ebiten/internal/graphicsdriver/opengl/gl/conversions_notwindows.go

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// SPDX-License-Identifier: MIT
// +build !js
// +build !windows
package gl
import (
"fmt"
"reflect"
"strings"
"unsafe"
)
// #include <stdlib.h>
import "C"
// Ptr takes a slice or pointer (to a singular scalar value or the first
// element of an array or slice) and returns its GL-compatible address.
//
// For example:
//
// var data []uint8
// ...
// gl.TexImage2D(gl.TEXTURE_2D, ..., gl.UNSIGNED_BYTE, gl.Ptr(&data[0]))
func Ptr(data interface{}) unsafe.Pointer {
if data == nil {
return unsafe.Pointer(nil)
}
var addr unsafe.Pointer
v := reflect.ValueOf(data)
switch v.Type().Kind() {
case reflect.Ptr:
e := v.Elem()
switch e.Kind() {
case
reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
reflect.Float32, reflect.Float64:
addr = unsafe.Pointer(e.UnsafeAddr())
default:
panic(fmt.Errorf("unsupported pointer to type %s; must be a slice or pointer to a singular scalar value or the first element of an array or slice", e.Kind()))
}
case reflect.Uintptr:
addr = unsafe.Pointer(v.Pointer())
case reflect.Slice:
addr = unsafe.Pointer(v.Index(0).UnsafeAddr())
default:
panic(fmt.Errorf("unsupported type %s; must be a slice or pointer to a singular scalar value or the first element of an array or slice", v.Type()))
}
return addr
}
// PtrOffset takes a pointer offset and returns a GL-compatible pointer.
// Useful for functions such as glVertexAttribPointer that take pointer
// parameters indicating an offset rather than an absolute memory address.
func PtrOffset(offset int) unsafe.Pointer {
return unsafe.Pointer(uintptr(offset))
}
// Str takes a null-terminated Go string and returns its GL-compatible address.
// This function reaches into Go string storage in an unsafe way so the caller
// must ensure the string is not garbage collected.
func Str(str string) *uint8 {
if !strings.HasSuffix(str, "\x00") {
panic("str argument missing null terminator: " + str)
}
header := (*reflect.StringHeader)(unsafe.Pointer(&str))
return (*uint8)(unsafe.Pointer(header.Data))
}
// GoStr takes a null-terminated string returned by OpenGL and constructs a
// corresponding Go string.
func GoStr(cstr *uint8) string {
return C.GoString((*C.char)(unsafe.Pointer(cstr)))
}
// Strs takes a list of Go strings (with or without null-termination) and
// returns their C counterpart.
//
// The returned free function must be called once you are done using the strings
// in order to free the memory.
//
// If no strings are provided as a parameter this function will panic.
func Strs(strs ...string) (cstrs **uint8, free func()) {
if len(strs) == 0 {
panic("Strs: expected at least 1 string")
}
// Allocate a contiguous array large enough to hold all the strings' contents.
n := 0
for i := range strs {
n += len(strs[i])
}
data := C.malloc(C.size_t(n))
// Copy all the strings into data.
dataSlice := *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
Data: uintptr(data),
Len: n,
Cap: n,
}))
css := make([]*uint8, len(strs)) // Populated with pointers to each string.
offset := 0
for i := range strs {
copy(dataSlice[offset:offset+len(strs[i])], strs[i][:]) // Copy strs[i] into proper data location.
css[i] = (*uint8)(unsafe.Pointer(&dataSlice[offset])) // Set a pointer to it.
offset += len(strs[i])
}
return (**uint8)(&css[0]), func() { C.free(data) }
}