extern "C" long Android_JNI_FileSeek(SDL_RWops* ctx, long offset, int whence)
{
long newPosition;
switch (whence) {
case RW_SEEK_SET:
newPosition = offset;
break;
case RW_SEEK_CUR:
newPosition = ctx->hidden.androidio.position + offset;
break;
case RW_SEEK_END:
newPosition = ctx->hidden.androidio.size + offset;
break;
default:
SDL_SetError("Unknown value for 'whence'");
return -1;
}
if (newPosition < 0) {
newPosition = 0;
}
if (newPosition > ctx->hidden.androidio.size) {
newPosition = ctx->hidden.androidio.size;
}
long movement = newPosition - ctx->hidden.androidio.position;
jobject inputStream = (jobject)ctx->hidden.androidio.inputStreamRef;
if (movement > 0) {
unsigned char buffer[1024];
// The easy case where we're seeking forwards
while (movement > 0) {
long amount = (long) sizeof (buffer);
if (amount > movement) {
amount = movement;
}
size_t result = Android_JNI_FileRead(ctx, buffer, 1, amount);
if (result <= 0) {
// Failed to read/skip the required amount, so fail
return -1;
}
movement -= result;
}
} else if (movement < 0) {
// We can't seek backwards so we have to reopen the file and seek
// forwards which obviously isn't very efficient
Android_JNI_FileClose(ctx, false);
Android_JNI_FileOpen(ctx);
Android_JNI_FileSeek(ctx, newPosition, RW_SEEK_SET);
}
ctx->hidden.androidio.position = newPosition;
return ctx->hidden.androidio.position;
}
extern "C" Sint64 Android_JNI_FileSeek(SDL_RWops* ctx, Sint64 offset, int whence)
{
Sint64 newPosition;
switch (whence) {
case RW_SEEK_SET:
newPosition = offset;
break;
case RW_SEEK_CUR:
newPosition = ctx->hidden.androidio.position + offset;
break;
case RW_SEEK_END:
newPosition = ctx->hidden.androidio.size + offset;
break;
default:
SDL_SetError("Unknown value for 'whence'");
return -1;
}
/* Validate the new position */
if (newPosition < 0) {
SDL_Error(SDL_EFSEEK);
return -1;
}
if (newPosition > ctx->hidden.androidio.size) {
newPosition = ctx->hidden.androidio.size;
}
Sint64 movement = newPosition - ctx->hidden.androidio.position;
if (movement > 0) {
unsigned char buffer[4096];
// The easy case where we're seeking forwards
while (movement > 0) {
Sint64 amount = sizeof (buffer);
if (amount > movement) {
amount = movement;
}
size_t result = Android_JNI_FileRead(ctx, buffer, 1, amount);
if (result <= 0) {
// Failed to read/skip the required amount, so fail
return -1;
}
movement -= result;
}
} else if (movement < 0) {
// We can't seek backwards so we have to reopen the file and seek
// forwards which obviously isn't very efficient
Android_JNI_FileClose(ctx, false);
Android_JNI_FileOpen(ctx);
Android_JNI_FileSeek(ctx, newPosition, RW_SEEK_SET);
}
return ctx->hidden.androidio.position;
}
extern "C" int Android_JNI_FileClose(SDL_RWops* ctx)
{
return Android_JNI_FileClose(ctx, true);
}