libbb/md5: code shrink

function                                             old     new   delta
md5_end                                              123     117      -6
md5_begin                                             49      42      -7
md5_hash                                             119     104     -15

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>

2 files changed, 26 insertions, 23 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 8d7beffe7..034016f4a 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1540,7 +1540,6 @@ typedef struct md5_ctx_t {
         uint32_t C;
         uint32_t D;
         uint64_t total;
-        uint32_t buflen;
         char buffer[128];
 } md5_ctx_t;
 #else
diff --git a/libbb/md5.c b/libbb/md5.c
index 9e5b496ce..1f9d59e6e 100644
--- a/libbb/md5.c
+++ b/libbb/md5.c
@@ -1,7 +1,7 @@
 /* vi: set sw=4 ts=4: */
 /*
- * md5.c - Compute MD5 checksum of strings according to the
- *         definition of MD5 in RFC 1321 from April 1992.
+ * Compute MD5 checksum of strings according to the
+ * definition of MD5 in RFC 1321 from April 1992.
  *
  * Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, 1995.
  *
@@ -34,7 +34,6 @@ void FAST_FUNC md5_begin(md5_ctx_t *ctx)
         ctx->C = 0x98badcfe;
         ctx->D = 0x10325476;
         ctx->total = 0;
-        ctx->buflen = 0;
 }
 
 /* These are the four functions used in the four steps of the MD5 algorithm
@@ -355,35 +354,39 @@ static void md5_hash_block(const void *buffer, md5_ctx_t *ctx)
         ctx->D = D;
 }
 
+/* The size of filled part of ctx->buffer: */
+#define BUFLEN(ctx) (((unsigned)ctx->total) & 63)
+
 /* Feed data through a temporary buffer to call md5_hash_aligned_block()
  * with chunks of data that are 4-byte aligned and a multiple of 64 bytes.
  * This function's internal buffer remembers previous data until it has 64
  * bytes worth to pass on.  Call md5_end() to flush this buffer. */
 void FAST_FUNC md5_hash(const void *buffer, size_t len, md5_ctx_t *ctx)
 {
-        char *buf = (char *)buffer;
+        const char *buf = buffer;
+        unsigned buflen = BUFLEN(ctx);
 
-        /* RFC 1321 specifies the possible length of the file up to 2^64 bits,
+        /* RFC 1321 specifies the possible length of the file up to 2^64 bits.
          * Here we only track the number of bytes.  */
         ctx->total += len;
 
         /* Process all input. */
-        while (len) {
-                unsigned i = 64 - ctx->buflen;
-
-                /* Copy data into aligned buffer. */
+        while (1) {
+                unsigned i = 64 - buflen;
                 if (i > len)
                         i = len;
-                memcpy(ctx->buffer + ctx->buflen, buf, i);
+                /* Copy data into aligned buffer. */
+                memcpy(ctx->buffer + buflen, buf, i);
                 len -= i;
-                ctx->buflen += i;
                 buf += i;
-
-                /* When buffer fills up, process it. */
-                if (ctx->buflen == 64) {
-                        md5_hash_block(ctx->buffer, ctx);
-                        ctx->buflen = 0;
-                }
+                buflen += i;
+                /* clever way to do "if (buflen != 64) break; ... ; buflen = 0;" */
+                buflen -= 64;
+                if (buflen != 0)
+                        break;
+                /* Buffer is filled up, process it. */
+                md5_hash_block(ctx->buffer, ctx);
+                /*buflen = 0; - already is */
         }
 }
 
@@ -396,18 +399,19 @@ void FAST_FUNC md5_end(void *resbuf, md5_ctx_t *ctx)
 {
         uint64_t total;
         char *buf = ctx->buffer;
-        int i;
+        unsigned i;
+        unsigned buflen = BUFLEN(ctx);
 
         /* Pad data to block size.  */
-        buf[ctx->buflen++] = 0x80;
-        memset(buf + ctx->buflen, 0, 128 - ctx->buflen);
+        buf[buflen++] = 0x80;
+        memset(buf + buflen, 0, 128 - buflen);
 
         /* Put the 64-bit file length, expressed in *bits*,
          * at the end of the buffer.
          */
+        /* clever way to do "if (buflen > 56) buf += 64": */
+        buf += ((buflen + 7) & 64);
         total = ctx->total << 3;
-        if (ctx->buflen > 56)
-                buf += 64;
         for (i = 0; i < 8; i++) {
                 buf[56 + i] = total;
                 total >>= 8;