[pmmail-list] Email sizes ??

[Rod.. Whitworth]

On Sat, 02 Aug 2003 21:26:30 -0700 (PDT), James F. Marshall wrote:

>On Sun, 03 Aug 2003 13:48:28 +1000, Andrew Z wrote:
>
>> " Anyone have any clues or have seen something similar?
>
>The attachment is converted to ASCII, which makes it bigger
>because 8-bit data is converted to 7-bit data?

6 bits actually + 2 bits to make the printable char.

As a result the size expands by 33%.

It is called base64 and every 3 8-bit bytes of dara (24 bits) become 4
6-bit bytes (no, bytes are not always 8 bits) which are padded with 2
bits each to form the character set [A-Za-z0-9+/] (that is 64 chars
representing 0-63) so we have now 32 bits sent as 4 chars.

If the stream of data is not a multiple of 3 bytes in length pad chars
are added on the end. For one over n*3 bytes of data another 2 zero
values (A) are added plus 2 = signs. For n*3+2 1 zero val and one = are
used to terminate the data.

HTH
HAND


"Write a wise saying and your name will live on forever."  - Anonymous
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