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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package asset
/*
#cgo LDFLAGS: -landroid
#include <android/asset_manager.h>
#include <android/asset_manager_jni.h>
#include <jni.h>
#include <stdlib.h>
// asset_manager is the asset manager of the app.
AAssetManager* asset_manager;
void asset_manager_init(uintptr_t java_vm, uintptr_t jni_env, uintptr_t ctx) {
JavaVM* vm = (JavaVM*)java_vm;
JNIEnv* env = (JNIEnv*)jni_env;
// Equivalent to:
// assetManager = ctx.getResources().getAssets();
jclass ctx_clazz = (*env)->FindClass(env, "android/content/Context");
jmethodID getres_id = (*env)->GetMethodID(env, ctx_clazz, "getResources", "()Landroid/content/res/Resources;");
jobject res = (*env)->CallObjectMethod(env, ctx, getres_id);
jclass res_clazz = (*env)->FindClass(env, "android/content/res/Resources");
jmethodID getam_id = (*env)->GetMethodID(env, res_clazz, "getAssets", "()Landroid/content/res/AssetManager;");
jobject am = (*env)->CallObjectMethod(env, res, getam_id);
// Pin the AssetManager and load an AAssetManager from it.
am = (*env)->NewGlobalRef(env, am);
asset_manager = AAssetManager_fromJava(env, am);
}
*/
import "C"
import (
"fmt"
"io"
"log"
"os"
"sync"
"unsafe"
"golang.org/x/mobile/internal/mobileinit"
)
var assetOnce sync.Once
func assetInit() {
err := mobileinit.RunOnJVM(func(vm, env, ctx uintptr) error {
C.asset_manager_init(C.uintptr_t(vm), C.uintptr_t(env), C.uintptr_t(ctx))
return nil
})
if err != nil {
log.Fatalf("asset: %v", err)
}
}
func openAsset(name string) (File, error) {
assetOnce.Do(assetInit)
cname := C.CString(name)
defer C.free(unsafe.Pointer(cname))
a := &asset{
ptr: C.AAssetManager_open(C.asset_manager, cname, C.AASSET_MODE_UNKNOWN),
name: name,
}
if a.ptr == nil {
return nil, a.errorf("open", "bad asset")
}
return a, nil
}
type asset struct {
ptr *C.AAsset
name string
}
func (a *asset) errorf(op string, format string, v ...interface{}) error {
return &os.PathError{
Op: op,
Path: a.name,
Err: fmt.Errorf(format, v...),
}
}
func (a *asset) Read(p []byte) (n int, err error) {
n = int(C.AAsset_read(a.ptr, unsafe.Pointer(&p[0]), C.size_t(len(p))))
if n == 0 && len(p) > 0 {
return 0, io.EOF
}
if n < 0 {
return 0, a.errorf("read", "negative bytes: %d", n)
}
return n, nil
}
func (a *asset) Seek(offset int64, whence int) (int64, error) {
// TODO(crawshaw): use AAsset_seek64 if it is available.
off := C.AAsset_seek(a.ptr, C.off_t(offset), C.int(whence))
if off == -1 {
return 0, a.errorf("seek", "bad result for offset=%d, whence=%d", offset, whence)
}
return int64(off), nil
}
func (a *asset) Close() error {
C.AAsset_close(a.ptr)
return nil
}