decompression same file on different platforms

[GoogleCodeExporter]

What steps will reproduce the problem?

1. compress data file on x86_64 using LZ4_compressHC() (first 4 bytes is 
uncompressed size)

2. decompression on same platform using LZ4_decompress_safe() will return right 
value

3. decompression same file (attached into project) on iOS iPad (arm) 
LZ4_decompress_safe() returns negative value

What is the expected output? What do you see instead?

correct decompression on iOS of file compressed on x86_64

What version of the product are you using? On what operating system?

1.5.0

Please provide any additional information below.

Original issue reported on code.google.com by capa...@gmail.com on 18 Feb 2015 at 9:40

[GoogleCodeExporter]

Hi Kapak

Sound like a fairly big issue.

First, a few questions, just to be sure :

- Version 1.5.0 mentioned in the report is the version of LZ4 library, hence 
latest one ?

- LZ4_compressHC & LZ4_decompress_safe() don't provide any header information. 
Therefore, compressed & uncompressed sizes must be transmitted independently. 
It's not part of data to decompress.
Is this part clear ?
(It seems fine because 2. decompression on x86_64 works fine, but I'm a bit 
worried by this sentence : first 4 bytes is uncompressed size)

- How is read header information on iOS platform (compressed & uncompressed 
size) ?
Did you verify they were properly interpreted ?
(very small risk of endianess issue, since ARM are bi-endian)
Are you sure you don't provide the size within the flow of data to decompress ?

- Any possibility to have access to one problematic sample for debugging ?

Regards

Original comment by yann.col...@gmail.com on 18 Feb 2015 at 11:07

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[GoogleCodeExporter]

hello,

I've spent few hours in debugging since I wrote this issue and problem was 
somewhere else.  In this expression:

out_buf = malloc(original_size);
..
return [[NSData alloc] initWithBytesNoCopy:out_buf length:original_size 
freeWhenDone:true];

I missed "freeWhenDone:true" and iOS fall early into undefined behavior.

Sorry for blunt.  You can close this issue.

Original comment by capa...@gmail.com on 19 Feb 2015 at 6:43

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[GoogleCodeExporter]

sure

Original comment by yann.col...@gmail.com on 19 Feb 2015 at 4:18

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