1 files changed, 85 insertions, 0 deletions

diff --git a/xs_hex.h b/xs_hex.h
new file mode 100644
index 0000000..2d87a65
--- /dev/null
+++ b/xs_hex.h
@@ -0,0 +1,85 @@
+/* copyright (c) 2022 - 2023 grunfink et al. / MIT license */
+
+#ifndef _XS_HEX_H
+
+#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);
+
+#ifdef XS_IMPLEMENTATION
+
+/** hex **/
+
+static char rev_hex_digits[] = "fedcba9876543210FEDCBA";
+
+xs_str *xs_hex_enc(const xs_val *data, int size)
+/* returns an hexdump of data */
+{
+    xs_str *s;
+    char *p;
+    int n;
+
+    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++;
+    }
+
+    *p = '\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;
+    char *p;
+    int n;
+
+    if (sz % 2)
+        return NULL;
+
+    p = s = xs_realloc(NULL, _xs_blk_size(sz / 2 + 1));
+
+    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);
+        }
+
+        *p++ = (0xf - ((d1 - rev_hex_digits) & 0xf)) << 4 |
+               (0xf - ((d2 - rev_hex_digits) & 0xf));
+    }
+
+    *p = '\0';
+    *size = sz / 2;
+
+    return s;
+}
+
+
+int xs_is_hex(const char *str)
+/* returns 1 if str is an hex string */
+{
+    while (*str) {
+        if (strchr(rev_hex_digits, *str++) == NULL)
+            return 0;
+    }
+
+    return 1;
+}
+
+
+#endif /* XS_IMPLEMENTATION */
+
+#endif /* _XS_HEX_H */