--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/f-demime/base64.c	Sat May 06 06:14:03 2023 +0000
@@ -0,0 +1,112 @@
+/*
+ * This module implements base64 decoding.
+ */
+
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include "defs.h"
+
+extern void (*dec_outf)();
+
+static unsigned b64_accum, b64_eq_flag;
+static int b64_state, last_partial;
+int b64_err_flag, b64_nonempty;
+
+void
+base64_dec_init()
+{
+	b64_accum = 0;
+	b64_eq_flag = 0;
+	b64_state = 0;
+	b64_err_flag = 0;
+	b64_nonempty = 0;
+	last_partial = 0;
+}
+
+static void
+process_unit()
+{
+	if (last_partial)
+		b64_err_flag = 1;
+	switch (b64_eq_flag) {
+	case 0:
+		dec_outf(b64_accum >> 16);
+		dec_outf((b64_accum >> 8) & 0xFF);
+		dec_outf(b64_accum & 0xFF);
+		last_partial = 0;
+		break;
+	case 1:
+		dec_outf(b64_accum >> 16);
+		dec_outf((b64_accum >> 8) & 0xFF);
+		last_partial = 1;
+		break;
+	case 3:
+		dec_outf(b64_accum >> 16);
+		last_partial = 1;
+		break;
+	default:
+		b64_err_flag = 1;
+	}
+	b64_accum = 0;
+	b64_eq_flag = 0;
+	b64_state = 0;
+}
+
+static void
+base64_input_char(ch)
+{
+	int code;
+
+	b64_nonempty = 1;
+	if (ch >= 'A' && ch <= 'Z')
+		code = ch - 'A';
+	else if (ch >= 'a' && ch <= 'z')
+		code = ch - 'a' + 26;
+	else if (ch >= '0' && ch <= '9')
+		code = ch - '0' + 52;
+	else switch (ch) {
+	case '+':
+		code = 62;
+		break;
+	case '/':
+		code = 63;
+		break;
+	case '=':
+		code = 64;
+		break;
+	default:
+		b64_err_flag = 1;
+		return;
+	}
+	b64_accum <<= 6;
+	b64_accum |= (code & 63);
+	b64_eq_flag <<= 1;
+	b64_eq_flag |= (code >> 6);
+	b64_state++;
+	if (b64_state >= 4)
+		process_unit();
+}
+
+void
+base64_input_line(line)
+	char *line;
+{
+	char *cp;
+	int c;
+
+	for (cp = line; *cp; ) {
+		c = *cp++;
+		if (!isspace(c))
+			base64_input_char(c);
+	}
+}
+
+void
+base64_dec_finish()
+{
+	if (b64_state)
+		b64_err_flag = 1;
+}