Exiv2

With r1755 the image is no longer loaded into memory for non-intrusive writing. The amount of memory allocated is therefore reduced by about the size of the image (for both write modes, since non-intrusive writing is always attempted first):

Non-intrusive writing

valgrind ./exiv2 -M'set Exif.Image.Software Exiv2' P1010003.TIF
malloc/free: 6,746 allocs, 6,746 frees, 650,106 bytes allocated.

Intrusive writing

valgrind ./exiv2 -M'set Exif.Image.Software The Exiv2 utility' P1010003.TIF
malloc/free: 6,102 allocs, 6,102 frees, 10,114,031 bytes allocated.

The backdraw of the change in r1755 is that in case Exiv2 crashes somewhere in the non-intrusive writing logic, this is now likely to result in modified and possibly corrupted image.

The next step is to replace the use of a Blob in the intrusive writing methods with a BasicIo. This will require an API change in the *Parser::encode methods.

r1918 finally implements the second step: In intrusive writing, the image is no longer written to a Blob but directly to a BasicIo instance, i.e., straight to a file instead of a memory buffer. With this change, the complete image is never loaded into memory anymore.

Non-intrusive writing:

valgrind ./exiv2 -M'set Exif.Image.Software Exiv2' P1010003.TIF
malloc/free: 6,322 allocs, 6,322 frees, 644,462 bytes allocated.

Intrusive writing:

valgrind ./exiv2 -M'set Exif.Image.Software The Exiv2 utility' P1010003.TIF
malloc/free: 5,627 allocs, 5,627 frees, 526,459 bytes allocated.

These changes also have an effect on performance when dealing with large TIFF images. For non-intrusive writing, the performance gain is huge, since the image is now modified in-place, without ever loading it. For intrusive writing, the time is now reasonably close to that of a simple copy operation.

The following tests were done with a 120MB TIFF image, trunk is roughly 0.18.2, unstable is r1918.

big.tif 126,172,596 bytes
time cp big.tif big1.tif
real    0m2.254s
user    0m0.001s
sys     0m0.205s

Non-intrusive writing

exiv2 -M'set Exif.Photo.DateTimeOriginal Yesterday' big.tif

      unstable            trunk
real  0.023s              3.101s
user  0.013s              0.117s
sys   0.011s              0.888s
mem   8,374,303 bytes     134,551,658 bytes

Intrusive writing

exiv2 -M'set Exif.Photo.DateTimeOriginal Yesterday noon exactly now' big.tif

      unstable            trunk
real  2.654s              3.790s
user  0.044s              0.802s
sys   0.744s              0.995s
mem   6,579,811 bytes     259,330,485 bytes