Generalized base64, adding lookup table pointers to the contexts.

4 files changed, 75 insertions, 48 deletions

diff --git a/ChangeLog b/ChangeLog
index 7859c142..9ee8aeae 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,20 @@
+2015-02-10  Niels Möller  <nisse@lysator.liu.se>
+
+	Base-64 generalization, contributed by Amos Jeffries.
+	* base64.h (struct base64_encode_ctx): Added pointer to alphabet.
+	(struct base64_decode_ctx): Added pointer to decoding table.
+	* base64-decode.c (base64_decode_init): Initialize table pointer.
+	Moved definition of table to local scope.
+	(base64_decode_single): Use the context's decoding table.
+	* base64-encode.c (ENCODE): Added alphabet argument. Updated all
+	uses.
+	(encode_raw): New static function, like base64_encode_raw
+	but with an alphabet argument.
+	(base64_encode_raw): Call encode_raw.
+	(base64_encode_init): Initialize alphabet pointer.
+	(base64_encode_single, base64_encode_update, base64_encode_final):
+	Use the context's alphabet.
+
 2015-02-09  Niels Möller  <nisse@lysator.liu.se>
 
 	* base64-encode.c (base64_encode): Deleted old #if:ed out
diff --git a/base64-decode.c b/base64-decode.c
index f622baac..337ea395 100644
--- a/base64-decode.c
+++ b/base64-decode.c
@@ -42,32 +42,32 @@
 #define TABLE_SPACE -2
 #define TABLE_END -3
 
-static const signed char
-decode_table[0x100] =
-{
-  /* White space is HT, VT, FF, CR, LF and SPC */
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -2, -2, -2, -1, -1, 
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-  -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
-  52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -3, -1, -1,
-  -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
-  15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
-  -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
-  41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-};
-
 void
 base64_decode_init(struct base64_decode_ctx *ctx)
 {
+  static const signed char base64_decode_table[0x100] =
+    {
+      /* White space is HT, VT, FF, CR, LF and SPC */
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -2, -2, -2, -2, -2, -1, -1, 
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
+      52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -3, -1, -1,
+      -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
+      15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
+      -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
+      41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    };
+
   ctx->word = ctx->bits = ctx->padding = 0;
+  ctx->table = base64_decode_table;
 }
 
 int
@@ -75,9 +75,7 @@ base64_decode_single(struct base64_decode_ctx *ctx,
 		     uint8_t *dst,
 		     uint8_t src)
 {
-  int data;
-  
-  data = decode_table[src];
+  int data = ctx->table[src];
 
   switch(data)
     {
diff --git a/base64-encode.c b/base64-encode.c
index b0b921f6..0e81b3f5 100644
--- a/base64-encode.c
+++ b/base64-encode.c
@@ -38,15 +38,11 @@
 
 #include "base64.h"
 
-static const uint8_t encode_table[64] =
-  "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-  "abcdefghijklmnopqrstuvwxyz"
-  "0123456789+/";
-
-#define ENCODE(x) (encode_table[0x3F & (x)])
+#define ENCODE(alphabet,x) ((alphabet)[0x3F & (x)])
 
-void
-base64_encode_raw(uint8_t *dst, size_t length, const uint8_t *src)
+static void
+encode_raw(const char *alphabet,
+	   uint8_t *dst, size_t length, const uint8_t *src)
 {
   const uint8_t *in = src + length;
   uint8_t *out = dst + BASE64_ENCODE_RAW_LENGTH(length);
@@ -61,45 +57,57 @@ base64_encode_raw(uint8_t *dst, size_t length, const uint8_t *src)
 	{
 	case 1:
 	  *--out = '=';
-	  *--out = ENCODE(in[0] << 4);
+	  *--out = ENCODE(alphabet, (in[0] << 4));
 	  break;
 	  
 	case 2:
-	  *--out = ENCODE( in[1] << 2);
-	  *--out = ENCODE((in[0] << 4) | (in[1] >> 4));
+	  *--out = ENCODE(alphabet, (in[1] << 2));
+	  *--out = ENCODE(alphabet, ((in[0] << 4) | (in[1] >> 4)));
 	  break;
 
