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Keep only the largest field as the public field #14

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Keep only the largest field as the public field #14

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41 changes: 21 additions & 20 deletions lib/union.js
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Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,7 @@ function Union () {

UnionType.defineProperty = defineProperty
UnionType.toString = toString
UnionType.fields = {}
UnionType.allFields = {}

// comply with ref's "type" interface
UnionType.size = 0
Expand All @@ -73,7 +73,7 @@ function Union () {
UnionType.get = get
UnionType.set = set

// Read the fields list
// Read the allFields list
var arg = arguments[0]
if (typeof arg === 'object') {
Object.keys(arg).forEach(function (name) {
Expand Down Expand Up @@ -102,7 +102,7 @@ function set (buffer, offset, value) {
var isUnion = value instanceof this
if (isUnion) {
// TODO: optimize - use Buffer#copy()
Object.keys(this.fields).forEach(function (name) {
Object.keys(this.allFields).forEach(function (name) {
// hopefully hit the setters
union[name] = value[name]
})
Expand Down Expand Up @@ -151,7 +151,7 @@ function defineProperty (name, type) {
var field = {
type: type
}
this.fields[name] = field
this.allFields[name] = field

// calculate the new size and alignment
recalc(this);
Expand All @@ -168,33 +168,34 @@ function defineProperty (name, type) {
}

function recalc (union) {
// reset size and alignment
union.size = 0
union.alignment = 0
var biggest
var fieldNames = Object.keys(union.allFields)

var fieldNames = Object.keys(union.fields)

// loop through to set the size of the union of the largest member field
// and the alignment to the requirements of the largest member
// find the largest member field by size / alignment
fieldNames.forEach(function (name) {
var field = union.fields[name]
var field = union.allFields[name]
var type = field.type

var size = type.indirection === 1 ? type.size : ref.sizeof.pointer
var alignment = type.alignment || ref.alignof.pointer
if (type.indirection > 1) {
alignment = ref.alignof.pointer
}
union.alignment = Math.max(union.alignment, alignment)
union.size = Math.max(union.size, size)
var fields = {}
fields[name] = { type: type }

var current = { fields: fields, size: size, alignment: alignment }

if (!biggest || size > biggest.size || alignment > biggest.alignment) {
biggest = current
}
})

// any padding
var left = union.size % union.alignment
if (left > 0) {
debug('additional padding to the end of union:', union.alignment - left)
union.size += union.alignment - left
}
union.alignment = biggest.alignment;
union.size = biggest.size;
// Pretend like we only have this one field so that
// ffi-napi doesn't overcount the size
union.fields = biggest.fields;
}


Expand Down
8 changes: 4 additions & 4 deletions test/union.js
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Original file line number Diff line number Diff line change
Expand Up @@ -51,9 +51,9 @@ describe('Union', function () {
, 'sval': 'string'
})

assert.strictEqual(ref.types.int, U.fields.ival.type)
assert.strictEqual(ref.types.long, U.fields.lval.type)
assert.strictEqual(ref.coerceType('string'), U.fields.sval.type)
assert.strictEqual(ref.types.int, U.allFields.ival.type)
assert.strictEqual(ref.types.long, U.allFields.lval.type)
assert.strictEqual(ref.coerceType('string'), U.allFields.sval.type)
})

})
Expand Down Expand Up @@ -86,7 +86,7 @@ describe('Union', function () {
assert.equal(expectedAlignment, unionType.alignment, 'test' + testNumber +
': __alignof__(): expected ' + unionType.alignment + ' to equal ' + expectedAlignment)
})
Object.keys(unionType.fields).forEach(function (name) {
Object.keys(unionType.allFields).forEach(function (name) {
if ('skip' == name) return;
// these tests just verify the assumption that the
// offset of every field is always 0
Expand Down