From 97baac1c3e72d18dfd5b790ad44e814b034bca5c Mon Sep 17 00:00:00 2001
From: Allanis <allanis@saracraft.net>
Date: Thu, 23 May 2013 21:30:49 +0100
Subject: [PATCH] [Add] Comments to base64.
---
src/base64.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/src/base64.c b/src/base64.c
index 726bce1..6d0167a 100644
--- a/src/base64.c
+++ b/src/base64.c
@@ -2,9 +2,9 @@
#include <string.h>
#include <stdint.h>
-// Encode table.
+// Encode table - base64 alphabet is defined by the rfc
static const char cb64[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
-// Decode table.
+// Generate decode table at compile time.
#define B64(_) \
((_) == 'A' ? 0 \
: (_) == 'B' ? 1 \
@@ -72,6 +72,7 @@ static const char cb64[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwx
: (_) == '/' ? 63 \
: -1)
+// Makes it much faster.
static const signed char cd64[256] = {
B64(0), B64(1), B64(2), B64(3),
B64(4), B64(5), B64(6), B64(7),
@@ -180,6 +181,7 @@ char* base64_encode(size_t* len, char* src, size_t sz) {
for(c = 0; c < pad; c++)
r[i-c-1] = '=';
+ // It'll be a valid string.
r[i] = '\0';
(*len) = i;
@@ -212,19 +214,23 @@ char* base64_decode(size_t* len, char* src, size_t sz) {
j = 0;
for(i = 0; i < sz; i++) {
if(src[i] == '=')
+ // Control padding.
pad++;
if(dec_valid(src[i]))
+ // Only allow valid characters.
dat[j++] = src[i];
}
// Fill r.
i = 0;
for(c = 0; c < j; c += 4) {
- n = dec_ch(dat[c+0]) << 18;
- n += (c+1<j) ? (dec_ch(dat[c+1]) << 12) : 0;
+ // Process the input from base 64.
+ n = dec_ch(dat[c+0]) << 18; // Guaranteed to be valid.
+ n += (c+1<j) ? (dec_ch(dat[c+1]) << 12) : 0; // Check if in bounds.
n += (c+2<j) ? (dec_ch(dat[c+2]) << 6) : 0;
n += (c+3<j) ? (dec_ch(dat[c+3]) << 0) : 0;
+ // Convert the 24 bits of encoded data into 3 8 bit chunks.
r[i++] = (n >> 16) & 255;
r[i++] = (n >> 8) & 255;
r[i++] = (n >> 0) & 255;
@@ -234,7 +240,7 @@ char* base64_decode(size_t* len, char* src, size_t sz) {
// Cleanup.
free(dat);
- (*len) = i - pad;
+ (*len) = i - pad; // Must decount the padding.
return r;
}