[PATCH] erofs-utils: dump: Add --cat flag to show file contents

[Juan Hernández]

Thanks for your feedback Gao! I will address your concerns.

On Thu, Jan 9, 2025 at 11:43 AM Gao Xiang <hsiangkao at linux.alibaba.com> wrote:
>
> Hi Juan,
>
> On 2025/1/9 17:55, Juan Hernandez wrote:
> > This patch adds a new '--cat' flag to the 'dump.erofs' command. When
> > used it will write to the standard output the content of the file
> > indicated by the '--path' or '--nid' options. For example, if there is a
> > '/mydir/myfile.txt' file containg the text 'mytext':
> >
> >      $ dump.erofs --cat --path=/mydir/myfile.txt myimage.erofs
> >      mytext
> >
> > Signed-off-by: Juan Hernandez <jhernand at redhat.com>
>
> Thanks for the patch!
> It looks good to me, just minor nits..
>
> > ---
> >   dump/main.c      | 72 ++++++++++++++++++++++++++++++++++++++++++++++++
> >   man/dump.erofs.1 | 13 +++++++--
> >   2 files changed, 83 insertions(+), 2 deletions(-)
> >
> > diff --git a/dump/main.c b/dump/main.c
> > index 372162e..ed8d44d 100644
> > --- a/dump/main.c
> > +++ b/dump/main.c
> > @@ -26,6 +26,7 @@ struct erofsdump_cfg {
> >       bool show_superblock;
> >       bool show_statistics;
> >       bool show_subdirectories;
> > +     bool show_file_content;
> >       erofs_nid_t nid;
> >       const char *inode_path;
> >   };
> > @@ -80,6 +81,7 @@ static struct option long_options[] = {
> >       {"path", required_argument, NULL, 4},
> >       {"ls", no_argument, NULL, 5},
> >       {"offset", required_argument, NULL, 6},
> > +     {"cat", no_argument, NULL, 7},
> >       {0, 0, 0, 0},
> >   };
> >
> > @@ -123,6 +125,7 @@ static void usage(int argc, char **argv)
> >               " -s              show information about superblock\n"
> >               " --device=X      specify an extra device to be used together\n"
> >               " --ls            show directory contents (INODE required)\n"
> > +             " --cat           show file contents (INODE required)\n"
> >               " --nid=#         show the target inode info of nid #\n"
> >               " --offset=#      skip # bytes at the beginning of IMAGE\n"
> >               " --path=X        show the target inode info of path X\n",
> > @@ -186,6 +189,9 @@ static int erofsdump_parse_options_cfg(int argc, char **argv)
> >                               return -EINVAL;
> >                       }
> >                       break;
> > +             case 7:
> > +                     dumpcfg.show_file_content = true;
> > +                     break;
> >               default:
> >                       return -EINVAL;
> >               }
> > @@ -672,6 +678,63 @@ static void erofsdump_show_superblock(void)
> >                       uuid_str);
> >   }
> >
> > +static void erofsdump_show_file_content(void)
> > +{
> > +     int err;
> > +     struct erofs_inode inode = { .sbi = &g_sbi, .nid = dumpcfg.nid };
> > +     size_t buffer_size;
> > +     char *buffer_ptr;
> > +     erofs_off_t pending_size;
> > +     erofs_off_t read_offset;
> > +     erofs_off_t read_size;
> > +
> > +     if (dumpcfg.inode_path) {
> > +             err = erofs_ilookup(dumpcfg.inode_path, &inode);
> > +             if (err) {
> > +                     erofs_err("read inode failed @ %s", dumpcfg.inode_path);
> > +                     return;
> > +             }
> > +     } else {
> > +             err = erofs_read_inode_from_disk(&inode);
> > +             if (err) {
> > +                     erofs_err("read inode failed @ nid %llu", inode.nid | 0ULL);
> > +                     return;
> > +             }
> > +     }
> > +
> > +     if (!S_ISREG(inode.i_mode)) {
>
> I think we could dump raw directory content too.
>
>
> > +             erofs_err("not a regular file @ nid %llu", inode.nid | 0ULL);
> > +             return;
> > +     }
> > +
> > +     buffer_size = erofs_blksiz(inode.sbi);
> > +     buffer_ptr = malloc(buffer_size);
> > +     if (!buffer_ptr) {
> > +             erofs_err("buffer allocation failed @ nid %llu", inode.nid | 0ULL);
> > +             return;
> > +     }
> > +
> > +     pending_size = inode.i_size;
> > +     read_offset = 0;
> > +     while (pending_size > 0) {
> > +             read_size = pending_size > buffer_size? buffer_size: pending_size;
> > +             err = erofs_pread(&inode, buffer_ptr, read_size, read_offset);
> > +             if (err) {
> > +                     erofs_err("read file failed @ nid %llu", inode.nid | 0ULL);
> > +                     goto out;
> > +             }
> > +             pending_size -= read_size;
> > +             read_offset += read_size;
> > +             fwrite(buffer_ptr, read_size, 1, stdout);
> > +     }
> > +     fflush(stdout);
> > +
> > +out:
> > +     free(buffer_ptr);
> > +}
> > +
> > +
> > +
>
> Reduntant new lines..
>
> Thanks,
> Gao Xiang
>