You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
111 lines
2.4 KiB
111 lines
2.4 KiB
const utils = require('./utils');
|
|
|
|
class Struct {
|
|
constructor(fields = {}) {
|
|
this.fields = fields;
|
|
}
|
|
|
|
decode(stream, parent, length = 0) {
|
|
const res = this._setup(stream, parent, length);
|
|
this._parseFields(stream, res, this.fields);
|
|
|
|
if (this.process != null) {
|
|
this.process.call(res, stream);
|
|
}
|
|
return res;
|
|
}
|
|
|
|
_setup(stream, parent, length) {
|
|
const res = {};
|
|
|
|
// define hidden properties
|
|
Object.defineProperties(res, {
|
|
parent: { value: parent },
|
|
_startOffset: { value: stream.pos },
|
|
_currentOffset: { value: 0, writable: true },
|
|
_length: { value: length }
|
|
});
|
|
|
|
return res;
|
|
}
|
|
|
|
_parseFields(stream, res, fields) {
|
|
for (let key in fields) {
|
|
var val;
|
|
const type = fields[key];
|
|
if (typeof type === 'function') {
|
|
val = type.call(res, res);
|
|
} else {
|
|
val = type.decode(stream, res);
|
|
}
|
|
|
|
if (val !== undefined) {
|
|
if (val instanceof utils.PropertyDescriptor) {
|
|
Object.defineProperty(res, key, val);
|
|
} else {
|
|
res[key] = val;
|
|
}
|
|
}
|
|
|
|
res._currentOffset = stream.pos - res._startOffset;
|
|
}
|
|
|
|
}
|
|
|
|
size(val, parent, includePointers) {
|
|
if (val == null) { val = {}; }
|
|
if (includePointers == null) { includePointers = true; }
|
|
const ctx = {
|
|
parent,
|
|
val,
|
|
pointerSize: 0
|
|
};
|
|
|
|
let size = 0;
|
|
for (let key in this.fields) {
|
|
const type = this.fields[key];
|
|
if (type.size != null) {
|
|
size += type.size(val[key], ctx);
|
|
}
|
|
}
|
|
|
|
if (includePointers) {
|
|
size += ctx.pointerSize;
|
|
}
|
|
|
|
return size;
|
|
}
|
|
|
|
encode(stream, val, parent) {
|
|
let 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);
|
|
|
|
for (let key in this.fields) {
|
|
type = this.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 = Struct;
|