如何将 Go 字符串数组转换为 C 字符串数组？

Question

我在一个项目中使用cgo，我想导出一个函数以供使用。这是我想要实现的示例：

package csplit

import (
    "C"
    "strings"
)

//export Split
/* The Split function takes two C strings, the second of which represents
   a substring to split on, and returns an array of strings. Example:
       Split("1,2", ",") // gives ["1", "2"]
*/
func Split(original *C.char, split *C.char) []*C.char {
        goResult := strings.Split(C.GoString(original), C.GoString(split))
        cResult := make([]*C.char, len(goResult))

        for idx, substring := range goResult {
                cResult[idx] = C.CString(substring)
        }

        return cResult
}

问题是返回类型是 Go 分配的数据，而不是移动到 C 堆中。这会引起恐慌：runtime error: cgo result has Go pointer

Answer 1

您正在返回一个 Go 切片，它是在 Go 中分配的，并且是与 C 数组不同的结构。您需要在 C 中分配一个数组：

//export Split
func Split(original *C.char, split *C.char) **C.char {
    goResult := strings.Split(C.GoString(original), C.GoString(split))
    cArray := C.malloc(C.size_t(len(goResult)) * C.size_t(unsafe.Sizeof(uintptr(0))))

    // convert the C array to a Go Array so we can index it
    a := (*[1<<30 - 1]*C.char)(cArray)

    for idx, substring := range goResult {
        a[idx] = C.CString(substring)
    }

    return (**C.char)(cArray)
}