[PATCH RFC 2/3] libfile: implement read_fd counterpart to read_file

[Ahmad Fatoum]

Hello Yann,

On 20.11.23 10:49, Yann Sionneau wrote:
> Hello Ahmad,
> 
> On 11/20/23 09:37, Ahmad Fatoum wrote:
>> Files opened with O_TMPFILE have no name, so read_file can't be used
>> with them. Therefore add a read_fd function, which slurps all a file's
>> contents into a buffer.
>>
>> Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
>> ---
>>   include/libfile.h |  2 ++
>>   lib/libfile.c     | 44 ++++++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 46 insertions(+)
>>
>> diff --git a/include/libfile.h b/include/libfile.h
>> index a353ccfa9ea9..423e7ffec5b7 100644
>> --- a/include/libfile.h
>> +++ b/include/libfile.h
>> @@ -12,6 +12,8 @@ char *read_file_line(const char *fmt, ...);
>>     void *read_file(const char *filename, size_t *size);
>>   +void *read_fd(int fd, size_t *size);
>> +
>>   int read_file_2(const char *filename, size_t *size, void **outbuf,
>>           loff_t max_size);
>>   diff --git a/lib/libfile.c b/lib/libfile.c
>> index e53ba08415a2..c257baaa2733 100644
>> --- a/lib/libfile.c
>> +++ b/lib/libfile.c
>> @@ -306,6 +306,50 @@ void *read_file(const char *filename, size_t *size)
>>   }
>>   EXPORT_SYMBOL(read_file);
>>   +/**
>> + * read_fd - read from a file descriptor to an allocated buffer
>> + * @filename:  The file descriptor to read
>> + * @size:      After successful return contains the size of the file
>> + *
>> + * This function reads a file descriptor from offset 0 until EOF to an
>> + * allocated buffer.
>> + *
>> + * Return: The buffer containing the file or NULL on failure
>> + */
>> +void *read_fd(int fd, size_t *out_size)
>> +{
>> +    off_t off;
>> +    ssize_t ret;
>> +    size_t size;
>> +    void *buf;
>> +
>> +    off = lseek(fd, SEEK_CUR, 0);
>> +    if (off >= 0) {
>> +        size = off;
>> +        off = lseek(fd, SEEK_SET, 0);
>> +    }
>> +    if (off < 0) {
>> +        ret = off;
>> +        goto close_fd;
>> +    }
>> +
>> +    buf = malloc(size + 3);
> 
> Maybe check the return value from malloc()?

Yes, I should.

> 
> Also, it's not clear to me why this +3 is needed and the 3 extra \0, maybe an in-code comment would help?

I added a comment in the fixup that I just sent.

Thanks for the review,
Ahmad

> 
>> +    ret = read_full(fd, buf, size);
>> +    if (ret < 0) {
>> +        free(buf);
>> +        goto close_fd;
>> +    }
>> +
>> +    memset(&buf[size], '\0', 3);
>> +    *out_size = size;
>> +
>> +close_fd:
>> +    close(fd);
>> +
>> +    return ret < 0 ? NULL : buf;
>> +}
>> +EXPORT_SYMBOL(read_fd);
>> +
>>   /**
>>    * write_file - write a buffer to a file
>>    * @filename:    The filename to write
> 
> Regards,
> 

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