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