libbb: merge mail and uudecode's base64 decoders

function                                             old     new   delta
read_base64                                            -     378    +378
uudecode_main                                        306     315      +9
parse                                                953     958      +5
read_stduu                                           250     254      +4
base64_main                                          217     219      +2
read_base64                                          358       -    -358
decode_base64                                        371       -    -371
------------------------------------------------------------------------------
(add/remove: 2/2 grow/shrink: 4/0 up/down: 398/-729)         Total: -331 bytes

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>

1 files changed, 78 insertions, 0 deletions

diff --git a/libbb/base64.c b/libbb/base64.c
new file mode 100644
index 0000000..b9d47ae
--- /dev/null
+++ b/libbb/base64.c
@@ -0,0 +1,78 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Utility routines.
+ *
+ * Copyright 2003, Glenn McGrath
+ * Copyright 2010, Denys Vlasenko
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+#include "libbb.h"
+
+//kbuild:lib-y += base64.o
+
+void FAST_FUNC read_base64(FILE *src_stream, FILE *dst_stream, int flags)
+{
+/* Note that EOF _can_ be passed as exit_char too */
+#define exit_char    ((int)(signed char)flags)
+#define uu_style_end (flags & BASE64_FLAG_UUEND)
+
+	int term_count = 0;
+
+	while (1) {
+		unsigned char translated[4];
+		int count = 0;
+
+		/* Process one group of 4 chars */
+		while (count < 4) {
+			char *table_ptr;
+			int ch;
+
+			/* Get next _valid_ character.
+			 * bb_uuenc_tbl_base64[] contains this string:
+			 *  0         1         2         3         4         5         6
+			 *  012345678901234567890123456789012345678901234567890123456789012345
+			 * "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=\n"
+			 */
+			do {
+				ch = fgetc(src_stream);
+				if (ch == exit_char && count == 0)
+					return;
+				if (ch == EOF)
+					bb_error_msg_and_die("truncated base64 input");
+				table_ptr = strchr(bb_uuenc_tbl_base64, ch);
+//TODO: add BASE64_FLAG_foo to die on bad char?
+//Note that then we may need to still allow '\r' (for mail processing)
+			} while (!table_ptr);
+
+			/* Convert encoded character to decimal */
+			ch = table_ptr - bb_uuenc_tbl_base64;
+
+			if (ch == 65 /* '\n' */) {
+				/* Terminating "====" line? */
+				if (uu_style_end && term_count == 4)
+					return; /* yes */
+				continue;
+			}
+			/* ch is 64 if char was '=', otherwise 0..63 */
+			translated[count] = ch & 63; /* 64 -> 0 */
+			if (ch == 64) {
+				term_count++;
+				break;
+			}
+			term_count = 0;
+			count++;
+		}
+
+		/* Merge 6 bit chars to 8 bit.
+		 * count can be < 4 when we decode the tail:
+		 * "eQ==" -> "y", not "y NUL NUL"
+		 */
+		if (count > 1)
+			fputc(translated[0] << 2 | translated[1] >> 4, dst_stream);
+		if (count > 2)
+			fputc(translated[1] << 4 | translated[2] >> 2, dst_stream);
+		if (count > 3)
+			fputc(translated[2] << 6 | translated[3], dst_stream);
+	} /* while (1) */
+}