 	default:
 	  abort();
 	}
-      *--out = ENCODE(in[0] >> 2);
+      *--out = ENCODE(alphabet, (in[0] >> 2));
     }
   
   while (in > src)
     {
       in -= 3;
-      *--out = ENCODE( in[2]);
-      *--out = ENCODE((in[1] << 2) | (in[2] >> 6));
-      *--out = ENCODE((in[0] << 4) | (in[1] >> 4));
-      *--out = ENCODE( in[0] >> 2);      
+      *--out = ENCODE(alphabet, (in[2]));
+      *--out = ENCODE(alphabet, ((in[1] << 2) | (in[2] >> 6)));
+      *--out = ENCODE(alphabet, ((in[0] << 4) | (in[1] >> 4)));
+      *--out = ENCODE(alphabet, (in[0] >> 2));
     }
   assert(in == src);
   assert(out == dst);
 }
 
+static const uint8_t base64_encode_table[64] =
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+  "abcdefghijklmnopqrstuvwxyz"
+  "0123456789+/";
+
+void
+base64_encode_raw(uint8_t *dst, size_t length, const uint8_t *src)
+{
+  encode_raw(base64_encode_table, dst, length, src);
+}
+
 void
 base64_encode_group(uint8_t *dst, uint32_t group)
 {
-  *dst++ = ENCODE(group >> 18);
-  *dst++ = ENCODE(group >> 12);
-  *dst++ = ENCODE(group >> 6);
-  *dst++ = ENCODE(group);
+  *dst++ = ENCODE(base64_encode_table, (group >> 18));
+  *dst++ = ENCODE(base64_encode_table, (group >> 12));
+  *dst++ = ENCODE(base64_encode_table, (group >> 6));
+  *dst++ = ENCODE(base64_encode_table, group);
 }
 
 void
 base64_encode_init(struct base64_encode_ctx *ctx)
 {
   ctx->word = ctx->bits = 0;
+  ctx->alphabet = base64_encode_table;
 }
 
 /* Encodes a single byte. */
@@ -115,7 +123,7 @@ base64_encode_single(struct base64_encode_ctx *ctx,
   while (bits >= 6)
     {
       bits -= 6;
-      dst[done++] = ENCODE(word >> bits);
+      dst[done++] = ENCODE(ctx->alphabet, (word >> bits));
     }
 
   ctx->bits = bits;
@@ -152,7 +160,7 @@ base64_encode_update(struct base64_encode_ctx *ctx,
     {
       assert(!(bulk % 3));
       
-      base64_encode_raw(dst + done, bulk, src);
+      encode_raw(ctx->alphabet, dst + done, bulk, src);
       done += BASE64_ENCODE_RAW_LENGTH(bulk);
       src += bulk;
       left = left_over;
@@ -180,7 +188,7 @@ base64_encode_final(struct base64_encode_ctx *ctx,
   
   if (bits)
     {
-      dst[done++] = ENCODE(ctx->word << (6 - ctx->bits));
+      dst[done++] = ENCODE(ctx->alphabet, (ctx->word << (6 - ctx->bits)));
       for (; bits < 6; bits += 2)
 	dst[done++] = '=';
 
diff --git a/base64.h b/base64.h
index a6fb8235..07a8e2b7 100644
--- a/base64.h
+++ b/base64.h
@@ -73,8 +73,10 @@ struct base64_encode_ctx
 {
   unsigned word;   /* Leftover bits */
   unsigned bits;  /* Number of bits, always 0, 2, or 4. */
+  const uint8_t *alphabet; /* Alphabet to use for encoding */
 };
 
+/* Initialize encoding context for base-64 */
 void
 base64_encode_init(struct base64_encode_ctx *ctx);
 
@@ -123,8 +125,10 @@ struct base64_decode_ctx
 
   /* Number of padding characters encountered */
   unsigned padding;
+  const signed char *table; /* Decoding table */
 };
 
+/* Initialize decoding context for base-64 */
 void
 base64_decode_init(struct base64_decode_ctx *ctx);