refactor for less looping

1 files changed, 16 insertions, 9 deletions

diff --git a/booki.c b/booki.c
index 2bd30bf..6840849 100644
--- a/booki.c
+++ b/booki.c
@@ -634,19 +634,26 @@ char* next_book(char* current_pos) {
 
 char* characters_from_end(char* str, int len, int number_of_chars) {
     assert(len >= number_of_chars);
-    int retchars = number_of_chars;
-    char* newptr = str + len - 1;
+
+    // let's not zoom past the beginning of the string
+    if (number_of_chars == 0)
+        return str;
+
+    // start at the end of the string, locate all code points
+    char* newptr = str + len; // will update to last character in do..while
     unsigned char ch;
-    int total_bytes = 0;
-    while (number_of_chars > 0) {
+    do {
+        // update the pointer, get the character
+        newptr--;
+        len--;
         ch = (unsigned char) *newptr;
-        // if we're at the first byte of a unicode point, adjust
+
+        // if we're at the first byte of a unicode point, we've found a whole character
         if (ch < 0x80 || ch >= 0xC3)
             number_of_chars--;
-        newptr--;
-        total_bytes++;
-    }
-    return newptr + 1;
+    } while (number_of_chars > 0 && len > 0);
+
+    return newptr;
 }
 
 /*** search ***/