Dear Marco,
In message 49D8E8F3.4010300@gmail.com you wrote:
- for (j = sectoroffset; j < sectorcount; ++j) {
i. e. add
if (lseek(fd, j*sectorsize, SEEK_SET) != j*sectorsize) { error handling goes here }Mmm...I don't well understand why. For example if a sector is 128k and the header size is for example of 100 byte, after the read below, at the beginning of the cycle, the offset will be 100 byte (we say that sectoroffset is 0) and for example we don't find any image. At next cycle if I do an lseek of 1*128K, I'll get (1*128K)+100 byte as offset, at next (2*128k) + 200 byte and so on. To do this I should do an lseek after the read as lseek(fd,-readbyte,SEEK_CUR).
Please think about this again. We use a single lseek() before each read() to position the read pointer at the next sector boundary, i.e. where we need it. We don't care whe reit is after the read().
...
- len = image_get_size(hdr);
- data = malloc(len * sizeof(char));
Come on. sizeof(char) ? You must be joking.
- if (!data) {
fprintf (stderr, "%s: Can't allocate memory: %s\n",cmdname, strerror(errno));exit(EXIT_FAILURE);- }
Get rid of this malloc(), too.
I can't know in this case the size of the data, to remove the malloc I have to allocate a fixed buffer of X byte, I think in this case a malloc is better.
No. Who claims you must read the whole image at once? Use a fixed buffer of a convenient size (say PAGE_SIZE), and read the data sequentially. No need to allocate zillions of megabytes of memory at once.
- lseek(fd, -len, SEEK_CUR);
Why would this lseek() be needed? [And ifit ws needed, you should check it's return value.]
It was needed to be aligned to sector boundary and set the file offset as before to call this function (see my comment above).
Your thinking is inverted. Don't try to fix the read pointer after each read(). Set it as needed before the read() when necessary.
Best regards,
Wolfgang Denk