最近用go，发现go slice 处理的时候，如果输入的长度满足要求则不会重新分配空间，长度不够的话重新分配空间
测试代码：
func PackDataCRC32(plainData []byte) []byte {
ieee := crc32.NewIEEE()
ieee.Write(plainData)
s := ieee.Sum32()
b := make([]byte, 4)
binary.BigEndian.PutUint32(b, s)
return append(plainData, b...)
}
func main {
testBytes := make([]byte, 10)
testBytes2 := make([]byte, 20)
fmt.Printf("Before:testBytes2 %p val is %v \r\n", testBytes2, testBytes2)
fmt.Printf("Before:testBytes %p val is %v \r\n", testBytes, testBytes)
PackDataCRC32(testBytes)
fmt.Printf("After: testBytes %p val is %v \r\n", testBytes, testBytes)
testBytes3 := testBytes2[:10]
fmt.Printf("Before:testBytes3 %p val is %v \r\n", testBytes3, testBytes3)
fmt.Printf("Before:testBytes2 %p val is %v \r\n", testBytes2, testBytes2)
PackDataCRC32(testBytes3, secretKey)
fmt.Printf("After: testBytes3 %p val is %v \r\n", testBytes3, testBytes3)
fmt.Printf("After: testBytes2 %p val is %v \r\n", testBytes2, testBytes2)
}
输出：
Before:testBytes2 0xc42001a4c0 val is [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
Before:testBytes 0xc420018690 val is [0 0 0 0 0 0 0 0 0 0]
plainText 0xc420018690 , plainTextWithCrc 0xc42001a4e0
After: testBytes 0xc420018690 val is [0 0 0 0 0 0 0 0 0 0]
Before:testBytes3 0xc42001a4c0 val is [0 0 0 0 0 0 0 0 0 0]
Before:testBytes2 0xc42001a4c0 val is [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
plainText 0xc42001a4c0 , plainTextWithCrc 0xc42001a4c0
After: testBytes3 0xc42001a4c0 val is [0 0 0 0 0 0 0 0 0 0]
After: testBytes2 0xc42001a4c0 val is [0 0 0 0 0 0 0 0 0 0 227 138 104 118 0 0 0 0 0 0]