change one func

lab_4/vlad's/fifo_server.c

@@ -35,27 +35,37 @@ static long long parse_ll(const char *s) {
 long long process_data(const char *input, size_t input_len, char *output, 
                        size_t output_size, long long max_replacements) {
     long long total_replacements = 0;
-    int at_line_start = 1;
-    unsigned char line_key = 0;
     size_t out_pos = 0;
+    size_t i = 0;
 
-    for (size_t i = 0; i < input_len && out_pos < output_size - 1; i++) {
+    while (i < input_len && out_pos < output_size - 1) {
         unsigned char c = (unsigned char)input[i];
 
-        if (at_line_start) {
-            line_key = c;
-            at_line_start = 0;
+        /* Try to form a non-overlapping pair with the next character.
+           Do not treat newline as part of a pair (preserve line structure). */
+        if (i + 1 < input_len) {
+            unsigned char next = (unsigned char)input[i + 1];
+            if (c != '\n' && next != '\n' && c == next && total_replacements < max_replacements) {
+                /* write first char of pair */
+                output[out_pos++] = (char)c;
+                if (out_pos >= output_size - 1) break;
+                /* write space instead of second char */
+                output[out_pos++] = ' ';
+                total_replacements++;
+                i += 2; /* skip both chars (non-overlapping) */
+                continue;
+            }
         }
 
-        unsigned char outc = c;
-        if (c == '\n') {
-            at_line_start = 1;
-        } else if (c == line_key && total_replacements < max_replacements) {
-            outc = ' ';
-            total_replacements++;
-        }
+        /* No valid pair -> write current char */
+        output[out_pos++] = (char)c;
+        i++;
+    }
 
-        output[out_pos++] = (char)outc;
+    /* If we stopped early but still have room, copy remaining bytes (without forming pairs)
+       until output buffer full or input ends. This preserves trailing data. */
+    while (i < input_len && out_pos < output_size - 1) {
+        output[out_pos++] = input[i++];
     }
 
     output[out_pos] = '\0';