: 0
};
ctx.pointerOffset = stream.pos + this.size(val, ctx, false);
if (typeof this.type !== 'string') {
this.type.encode(stream, val.version);
}
if (this.versions.header) {
for (key in this.versions.header) {
type = this.versions.header[key];
if (type.encode != null) {
type.encode(stream, val[key], ctx);
}
}
}
const fields = this.versions[val.version];
for (key in fields) {
type = fields[key];
if (type.encode != null) {
type.encode(stream, val[key], ctx);
}
}
let i = 0;
while (i < ctx.pointers.length) {
const ptr = ctx.pointers[i++];
ptr.type.encode(stream, ptr.val, ptr.parent);
}
}
}
module.exports = VersionedStruct;