mirror of https://github.com/tidwall/tile38.git
96 lines
2.3 KiB
Go
96 lines
2.3 KiB
Go
package item
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import (
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"reflect"
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"unsafe"
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)
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func getFieldAt(data unsafe.Pointer, index int) float64 {
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return *(*float64)(unsafe.Pointer(uintptr(data) + uintptr(index*8)))
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}
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func setFieldAt(data unsafe.Pointer, index int, value float64) {
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*(*float64)(unsafe.Pointer(uintptr(data) + uintptr(index*8))) = value
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}
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func (item *Item) dataBytes() []byte {
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return *(*[]byte)((unsafe.Pointer)(&reflect.SliceHeader{
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Data: uintptr(unsafe.Pointer(item.data)),
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Len: item.fieldsDataSize() + item.idDataSize(),
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Cap: item.fieldsDataSize() + item.idDataSize(),
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}))
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}
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func bytesToFloats(f []byte) []float64 {
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return *(*[]float64)((unsafe.Pointer)(&reflect.SliceHeader{
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Data: ((*reflect.SliceHeader)(unsafe.Pointer(&f))).Data,
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Len: len(f) / 8,
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Cap: len(f) / 8,
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}))
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}
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func (item *Item) unpackedGenerateFieldBytes(values []float64) []byte {
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return *(*[]byte)((unsafe.Pointer)(&reflect.SliceHeader{
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Data: ((*reflect.SliceHeader)(unsafe.Pointer(&values))).Data,
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Len: len(values) * 8,
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Cap: len(values) * 8,
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}))
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}
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func (item *Item) unpackedSetField(index int, value float64) (updated bool) {
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numFields := item.fieldsDataSize() / 8
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if index < numFields {
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// field exists
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if getFieldAt(item.data, index) == value {
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return false
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}
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} else if value == 0 {
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return false
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} else {
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// make room for new field
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oldBytes := item.dataBytes()
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newData := make([]byte, (index+1)*8+item.idDataSize())
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// copy the existing fields
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copy(newData, oldBytes[:item.fieldsDataSize()])
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// copy the id
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copy(newData[(index+1)*8:], oldBytes[item.fieldsDataSize():])
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// update the fields length
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item.setFieldsDataSize((index + 1) * 8)
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// update the raw data
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item.data = unsafe.Pointer(&newData[0])
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}
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// set the new field
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setFieldAt(item.data, index, value)
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return true
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}
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func (item *Item) unpackedForEachField(
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count int, iter func(value float64) bool,
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) {
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fields := bytesToFloats(item.fieldsBytes())
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var n int
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if count < 0 {
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n = len(fields)
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} else {
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n = count
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}
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for i := 0; i < n; i++ {
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var field float64
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if i < len(fields) {
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field = fields[i]
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}
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if !iter(field) {
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return
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}
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}
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}
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func (item *Item) unpackedGetField(index int) float64 {
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numFields := item.fieldsDataSize() / 8
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if index < numFields {
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return getFieldAt(item.data, index)
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}
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return 0
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}
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