feat(dotter): Ensure null termination and robust buffer handling

-    Explicitly null-terminating the output strings in both slipstream_inline_dotify and slipstream_inline_undotify.
-    Improving the buffer size check in slipstream_inline_dotify to correctly account for the null terminator.
-    Enhancing the handling of empty input strings in slipstream_inline_dotify.

src/slipstream_inline_dots.c

@@ -1,29 +1,35 @@
 #include "slipstream_inline_dots.h"
 
 size_t slipstream_inline_dotify(char * __restrict__ buf, size_t buflen, size_t len) {
-    size_t dots = len / 57;  // Number of dots to insert
-    size_t new_len = len + dots;
-
-    // Check if result would exceed buffer
-    if (new_len > buflen) {
-        return -1;  // Error condition
+    if (len == 0) { // If there's nothing to do, we do nothing. Efficient, right?
+        if (buflen > 0) buf[0] = '\0';
+        return 0;
     }
 
-    // Start from the end and work backwards
-    char *src = buf + len - 1;    // Points to last char of original string
-    char *dst = buf + new_len - 1;  // Points to where last char will end up
+    size_t dots = len / 57;             // Every 57 bytes, a dot. It's the law.
+    size_t new_len = len + dots;
+
+    if (new_len + 1 > buflen) {
+        return (size_t)-1;              // Err -> .h? Meh.
+    }
+
+    buf[new_len] = '\0';                // Amen.
+
+    char *src = buf + len - 1;          // Points to last char of original string
+    char *dst = buf + new_len - 1;      // Points to where last char will end up
 
     // Avoid modulo operation in tight loop
     size_t next_dot = len - (len % 57);
+
     size_t current_pos = len;
 
     // Move characters right-to-left, inserting dots
     while (current_pos > 0) {
         if (current_pos == next_dot) {
-            *dst-- = '.';
-            next_dot -= 57;
-            current_pos--;
-            continue;
+            *dst-- = '.';               // Dot. Because rules are rules, even for dots.
+            next_dot -= 57;             // Next dot is 57 chars back.
+            current_pos--;              // Account for the char space the dot took.
+            continue;                   // Skip the copy for this iteration, already placed dot.
         }
         *dst-- = *src--;
         current_pos--;
@@ -36,14 +42,12 @@ size_t slipstream_inline_undotify(char * __restrict__ buf, size_t len) {
     char *reader = buf;
     char *writer = buf;
 
-    // For ~255 byte buffer with dots every ~50 chars
-    // Simple loop is most efficient since dots are sparse
-    while (len--) {
+    for (size_t i = 0; i < len; ++i) {
         char c = *reader++;
-        if (c != '.') {
-            *writer++ = c;
-        }
+        if (c != '.')
+            *writer++ = c;              // Filter out the noise. Only the good stuff.
     }
 
+    *writer = '\0';                     // Rewind the tape. The future is clean.
     return writer - buf;
-}
+}