iOS ALAssetsLibrary和NSFileHandle读取文件内容

Question

我想在iOS中阅读资产库文件的内容

NSFileHandle fileHandleForReadingFromUrl使用资产defaultRepresentation网址似乎总是返回0x0...

我会一直在寻找解决方案.

编辑:

看起来Anomie的答案 可能就是我想要的:

NSUInteger length = [representation getBytes:bytes fromOffset:0 length:[representation size] error:&error];

Answer 1

对于较大的文件,您可能希望通过循环复制出来以读取块中的X字节,否则您可能会耗尽设备上的内存.

NSUInteger chunkSize = 100 * 1024;
uint8_t *buffer = malloc(chunkSize * sizeof(uint8_t));

ALAssetRepresentation *rep = [myasset defaultRepresentation];
NSUInteger length = [rep size];

NSFileHandle *file = [[NSFileHandle fileHandleForWritingAtPath: tempFile] retain];

if(file == nil) {
    [[NSFileManager defaultManager] createFileAtPath:tempFile contents:nil attributes:nil];
    file = [[NSFileHandle fileHandleForWritingAtPath:tempFile] retain];
}

NSUInteger offset = 0;
do {
    NSUInteger bytesCopied = [rep getBytes:buffer fromOffset:offset length:chunkSize error:nil];
    offset += bytesCopied;
    NSData *data = [[NSData alloc] initWithBytes:buffer length:bytesCopied];
    [file writeData:data];
    [data release];
    } while (offset < length);

[file closeFile];
[file release];
free(buffer);
buffer = NULL;