From: mar77i <mar77i@protonmail.ch>
Date: Mon, 7 Aug 2017 13:51:01 +0000 (+0200)
Subject: use an easier to understand base32 decoder
X-Git-Url: https://git.mar77i.info/?a=commitdiff_plain;h=5865c1396c7ccd8a18d5147ef238e86c75dee93e;p=ga-cli

use an easier to understand base32 decoder
---

diff --git a/otp.c b/otp.c
index de06a61..1584d30 100644
--- a/otp.c
+++ b/otp.c
@@ -41,31 +41,56 @@ int concat(char *dest, size_t *dest_used, size_t dest_size, char *src) {
 
 int b32_decode(unsigned char *buf, size_t *len) {
 	const char alphabet[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
-	size_t i = 0;
-	char x = 0, *ptr;
-	unsigned char *output = buf, count, lsh;
-	if(buf == NULL)
-		return -1;
-	for(count = 1;; count++) {
-		while(isspace(buf[i]))
+	size_t i = 0, used = 0;
+	unsigned char x, *output = buf;
+	char *ptr;
+	for(;;) {
+		while(isspace(buf[i]) || buf[i] == '\n')
 			i++;
-		if(buf[i] == '\0')
+		if(buf[i] == '\0' || buf[i] == '=')
 			break;
 		ptr = strchr(alphabet, toupper(buf[i++]));
 		if(ptr == NULL || *ptr == '\0')
 			return -1;
 		x = ptr - alphabet;
-		if(x < 0)
-			return -1;
-		lsh = (count * 3) % 8;
-		if(lsh > 3)
-			*output |= x >> (8 - lsh);
-		if(lsh + (count > 1) > 3)
+		switch(used++ % 8) {
+		case 0:
+			*output = x << 3;
+			break;
+		case 1:
+			*output |= x >> 2;
+			output++;
+			*output = x << 6;
+			break;
+		case 2:
+			*output |= x << 1;
+			break;
+		case 3:
+			*output |= x >> 4;
+			output++;
+			*output = x << 4;
+			break;
+		case 4:
+			*output |= x >> 1;
+			output++;
+			*output = x << 7;
+			break;
+		case 5:
+			*output |= x << 2;
+			break;
+		case 6:
+			*output |= x >> 3;
 			output++;
-		*output = (x << lsh) | ((lsh < 3) * *output);
+			*output = x << 5;
+			break;
+		case 7:
+			*output |= x;
+			output++;
+			break;
+		}
 	}
 	if(len != NULL)
-		*len = output - buf + 1;
+		*len = output - buf;
 	return 0;
 }