15c7d93ea9
This might sound crazy, but I think it's better to enable the GC by default to avoid surprises. It costs 1130 bytes of flash and 16 bytes of RAM (plus heap overhead) so it's not exactly free, but if needed it can easily be disabled with `-gc=leaking`. On the Uno (32kB flash, 2kB RAM) that's not massive, on the DigiSpark (8kB flash, 0.5kB RAM) that may be too much depending on the application.
66 строки
1,6 КиБ
Go
66 строки
1,6 КиБ
Go
package main
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var xorshift32State uint32 = 1
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func xorshift32(x uint32) uint32 {
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// Algorithm "xor" from p. 4 of Marsaglia, "Xorshift RNGs"
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x ^= x << 13
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x ^= x >> 17
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x ^= x << 5
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return x
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}
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func randuint32() uint32 {
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xorshift32State = xorshift32(xorshift32State)
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return xorshift32State
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}
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func main() {
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testNonPointerHeap()
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}
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var scalarSlices [4][]byte
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var randSeeds [4]uint32
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func testNonPointerHeap() {
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maxSliceSize := uint32(1024)
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if ^uintptr(0) <= 0xffff {
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// 16-bit and lower devices, such as AVR.
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// Heap size is a real issue there, while it is still useful to run
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// these tests. Therefore, lower the max slice size.
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maxSliceSize = 64
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}
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// Allocate roughly 0.5MB of memory.
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for i := 0; i < 1000; i++ {
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// Pick a random index that the optimizer can't predict.
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index := randuint32() % 4
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// Check whether the contents of the previous allocation was correct.
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rand := randSeeds[index]
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for _, b := range scalarSlices[index] {
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rand = xorshift32(rand)
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if b != byte(rand) {
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panic("memory was overwritten!")
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}
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}
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// Allocate a randomly-sized slice, randomly sliced to be smaller.
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sliceLen := randuint32() % maxSliceSize
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slice := make([]byte, sliceLen)
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cutLen := randuint32() % maxSliceSize
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if cutLen < sliceLen {
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slice = slice[cutLen:]
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}
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scalarSlices[index] = slice
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// Fill the slice with a pattern that looks random but is easily
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// calculated and verified.
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rand = randuint32() + 1
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randSeeds[index] = rand
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for i := 0; i < len(slice); i++ {
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rand = xorshift32(rand)
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slice[i] = byte(rand)
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}
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}
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println("ok")
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}
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