sick

commit 8607d9671280e57b2dac351bf74ad3b4292bd586
parent 565aac4be8c959bd7627836c2dae8823abca449a
Author: z3bra <willyatmailoodotorg>
Date:   Tue May 10 19:39:01 +12000

Implement base64_decode()

Diffstat:
base64.c
 | 
34
+++++++++++++++++++++++++++++++---
base64.h
 | 
1
+
2 files changed, 32 insertions(+), 3 deletions(-)
diff --git a/base64.c b/base64.c
@@ -3,6 +3,7 @@
 #include <string.h>
 #include <stdint.h>
 #include <unistd.h>
+#include <limits.h>
 
 #include "base64.h"
 
@@ -10,6 +11,19 @@
 
 const char base64_table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
+uint8_t
+base64_index(const char *base64, char ch)
+{
+	uint8_t idx = 0;
+
+	for (idx = 0; idx < 64; idx++)
+		if (base64[idx] == ch)
+			break;
+
+	return idx;
+}
+
+
 size_t
 base64_encode(char **buf, const unsigned char *msg, size_t len)
 {
@@ -25,7 +39,8 @@ base64_encode(char **buf, const unsigned char *msg, size_t len)
 
 	for (i = j = 0; i < len; i+=3) {
 		/* concatenate 3 bytes into one 24 bits quantum, or 0 */
-		b64 = 0 | (msg[i]<<16);
+		b64 = 0;
+		b64 |= (msg[i]<<16);
 		b64 |= ((i+1 < len ? msg[i+1] : 0) << 8);
 		b64 |= i+2 < len ? msg[i+2] : 0;
 
@@ -42,15 +57,28 @@ base64_encode(char **buf, const unsigned char *msg, size_t len)
 size_t
 base64_decode(char **buf, const unsigned char *msg, size_t len)
 {
-	size_t size;
+	uint64_t b64;
+	size_t size, i, j;
 
-	size = 1 + (len * 3) / 4;
+	size = (len * 3) / 4;
 	size -= msg[len - 1] == '=' ? 1 : 0;
 	size -= msg[len - 2] == '=' ? 1 : 0;
 
 	*buf = malloc(size);
 	memset(*buf, 0, size);
 
+	for (i = j = 0; i < len; i+=4) {
+		b64 = 0;
+		b64 |= (base64_index(base64_table, msg[i])<<18);
+		b64 |= (base64_index(base64_table, msg[i+1])<<12);
+		b64 |= i + 2 < len ? (base64_index(base64_table, msg[i+2])<<6) : 0;
+		b64 |= i + 3 < len ? (base64_index(base64_table, msg[i+3])) : 0;
+
+		(*buf)[j++] = 255 & (b64>>16);
+		(*buf)[j++] = 255 & (b64>>8);
+		(*buf)[j++] = 255 & (b64);
+	}
+
 	return size;
 }
 
diff --git a/base64.h b/base64.h
@@ -1,6 +1,7 @@
 #ifndef BASE64_H__
 #define BASE64_H__
 
+uint8_t base64_index(const char *base64, char ch);
 size_t base64_encode(char **buf, const unsigned char *msg, size_t len);
 size_t base64_decode(char **buf, const unsigned char *msg, size_t len);
 size_t base64_fold(FILE *out, char *msg, size_t len, size_t fold);