Implement uc_hex_encode_delim without snprintf, fix length of

uc_hex_encode_delim when truncated output.

src/hex.c

@@ -1,16 +1,18 @@
 #include <stdint.h>
 #include <stddef.h>
-#include <stdio.h>
+#include <string.h>
 #include "ucore/string.h"
+#include "ucore/utils.h"
 
 static const char hx_chars[] = "0123456789ABCDEF" ;
 
 char*
 uc_hex_encode(const uint8_t *in, size_t len, char *out)
 {
-    unsigned int i, t, hn, ln;
+    unsigned int i, t;
 
     for (i = 0, t = 0; i < len; ++i,t+=2) {
+        unsigned int hn, ln;
 
         hn = (in[i] & 0xF0) >> 4 ;
         ln =  in[i] & 0x0F ;
@@ -27,19 +29,34 @@ uc_hex_encode(const uint8_t *in, size_t len, char *out)
 char*
 uc_hex_encode_delim(const uint8_t *in, size_t inlen, char *out, int outlen, char *delim)
 {
-    unsigned int i;
+    size_t i;
     char *outp = out;
 
-    out[0] = 0;
+    for (i = 0; i < inlen; i++) {
+        unsigned int hn, ln;
+        char *delimp = delim;
 
-    for (i = 0; i < inlen && outlen > 0; i++) {
-        int rc = snprintf(outp, outlen, "%02X%s", in[i], delim);
-        if (rc <= 0)
+        /** Truncate at a full byte */
+        if (outlen <= 2) {
             break;
-        outp += rc;
-        outlen -= rc;
+        }
+
+        hn = (in[i] & 0xF0) >> 4 ;
+        ln =  in[i] & 0x0F ;
+
+        outp[0]   = hx_chars[hn];
+        outp[1] = hx_chars[ln];
+        outlen -= 2;
+        outp += 2;
+
+        while (outlen > 1 && *delimp) {
+            *outp++ = *delimp++;
+            outlen--;
+        }
     }
 
+    *outp = 0;
+
     return outp;
 }