英文:
Zlib inflate works differently to C?
问题
我正在尝试在Java中对字节数组进行zlib解压缩，但是在解压缩时未返回Z_STREAM_END。我的代码与我查看的一些C代码完全相同，这些C代码与相同的数据、滑动窗口和其他参数一起使用，我认为是吗？我正在使用JZlib。以下是我的Java代码（dgboff只是文件中此zlib字节数组的偏移量）：
private byte[] z_decompress(byte[] in, int insize, byte[] out, int outsize) {ZStream zlib = new ZStream();zlib.inflateInit(15); // 32k window (2^15)zlib.next_in = in;zlib.avail_in = insize;zlib.next_out = out;zlib.avail_out = outsize;if (zlib.inflate(JZlib.Z_FINISH) != JZlib.Z_STREAM_END) {System.out.println("Incomplete zlib input at offset " + dgboff + ". Compressed size: " + insize + ", uncompressed size: " + outsize);System.exit(1);}zlib.inflateEnd();return zlib.next_out;}
以下是可以正常工作的C代码（忽略混乱的间距）：
z = calloc(1, sizeof(z_stream));if (!z) std_err();z->zalloc = (alloc_func)0;z->zfree = (free_func)0;z->opaque = (voidpf)0;if (inflateInit2(z, 15)) {printf("\nError: initialization error\n");exit(1);}inflateReset(z);z->next_in = in;z->avail_in = insz;z->next_out = out;z->avail_out = outsz;if (inflate(z, Z_FINISH) != Z_STREAM_END) {printf("\nError: the compressed zlib/deflate input at offset 0x%08x (%d -> %d) is wrong or incomplete\n", (int)g_dbg_offset, (int)insz, (int)outsz);exit(1);}// 在C代码中到达这里
如果我漏掉了什么，请告诉我！
我正在测试的数据的zlib头部是0x649d。
英文:
I am trying to zlib inflate a byte array in java, however I am not getting the Z_STREAM_END returned when I inflate it.
I have the code exactly the same as some C code I viewed which worked with the same data, sliding window and other parameters (I think?).
I am using JZlib. Here is my Java code (dgboff is just the offset of this zlib byte array in a file):
private byte[] z_decompress(byte[] in,int insize,byte[] out,int outsize) {ZStream zlib = new ZStream();zlib.inflateInit(15);//32k window (2^15)zlib.next_in=in;zlib.avail_in=insize;zlib.next_out=out;zlib.avail_out=outsize;if(zlib.inflate(JZlib.Z_FINISH)!=JZlib.Z_STREAM_END) {System.out.println("Incomplete zlib input at offset "+dgboff+". Compressed size: "+insize+", uncompressed size: "+outsize);System.exit(1);}zlib.inflateEnd();return zlib.next_out;}
and here is the C code, which works (ignore the messy spacing):
z = calloc(1, sizeof(z_stream));if(!z) std_err();z->zalloc = (alloc_func)0;z->zfree = (free_func)0;z->opaque = (voidpf)0;if(inflateInit2(z, 15)) {printf("\nError: initialization error\n");exit(1);}inflateReset(z);z->next_in = in;z->avail_in = insz;z->next_out = out;z->avail_out = outsz;if(inflate(z, Z_FINISH) != Z_STREAM_END) {printf("\nError: the compressed zlib/deflate input at offset 0x%08x (%d -> %d) is wrong or incomplete\n", (int)g_dbg_offset, (int)insz, (int)outsz);exit(1);}//gets to here in C
If there is anything I am missing please tell me!
The zlib header for the data I am testing is 0x649d.
答案1
得分: 1
你的数据不是一个zlib流，也没有zlib头部。它是一个原始的deflate流。你展示的两个代码示例都不能正常工作。你所说的“这是可行的C代码”肯定是其他的C代码。
要解压原始的inflate数据，你需要在inflateInit2()的第二个参数中使用-15（而不是15）。
顺便说一下，你提供的链接中的deflate压缩数据是不完整的。它在所涵盖的部分上是正确的，但没有终止标志。
英文:
Your data is not a zlib stream, and does not have a zlib header. It is a raw deflate stream. Neither of your code examples as shown could have worked. Your "here is the C code, which works" must have been some other C code.
To decompress raw inflate data, you need to use -15 (instead of 15) as the second argument of inflateInit2().
By the way, the deflate compressed data you provided a link for is incomplete. It is correct as far as it goes, but it does not terminate.
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