1 files changed, 103 insertions, 35 deletions

diff --git a/xs_hex.h b/xs_hex.h
index 2d87a65..21183f4 100644
--- a/xs_hex.h
+++ b/xs_hex.h
@@ -4,65 +4,129 @@
 
 #define _XS_HEX_H
 
-xs_str *xs_hex_enc(const xs_val *data, int size);
-xs_val *xs_hex_dec(const xs_str *hex, int *size);
-int xs_is_hex(const char *str);
+ int xs_is_hex_digit(char str);
+ void xs_hex_enc_1(char **dst, const char **src);
+ int xs_hex_dec_1(char **dst, const char **src);
+ char *_xs_hex_enc(char *dst, const char *src, int src_size);
+ char *_xs_hex_dec(char *dst, const char *src, int src_size);
+
+#ifdef _XS_H
+ xs_str *xs_hex_enc(const xs_val *data, int size);
+ xs_val *xs_hex_dec(const xs_str *hex, int *size);
+ int xs_is_hex(const char *str);
+#endif /* _XS_H */
+
 
 #ifdef XS_IMPLEMENTATION
 
+#include <string.h>
+
 /** hex **/
 
 static char rev_hex_digits[] = "fedcba9876543210FEDCBA";
 
-xs_str *xs_hex_enc(const xs_val *data, int size)
-/* returns an hexdump of data */
+int xs_is_hex_digit(char str)
+/* checks if the char is an hex digit */
 {
-    xs_str *s;
-    char *p;
-    int n;
+    return strchr(rev_hex_digits, str) != NULL;
+}
 
-    p = s = xs_realloc(NULL, _xs_blk_size(size * 2 + 1));
 
-    for (n = 0; n < size; n++) {
-        *p++ = rev_hex_digits[0xf - (*data >> 4 & 0xf)];
-        *p++ = rev_hex_digits[0xf - (*data      & 0xf)];
-        data++;
+void xs_hex_enc_1(char **dst, const char **src)
+/* decodes one character into two hex digits */
+{
+    const char *i = *src;
+    char *o = *dst;
+
+    *o++ = rev_hex_digits[0xf - (*i >> 4 & 0xf)];
+    *o++ = rev_hex_digits[0xf - (*i      & 0xf)];
+
+    *src = i + 1;
+    *dst = o;
+}
+
+
+int xs_hex_dec_1(char **dst, const char **src)
+/* decodes two hex digits (returns 0 on error) */
+{
+    const char *i = *src;
+    char *o = *dst;
+
+    char *d1 = strchr(rev_hex_digits, *i++);
+    char *d2 = strchr(rev_hex_digits, *i++);
+
+    if (!d1 || !d2) {
+        /* decoding error */
+        return 0;
     }
 
-    *p = '\0';
+    *o++ = (0xf - ((d1 - rev_hex_digits) & 0xf)) << 4 |
+           (0xf - ((d2 - rev_hex_digits) & 0xf));
 
-    return s;
+    *src = i;
+    *dst = o;
+    return 1;
 }
 
 
-xs_val *xs_hex_dec(const xs_str *hex, int *size)
-/* decodes an hexdump into data */
+char *_xs_hex_enc(char *dst, const char *src, int src_size)
+/* hex-encodes the src buffer into dst, which has enough size */
 {
-    int sz = strlen(hex);
-    xs_val *s = NULL;
-    char *p;
-    int n;
+    const char *e = src + src_size;
 
-    if (sz % 2)
-        return NULL;
+    while (src < e)
+        xs_hex_enc_1(&dst, &src);
 
-    p = s = xs_realloc(NULL, _xs_blk_size(sz / 2 + 1));
+    return dst;
+}
 
-    for (n = 0; n < sz; n += 2) {
-        char *d1 = strchr(rev_hex_digits, *hex++);
-        char *d2 = strchr(rev_hex_digits, *hex++);
 
-        if (!d1 || !d2) {
-            /* decoding error */
-            return xs_free(s);
-        }
+char *_xs_hex_dec(char *dst, const char *src, int src_size)
+/* hex-decodes the src string int dst, which has enough size.
+   return NULL on decoding errors or the final position of dst */
+{
+    if (src_size % 2)
+        return NULL;
 
-        *p++ = (0xf - ((d1 - rev_hex_digits) & 0xf)) << 4 |
-               (0xf - ((d2 - rev_hex_digits) & 0xf));
+    const char *e = src + src_size;
+
+    while (src < e) {
+        if (!xs_hex_dec_1(&dst, &src))
+            return NULL;
     }
 
-    *p = '\0';
+    return dst;
+}
+
+
+#ifdef _XS_H
+
+xs_str *xs_hex_enc(const xs_val *data, int size)
+/* returns an hexdump of data */
+{
+    xs_str *s = xs_realloc(NULL, _xs_blk_size(size * 2 + 1));
+
+    char *q = _xs_hex_enc(s, data, size);
+
+    *q = '\0';
+
+    return s;
+}
+
+
+xs_val *xs_hex_dec(const xs_str *hex, int *size)
+/* decodes an hexdump into data */
+{
+    int sz = strlen(hex);
+    xs_val *s = NULL;
+
     *size = sz / 2;
+    s = xs_realloc(NULL, _xs_blk_size(*size + 1));
+
+    if (!_xs_hex_dec(s, hex, sz))
+        return xs_free(s);
+
+    s[*size] = '\0';
 
     return s;
 }
@@ -71,14 +135,18 @@ xs_val *xs_hex_dec(const xs_str *hex, int *size)
 int xs_is_hex(const char *str)
 /* returns 1 if str is an hex string */
 {
+    if (strlen(str) % 2)
+        return 0;
+
     while (*str) {
-        if (strchr(rev_hex_digits, *str++) == NULL)
+        if (!xs_is_hex_digit(*str++))
             return 0;
     }
 
     return 1;
 }
 
+#endif /* _XS_H */
 
 #endif /* XS_IMPLEMENTATION */