email: Support email with mixed encoding of characters.

Prior to this, parse-email would accept email in the form of a
string. A string is constrained to use the same encoding for all its
characters whereas an email can have characters encoded using
different encoding schemes. Therefore, it is more correct that
parse-email deals with bytevectors instead of strings.

* email/utils.scm (read-bytes-till): New function.
* email/email.scm (body->mime-entities, email->headers+body,
decode-body): Deal with emails as bytevectors instead of strings.
(parse-mime-entity): Rename text argument to bv.
(parse-email, parse-email-body): Overload to handle input in the form
of a string or bytevector.
* doc/guile-email.texi (Parsing e-mail): Document overloading of
parse-email and parse-email-body.
* tests/email.scm ("handle truncated multipart message gracefully"):
Deal in bytevectors instead of strings.
("email with 8 bit encoding and non UTF-8 charset", "multipart email
with a 8 bit encoding and non UTF-8 charset part"): New tests.
* tests/email-with-8bit-encoding-and-non-utf8-charset,
tests/multipart-email-with-a-8bit-encoding-and-non-utf8-charset-part:
New files.

Reported-by: Jack Hill <jackhill@jackhill.us>

1 files changed, 9 insertions, 0 deletions

diff --git a/tests/email-with-8bit-encoding-and-non-utf8-charset b/tests/email-with-8bit-encoding-and-non-utf8-charset
new file mode 100644
index 0000000..a4f4a6e
--- /dev/null
+++ b/tests/email-with-8bit-encoding-and-non-utf8-charset
@@ -0,0 +1,9 @@
+From: John Doe <jdoe@machine.example>
+To: Mary Smith <mary@example.net>
+Subject: Saying Hello
+Date: Fri, 21 Nov 1997 09:55:06 -0600
+Message-ID: <1234@local.machine.example>
+Content-Type: text/plain; charset=ISO-8859-7
+Content-Transfer-Encoding: 8bit
+
+Hello Foo˘.
\ No newline at end of file