IReadBlock / IWriteBlock fail to seek

[lucasvr]

The SAGA Raster module may fail to seek to certain file offsets depending on the input file size.

The computation of the offset performed in SAGARasterBand::{IReadBlock,IWriteBlock} on n_mBits, nRasterXSize, nRasterYSize and nBlockYOff results in a signed 32-bit temporary value. As a consequence, if the resulting offset is not within the 32-bit range, a truncated or potentially negative value could be provided to VSIFSeekL(), causing runtime errors such as:

ERROR 3: Unable to seek to beginning of grid row. ERROR 1: IReadBlock failed at X offset 0, Y offset 6684 ERROR 3: Unable to seek to beginning of grid row. ERROR 1: IReadBlock failed at X offset 0, Y offset 6685 ERROR 3: Unable to seek to beginning of grid row. [...]

[lucasvr]

Proposal fix for the problem, based on GDAL 1.8.0.

[Even Rouault]

Patch applied in trunk (r22478) and in branches/1.8 (r22479). Thanks